emotion

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

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Improve learning with co-occurring novelty

  • An animal study shows that following learning with a novel experience makes the learning stronger.
  • A human study shows that giving information positive associations improves your memory for future experiences with similar information.

We know that the neurotransmitter dopamine is involved in making strong memories. Now a mouse study helps us get more specific — and suggests how we can help ourselves learn.

The study, involving 120 mice, found that mice tasked with remembering where food had been hidden did better if they had been given a novel experience (exploring an unfamiliar floor surface) 30 minutes after being trained to remember the food location.

This memory improvement also occurred when the novel experience was replaced by the selective activation of dopamine-carrying neurons in the locus coeruleus that go to the hippocampus. The locus coeruleus is located in the brain stem and involved in several functions that affect emotion, anxiety levels, sleep patterns, and memory. The dopamine-carrying neurons in the locus coeruleus appear to be especially sensitive to environmental novelty.

In other words, if we’re given attention-grabbing experiences that trigger these LC neurons carrying dopamine to the hippocampus at around the time of learning, our memories will be stronger.

Now we already know that emotion helps memory, but what this new study tells us is that, as witness to the mice simply being given a new environment to explore, these dopamine-triggering experiences don’t have to be dramatic. It’s suggested that it could be as simple as playing a new video game during a quick break while studying for an exam, or playing tennis right after trying to memorize a big speech.

Remember that we’re designed to respond to novelty, to pay it more attention — and, it seems, that attention is extended to more mundane events that occur closely in time.

Emotionally positive situations boost memory for similar future events

In a similar vein, a human study has found that the benefits of reward extend forward in time.

In the study, volunteers were shown images from two categories (objects and animals), and were financially rewarded for one of these categories. As expected, they remembered images associated with a reward better. In a second session, however, they were shown new images of animals and objects without any reward. Participants still remembered the previously positively-associated category better.

Now, this doesn’t seem in any way surprising, but the interesting thing is that this benefit wasn’t seen immediately, but only after 24 hours — that is, after participants had slept and consolidated the learning.

Previous research has shown similar results when semantically related information has been paired with negative, that is, aversive stimuli.

https://www.eurekalert.org/pub_releases/2016-09/usmc-rim090716.php

http://www.eurekalert.org/pub_releases/2016-06/ibri-eps061516.php

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Correlation between emotional intelligence and IQ

February, 2013

A study shows that IQ and conscientiousness significantly predict emotional intelligence, and identifies shared brain areas that underlie this interdependence.

By using brain scans from 152 Vietnam veterans with a variety of combat-related brain injuries, researchers claim to have mapped the neural basis of general intelligence and emotional intelligence.

There was significant overlap between general intelligence and emotional intelligence, both in behavioral measures and brain activity. Higher scores on general intelligence tests and personality reliably predicted higher performance on measures of emotional intelligence, and many of the same brain regions (in the frontal and parietal cortices) were found to be important to both.

More specifically, impairments in emotional intelligence were associated with selective damage to a network containing the extrastriate body area (involved in perceiving the form of other human bodies), the left posterior superior temporal sulcus (helps interpret body movement in terms of intentions), left temporo-parietal junction (helps work out other person’s mental state), and left orbitofrontal cortex (supports emotional empathy). A number of associated major white matter tracts were also part of the network.

Two of the components of general intelligence were strong contributors to emotional intelligence: verbal comprehension/crystallized intelligence, and processing speed. Verbal impairment was unsurprisingly associated with selective damage to the language network, which showed some overlap with the network underlying emotional intelligence. Similarly, damage to the fronto-parietal network linked to deficits in processing speed also overlapped in places with the emotional intelligence network.

Only one of the ‘big five’ personality traits contributed to the prediction of emotional intelligence — conscientiousness. Impairments in conscientiousness were associated with damage to brain regions widely implicated in social information processing, of which two areas (left orbitofrontal cortex and left temporo-parietal junction) were also involved in impaired emotional intelligence, suggesting where these two attributes might be connected (ability to predict and understand another’s emotions).

It’s interesting (and consistent with the growing emphasis on connectivity rather than the more simplistic focus on specific regions) that emotional intelligence was so affected by damage to white matter tracts. The central role of the orbitofrontal cortex is also intriguing – there’s been growing evidence in recent years of the importance of this region in emotional and social processing, and it’s worth noting that it’s in the right place to integrate sensory and bodily sensation information and pass that onto decision-making systems.

All of this is to say that emotional intelligence depends on social information processing and general intelligence. Traditionally, general intelligence has been thought to be distinct from social and emotional intelligence. But humans are fundamentally social animals, and – contra the message of the Enlightenment, that we have taken so much to heart – it has become increasingly clear that emotions and reason are inextricably entwined. It is not, therefore, all that surprising that general and emotional intelligence might be interdependent. It is more surprising that conscientiousness might be rooted in your degree of social empathy.

It’s also worth noting that ‘emotional intelligence’ is not simply a trendy concept – a pop quiz question regarding whether you ‘have a high EQ’ (or not), but that it can, if impaired, produce very real problems in everyday life.

Emotional intelligence was measured by the Mayer, Salovey, Caruso Emotional Intelligence Test (MSCEIT), general IQ by the Wechsler Adult Intelligence Scale, and personality by the Neuroticism-Extroversion-Openness Inventory.

One of the researchers talks about this study on this YouTube video and on this podcast.

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The role of motivation on academic performance

January, 2013

A study shows how easily you can affect motivation, producing a significant effect on college test scores, while a large German study finds that motivational and strategy factors, but not intelligence, affects growth in math achievement at high school.

I’ve spoken before about the effects of motivation on test performance. This is displayed in a fascinating study by researchers at the Educational Testing Service, who gave one of their widely-used tests (the ETS Proficiency Profile, short form, plus essay) to 757 students from three institutions: a research university, a master's institution and a community college. Here’s the good bit: students were randomly assigned to groups, each given a different consent form. In the control condition, students were told: “Your answers on the tests and the survey will be used only for research purposes and will not be disclosed to anyone except the research team.” In the “Institutional” condition, the rider was added: “However, your test scores will be averaged with all other students taking the test at your college.” While in the “Personal” condition, they were told instead: “However, your test scores may be released to faculty in your college or to potential employers to evaluate your academic ability.”

No prizes for guessing which of these was more motivating!

Students in the “personal” group performed significantly and consistently better than those in the control group at all three institutions. On the multi-choice part of the test, the personal group performed on average .41 of the standard deviation higher than the control group, and the institutional group performed on average .26 SD higher than the controls. The largest difference was .68 SD. On the essay, the largest effect size was .59 SD. (The reason for the results being reported this way is because the focus of the study was on the use of such tests to assess and compare learning gains by colleges.)

The effect is perhaps less dramatic at the individual level, with the average sophomore score on the multichoice test being 460, compared to 458 and 455, for personal, institutional, and control groups, respectively. Interestingly, this effect was greater at the senior level: 469 vs 466 vs 460. For the essay question, however, the effect was larger: 4.55 vs 4.35 vs 4.21 (sophomore); 4.75 vs 4.37 vs 4.37 (senior). (Note that these scores have been adjusted by college admission scores).

Students also reported on motivation level, and this was found to be a significant predictor of test performance, after controlling for SAT or placement scores.

Student participants had received at least one year of college, or (for community colleges) taken at least three courses.

The findings confirm recently expressed concern that students don’t put their best efforts into low-stakes tests, and that, when such tests are used to make judgments about institutional performance (how much value they add), they may well be significantly misleading, if different institutions are providing different levels of motivation.

On a personal level, of course, the findings may be taken as further confirmation of the importance of non-academic factors in academic achievement. Something looked at more directly in the next study.

Motivation, study habits—not IQ—determine growth in math achievement

Data from a large German longitudinal study assessing math ability in adolescents found that, although intelligence was strongly linked to students' math achievement, this was only in the initial development of competence. The significant predictors of growth in math achievement, however, were motivation and study skills.

Specifically (and excitingly for me, since it supports some of my recurring themes!), at the end of Grade 5, perceived control was a significant positive predictor for growth, and surface learning strategies were a significant negative predictor. ‘Perceived control’ reflects the student’s belief that their grades are under their control, that their efforts matter. ‘Surface learning strategies’ reflect the use of rote memorization/rehearsal strategies rather than ones that encourage understanding. (This is not to say, of course, that these strategies don’t have their place — but they need to be used appropriately).

At the end of Grade 7, however, a slightly different pattern emerged, with intrinsic motivation and deep learning strategies the significant positive predictors of growth, while perceived control and surface learning strategies were no longer significant.

In other words, while intelligence didn’t predict growth at either point, the particular motivational and strategy variables that affected growth were different at different points in time, reflecting, presumably, developmental changes and/or changes in academic demands.

Note that this is not to say that intelligence doesn’t affect math achievement! It is, indeed, a strong predictor — but through its effect on getting the student off to a good start (lifting the starting point) rather than having an ongoing benefit.

There was, sadly but unfortunately consistent with other research, an overall decline in motivation from grade 5 to 7. There was also a smaller decline in strategy use (any strategy! — presumably reflecting the declining motivation).

It’s also worth noting that (also sadly but unsurprisingly) the difference between school types increased over time, with those in the higher track schools making more progress than those in the lowest track.

The last point I want to emphasize is that extrinsic motivation only affected initial levels, not growth. The idea that extrinsic motivation (e.g., wanting good grades) is of only short-term benefit, while intrinsic motivation (e.g., being interested in the subject) is far more durable, is one I have made before, and one that all parents and teachers should pay attention to.

The study involved 3,520 students, following them from grades 5 to 10. The math achievement test was given at the end of each grade, while intelligence and self-reported motivation and strategy use were assessed at the end of grades 5 and 7. Intelligence was assessed using the nonverbal reasoning subtest of Thorndike’s Cognitive Abilities Test (German version). The 42 schools in the study were spread among the three school types: lower-track (Hauptschule), intermediate-track (Realschule), and higher-track (Gymnasium). These school types differ in entrance standards and academic demands.

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Meditation can produce enduring changes in emotional processing

December, 2012

A new study provides more evidence that meditation changes the brain, and different types of meditation produce different effects.

More evidence that even an 8-week meditation training program can have measurable effects on the brain comes from an imaging study. Moreover, the type of meditation makes a difference to how the brain changes.

The study involved 36 participants from three different 8-week courses: mindful meditation, compassion meditation, and health education (control group). The courses involved only two hours class time each week, with meditation students encouraged to meditate for an average 20 minutes a day outside class. There was a great deal of individual variability in the total amount of meditation done by the end of the course (210-1491 minutes for the mindful attention training course; 190-905 minutes for the compassion training course).

Participants’ brains were scanned three weeks before the courses began, and three weeks after the end. During each brain scan, the volunteers viewed 108 images of people in situations that were either emotionally positive, negative or neutral.

In the mindful attention group, the second brain scan showed a decrease in activation in the right amygdala in response to all images, supporting the idea that meditation can improve emotional stability and response to stress. In the compassion meditation group, right amygdala activity also decreased in response to positive or neutral images, but, among those who reported practicing compassion meditation most frequently, right amygdala activity tended to increase in response to negative images. No significant changes were seen in the control group or in the left amygdala of any participant.

The findings support the idea that meditation can be effective in improving emotional control, and that compassion meditation can indeed increase compassionate feelings. Increased amygdala activation was also correlated with decreased depression scores in the compassion meditation group, which suggests that having more compassion towards others may also be beneficial for oneself.

The findings also support the idea that the changes brought about by meditation endure beyond the meditative state, and that the changes can start to occur quite quickly.

These findings are all consistent with other recent research.

One point is worth emphasizing, in the light of the difficulty in developing a training program that improves working memory rather than simply improving the task being practiced. These findings suggest that, unlike most cognitive training programs, meditation training might produce learning that is process-specific rather than stimulus- or task-specific, giving it perhaps a wider generality than most cognitive training.

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Dopamine decline underlies episodic memory decline in old age

December, 2012

Findings supporting dopamine’s role in long-term episodic memory point to a decline in dopamine levels as part of the reason for cognitive decline in old age, and perhaps in Alzheimer’s.

The neurotransmitter dopamine is found throughout the brain and has been implicated in a number of cognitive processes, including memory. It is well-known, of course, that Parkinson's disease is characterized by low levels of dopamine, and is treated by raising dopamine levels.

A new study of older adults has now demonstrated the effect of dopamine on episodic memory. In the study, participants (aged 65-75) were shown black and white photos of indoor scenes and landscapes. The subsequent recognition test presented them with these photos mixed in with new ones, and required them to note which photos they had seen before. Half of the participants were first given Levodopa (‘L-dopa’), and half a placebo.

Recognition tests were given two and six hours after being shown the photos. There was no difference between the groups at the two-hour test, but at the six-hour test, those given L-dopa recognized up to 20% more photos than controls.

The failure to find a difference at the two-hour test was expected, if dopamine’s role is to help strengthen the memory code for long-term storage, which occurs after 4-6 hours.

Individual differences indicated that the ratio between the amount of Levodopa taken and body weight is key for an optimally effective dose.

The findings therefore suggest that at least part of the reason for the decline in episodic memory typically seen in older adults is caused by declining levels of dopamine.

Given that episodic memory is one of the first and greatest types of memory hit by Alzheimer’s, this finding also has implications for Alzheimer’s treatment.

Caffeine improves recognition of positive words

Another recent study also demonstrates, rather more obliquely, the benefits of dopamine. In this study, 200 mg of caffeine (equivalent to 2-3 cups of coffee), taken 30 minutes earlier by healthy young adults, was found to improve recognition of positive words, but had no effect on the processing of emotionally neutral or negative words. Positive words are consistently processed faster and more accurately than negative and neutral words.

Because caffeine is linked to an increase in dopamine transmission (an indirect effect, stemming from caffeine’s inhibitory effect on adenosine receptors), the researchers suggest that this effect of caffeine on positive words demonstrates that the processing advantage enjoyed by positive words is driven by the involvement of the dopaminergic system.

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How emotion keeps some memories vivid

September, 2012

Emotionally arousing images that are remembered more vividly were seen more vividly. This may be because the amygdala focuses visual attention rather than more cognitive attention on the image.

We know that emotion affects memory. We know that attention affects perception (see, e.g., Visual perception heightened by meditation training; How mindset can improve vision). Now a new study ties it all together. The study shows that emotionally arousing experiences affect how well we see them, and this in turn affects how vividly we later recall them.

The study used images of positively and negatively arousing scenes and neutral scenes, which were overlaid with varying amounts of “visual noise” (like the ‘snow’ we used to see on old televisions). College students were asked to rate the amount of noise on each picture, relative to a specific image they used as a standard. There were 25 pictures in each category, and three levels of noise (less than standard, equal to standard, and more than standard).

Different groups explored different parameters: color; gray-scale; less noise (10%, 15%, 20% as compared to 35%, 45%, 55%); single exposure (each picture was only presented once, at one of the noise levels).

Regardless of the actual amount of noise, emotionally arousing pictures were consistently rated as significantly less noisy than neutral pictures, indicating that people were seeing them more clearly. This was true in all conditions.

Eye-tracking analysis ruled out the idea that people directed their attention differently for emotionally arousing images, but did show that more eye fixations were associated both with less noisy images and emotionally arousing ones. In other words, people were viewing emotionally important images as if they were less noisy.

One group of 22 students were given a 45-minute spatial working memory task after seeing the images, and then asked to write down all the details they could remember about the pictures they remembered seeing. The amount of detail they recalled was taken to be an indirect measure of vividness.

A second group of 27 students were called back after a week for a recognition test. They were shown 36 new images mixed in with the original 75 images, and asked to rate them as new, familiar, or recollected. They were also asked to rate the vividness of their recollection.

Although, overall, emotionally arousing pictures were not more likely to be remembered than neutral pictures, both experiments found that pictures originally seen as more vivid (less noise) were remembered more vividly and in more detail.

Brain scans from 31 students revealed that the amygdala was more active when looking at images rated as vivid, and this in turn increased activity in the visual cortex and in the posterior insula (which integrates sensations from the body). This suggests that the increased perceptual vividness is not simply a visual phenomenon, but part of a wider sensory activation.

There was another neural response to perceptual vividness: activity in the dorsolateral prefrontal cortex and the posterior parietal cortex was negatively correlated with vividness. This suggests that emotion is not simply increasing our attentional focus, it is instead changing it by reducing effortful attentional and executive processes in favor of more perceptual ones. This, perhaps, gives emotional memories their different ‘flavor’ compared to more neutral memories.

These findings clearly need more exploration before we know exactly what they mean, but the main finding from the study is that the vividness with which we recall some emotional experiences is rooted in the vividness with which we originally perceived it.

The study highlights how emotion can sharpen our attention, building on previous findings that emotional events are more easily detected when visibility is difficult, or attentional demands are high. It is also not inconsistent with a study I reported on last year, which found some information needs no repetition to be remembered because the amygdala decrees it of importance.

I should add, however, that the perceptual effect is not the whole story — the current study found that, although perceptual vividness is part of the reason for memories that are vividly remembered, emotional importance makes its own, independent, contribution. This contribution may occur after the event.

It’s suggested that individual differences in these reactions to emotionally enhanced vividness may underlie an individual’s vulnerability to post-traumatic stress disorder.

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Second language processing differs for negative words

June, 2012

A study involving Chinese-English bilinguals shows how words with negative emotional connotations don’t automatically access native translations, while those with positive or neutral emotions do.

Here’s an intriguing study for those interested in how language affects how we think. It’s also of interest to those who speak more than one language or are interested in learning another language, because it deals with the long-debated question as to whether bilinguals working in their non-native language automatically access the native-language representations in long-term memory, or whether they can ‘switch off’ their native language and use only the target language memory codes.

The study follows on from an earlier study by the same researchers that indicated, through the demonstration of hidden priming effects, that bilinguals subconsciously access their first language when reading in their second language. In this new study, 45 university students (15 native English speakers, 15 native Chinese speakers, and 15 Chinese-English bilinguals) were shown two blocks of 90 word pairs. The pairs could have positive emotional value (e.g., honesty-program), negative valence (failure-poet), or neutral valence (aim-carpenter); could be semantically related (virus-bacteria; love-rose) or unrelated (weather-gender). The English or Chinese words were flashed on the screen one at a time, with a brief interval between the first and second word. The students had to indicate whether the second word was related in meaning to the first, and their brain activity was monitored.

The English and Chinese speakers acted as controls — it was the bilinguals, of course, who were the real interest. Some of the English word pairs shared a sound in the Chinese translation. If the Chinese words were automatically activated, therefore, the sound repetition would have a priming effect.

This is indeed what was found (confirming the earlier finding and supporting the idea that native language translations are automatically activated) — but here’s the interesting thing: the priming effect occurred only for positive and neutral words. It did not occur when the bilinguals saw negative words such as war, discomfort, inconvenience, and unfortunate.

The finding, which surprised the researchers, is nonetheless consistent with previous evidence that anger, swearing or discussing intimate feelings has more power in a speaker's native language. Parents, too, tend to speak to their infants in their native tongue. Emotion, it seems, is more strongly linked to our first language.

It’s traditionally thought that second language processing is fundamentally determined by the age of acquisition and the level of proficiency. The differences in emotional resonance have been, naturally enough, attributed to the native language being acquired first. This finding suggests the story is a little more complicated.

The researchers theorize that they have touched on the mechanism by which emotion controls our fundamental thought processes. They suggest that the brain is trying to protect us by minimizing the effect of distressing or disturbing emotional content, by shutting down the unconscious access to the native language (in which the negative words would be more strongly felt).

A few more technical details for those interested:

The Chinese controls demonstrated longer reaction times than the English controls, which suggests (given that 60% of the Chinese word pairs had overt sound repetitions but no semantic relatedness) that this conjunction made the task substantially more difficult. The bilinguals, however, had reaction times comparable to the English controls. The Chinese controls showed no effect of emotional valence, but did show priming effects of the overt sound manipulation that were equal for all emotion conditions.

The native Chinese speakers had recently arrived in Britain to attend an English course. Bilinguals had been exposed to English since the age of 12 and had lived in Britain for an average of 20.5 months.

Reference: 

[2969] Wu YJ, Thierry G. How Reading in a Second Language Protects Your Heart. The Journal of Neuroscience [Internet]. 2012 ;32(19):6485 - 6489. Available from: http://www.jneurosci.org/content/32/19/6485

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Sleep preserves your feelings about traumatic events

January, 2012

New research suggests that sleeping within a few hours of a disturbing event keeps your emotional response to the event strong.

Previous research has shown that negative objects and events are preferentially consolidated in sleep — if you experience them in the evening, you are more likely to remember them than more neutral objects or events, but if you experience them in the morning, they are not more likely to be remembered than other memories (see collected sleep reports). However, more recent studies have failed to find this. A new study also fails to find such preferential consolidation, but does find that our emotional reaction to traumatic or disturbing events can be greatly reduced if we stay awake afterward.

Being unable to sleep after such events is of course a common response — these findings indicate there’s good reason for it, and we should go along with it rather than fighting it.

The study involved 106 young adults rating pictures on a sad-happy scale and their own responses on an excited-calm scale. Twelve hours later, they were given a recognition test: noting pictures they had seen earlier from a mix of new and old pictures. They also rated all the pictures on the two scales. There were four groups: 41 participants saw the first set late in the day and the second set 12 hours later on the following day (‘sleep group’); 41 saw the first set early and the second set 12 hours later on the same day; 12 participants saw both sets in the evening, with only 45 minutes between the sets; 12 participants saw both sets in the morning (these last two groups were to rule out circadian effects). 25 of the sleep group had their brain activity monitored while they slept.

The sleep group performed significantly better on the recognition test than the same-day group. Negative pictures were remembered better than neutral ones. However, unlike earlier studies, the sleep group didn’t preferentially remember negative pictures more than the same-day group.

But, interestingly, the sleep group was more likely to maintain the strength of initial negative responses. The same-day group showed a weaker response to negative scenes on the second showing.

It’s been theorized that late-night REM sleep is critical for emotional memory consolidation. However, this study found no significant relationship between the amount of time spent in REM sleep and recognition memory, nor was there any relationship between other sleep stages and memory. There was one significant result: those who had more REM sleep in the third quarter of the night showed the least reduction of emotional response to the negative pictures.

There were no significant circadian effects, but it’s worth noting that even the 45 minute gap between the sets was sufficient to weaken the negative effect of negative scenes.

While there was a trend toward a gender effect, it didn’t reach statistical significance, and there were no significant interactions between gender and group or emotional value.

The findings suggest that the effects of sleep on memory and emotion may be independent.

The findings also contradict previous studies showing preferential consolidation of emotional memories during sleep, but are consistent with two other recent studies that have also failed to find this. At this stage, all we can say is that there may be certain conditions in which this occurs (or doesn’t occur), but more research is needed to determine what these conditions are. Bear in mind that there is no doubt that sleep helps consolidate memories; we are talking here only about emphasizing negative memories at the expense of emotionally-neutral ones.

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