Memory

Information about the brain and the mechanisms of cognition

The role of emotion in memory

Does emotion help us remember? That's not an easy question to answer, which is unsurprising when you consider the complexities of emotion.

First of all, there are two, quite different, elements to this question. The first concerns the emotional content of the information you want to remember. The second concerns the effect of your emotional state on your learning and remembering.

The effect of emotional content

It does seem clear that, as a general rule, we remember emotionally charged events better than boring ones.

Latest research suggests that it is the emotions aroused, not the personal significance of the event, that makes such events easier to remember.

The memory of strongly emotional images and events may be at the expense of other information. Thus, you may be less likely to remember information if it is followed by something that is strongly emotional. This effect appears to be stronger for women.

It does seem that memories are treated differently depending on whether they are associated with pleasant emotions or unpleasant ones, and that this general rule appears to be affected by age and other individual factors. Specifically, pleasant emotions appear to fade more slowly from our memory than unpleasant emotions, but among those with mild depression, unpleasant and pleasant emotions tend to fade evenly, while older adults seem to regulate their emotions better than younger people, and may encode less information that is negative.

An investigation of autobiographical memories found that positive memories contained more sensorial and contextual details than neutral or negative memories (which didn't significantly differ from each other in this regard). This was true regardless of individual's personal coping styles.

  • Emotionally charged events are remembered better
  • Pleasant emotions are usually remembered better than unpleasant ones
  • Positive memories contain more contextual details (which in turn, helps memory)
  • Strong emotion can impair memory for less emotional events and information experienced at the same time
  • It's the emotional arousal, not the importance of the information, that helps memory

The effect of mood

Another aspect of emotion is mood - your emotional state at the time of encoding or retrieving. There has been quite a lot of research on the effect of mood on memory. It is clear that mood affects what is noticed and encoded. This is reflected in two (similar but subtly different) effects:

  • mood congruence: whereby we remember events that match our current mood (thus, when we're depressed, we tend to remember negative events), and
  • mood dependence: which refers to the fact that remembering is easier when your mood at retrieval matches your mood at encoding (thus, your chances of remembering an event or fact are greater if you evoke the emotional state you were in at the time of experiencing the event or learning the fact).

An interesting issue in the study of emotion is the degree to which what we feel is influenced by our expression of it. In other words, does a person who conceals what they are feeling feel as deeply as a person who openly displays their emotion? Does the expression of emotion, in itself, affect what we feel?

I remember reading Paul Ekman (the guru of interpreting facial expressions, and author of several books on the subject) say that, when practicing the expressions, he found himself experiencing the emotions they expressed. However, accurate expression of emotion does seem to require considerable expertise (if the emotion is not, in fact, being felt) - people are very good at distinguishing false expressions of emotion.

The way people go about controlling their reactions to emotional events does seem to affect their memory of the event. People shown a video of an emotional event and instructed not to let their emotions show were found to have a poorer memory for what was said and done than did those who were given no such instructions.

However, as with emotional content, we cannot simply say that emotional state affects memory. The nature of the emotion being felt is also important. And this, too, is not straightforward. We cannot simply say, for example, that anxiety impairs memory and happiness improves it.

A small study in which participants performed difficult cognitive tasks after watching short videos designed to elicit one of three emotional states ( pleasant, neutral or anxious), found that mild anxiety improved performance on some tasks, but hurt performance on others. Similarly, being in a pleasant mood boosted some kinds of performance but impaired other kinds.

This may have something to do with different emotions being involved with different brain regions.

  • Remembering is easier when your mood matches the mood you were in when experiencing/learning the information
  • The stronger the emotions aroused, the greater the effect on memory
  • Emotions can be evoked, or minimized, by displaying or suppressing expressions of emotion
  • Different emotional states may impair or help memory, for different memory tasks

Brain regions involved in the emotion-memory interaction

The brain region most strongly implicated in emotional memory is the amygdala. The amygdala is critically involved in calculating the emotional significance of events, and, through its connection to brain regions dealing with sensory experiences, also appears to be responsible for the influence of emotion on perception - alerting us to notice emotionally significant events even when we're not paying attention. The amygdala appears to be particularly keyed to negative experiences.

But it is not only the amygdala that is involved in this complex interaction. The cerebellum, most strongly associated with motor coordination skills, may also be involved in remembering strong emotions, in particular, in the consolidation of long-term memories of fear.

Parts of the prefrontal cortex also appear to be involved. One study found that a region of the prefrontal cortex was jointly influenced by a combination of mood state and cognitive task, but not by either one alone. Another study found that the dorsolateral prefrontal cortex is more active when the participants were surprised by unexpected responses.

Is surprise an emotion? I think surprise is right there in the fuzzy border between two related phenomena - emotion and attention. Interestingly, our understanding of these two phenomena is about on a par - still woefully inadequate (but greatly improving!).

The relationship between emotion and attention

Research suggests that emotional stimuli and "attentional functions" move in parallel streams through the brain before being integrated in a specific part of the brain's prefrontal cortex (the anterior cingulate). This is why emotional stimuli are more likely than simple distractions to interfere with your concentration on a task such as driving.

We now think that attention is not, as has been thought, a global process, but consists of at least three distinct processes, each located in different parts of the frontal lobes. These are:

  1. a system that helps us maintain a general state of readiness to respond;
  2. a system that sets our threshold for responding to an external stimulus; and
  3. a system that helps us selectively attend to appropriate stimuli.

Correspondingly, emotional arousal helps us maintain a "readiness to respond", and also has a selective effect on the particular stimuli we notice and encode. Perhaps, indeed, attention may be thought of as a state of activity that is triggered by various kinds of emotional arousal, and modulated by such arousal.

How do emotions affect memory?

Well, we're still foggy on details, but there appear to be two main aspects to this. One is that stress hormones, such as cortisol, interact with the amygdala. The other is that the amygdala can alter the activity of other brain regions. One of the ways in which it does this is by acting on consolidation processes (principally in the hippocampus).

It is perhaps this effect on consolidation that is reflected in a study using facial stimuli (involving inversion of eyes and mouth to change the emotional impact of a face without significantly changing its visual features), that indicated that the emotional load of a stimulus does not in fact affect the way we perceive it but does have an effect on how we become used to it if we see it many times.

Notwithstanding this study, however, it does seem clear that, in some circumstances and for some types of stimuli, at least, the emotional attributes of a stimulus do affect the way we perceive it and process it - that is, the encoding of the memory.

One of the ways in which it might do this is through the involvement of different brain regions depending on the nature of the emotion experienced. A recent imaging study found that positive emotional contexts evoked activity in the right fusiform gyrus (among other regions), and negative emotional contexts evoked activity in the right amygdala.

Another way in which emotions might affect memory encoding is through working memory. It has been suggested that, in the case of anxiety, part of working memory may be taken up with our awareness of fears and worries, leaving less capacity available for processing. In support of this theory, one study found that math-anxious people have working memory problems as they do math.

Age and gender differences

It also seems that there are differences in the way men and women process emotional memories. Women are better at remembering emotional memories. They also seem to be more likely to forget information presented immediately before emotionally charged information. This suggests that women are more affected by emotional content - a suggestion compatible with the finding that women and men tend to encode emotional experiences in different parts of the brain. In women, it seems that evaluation of emotional experience and encoding of the memory is much more tightly integrated.

There is also an age difference. The tendency to let unpleasant memories fade faster than pleasant ones gets stronger as we age. This is perhaps a reflection of older people's apparent ability to regulate their emotions more effectively than younger people, by maintaining positive feelings and lowering negative feelings. Preliminary brain research suggests that in older adults, the amygdala is activated equally to positive and negative images, whereas in younger adults, it is activated more to negative images. It may be that older adults encode less information about negative images.

It has also been speculated that age-related cognitive decline may be partly caused by a greater cortisol responsivity to stress.

  • The key player in the processing of emotional memories appears to be the amygdala
  • Other brain regions, in particular the prefrontal cortex and the cerebellum, are also involved
  • While these regions are important for all, men and women do show differences in the parts of the brain they use to encode emotion
  • Emotion and attention are related phenomena
  • Emotion acts on memory at all points of the memory cycle - at encoding, consolidation, and retrieval
  • Emotion acts on memory in various ways, including the production of stress hormones, use of working memory capacity, and involvement of particular brain regions

 

References
  • Anderson, A.K. & Phelps, E.A. 2001. Lesions of the human amygdala impair enhanced perception of emotionally salient events. Nature, 411, 305-309.
  • Canli, T., Desmond, J.E., Zhao, Z. & Gabrieli, J.D.E. 2002. Sex differences in the neural basis of emotional memories. Proceedings of the National Academy of Sciences, 99, 10789-10794.
  • Charles, S.T., Mather, M. & Carstensen, L.L. 2003. Aging and Emotional Memory: The Forgettable Nature of Negative Images for Older Adults. Journal of Experimental Psychology: General, 132(2), 310-24.
  • D'Argembeau, A., Comblain, C. & Van der Linden, M. 2002. Phenomenal characteristics of autobiographical memories for positive, negative, and neutral events. Applied Cognitive Psychology, 17(3), 281-94.
  • Erk, S. et al. 2003. Emotional context modulates subsequent memory effect. Neuroimage, 18, 439-447.
  • Fletcher, P.C., Anderson, J.M., Shanks, D.R., Honey, R., Carpenter, T.A., Donovan, T., Papadakis, N. & Bullmore, E.T. 2001. Responses of human frontal cortex to surprising events are predicted by formal associative learning theory. Nature Neuroscience, 4, 1043-1048.
  • Gray, J.R., Braver, T.S. & Raichle, M.E. Integration of emotion and cognition in the lateral prefrontal cortex. Proceedings of the National Academy of Sciences, 99, 4115-4120.
  • Hamann, S. 2001. Cognitive and neural mechanisms of emotional memory. Trends in Cognitive Sciences, 5 (9), 394-400.
  • Lewis, P.A. & Critchley, H.D. 2003. Mood-dependent memory. Trends in Cognitive Sciences, 7 (9).
  • Lupien, S.J., Gaudreau, S., Tchiteya, B.M., Maheu, F., Sharma, S., Nair, N.P.V., Hauger, R.L., McEwen, B.S. & Meaney, M.J. 1997. Stress-Induced Declarative Memory Impairment in Healthy Elderly Subjects: Relationship to Cortisol Reactivity. The Journal of Clinical Endocrinology & Metabolism, 82 (7), 2070-2075.
  • Nielson, K.A., Yee, D. & Erickson, K.I. 2002. Modulation of memory storage processes by post-training emotional arousal from a semantically unrelated source. Paper presented at the Society for Neuroscience annual meeting in Orlando, Florida, 4 November.
  • Nijholt, I., Farchi, N., Kye, M-J., Sklan, E.H., Shoham, S., Verbeure, B., Owen, D., Hochner, B., Spiess, J., Soreq, H. & Blank, T. 2003. Stress-induced alternative splicing of acetylcholinesterase results in enhanced fear memory and long-term potentiation. Molecular Psychiatry advance online publication, 28 October 2003.
  • Richards, J.M. & Gross, J.J. (2000). Emotion Regulation and Memory: The Cognitive Costs of Keeping One's Cool. Journal of Personality and Social Psychology, 79 (3), 410-424.
  • Richeson, J. & Shelton, N. 2003. When Prejudice Does Not Pay: Effects of Interracial Contact on Executive Function. Psychological Science, 14(3).
  • Sacchetti, B., Baldi, E., Lorenzini, C.A. & Bucherelli, C. 2002. Cerebellar role in fear-conditioning consolidation. Proc. Natl. Acad. Sci. U.S.A., 99 (12), 8406-8411.
  • Strange, B.A., Hurleman, R. & Dolan, R.J. In press. An emotion-induced retrograde amnesia in humans is amygdala and b-adrenergic dependent. Proceedings of the National Academy of Sciences.
  • Stuss, D.T., Binns, M.A., Murphy, K.J. & Alexander, M.P. 2002. Dissociations Within the Anterior Attentional System: Effects of Task Complexity and Irrelevant Information on Reaction-Time Speed and Accuracy. Neuropsychology, 16 (4), 500–513.
  • Walker, W.R., Skowronski, J.J. & Thompson, C.P. 2003. Life Is Pleasant -- and Memory Helps to Keep It That Way! Review of General Psychology, 7(2),203-10.
  • Yamasaki, H., LaBar, K.S. & McCarthy, G. Dissociable prefrontal brain systems for attention and emotion. Proc. Natl. Acad. Sci. USA, 99(17), 11447-51.

 

For more, see the research reports

The question of innate talent

Some personal experience

I have two sons. One of them was a colicky baby. Night after night my partner would carry him around the room while I tried to get a little sleep. One night, for his own amusement, my partner chose a particular CD to play. Magic! As the haunting notes of the hymns of the 12th century abbess Hildegard of Bingen rang through the room, the baby stopped crying. And stayed stopped. As long as the music played. Experimentation revealed that our son particularly liked very early music (plainchant from the 15th century Josquin des Pres was another favorite).

We felt sorry for all those parents with crying babies who hadn't discovered this magic cure-all.

And then we had another son.

This one didn't like music. No magic this time. And we realized, it wasn't that 12th century music had magical properties to calm a crying baby. No, it was this particular baby that responded to this sort of music.

The years went on. Nothing we saw contradicted that first impression - one son was "musical", and one was not. It seemed pretty clear to us. One son took after me, and one took after my partner.

My partner plays the piano, and the pipe organ, and the harpsichord. He is "into" Bach. He has played in churches and concerts. He has a shelf full of books on music and cupboards full of music scores, CDs by the score.

Me? I like to sing, to myself. I learned the violin for a while in my youth. I like to listen to CDs of jazz, and popular show tunes. I like music, but I'm not sophisticated about it. It's background to me. My partner actually listens to it.

So which child took after which parent?

Well, we believe the "musical" one took after me, and the "non-musical" one took after my partner. Because - he got there by training. By practicing and learning and persevering and taking an interest. He has no sense of rhythm, no particularly keen sense of pitch. But he's the one who can produce music. Me, I have an ear for music. Remembering a rhythm is effortless for me; I respond, instinctively, to music. But I could never bother to practice, and my response to music has stayed at the same level. Instinctive.

Our "musical" son has been involved in learning music the Suzuki way since he was four. We never particularly encouraged our other son to do likewise, simply told him he could if he wanted to. His brother persuaded him he did want to. So, fine, we said.

You can guess, I'm sure, how things have been. It's been obvious, watching and listening to our older son, that he has a talent for music, that it comes easily to him. Equally obvious that it hasn't come that easily to our younger son. But it's the younger son who has made much faster progress in the past year, because he practices more, because he's keen to learn. And it's been amazing to watch his ear for music develop.

Do you need an inborn talent to do well?

Suzuki flew in the face of "common-sense" when he decided very young children with no demonstrable genius could be taught to play the violin. I can only imagine the stunned amazement with which the first Suzuki concerts were greeted. They still amaze today.

Suzuki himself, while he supported the training of all children, believed that, of course, some would be "naturally" gifted, and that outstanding performance would require a gift, as well as training. However, as his experience with children and his method increased, he grew to believe that “every child can be highly educated if he is given the proper training” and blamed early training failures on incorrect methods.

Howard Gardner (inventor of the Multiple Intelligences theory) reviewed the exceptional music performance attained by children trained in the Suzuki method, and noted many of these children, who displayed no previous signs of musical talent, attained levels comparable to music prodigies of earlier times. Therefore, he concluded, the important aspect of talent must be the potential for achievement and the capacity to rapidly learn material relevant to one of the intelligences. That is, since we didn't see the talent before we started training, and since the fact that they do perform so well demonstrates that they must have talent, then the talent must have existed in potential.

This is, of course, a wholly circular argument.

And one that is widely believed. According to an informal British survey, more than ¾ of music educators believe children can’t do well unless they have special innate gifts10. It is believed that saying that someone has a “gift” for something explains why they have excelled at something - although it is an entirely circular argument: Why do they do well? Because they have a gift. How do you know they have a gift? Because they do well.

It is also widely believed that such innate talents can be detected in early childhood.

The problem with this view is that many children are denied the opportunities and support to achieve excellence, because it has been decreed that they don’t “have” an appropriate talent.

The circular argument becomes truly a vicious circle. You don't do this easily first time, therefore you don't have any talent, therefore it's not worth pushing you to do well, therefore you won't do well - which proves what we told you in the first place, you have no talent!

So how much justification is there for believing excellence requires a "natural" talent?

Is there such a thing as inborn talent?

A questionnaire study found that early interest and delight in musical sounds fails to predict later musical competence25.

We have all heard stories of child prodigies who supposedly could do amazing things from a very young age. In no case however, is this very early explosion of skills (in the first three years) observed directly by an impartial observer – the accounts all being (naturally enough you might think), retrospective and anecdotal. Noone denies that very young children, from 3 years old, have been observed to have remarkable skills for their age, but although the parents typically say the child learned these skills entirely unaided, this is not supported by the evidence. For example, in a typical case, the parents claimed (and no doubt sincerely believed) that their child learned to read entirely unaided and that they only discovered this on seeing her reading Heidi. However they had kept detailed records of her accomplishments. As Fowler19 pointed out, it is difficult to believe that parents who keep such accounts have not been actively involved in the child’s early learning.

Music is an area where infant prodigies abound – many famous composers are reported to have displayed unusual musical ability at a very young age. Again, however, such accounts are reported many years later (after the composer has become famous). Early biographies of prominent composers reveal they all received intensive and regular supervised practice sessions29. “The emergence of unusual skills typically followed rather than preceded a period during which unusual opportunities were provided, often combined with a strong expectation that the child would do well."

Art is another area where infant "geniuses" are occasionally cited. However, although some 2 and 3 year olds have produced drawings considerably more realistic than is the norm45, among major artists, few are known to have produced drawings that display exceptional promise before age 8 or so44.

There is no doubt that some individuals acquire some skills more easily than others, but this doesn’t necessarily have anything to do with 'talent'. Motivational and personality factors, as well as previous learning experiences, can all affect such facility.

Biological factors that might underlie "talent"

There are various underlying factors that are at least partly genetic and no doubt influence ability – for example response speed2 and working memory capacity8,9 - but there is no clear neural correlate for any specific exceptional skill.

The closest such correlate is that of "perfect" pitch. There does appear to be a structural difference in the brain of those who have absolute pitch, and certainly some young children have been shown to have perfect pitch. However, even if this difference in the brain is innate and not, as it could well be, the result of differences in learning or experience, having perfect pitch is no guarantee that you will excel at music. Moreover, it appears that it can be learned. It’s relatively common in musicians given extensive musical training before five or six12, and even appears to be learnable by adults, although with considerably more difficulty3,42.

It is always difficult to demonstrate that an observed neurological or physical difference is innate rather than the product of training or experience. For example, many people have pointed to particular physical features as being the reason for particular sports people to excel at their particular sport. However, while individual differences in the composition of certain muscles are reliable predictors of differences in athletic performance, the differences in the proportion of the slow-twitch muscle fibers that are essential for success in long-distance running, for example, are largely the result of extended practice, rather than the cause of differential ability11. Differences between athletes and others in the proportions of particular kinds of muscle fibers are specific to those muscles that are most fully exercised in the athletes’ training22.

There is little evidence, too, for the idea that exceptional athletes are born with superior motor and perceptual abilities. Tests for basic motor and perceptual abilities fail to predict performance15. Exceptional sportspeople do not reliably score higher than lesser mortals on such basic tests.

Savants

So-called idiot-savants are widely cited in support of the idea of innate talent. However, studies of cases have found the opportunities, support and encouragement for learning the skill have preceded performance by years or even decades12,23,43. Moreover, their skills are learnable by others.

The only ability that can’t be reproduced after brief training is the reputed ability to reproduce a piece of music after a single hearing. However, in a study of one such savant5 it was shown that such reproduction depended on the familiarity of the sequences of notes. Tonally unconventional pieces were remembered poorly. Thus, musical savants, like normal experts, need access to stored patterns and retrieval structures to enable them to retain long, unfamiliar musical patterns.

Predicting adult performance

Several interview and biographical studies of exceptional people have been carried out (e.g., pianists40,41; musicians31; tennis players35; artists37; swimmers26; mathematicians20). In no case could you have predicted their eventual success from their early childhood behavior; few showed signs of exceptional promise prior to receiving parental encouragement.

Composers21, chess players36, mathematicians20, sportspeople26,32 have all been shown to require many years of sustained practice and training to reach high levels of expertise.

Twin studies

Twin studies support the view that family experience is more important than genes for the development of specific abilities (e.g., The Minnesota Study of Twins Reared Apart found self-ratings of musical talent correlated .44 among identical twins reared apart, compared to .69 for identical twins reared together30; correlations on a number of measures of musical ability were not much lower for fraternal twins (.34 to .83) than for identical twins (.44 to .9)7.

Moreover, the importance of inherited factors reduces as training and practice increases1,28,15.

Practice and performance level

The performance level of student violinists in their 20s is strongly correlated with the number of hours that they practiced13,14. Similarly with pianists27. No significant differences have been found between highly successful young musicians and other children in the amount of practice time they required to make a given amount of progress between successive grades in the British musical board exams; achieving the highest level (grade 8) required an average of some 3300 hours of practice regardless of the ability group to which the student had been assigned39. Another study found that by age 20, the top-level violinists had practiced an average of more than 10000 hrs, some 2500 hrs more than the next most accomplished group15.

Practice accounts for far more than most of us might realize. Several studies have demonstrated the high levels of performance (often higher than experts had regarded as possible) that can be attained by perfectly ordinary adults, given enough practice4,6,12.

It has been argued that talent encourages children to practice more, but this is contradicted by the finding that, even among highly successful young musicians, most admit they would never have regularly practiced at the required level without strong parental encouragement38,24.

The top of the cream?

It may well be, of course, that there is a quality to the exceptionally talented person’s performance that is missing from others, however hard they have practiced.

It is also possible that, although practice, training, and other influences may account for performance differences in most people, there is a small number of people to whom this doesn’t apply.

However, there is at this time no evidence that this is true.

What is clear is that “no case has been encountered of anyone reaching the highest levels of achievement in chess-playing, mathematics, music, or sports without devoting thousands of hours to serious training” (Howe et al 1999).

The pattern of learning seems to be the same for everyone, arguing against some qualitative difference between "geniuses" and ordinary folk. Studies of prodigies in chess and music show that the skills are acquired in the same manner by everyone, but that prodigies reach higher levels faster and younger16,17. Moreover, rather than acquiring their skills in a vacuum, it appears that “the more powerful and specific the gift, the more need for active, sustained and specialized intervention” (Feldman, 1986, p123).

The producing of an outstanding talent indeed, seems to require a great deal of parental support and early intervention.

It is particularly instructive to observe the case of the Polgar daughters. With no precocious love for the chess board observable in their three daughters, Laslo & Klara Polgar, simply as an educational experiment, decided to raise their daughters to be chess experts. All did extraordinarily well, and one became the youngest international chess grand master ever18.

It has been noted that the performance of experts of yesteryear is now attainable by many. When Tchaikovsky asked two of the greatest violinists of the day to play his violin concerto, it is said, they refused, deeming it unplayable33 - now it is standard repertoire for top violinists. Paganini, it is claimed, would cut a sorry figure on a concert stage today34. Such is the standard we have come to expect from our top performers.

And we are all familiar with the way sports records keep being broken – the winning time for the 1st Olympic marathon is now the qualifying time for the Boston marathon.

Are we suddenly breeding more talent?

No. But training has improved immeasurably.

Practicing effectively

It is not, then, simply practice that is important. It is the right practice. Ericsson & Charness distinguish between deliberate practice – which involves specifically tailored instruction and training, with feedback, and supervision - and the sort of playful repetition more characteristic of people who enjoy an activity and do it a lot. Most people reach an acceptable level of performance, and then are satisfied. The "talented" ... keep on.

References
  1. Ericsson, K.A. & Charness, N. Expert performance: Its structure and acquisition. In S.J. Ceci & Wendy M. Williams (eds) The nature-nurture debate: The essential readings. Essential Readings in Developmental Psychology. Oxford: Blackwell. Pp200-255.
  2. Howe, M.J.A., Davidson, J.W. & Sloboda, J.A. 1999. Innate talents: Reality of myth? In S.J. Ceci & Wendy M. Williams (eds) The nature-nurture debate: The essential readings. Essential Readings in Developmental Psychology. Oxford: Blackwell. Pp168-175.

Footnoted references

  1. Ackerman, P.L. 1988. Determinants of individual differences during skill acquisition: cognitive abilities and information processing. Journal of Experimental Psychology: General, 117, 299-318.
  2. Bouchard, T.J., Lykken, D.T., McGue, M., Segal, N.L. & Tellegen, A. 1990. Sources of human psychological differences: the Minnesota Study of Twins Reared Apart. Science, 250, 223-8.
  3. Brady, P.T. 1970. The genesis of absolute pitch. Journal of the Acoustical Society of America, 48, 883-7.
  4. Ceci, S.J., Baker, J.G. & Bronfenbrenner, U. 1988. Prospective remembering, temporal calibration, and context. In M. Gruneberg, P. Morris, & R. Sykes (eds). Practical aspects of memory: Current research and issues. Wiley.
  5. Charness N Clifton J & MacDonald L. 1988. Case study of a musical mono-savant. IN LK Obler & DA Fein (eds) The exceptional brain: Neuropsychology of talent and special abilities (pp277-93). NY: Guilford Press.
  6. Chase, W.G. & Ericsson, K.A. 1981. Skilled memory. In J.R. Anderson (ed). Cognitive skills and their acquisition. Erlbaum.
  7. Coon, H. & Carey, G. 1989. Genetic and environmental determinants of musical ability in twins. Behavior Genetics, 19, 183-93.
  8. Dark, V.J. & Benbow, C.P. 1990. Enhanced problem translation and short-term memory: components of mathematical talent. Journal of Educational Psychology, 82, 420-9.
  9. Dark, V.J. & Benbow, C.P. 1991. The differential enhancement of working memory with mathematical versus verbal precocity. Journal of Educational Psychology, 83, 48-60.
  10. Davis, M. 1994. Folk music psychology. Psychologist, 7, 537.
  11. Ericsson, K.A. 1990. Peak performance and age: an examination of peak performance in sports. In P.B. Baltes & & M.M. Baltes (eds). Successful aging: Perspectives from the Behavioral Sciences. Cambridge University Press.
  12. Ericsson, K.A. & Faivre, I.A. 1988. What's exceptional about exceptional abilities? In K. Obler & D. Fein (eds). The exceptional brain. Guilford Press.
  13. Ericsson, K.A., Tesch-Romer, C. & Krampe, R. Th. 1990. The role of practice and motivation in the acquisition of expert-level performance in real life. In M.J.A. Howe (ed). Encouraging the development of exceptional abilities and talents. British Psychological Society.
  14. Ericsson, K.A., Krampe, R.Th. & Heizmann, S. 1993. Can we create gifted people? In G.R. Bock & K. Ackrill (eds). The origins and development of high ability. CIBA Foundation Symposium, 178. Wiley.
  15. Ericsson, K.A., Krampe, R.Th. & Tesch-Romer, C. 1993. The role of deliberate practice in the acquisition of expert performance. Psychological Review, 100, 363-406.
  16. Feldman, D.H. 1980. Beyond universals in cognitive development. Norwood, NJ: Ablex.
  17. Feldman, D.H. 1986. Nature's gambit: Child prodigies and the development of human potential. NY: Basic Books.
  18. Forbes, C. 1992. The Polgar sisters: Training or genius? NY: Henry Holt.
  19. Fowler, W. 1981. Case studies of cognitive precocity: the role of exogenous and endogenous stimulation in early mental development. Journal of Applied Developmental Psychology, 2, 319-67.
  20. Gustin, W.C. 1985. The development of exceptional research mathematicians. In B.S. Bloom (ed). Developing talent in young people. Ballantine.
  21. Hayes, J.R. 1981. The complete problem solver. Franklin Institute Press.
  22. Howald, H. 1982. Training-induced morphological and functional changes in skeletal muscle. International Journal of Sports Medicine, 3, 1-12.
  23. Howe, M.J.A. 1990. The origins of exceptional abilities. Oxford, UK: Blackwell.
  24. Howe, M.J.A. & Sloboda, J.A. 1991. Young musicians' accounts of significant influences in their early lives: 2. Teachers, practising and performing. British Journal of Music Education, 8, 53-63.
  25. Howe, M.J.A., Davidson, J.W., Moore, D.G. & Sloboda, J.A. 1995. Are there early childhood signs of musical ability? Psychology of Music, 23, 162-76.
  26. Kalinowski, A.G. 1985. The development of Olympic swimmers. In B.S. Bloom (ed). Developing talent in young people. Ballantine.
  27. Krampe, R.Th. 1994. Maintaining excellence: cognitive-motor performance in pianists differing in age and skill level. Max-Planck-Institut fur Bildungsforschung.
  28. Krampe, R.Th. & Ericsson, K.A. 1996. Maintaining excellence: cognitive-motor performance in pianists differing in age and skill level. Journal of Experimental Psychology: General, 125, 331-68.
  29. Lehmann, A.C. 1997. The acquisition of expertise in music: efficiency of deliberate practice as a moderating variable in accounting for sub-expert performance. In J.A. Sloboda & I. Deliege (eds). Perception and cognition of music. Erlbaum.
  30. Lykken, D. 1998. The genetics of genius. In A. Steptoe (ed). Genius and the mind. Oxford University Press.
  31. Manturzewska, M. 1986. Musical talent in the light of biographical research. In Musikalische Begabung Finden und Forden, Bosse.
  32. Monsaas, J. 1985. Learning to be a world-class tennis player. In B.S. Bloom (ed). Developing talent in young people. Ballantine.
  33. Platt, R. 1966. General introduction. In J.E. Meade & A.S. Parkes (eds). Genetic and environmental factors in human ability. Edinburgh: Oliver & Boyd.
  34. Roth H 1982 . Master violinists in performance. Neptune City, NJ: Paganinia
  35. Schneider, W. 1993. Acquiring expertise: determinants of exceptional performance. In K.A. Heller, F.J. Monks & A.H. Passow (eds). International Handbook of Research and Development of Giftedness and Talent. Pergamon.
  36. Simon, H.A. & Chase, W.D. 1973. Skill in chess. American Scientist, 61, 394-403.
  37. Sloan, K.D. & Sosniak, L.A. 1985. The development of accomplished sculptors. In B.S. Bloom (ed). Developing talent in young people. Ballantine.
  38. Sloboda, J.A. & Howe, M.J.A. 1991. Biographical precursors of musical excellence: an interview study. Psychology of Music, 19, 3-21.
  39. Sloboda, J.A., Davidson, J.W., Howe, M.J.A. & Moore, D.G. 1996. The role of practice in the development of performing musicians. British Journal of Psychology, 87, 287-309.
  40. Sosniak, L.A. 1985. Learning to be a concert pianist. In B.S. Bloom (ed). Developing talent in young people. Ballantine.
  41. Sosniak, L.A. 1990. The tortoise, the hare, and the development of talent. In M.J.A. Howe (ed). Encouraging the development of exceptional abilities and talents. British Psychological Society.
  42. Takeuchi, A.H. & Hulse, S.H. 1993. Absolute pitch. Psychological Bulletin, 113, 345-61.
  43. Treffert DA 1989 Extraordinary people: Understanding “Idiot Savants”. NY: Harper & Row.
  44. Winner, E. & Martino, G. 1993. Giftedness in the visual arts and music. In K.A. Heller, F.J. Monks & A.H. Passow (eds). International Handbook of Research and Development of Giftedness and Talent. Pergamon.
  45. Winner, E. 1996. The rage to master: the decisive role of talent in the visual arts. In K.A. Ericsson (ed). The road to excellence: The acquisition of expert performance in the arts and sciences. Erlbaum.

What is intelligence?

Intelligence in a cultural context

One theory of intelligence sees intelligence in terms of adaptiveness. Thus: "What constitutes intelligence depends upon what the situation demands" (Tuddenham 1963). Intelligence in these terms cannot be understood outside of its cultural context. Naturally to us it may seem self-evident that intelligence has to do with analytical and reasoning abilities, but we are perceiving with the sight our culture taught us.

If we lived, for example, in a vast desert, where success relied on your ability to find plants, water, prey and to remember these locations, an "intelligent" person would be one who was skilled at finding their way around and remembering what they'd seen and where they'd seen it. In a society where people are stuck within a limited social group, where people are forced to get on with each other because they can't escape each other, and where survival requires you to depend on these people, social skills will be highly valued. An "intelligent" person might well be a person who is skilled in social relations.

If I lived in such a society, would I have become skilled in these areas?

If I had spent my childhood playing with construction toys such as Lego, would I be better at spatial relations?

In other words, is intelligence something that you simply have in some measure, which manifests itself in the skills that you practice when young / that are valued in your society or within your family? Or are you born instead with particular talents that, if you are lucky, are valued by your society and thus seen as signs of intelligence?

Here's one of my favorite stories.

An anthropologist, Joe Glick, was studying a tribe in Africa1. The Kpelle tribe. Glick asked adults to sort items into categories. Rather than producing taxonomic categories (e.g. "fruit" for apple), they sorted into functional groups (e.g. "eat" for apple). Such functional grouping is something only very young children in our culture would do usually. Glick tried, and failed, to teach them to categorize items. Eventually he decided they simply didn't have the mental ability to categorize in this way. Then, as a last resort, he asked them how a stupid person would do this task. At this point, without any hesitation, they sorted the items into taxonomic categories!

They could do it, but in their culture, it was of no practical value. It was stupid.

Our IQ tests use categorization, and assumptions of how items relate to each other, to test "intelligence". (And how many of us, when filling in IQ tests, thought of different ways to answer questions, but answered the way we knew would be considered "right"?) These tests measure our ability to understand the mind of the test setter / marker. Do they measure anything else?

Multiple intelligences

One theory of intelligence that has had a certain influence on educational policy in the last 10-15 years is that of Howard Gardner’s idea of multiple intelligences (Gardner 1983). Gardner suggested that there are at least seven separate, relatively independent intelligences: linguistic, logical-mathematical, spatial, bodily kinaesthetic, intrapersonal, interpersonal, and musical.

Each intelligence has core components, such as sensitivity to the sounds, rhythms and meaning of words (linguistic), and has a developmental pattern relatively independent of the others. Gardner suggested the relative strengths of these seven intelligences are biologically determined, but the development of each intelligence depends on environmental influences, most particularly on the interaction of the child with adults.

This model of intelligence has positively influenced education most particularly by perceiving intelligence as much broader than the mathematical-language focus of modern education, and thus encouraging schools to spend more time on other areas of development.

It also, by seeing the development of particular intelligences as dependent on the child’s interaction with adults, encourages practices such as mentoring and apprenticeships, and supports parental and community involvement in educational environments. Because intelligence is seen as developing in a social context, grounding education in social institutions and in “real” environments takes on particular value.

All these are very positive aspects of the influence of this theory. On the downside, the idea of intelligence as being biologically determined is a potentially dangerous one. Gardner claims that a preschool child could be given simple tests that would demonstrate whether or not they had specific talents in any of those seven intelligences. The child could then be given training tailored to that talent.

Should we then deny that training to those who don't have that talent?

Do you know how many outstanding people - musicians, artists, mathematicians, writers, scientists, dancers, etc - showed signs of remarkable talent as very young children? Do you know how many so-called child prodigies went on to become outstanding in their field when adult? In both cases, not many.

The idea of "talent" is grounded in our society, but in truth, we have come no further in demonstrating its existence than the circular argument: he's good at that, therefore he has a talent for it; how do we know he has a talent? because he's good at it. Early ability does not demonstrate an innate talent unless the child has had no special opportunity to learn and practice the ability (and notwithstanding parental claims and retrospective reports, independent observation of this is lacking). (More on the question of innate talent)

Schooling and intelligence

The more we believe in innate talent, or innate intelligence, the less effort we will put into educating those who don't exhibit ability - although there are many environmental reasons for such failures.

The whole province of intelligence testing is, I believe, a dangerous one. Indeed, I was appalled to hear of its prevalence in American education. While intelligence was seen as some inborn talent unaffected by training or experience by the early makers and supporters of psychometric tests, recent research strongly suggests that schooling affects IQ score.

If you take two children who at age 13 have identical IQs and grades and then retest them five years later, after one child has finished high school while the other has dropped out of school in ninth grade, you find that the child who dropped out of school has lost around 1.8 IQ points for every year of missed school (Ceci, 1999).

Starting school late or leaving early results in a decrease in IQ relative to a matched peer who received more schooling. In families where children attend school intermittently, there is a high negative correlation between age and IQ, implying that as the children got older, their IQ dropped commensurately.

The most obvious, and simplest, explanation is that much of what is tested in IQ tests is either directly or indirectly taught in school. This is not to say schooling has any effect on intelligence itself (whatever that is).

References
  • Ceci, S. J. 1999. Schooling and intelligence. In S.J. Ceci & Wendy M. Williams (eds) The nature-nurture debate: The essential readings. Essential Readings in Developmental Psychology. Oxford: Blackwell. Pp168-175.
  • Ericsson, K.A. & Charness, N. Expert performance: Its structure and acquisition. In S.J. Ceci & Wendy M. Williams (eds) The nature-nurture debate: The essential readings. Essential Readings in Developmental Psychology. Oxford: Blackwell. Pp200-255.

1. Sternberg, R.J. 1997. Successful intelligence: How practical and creative intelligence determine your success in life. Plume.

Right-Brain/Left-Brain

Are you right-brained or left-brained?

One of the dumber questions around.

I think it’s safe to say that if you only had one hemisphere of your brain, you wouldn’t be functioning.

Of course, that’s not the point. But the real point is little more sensible. The whole idea of right brain vs left brain did come out of scientific research, but as is so often the case, the myth that developed is light years away from the considerably duller scientific truths that spawned it.

It is true that, for most of us, language is processed predominantly in the left hemisphere. But what is becoming increasingly more evident is that even the most specialized tasks activate areas across the brain.

In any case, I don’t think the real meaning behind this simplistic dichotomy of right-brain / left-brain has much to do with the physical nature of the brain. People hope by rooting the concept in something that is physically real, that they will thereby make the concept real. Well, I’m sorry, but the supposed scientific foundation for the concept doesn’t exist. However, what we can ask is, is the concept valid? Are some people logical, analytical, sequential thinkers? Are others holistic, intuitive, creative thinkers?

Yes, of course. This is news?

But I don’t like dichotomies. It should never be forgotten that people aren’t either/or. Attributes invariably belong on a continuum, and we are all capable of responding in ways that differ as a function of the task we are confronted with, and the context in which it appears (especially, for example, the way something is phrased). Rather than saying a person is an analytical thinker, we should say, does a person tend to approach most problems in an analytical manner? This is not simply a matter of semantics; there’s an important distinction here.

But there are other personal attributes of importance in learning and problem-solving. For example, working memory capacity, imagery ability, anxiety level, extraversion / introversion, self-esteem (in this case, meaning assessment of one’s own abilities), field-dependence / field-independence (field dependence represents the tendency to perceive and adhere to an existing, externally imposed framework while field independence represents the tendency to restructure perceived information into a different framework). Which attributes are most important? Is this in fact a meaningful question?

The fact is, different personal attributes interact with different task and situational variables in different ways. While it’s probably always good to have a high working memory capacity (the capacity to hold more items in conscious memory at one time), it’s more important in some situations than others. To be a “high-imagery” person may sound a good thing, but if you realize it’s measured on a verbal-imagery continuum, you can see that it’s a trade-off. Personally, I’ve never found being high-verbal, low-imagery a drawback!

The point is, of course, that different styles lend themselves to different tasks (by which I mean, different ways of doing different tasks). It’s not so much what you are, as that you recognize what your strengths and weaknesses are, and realize, too, the pluses and minuses of those abilities / conditions.

For example, a study of 13-year olds investigated the question of interaction between working memory capacity and cognitive style, measured on two dimensions, Wholist-Analytic, and Verbaliser - Imager. They found working memory capacity made a marked difference for Analytics but had little effect for Wholists, and similarly, Verbalisers were affected but not Imagers [1].

Thus, if your working memory capacity is low, in demanding tasks you might find yourself better to approach it holistically – looking at the big picture, rather than focusing on the details.

Once you recognize your strengths and weaknesses, you can consciously apply strategies that work for you, and approach tasks in ways that are better for you. You can also work on your weaknesses. An interesting recent study that I believe has wider applicability than the elderly population who participated in it, found elderly people who draw on both sides of the brain seem to do better at some mental tasks than those who use just one side [2].

Web resources

Cognitive style

There’s an article about cognitive style from a business perspective:
http://www.elsinnet.org.uk/abstracts/aom/sad-aom.htm

If you’re really interested in cognitive style, the Wholist-Analytic, Verbal-Imager inventory was constructed by R.J. Riding, and he’s written a, fairly scholarly, book, entitled “Cognitive Styles and Learning Strategies: Understanding Style Differences in Learning and Behaviour”
http://tinyurl.com/6gpu8

Left-brain / Right-brain

You can also read an essay by William H. Calvin, an affiliate professor at the University of Washington School of Medicine in Seattle, Washington: Left Brain, Right Brain: Science or the New Phrenology?
http://williamcalvin.com/bk2/bk2ch10.htm

And an article first published in the New Scientist on 'Right Brain' or 'Left Brain' - Myth Or Reality? by John McCrone.
http://www.rense.com/general2/rb.htm

This article originally appeared in the January 2005 newsletter.

References
  1. Riding. R.J., Grimley, M., Dahraei, H. & Banner, G. 2003. Cognitive style, working memory and learning behaviour and attainment in school subjects. British Journal of Educational Psychology, 73 (2), 149–169.
  2. Cabeza, R., Anderson, N.D., Locantore, J.K. & McIntosh, A.R. 2002. Aging Gracefully: Compensatory Brain Activity in High-Performing Older Adults. NeuroImage, 17(3), 1394-1402.

Gray matter

  • Brain tissue is made up of cell bodies ("gray matter") and the filaments that extend from the cell bodies ("white matter").
  • The density of cells (volume of gray matter) in a particular region of the brain appears to correlate positively with various abilities and skills.
  • The density of cells is determined by both genes and environmental factors, such as experience.
  • The speed with which we can process information is governed by the white matter.

Brain tissue is divided into two types: gray matter and white matter. These names derive very simply from their appearance to the naked eye. Gray matter is made up of the cell bodies of nerve cells. White matter is made up of the long filaments that extend from the cell bodies - the "telephone wires" of the neuronal network, transmitting the electrical signals that carry the messages between neurons.

The volume of gray matter tissue - a measure you will see cited in various reports - is a measure of the density of brain cells in a particular region.

Recently, the most comprehensive structural brain-scan study of intelligence to date has supported an association between general intelligence and the volume of gray matter tissue in specific regions of the brain (you can see a picture of these areas here). These structures are the same ones implicated in memory, attention and language.

Previous research has shown the regional distribution of gray matter in humans is highly heritable. But it also clearly has a strong environmental influence. Recent studies have found:

  • an increased volume of gray matter in Broca's area of professional musicians, apparently reflecting, at least in part, the number of years devoted to musical training
  • an increased volume of gray matter in the posterior hippocampus of experienced London taxi drivers (a brain region involved in spatial navigation), with volume correlated with length of taxi-driving experience
  • an increase in the development of new brain cells in older adults who underwent an aerobic training program compared with those who did not

The brain-scan study also found age differences: in middle age, more of the frontal and parietal lobes were related to IQ; less frontal and more temporal areas were related to IQ in the younger adults.

Age differences have already been found to exist in gray matter volume and distribution.

Mapping of the progressive maturation of the human brain in childhood and adolescence has found an initial overproduction of synapses in the gray matter after birth, which is followed, for the most part just before puberty, with their systematic pruning. This process occurs in different regions at different times, with gray matter loss beginning first in the motor and sensory parts of the brain, and then slowly spreading downwards and forwards, to areas involved in spatial orientation, speech and language development, and attention (upper and lower parietal lobes), then to the areas involved in executive functioning, attention or motor coordination (frontal lobes), and finally to the areas that integrate these functions (temporal lobe). The sequence appears to agree with regionally relevant milestones in cognitive development.

Various learning and memory problems have been associated with decreased gray matter in particular regions of the brain:

  • children with selective problems in short term phonological memory and others diagnosed with specific language impairment had less gray matter in both sides of the cerebellum compared to controls
  • adolescents had less gray matter in an area in the left parietal lobe if they had a deficit in calculation ability, compared to those who had no such deficit

Gray matter is not the sole arbiter of ability and knowledge, of course. The number of neurons is clearly important, but so is the connectivity of the neuronal network. Interestingly, although gray matter declines steadily from adolescence, white matter keeps growing until our late forties. This is consistent with a large-scale study of mental abilities in adults, that found that mental faculties were unchanged until the mid-40s, when a marked decline began and continued at a constant rate. Accuracy did not seem to be affected, only speed. White matter governs the speed with which signals travel in the brain.

The mediotemporal lobe

  • The mediotemporal lobe is critically involved in both initial learning of facts and events and their later consolidation.
  • Dysfunction in the mediotemporal lobe is a major factor in age-related cognitive decline.
  • The most significant component of the MTL is the hippocampus.
  • The hippocampus contains specialized neurons that categorize incoming sensory information, and others that are involved in the forming of new associations.
  • The hippocampus is crucial for episodic memory - the remembering of specific events and experiences. It is also particularly involved in spatial memory.
  • The hippocampus appears to be involved in consolidation processes, but only in the initial stages and for the first few years. The part of the hippocampus called the dentate gyrus is crucial for encoding new information (and is thus implicated in working memory).
  • The dentate gyrus is one of the few brain regions in which new nerve cells can be created in adult brains.
  • The main processing part of the hippocampus, the cornu ammonis, is distinguished by a high number of neurons which loop back on themselves - enabling the output of the neuron to influence its input; this may be critical for associative power.
  • Other components of the mediotemporal lobe include the rhinal cortex and the amygdala.
  • The entorhinal cortex appears to be involved in long-term memory consolidation beyond the first few years. It is one of the first regions damaged in Alzheimer's.
  • The perirhinal cortex is crucial for object recognition.
  • The amygdala is primarily responsible for processing emotional responses. The connection between hippocampus and amygdala underlies the role of emotion in memory.

The mediotemporal lobe (MTL) is a concept rather than a defined brain structure. It includes the hippocampus, the amygdala, and the entorhinal and perirhinal cortices - all structures within the medial area of the temporal lobe.The temporal lobe is in general primarily concerned with sensory experience - specifically, with hearing, and with the integration of information from multiple senses. Part of the temporal lobe also plays a role in memory processing. It is situated below the frontal and parietal lobes, and above the hindbrain.

Originally conceived as an integrated memory system with a common function, this view of the MTL has recently been questioned. For one thing, the region didn’t evolve as one unit — the different regions arose at different times during primate evolution. Therefore, can it really be an integrated system with a common function? Work with rhesus monkeys suggests rather that these different parts may serve cooperative and even competitive functions.

This question, however, is really one for the specialist. As far as most of us are concerned, the concept of a "mediotemporal lobe" serves as a handy label for a group of connected brain structures that are all absolutely crucial for learning and memory (and reminds us of the location of these structures).

It should also be remembered that brain structures are notoriously "fuzzy" — different researchers will use different names, and group different structures. For example, one report has contrasted the functions of the MTL with that of the basal ganglia, although the amygdala is a member of both. Other studies talk of the hippocampus AND the dentate gyrus, although others put the dentate gyrus as a substructure of the hippocampus. I mention this only to warn you, if you find trawl through various reports and find such discrepancies. They can be confusing. I have tried to integrate such discrepancies into a consistent description that seems to make most sense. Just bear in mind that dividing the brain into separate structures is not an exact science.

Functions of the MTL

The MTL has been particularly implicated in the process of memory consolidation - the process by which new memories become progressively more stable (see my article on consolidation for more details). Lesions in the MTL typically produce amnesia characterized by the disproportionate loss of recently acquired memories. A recent imaging study confirms this view by showing temporally graded changes in MTL activity in healthy older adults.

Progressive atrophy in the mediotemporal lobe also appears to be the most significant predictor of cognitive decline in seniors. Elderly persons with a poor memory have less activity in the mediotemporal lobe when storing new information than elderly persons with a normally functioning memory.

The MTL also appears to be particularly important during initial learning. Research has found rapid modulation of activity in the MTL at the beginning of learning, with this activity rapidly declining with training.

All this indicates that the MTL is not only hugely important, but that it covers a quite extraordinary range of functions. The reason for this lies in the fact that the MTL is not a single brain structure.

Components of the MTL

It is probably fair to say that the original concept of the MTL was, at least in part, a reflection of the inability of early researchers to "see" the activity in the brain in very much detail. Now, of course, neurological techniques have progressed to the point of being able to pinpoint activity to a quite fantastic level. It is therefore now possible to some degree to disentangle the functions of the various components of the MTL.

The most significant of the individual components of the MTL is the hippocampus. The hippocampus, one of the oldest parts of the brain, is important for the forming, and perhaps long-term storage, of associative and episodic memories. It is thus absolutely critical for learning and memory, and a brain region much studied by researchers.

The hippocampus

In recent years, the hippocampus has been specifically implicated in (among other things) the encoding of face-name associations, the retrieval of face-name associations, the encoding of events, the recall of personal memories in response to smells. It may also be involved in the processes by which memories are consolidated during sleep.

A variety of specialized neurons have been found in the hippocampus. For example,

  • "categorizing cells", which streamline and simplify sensory information, markedly reducing the brain's workload, by categorizing stimuli into various classes (categories that have been acquired through experience).
  • "changing cells", which appear to be involved in the initial formation of new associative memories, and may also, in some cases, be involved in the eventual storage of the associations in long-term memory.
  • "place cells", which become active in response to specific spatial locations; some of these cells also seem to be sensitive to recent or impending events, thus enabling you to place location within a temporal context (e.g., is this somewhere I've just been, or somewhere I intended to go?).

The existence of place cells is supported by other evidence for the role of the hippocampus in spatial navigation and memory. For example, London taxi drivers (famous for their extensive knowledge of London - a spatial task) have been found to have, on average, significantly bigger hippocampuses than "ordinary motorists". In similar vein, the chickadee, a tiny songbird, gathers and stores seeds in the fall, and at this time its hippocampus expands in volume by some 30% by adding new nerve cells. It shrinks back in the spring.

The role of the hippocampus in episodic (event) memory is underscored by findings that deficiencies in the hippocampus play a key role in alcoholism-related Korsakoff's syndrome (a memory disorder), as well as Alzheimer's disease.

The hippocampus has also been implicated in memory consolidation processes, but evidence now suggests the hippocampus may participate only in consolidation processes lasting a few years. It is probably critical for the initial consolidation of memories that appears to take place during sleep. Rat studies have found that, during sleep (mostly the slow-wave phase), the thalamus at the base of their brains produced bursts of electrical activity, which were then detected in the somatosensory neocortex. Some 50 msec later, the hippocampus responded with a pulse of electricity. It’s suggested that this pulse is the hippocampus sending back compressed waves of the information learned during the day to the neocortex where they are filed away for future reference.

The evidence that some memories might be held in the hippocampus for several years, only to move on, as it were, to another region, is an interesting complication to our earlier simple view of memory dividing into "short-term memory" and "long-term memory". It seems that long-term memory, now better labeled as permanent memory, is far from being the straightforward storage system that we once envisaged. Not only do memories become reconstructed, but they become, it would seem, re-filed. The implications of this, still speculative, relocation, are as yet unknown. Perhaps memories in this "permastore" are more resistant to change.

Substructures of the hippocampus

There are several substructures within the hippocampus. It is only very recently that researchers have been able to go inside the hippocampus, as it were, and pinpoint hippocampal activity to particular substructures.

  • the dentate gyrus: is the main entry point for nerve fibers into the hippocampal formation. Rat studies suggest that the dentate gyrus is crucial for the acquiring of new information, and the functioning of working memory. Most recently, it has been implicated with the cornu ammonis as being highly active during encoding offace-name pairs. The dentate gyrus is one of the very few regions in the adult brain that appears to allow neurogenesis (creation of new nerve cells). Neurogenesis in the dentate gyrus has been found to be significantly reduced in marmoset monkeys when exposed to stress. Dysfunction in the dentate gyrus appears to be linked to cognitive deficits in those suffering from Alzheimer's. The granule cells in the dentate gyrus project to the pyramidal cells in the cornu ammonis.
  • the cornu ammonis: is thought to be the main site of memory processing in the hippocampal formation. Most recently, it has been implicated with the dentate gyrus as being highly active during encoding offace-name pairs. Part of the cornu ammonis (CA3) has been of special interest due to its high number of recursive neurons (nerve fibers which loop back on themselves - enabling the output of the neuron to influence its input). Most recently, the CA3 has been found to be crucial for recalling memories from partial representations of the original stimulus (for example, when memories are triggered by smells).
  • the subiculum: can be thought of as the "last stage" of processing in the hippocampal formation. It is the primary target of the pyramidal cells in CA1. The subiculum is connected to the perirhinal, entorhinal and prefrontal cortices, and thus is in a position to integrate information from several sources and pass this information on. The subiculum however has been much less studied than the other substructures of the hippocampal formation. Recently, it has been found to be active during the retrieval of newly learned face-name associations.

The rhinal cortex

The entorhinal cortex is a region upon which nerve fibers from many sensory systems converge. It is the main input to the hippocampus, and also the main output. This is why damage to this region is so serious. The entorhinal cortex is one of the first regions damaged in the early stages of Alzheimer's.

It has also been suggested that the entorhinal cortex handles “incremental learning” — learning that requires repeated experiences. “Episodic learning” — memories that are stored after only one occurrence — might be mainly stored in the hippocampus.

While the hippocampus appears to participate in memory consolidation processes only for the first few years, the entorhinal cortex seems to be associated with temporally graded changes extending up to 20 years - suggesting that it is the entorhinal cortex, rather than the hippocampus, that participates in memory consolidation over decades.

The perirhinal cortex has been a largely neglected region. It is adjacent to the visual processing area, as well as the entorhinal cortex, and recent research demonstrates that it is important for recognizing objects. In particular, it is crucial for recognizing the many features of an object, while still recognizing it as a single entity. The perirhinal cortex also appears to be involved in associating objects with other objects, and even with abstractions such as a goal. Unsurprisingly, in view of its involvement in recognition memory, it appears to play a critical role in establishing the familiarity of an item.

While the hippocampus is also involved in object recognition, the functions of the two regions appear quite different.

The amygdala

The amygdala is part of the basal ganglia, large "knots" of nerve cells deep in the cerebrum, thought to be involved in various aspects of motor behavior (Parkinson's disease, for example, is an affliction of the basal ganglia). The amygdala has many connections with other parts of the brain, and is critically involved in computing the emotional significance of events. Recent research indicates it is responsible for the influence of emotion on perception, through its connections with those brain regions that process sensory experiences. Rat studies also suggest that the amygdala, in tandem with the orbitofrontal cortex, is involved in the forming of new associations between cues and outcomes - in other words, it is the work of the amygdala to teach us what happens to us when we do something.

The connection between the amygdala and the hippocampus helps explain why emotion can have such powerful effect on learning and memory (to put it crudely, the amygdala remembers the feelings, and the hippocampus remembers what event elicited those feelings). (see article on emotion and memory)

The brain is a network

It must always be remembered that no structure within the brain acts on its own. This is reinforced by a recent study that found that, as subjects studied word lists, clusters of neurons in the rhinal cortex and the hippocampus fired synchronized electrical bursts, with this coordinated activity plummeting for a fraction of a second just after participants remembered a word from the list. This has led to speculation that memory relies more on the timing (coordination) than on the strength of neural activity.

We still know very little about the ways in which these structures interact; only as we gain more knowledge about this will we know whether we are justified in talking about a "mediotemporal lobe". Nevertheless, this region of the brain is undoubtedly vital for what we might term "stereotypical" memory - the memory domains we are most likely to be thinking of when we think of memory.

References

Anderson, A.K. & Phelps, E.A. 2001. Lesions of the human amygdala impair enhanced perception of emotionally salient events. Nature, 411, 305-309.

Ekstrom, A.D., Kahana, M.J., Caplan, J.B., Fields, T.A., Isham, E.A., Newman, E.L. & Fried, I. 2003. Cellular networks underlying human spatial navigation.Nature, 425 (6954), 184-7.

Fell, J., Klaver, P., Lehnertz, K., Grunwald, T., Schaller, C., Elger, C.E. & Fernández, G. 2001. Human memory formation is accompanied by rhinal-hippocampal coupling and decoupling. Nature Neuroscience 4(12), 1259-1264.

Haist, F., Gore, J.B. & Mao, H. 2001. Consolidation of human memory over decades revealed by functional magnetic resonance imaging. Nature neuroscience, 4 (11), 1139-1145.

Hampson, R.E., Pons, T.P., Stanford, T.R. & Deadwyler, S.A. 2004. Categorization in the monkey hippocampus: A possible mechanism for encoding information into memory. PNAS, 101, 3184-3189.

McLeod, P., Plunkett, K. & Rolls, E.T. 1998. Introduction to Connectionist Modelling of Cognitive Processes. Oxford: Oxford University Press.

Nakazawa, K., Quirk, M.C., Chitwood, R.A., Watanabe, M., Yeckel, M.F., Sun, L.D., Kato, A., Carr, C.A., Johnston, D., Wilson, M.A. & Tonegawa, S. 2002. Requirement for Hippocampal CA3 NMDA Receptors in Associative Memory Recall. Science 297, 211-218.

Poldrack, R.A., Clark, J., Paré-blagoev, E.J., Shohamy, D., Moyano, J.C., Myers, C. & Gluck, M.A. 2001. Interactive memory systems in the human brain. Nature, 414, 546-550.

Ribeiro, S., Gervasoni, D., Soares, E.S., Zhou, Y., Lin, S-C., Pantoja, J., Lavine, M. & Nicolelis, M.A.L. 2004. Long-Lasting Novelty-Induced Neuronal Reverberation during Slow-Wave Sleep in Multiple Forebrain Areas. PLoS Biol 2(1): e24 DOI:10.1371/journal.pbio.0020024.

Rusinek, H., De Santi, S., Frid, D., Tsui, W-H., Tarshish, C.Y., Convit, A., & de Leon, M.J. 2003. Regional Brain Atrophy Rate Predicts Future Cognitive Decline: 6-year Longitudinal MR Imaging Study of Normal Aging. Radiology, 229, 691-696.

Schoenbaum, G., Setlow, B., Saddoris, M.P. & Gallagher, M. 2003. Encoding Predicted Outcome and Acquired Value in Orbitofrontal Cortex during Cue Sampling Depends upon Input from Basolateral Amygdala. Neuron, 39, 855-867.

Sirota, A., Csicsvari, J., Buhl, D. & Buzsáki, G. 2003. Communication between neocortex and hippocampus during sleep in rodents. Proc. Natl. Acad. Sci. USA, 100 (4), 2065-2069.

Wirth, S., Yanike, M., Frank, L.M., Smith, A.C., Brown, E.N. & Suzuki, W.A. 2003. Single Neurons in the Monkey Hippocampus and Learning of New Associations. Science, 300, 1578-1581.

Zeineh, M.M., Engel, S.A., Thompson, P.M. & Bookheimer, S.Y. 2003. Dynamics of the Hippocampus During Encoding and Retrieval of Face-Name Pairs, Science, 299, 577-580.