Latest Research News
Obstructive sleep apnea (OSA) occurs when a person's breathing is interrupted during sleep.
People with OSA are known to suffer memory problems and also have higher rates of depression.
A new study connects the two by finding that people with untreated OSA had problems recalling specific details about their lives. Previous research has established that persistent depression is associated with overly general autobiographical memories, where people don't remember many specific details of life events.
It may be that sleep apnea impairs the ability to either encode or consolidate certain types of life memories.
The study, involvidng 44 adults with untreated OSA and 44 healthy age-matched controls (average age 49), found that those with OSA had significantly more overgeneral memories: 52.3% compared with 18.9% of the controls.
OSA participants also had significantly poorer semantic recall of early adult life (facts from your personal history, like the names of your school teachers).
Across both groups, being older was associated with having a higher number of overgeneral autobiographical memories while higher depression was linked to having worse semantic memory.
A laboratory study has found that sleeping after watching a trauma event reduced emotional distress and memories related to traumatic events. The laboratory study involved 65 women being shown a neutral and a traumatic video. Typically, recurring memories of certain images haunted the test subjects for a few days (these were recorded in detail in a diary). Some participants slept in the lab for a night after the video, while the other group remained awake.
Those who slept after the film had fewer and less distressing recurring emotional memories than those who were awake. This effect was particularly evident after several days.
One of the reasons for this benefit is thought to be that the memory consolidation processes that happen during sleep help contextualize the memories. This is interesting in view of the recent theory that PTSD is associated with a deficit in contextual processing.
However, I'd note that there is conflicting evidence about the effects of sleep on negative memories (for example, see http://www.memory-key.com/research/news/sleep-preserves-your-feelings-about-traumatic-events).
An interesting new theory for PTSD suggests that the root of the problem lies in context processing problems.
Context processing allows people and animals to recognize that a particular stimulus may require different responses depending on the context in which it is encountered. So, for example, a lion in the zoo evokes a different response than one encountered in your backyard.
The idea that a disruption in this circuit can interfere with context processing can explain most of the symptoms and much of the biology of PTSD. Previous models have focused on one aspect of the disorder:
- on abnormal fear learning, which is rooted in the amygdala
- on exaggerated threat detection, which is rooted in a network involving the amygdala, the anterior cingulate cortex and insula
- on executive function and emotion regulation, which is mainly rooted in the prefrontal cortex.
The researchers suggest that a deficit in context processing would lead PTSD patients to feel "unmoored" from the world around them, unable to shape their responses to fit their current contexts. Instead, their brains impose an "internalized context", one that always expects danger.
This type of deficit, arising from a combination of genes and life experiences, may create vulnerability to PTSD in the first place.
The researchers are now testing their model.
Can you help protect yourself from the memory of traumatic events? A new study suggests that, by concentrating on concrete details as you live through the event, you can reduce the number of intrusive memories later experienced.
The study, aimed particularly at those who deliberately expose themselves to the risk of PTSD (e.g., emergency workers, military personnel, journalists in conflict zones), involved 50 volunteers who rated their mood before watching several films with traumatic scenes. After the first film, they rated their feelings. For the next four films, half the participants were asked to consider abstract questions, such as why such situations happened. The other half were asked to consider concrete questions, such as what they could see and hear and what needed to be done from that point. Afterward, they gave another rating on their mood. Finally, they were asked to watch a final film in the same way as they had practiced, rating feelings of distress and horror as they had for the first film.
The volunteers were then given a diary to record intrusive memories of anything they had seen in the films for the next week.
Both groups, unsurprisingly, saw their mood decline after the films, but those who had been practicing concrete thinking were less affected, and also experienced less intense feelings of distress and horror when watching the final film. Abstract thinkers experienced nearly twice as many intrusive memories in the following week.
The study follows previous findings that emergency workers who adopted an abstract processing approach showed poorer coping, and that those who processed negative events using abstract thinking experienced a longer period of low mood, compared to those using concrete thinking.
Further study to confirm this finding is of course needed in real-life situations, but this does suggest a strategy that people who regularly experience trauma could try. It is particularly intriguing because, on the face of it, it would seem like quite the wrong strategy. Distancing yourself from the trauma you're experiencing, trying to see it as something less real, seems a more obvious coping strategy. This study suggests it is exactly the wrong thing to do.
It also seems likely that this tendency to use concrete or abstract processing may reflect a more general trait. Self-reported proneness to intrusive memories in everyday life was significantly correlated with intrusive memories of the films. Perhaps we should all think about the way we view the world, and those of us who tend to take a more abstract approach should try paying more attention to concrete details. This is, after all, something I've been recommending in the context of fighting sensory impairment and age-related cognitive decline!
Abstract thinking certainly has its place, but as I've said before, we need flexibility. Effective cognitive management is about tailoring your style of thinking to the task's demands.
A study involving 66 healthy young adults (average age 24) has revealed that different individuals have distinct brain connectivity patterns that are associated with different ways of experiencing and remembering the past.
The participants completed an online questionnaire on how well they remember autobiographical events and facts, then had their brains scanned. Brain scans found that those with richly-detailed autobiographical memories had higher mediotemporal lobe connectivity to regions at the back of the brain involved in visual perception, whereas those tending to recall the past in a factual manner showed higher mediotemporal lobe connectivity to prefrontal regions involved in organization and reasoning.
The finding supports the idea that those with superior autobiographical memory have a greater ability or tendency to reinstate rich images and perceptual details, and that this appears to be a stable personality trait.
The finding also raises interesting questions about age-related cognitive decline. Many people first recognize cognitive decline in their increasing difficulty retrieving the details of events. But this may be something that is far more obvious and significant to people who are used to retrieving richly-detailed memories. Those who rely on a factual approach may be less susceptible.
Full text available at http://www.sciencedirect.com/science/article/pii/S0010945215003834
Training in a mental imagery technique has been found to help multiple sclerosis patients in two memory domains often affected by the disease: autobiographical memory and episodic future thinking.
The study involved 40 patients with relapsing-remitting MS, all of whom were receiving regular drug therapy and all of whom had significant brain atrophy. Participants were randomly assigned to one of three groups, one of which received the imagery training (17 participants), while the other two were controls — a control receiving a sham verbal training (10) and a control receiving no training (13). The six training sessions lasted two hours and occurred once or twice a week.
The training involved:
- mental visualization exercises of increasing difficulty, using 10 items that the patient had to imagine and describe, looking at both static aspects (such as color and shape) and an action carried out with the item
- guided construction exercises, using 5 scenarios involving several characters (so, for example, the patient might start with the general idea of a cook preparing a meal, and be guided through more complexities, such as the type of table, the ingredients being used, etc)
- self-visualization exercises, in which the patient imagined themselves within a scenario.
Autobiographical memory and episodic future thinking were assessed, before and after, using an adapted version of the Autobiographical Interview, which involves subjects recalling events from earlier periods in their life, in response to specific cue words. The events are supposed to be unique, and the subjects are asked to recall as many details as possible.
Only those receiving the training showed a significant improvement in their scores.
Those who had the imagery training also reported an increase in general self-confidence, with higher levels of control and vitality.
Remembering past events and imagining future ones are crucial cognitive abilities, with more far-reaching impacts than may be immediately obvious. For example, episodic future thought is important for forming and carrying out intentions.
These are also areas which may be affected by age. A recent study, for example, found that older adults are less likely to spontaneously acquire items that would later allow a problem to be solved, and are also less likely to subsequently use these items to solve the problems. An earlier study found that older adults have more difficulty in imagining future experiences.
These results, then, that show us that people with deficits in specific memory domains can be helped by specific training, is not only of interest to those with MS, but also more generally.
We talk about memory for ‘events’, but how does the brain decide what an event is? How does it decide what is part of an event and what isn’t? A new study suggests that our brain uses categories it creates based on temporal relationships between people, objects, and actions — i.e., items that tend to—or tend not to—pop up near one another at specific times.
This explanation is much more in line with the way semantic memory is organized, but challenges the dominant theory that says our brain draws a line between the end of one event and the start of another when things take an unexpected turn.
“Everyone agrees that ‘having a meeting’ or ‘chopping vegetables’ is a coherent chunk of temporal structure, but it’s actually not so obvious why that is if you’ve never had a meeting or chopped vegetables before. You have to have experience with the shared temporal structure of the components of the events in order for the event to hold together in your mind.”
In the study, participants were shown sequences of abstract symbols and patterns, which, unbeknownst to the participants, were grouped into three “communities” of five symbols with shapes in the same community tending to appear near one another in the sequence.
After watching these sequences for roughly half an hour, participants were asked to segment the sequences into events in a way that felt natural to them. They tended to break the sequences into events that coincided with the communities the researchers had prearranged. Images in the same community also produced similar activity in neuron groups at the border of the brain’s frontal and temporal lobes, a region involved in processing meaning.
All of which is to say that event memory seems to be less different from semantic memory than thought - perhaps this is true of other memory domains too?
Autobiographical memory is an interesting memory domain, given its inextricable association with identity. One particularly fascinating aspect of it is its unevenness - why do we remember so little from the first years of life ('childhood amnesia'), why do we remember some periods of our life so much more vividly than others? There are obvious answers (well, nothing interesting happened in those other times), but the obvious is not always correct. Intriguing, then, to read about a new study that links those memorable periods to self-identity. (Is that part of why little children remember so little? because their self is so undeveloped?)
Katy Waldman at Slate:
… a team of scientists from England’s University of Leeds devised a clever experiment. Noting that developmental psychologists have isolated the second and third decades as times of identity formation, they gathered a group of volunteers and tried to map the emergence of their self-perceptions. Participants were asked to complete 20 “I am” statements (e.g., “I am quick-tempered”; “I am a mother”). Then they were instructed to pick three statements and come up with 10 memories that seemed relevant to each. Finally, the volunteers were told to pinpoint as best they could the ages at which their three personality traits surfaced. If it’s true that we remember more assiduously during bursts of self-making—and that these self-making periods tend to span our late teens and early 20s—a few things should happen, the researchers reasoned. First, participants should frequently date the unfurling of their “I am” statements to young adulthood. Second, the memories they summoned to support each “I am” statement should constellate around the age at which they believed the “I am” statement started to apply.
That was exactly what transpired. A majority of the memories associated with a particular self-image came from the very same year that the self-image developed. It seemed clear that the more salient a past experience was to your identity, the more luminous it grew in your memory. And what turned out to be the median age at which all these traits and self-concepts were acquired? 22.9.
We know that people with depression tend to focus on, and remember, negative memories rather than positive. Interestingly, it’s not simply an emotion effect. People with depression, and even those at risk of depression (including those who have had depression), tend to have trouble remembering specific autobiographical memories. That is, memories of events that happened to them at a specific place and time (as opposed to those generalized event memories we construct from similar events, such as the ‘going to the dentist’ memory).
This cognitive difficulty seems to exacerbate their depression, probably through its effect on social encounters and relationships.
A new study, however, has found that a particular training program (“Memory Specificity Training”) can help both their memory for specific events and their symptoms of depression.
The study involved 23 adolescent Afghani refugees in Iran, all of whom had lost their fathers in the war in Afghanistan and who showed symptoms of depression. Half were randomly assigned to the five-week memory training program and half received no training.
The training program involved a weekly 80-minute group session, in which participants learned about different types of memory and memory recall, and practiced recalling specific memories after being given positive, neutral, and negative keywords.
Participants’ memory for specific events was tested at the start of the study, at the end of the five-week training period, and two months after the end of the training. Compared to the control group, those given the training were able to provide more specific memories after the training, and showed fewer symptoms of depression at the two month follow-up (but not immediately after the end of training).
The study follows on from a pilot study in which ten depressed female patients were given four weekly one-hour sessions of memory training. Improvements in memory retrieval were associated with less rumination (dwelling on things), less cognitive avoidance, and improvements in problem-solving skills.
It’s somewhat unfortunate that the control group were given no group sessions, indeed no contact (apart from the tests) of any kind. Nevertheless, and bearing in mind that these are still very small studies, the findings do suggest that it would be helpful to include a component on memory training in any cognitive behavioral therapy for depression.
Full text available at http://cpx.sagepub.com/content/early/2012/09/07/2167702612454613.abstract
A new study has found that, when delivered quickly, a modified form of prolonged exposure therapy reduces post-traumatic stress reactions and depression.
The study involved 137 patients being treated in the emergency room of a major trauma center in Atlanta. The patients were chosen from survivors of traumatic events such as rape, car or industrial accidents, and shooting or knife attacks. Participants were randomly assigned to either receive three sessions of therapy beginning in the emergency department (an average of 12 hours after the event), or assessment only. Stress reactions were assessed at 4 and 12 weeks, and depression at baseline and 4 weeks.
Those receiving the therapy reported significantly lower post-traumatic stress at 4 weeks and 12 weeks, and significantly lower depression at 4 weeks. Analysis of subgroups revealed that the therapy was most effective in rape victims. In the cases of transport accidents and physical (non-sexual) assault, the difference between therapy and assessment-only was only barely significant (for transport at 4 weeks) or non-significant. In both subgroups, the effect was decidedly less at 12 weeks than at 4 weeks.
The therapy, carried out by trained therapists, involved participants describing the trauma they had experienced while the therapist recorded the description. The bulk of the hour-long session was taken up with reliving and processing the experience. There were three sessions spaced a week apart. The patients were instructed to listen to their recordings every day, and 85% were compliant. The therapists also explained normal reactions to trauma, helped the patients look at obtrusive thoughts of guilt or responsibility, and taught them a brief breathing or relaxation technique and self care.
While this study doesn’t itself compare the effects of immediate vs delayed therapy, the assumption that delivering the therapy so soon after the trauma is a crucial factor in its success is in line with other research (mainly to do with fear-conditioning in rodent and human laboratory studies). Moreover, while brief cognitive-behavioral therapy has previously been shown to be effective with people diagnosed with acute stress disorder, such therapy is normally begun some 2-4 weeks after trauma, and a study of female assault survivors found that although such therapy did indeed accelerate recovery compared with supportive counseling, after 9 months, PTSD severity was similar in both groups.
Another, severe, limitation of this study is that the therapy involved multiple items. We cannot assume that it was the repeated re-experiencing of the event that is critical.
However, this study is only a pilot study, and its findings are instructive rather than decisive. But at the least it does support the idea that immediate therapy is likely to help victims of trauma recover more quickly.
One final, important, note: It should not, of course, be assumed that simply having the victim describe the events — say to police officers — is in itself therapeutic. Done badly, that experience may itself be traumatic.
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.
Certainly experiences that arouse emotions are remembered better than ones that have no emotional connection, but whether negative or positive memories are remembered best is a question that has produced equivocal results. While initial experiments suggested positive events were remembered better than negative, more recent studies have concluded the opposite.
The idea that negative events are remembered best is consistent with a theory that negative emotion signals a problem, leading to more detailed processing, while positive emotion relies more heavily on general scripts.
However, a new study challenges those recent studies, on the basis of a more realistic comparison. Rather than focusing on a single public event, to which some people have positive feelings while others have negative feelings (events used have included the OJ Simpson trial, the fall of the Berlin Wall, and a single baseball championship game), the study looked at two baseball championships each won by different teams.
The experiment involved 1,563 baseball fans who followed or attended the 2003 and 2004 American League Championship games between the New York Yankees (2003 winners) and the Boston Red Sox (2004 winners). Of the fans, 1,216 were Red Sox fans, 218 were Yankees fans, and 129 were neutral fans. (Unfortunately the selection process disproportionately collected Red Sox fans.)
Participants were reminded who won the championship before answering questions on each game. Six questions were identical for the two games: the final score for each team, the winning and losing pitchers (multiple choice of five pitchers for each team), the location of the game, and whether the game required extra innings. Participants also reported how vividly they remembered the game, and how frequently they had thought about or seen media concerning the game.
Both Yankee and Red Sox fans remembered more details about their team winning. They also reported more vivid memories for the games their team won. Accuracy and vividness were significantly correlated. Fans also reported greater rehearsal of the game their team won, and again, rehearsal and accuracy were significantly correlated.
Analysis of the data revealed that rehearsal completely mediated the correlation between accuracy and fan type, and partially mediated the correlation between vividness and fan type.
In other words, improved memory for emotion-arousing events has everything to do with how often you think about or are reminded of the event.
PTSD, for example, is the negative memory extreme. And PTSD is characterized by the unavoidable rehearsal of the event over and over again. Each repetition makes memory for the event stronger.
In the previous studies referred to earlier, media coverage provided a similarly unavoidable repetition.
While most people tend to recall more positive than negative events (and this tendency becomes greater with age), individuals who are depressed or anxious show the opposite tendency.
So whether positive or negative events are remembered better depends on you, as well as the event.
When it comes down to it, I'm not sure it's really a helpful question - whether positive or negative events are remembered better. An interesting aspect of public events is that their portrayal often changes over time, but this is just a more extreme example of what happens with private events as well — as we change over time, so does our attitude toward those events. Telling friends about events, and receiving their comments on them, can affect our emotional response to events, as well as having an effect on our memory of those events.
When a middle-aged woman loses her memory after sex, it naturally makes the headlines. Many might equate this sort of headline to “Man marries alien”, but this is an example of a rare condition — temporary, you will be relieved to hear — known as transient global amnesia. Such abrupt, localized loss of autobiographical memory is usually preceded by strenuous physical activity or stressful events. It generally occurs in middle-aged or older adults, but has been known to occur in younger people. In those cases, there may be a history of migraine or head trauma.
Following an earlier study in which 29 of 41 TGA patients were found to have small lesions in the CA1 region of the hippocampus, scanning of another 16 TGA patients has revealed 14 had these same lesions. It seems likely that all the patients had such lesions, but because they are very small and don’t last long, they’re easy to miss. The lesion is best seen after 24-72 hours, but is gone after 5-6 days.
At the start of one of these attacks, memory for the first 30 years of life was significantly impaired, but still much better than memory for the years after that. There was a clear temporal gradient, with memory increasingly worse for events closer in time. There was no difference between events in the previous year and events in the previous five years, but a clear jump at that five-year point.
The exact location of the lesions was significant: when the lesion was in the anterior part of the region, memory for recent events was more impaired.
The hippocampus is known to be crucially involved in episodic memory (memory for events), and an integral part of the network for autobiographical memory. In recent years, it has come to be thought that such memories are only hosted temporarily by the hippocampus, and over a few years come to be permanently lodged in the neocortex (the standard consolidation model). Evidence from a number of studies of this change at the five-year mark has been taken as support for this theory. According to this, then, older memories should be safe from hippocampal damage.
An opposing theory, however, is that the hippocampus continues to be involved in such memories, with both the neocortex and the hippocampus involved in putting together reconsolidated memories (the multiple trace model). According to this model, each retrieval of an episodic memory creates a new version in the hippocampus. The more versions, the better protected a memory will be from any damage to the hippocampus.
The findings from this study show that while there is indeed a significant difference between older and more recent memories, the CA1 region of the hippocampus continues to be crucial for retrieving older memories, and for our sense of self-continuity.
Interestingly, some studies have also found a difference between the left and right hemispheres, with the right hippocampus showing a temporal gradient and the left hippocampus showing constant activation across all time periods. Such a hemisphere difference was not found in the present study. The researchers suggest that the reason may lie in the age of the participants (average age was 68), reflecting a reduction in hemispheric asymmetry with age.
There’s another message in this study. In these cases of TGA, memory function is restored within 24 hours (and generally sooner, within 6-10 hours). This shows how fast the brain can repair damage. Similarly, the fact that such tiny lesions have temporary effects so much more dramatic than the more lasting effects of larger lesions, is also a tribute to the plasticity of the brain.
The findings are consistent with findings of a preferential degeneration of CA1 neurons in the early stages of Alzheimer's disease, and suggest a target for treatment.
Childhood amnesia — our inability to remember almost everything that happened to us when very young — is always interesting. It’s not as simple as an inability to form long-term memories. Most adults can’t remember events earlier than 3-4 years (there is both individual and cultural variability), even though 2-year-olds are perfectly capable of remembering past events (side-note: memory durability increases from about a day to a year from age six months to two years). Additionally, research has shown that young children (6-8) can recall events that happened 4-6 years previously.
Given that the ability to form durable memories is in place, what governs which memories are retained? The earliest memories adults retain tend to be of events that have aroused emotions. Nothing surprising about that. More interesting is research suggesting that children can only describe memories of events using words they knew when the experience occurred — the study of young children (27, 33 or 39 months) found that, when asked about the experimental situation (involving a "magic shrinking machine") six months later, the children easily remembered how to operate the device, but were only able to describe the machine in words they knew when they first learned how to operate it.
Put another way this isn’t so surprising: our memories depend on how we encode them at the time. So two things may well be in play in early childhood amnesia: limited encoding abilities (influenced but not restricted to language) may mean the memories made are poor in quality (whatever that might mean); the development of encoding abilities means that later attempts to retrieve the memory may be far from matching the original memory. Or as one researcher put it, the format is different.
A new study about childhood amnesia looks at a different question: does the boundary move? 140 children (aged 4-13) were asked to describe their three earliest memories, and then asked again two years later (not all could provide as many as three early memories; the likelihood improved with age).
While more than a third of the 10- to 13-year-olds described the same memory as their very earliest on both occasions, children between 4 and 7 at the first interview showed very little overlap between the memories (only 2 of the 27 4-5 year-olds, and 3 of the 23 6-7 year-olds). There was a clear difference between the overlap seen in this youngest group (4-7) and the oldest (10-13), with the in-between group (8-9) being placed squarely between the two (20.7% compared to 10% and 36%).
Moreover, children under 8 at the first interview mostly had no overlap between any of the memories they provided at the two interviews, while those who were at least 8 years old did. For the oldest groups (10-13), more than half of all the memories they provided were the same.
The children were also given recall cues for memories they hadn’t spontaneously recalled. That is, they were told synopses of memories belonging to both their own earlier memories, and other children’s earlier memories. Almost all of the false memories were correctly rejected (the exceptions mostly occurred with the youngest group, those initially aged 4-5). However, the youngest children didn’t recognize over a third of their own memories, while almost all the oldest children’s memories were recognized (90% by 8-11 year-olds; all but one by 12-13 year-olds). Their age at the time of the event didn’t seem to affect the oldest or the very youngest groups, but 6-9 year-olds were more likely to recall after cuing events that happened at least a year later than those events that weren’t recalled after cuing.
In general, the earliest memories were several months later at the follow-up than they had been previously. The average age at the time of the earliest memory was 32 months, and 39.6 months on the follow-up interview. This shift in time occurred across all ages. Moreover, for the very earliest memory, the time-shift was even greater: a whole year.
In connection with the earlier study I mentioned, regarding the importance of language and encoding, it is worth noting that by and large, when the same memories were recalled, the same amount of information was recalled.
There was no difference between the genders.
The findings don’t rule out theories of the role of language. It seems clear to me that more than one thing is going on in childhood amnesia. These findings bear on another aspect: the forgetting curve.
It has been suggested that forgetting in children reflects a different function than forgetting in adults. Forgetting in adults matches a power function, reflecting the fact that forgetting slows over time (as is often quoted, most forgetting occurs in the first 24 hours; the longer you remember something, the more likely you are to remember it forever). However, there is some evidence that forgetting in children is best modeled in an exponential function, reflecting the continued vulnerability of memories. It seems they are not being consolidated in the way adults’ memories are. This may be because children don’t yet have the cognitive structures in place that allow them to embed new memories in a dense network.
Children’s ability to remember past events improves as they get older. This has been thought by many to be due to the slow development of the prefrontal cortex. But now brain scans from 60 children (8-year-olds, 10- to 11-year-olds, and 14-year-olds) and 20 young adults have revealed marked developmental differences in the activity of the mediotemporal lobe.
The study involved the participants looking at a series of pictures (while in the scanner), and answering a different question about the image, depending on whether it was drawn in red or green ink. Later they were shown the pictures again, in black ink and mixed with new ones. They were asked whether they had seen them before and whether they had been red or green.
While the adolescents and adults selectively engaged regions of the hippocampus and posterior parahippocampal gyrus to recall event details, the younger children did not, with the 8-year-olds indiscriminately using these regions for both detail recollection and item recognition, and the 10- to 11-year-olds showing inconsistent activation. It seems that the hippocampus and posterior parahippocampal gyrus become increasingly specialized for remembering events, and these changes may partly account for long-term memory improvements during childhood.
Rodent studies have demonstrated the existence of specialized neurons involved in spatial memory. These ‘grid cells’ represent where an animal is located within its environment, firing in patterns that show up as geometrically regular, triangular grids when plotted on a map of a navigated surface. Now for the first time, evidence for these cells has been found in humans. Moreover, those with the clearest signs of grid cells performed best in a virtual reality spatial memory task, suggesting that the grid cells help us to remember the locations of objects. These cells, located particularly in the entorhinal cortex, are also critical for autobiographical memory, and are amongst the first to be affected by Alzheimer's disease, perhaps explaining why getting lost is one of the most common early symptoms.
A study in which nearly 50 participants consumed either alcohol (.4 or .8 g/kg, around 2 or 4 glasses of wine) or a placebo drink, performed a memory task, then were shown a video of serious road traffic accidents, has found that those given the smaller amount of alcohol experienced more flashbacks during the next week than those given the larger amount of alcohol, and those given no alcohol. Although that may seem to suggest drinking a large amount of alcohol might result in less involuntary re-experiencing of the event, excessive alcohol produced an overall reduction in memory which may be even more distressing if they then imagine a 'worse case scenario.' The findings support the view that flashbacks reflect the reactivation of image-based egocentric representations (based on sensory features) in the absence of a corresponding allocentric representing (incorporating the spatiotemporal context). Alcohol appears to impair allocentric (contextual) memory first.
Older news items (pre-2010) brought over from the old website
- The role of emotion
- Where are our personal experiences stored in the brain?
- Why some people remember events better than others
- How familiarity can mislead
The role of emotion
Life-defining events remembered more favorably
A study has found that when people feel an event has had a large impact on them, they downplay the negative and emphasize the positive. For such significant events, when asked to reflect on negative events, people reported less negative emotion and more positive emotion compared to how they recalled feeling at the time. Similarly, for positive events, people reported more positive emotion and less negative emotion compared to how they recalled feeling at the time.
Conway, M. & Wood, W-J. 2006. Subjective Impact, Meaning Making, and Current and Recalled Emotions for Self-Defining Memories. Journal of Personality, 74, 811-
Memories of crime stories influenced by racial stereotypes
The influence of stereotypes on memory, a well-established phenomenon, has been demonstrated anew in a study concerning people's memory of news photographs. In the study, 163 college students (of whom 147 were White) examined one of four types of news stories, all about a hypothetical Black man. Two of the stories were not about crime, the third dealt with non-violent crime, while the fourth focused on violent crime. All four stories included an identical photograph of the same man. Afterwards, participants reconstructed the photograph by selecting from a series of facial features presented on a computer screen. It was found that selected features didn’t differ from the actual photograph in the non-crime conditions, but for the crime stories, more pronounced African-American features tended to be selected, particularly so for the story concerning violent crime. Participants appeared largely unaware of their associations of violent crime with the physical characteristics of African-Americans.
Oliver, M.B., Jackson, R.L.II., Moses, N.N. & Dangerfield, C.L. 2004. The Face of Crime: Viewers' Memory of Race-Related Facial Features of Individuals Pictured in the News. Journal of Communication, 54, 88-104.
How memory helps make life pleasant
Surveys consistently show that people are generally happy with their lives. A review of research into autobiographical memory suggests why - human memory is biased toward happiness. Across 12 studies conducted by five different research teams, people of different racial and ethnic backgrounds and of different ages consistently reported experiencing more positive events in their lives than negative events, suggesting that pleasant events do in fact outnumber unpleasant events because people seek out positive experiences and avoid negative ones. Our memory also treats pleasant emotions differently from unpleasant emotions. Pleasant emotions appear to fade more slowly from our memory than unpleasant emotions. This is not repression; people do remember negative events, they just remember them less negatively. Among those with mild depression, however, unpleasant and pleasant emotions tend to fade evenly.
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.
Suppressing your expression of emotion affects your memory for the event
The way people go about controlling their reactions to emotional events affects their memory of the event. In a series of experiments designed to assess the effect of suppressing the expression of emotion, it was found that, when people were shown a video of an emotional event and instructed not to let their emotions show, they had poorer memory for what was said and done than did those people who were given no such instructions. However, when shown slides of people who had been injured, people in both groups were equally good at picking which in an array of subtly different versions of each slide had been shown earlier - but when prompted to recall information that had been presented verbally with each slide, those in the suppression group again remembered fewer details. People who were asked to adopt the neutral attitude of a medical profession however, performed better than the control group on nonverbal recall, indicating the regulation of emotions via reappraisal was not associated with any memory impairment. These experimental results were supported by a naturalistic study.
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.
Brain hub links music and autobiographical memory
We all know that songs from our youth can evoke strong autobiographical memories. Now a new study explains why. Brain scans of students listening to excerpts of 30 different popular tunes found that a student recognized on average about 17 of the 30 excerpts, and of these, about 13 were moderately or strongly associated with an autobiographical memory. The strength of that memory was reflected in the amount of activity in the upper (dorsal) part of the medial prefrontal cortex, a region critically involved in integrating sensory information with self-knowledge and the retrieval of autobiographical information. Moreover, mapping the tones of each excerpt showed that the brain was tracking these tonal progressions in the same region as it was experiencing the memories: in the dorsal part of the medial prefrontal cortex, and the regions immediately adjacent to it. Again, the stronger the autobiographical memory, the greater the tracking activity. The finding explains why memory for autobiographically important music lingers in Alzheimer’s sufferers — the area is one of the last to be affected.
Janata, P. 2009. The Neural Architecture of Music-Evoked Autobiographical Memories. Cerebral Cortex, Advance Access published on February 24. Full text available at http://cercor.oxfordjournals.org/cgi/content/abstract/bhp008
Long-term storage of autobiographical memories
By studying in detail the ability of patients with selective brain damage to recall events in their past, researchers have helped settle a long-standing controversy about whether long-term memory of one's personal experiences continue to be stored in the medial temporal lobe, or whether they gradually become independent of this area. The evidence from this new study suggests that autobiographical memories gradually become distributed throughout the neocortex.
Bayley, P.J., Gold, J.J., Hopkins, R.O. & Squire, L.R. 2005. The Neuroanatomy of Remote Memory. Neuron, 46, 799–810.
What happens in the brain when we remember our own past?
A new imaging study has managed to distinguish between two types of autobiographical memory — the “facts” of our lives (e.g., knowing that you attended your cousin’s wedding last year), and the experiences of our lives (e.g., remembering traveling to the wedding, the events and people). As with much autobiographical memory research, the study used a diary-type procedure, whereby volunteers spent several months recording the events of their lives on a micro cassette recorder, as well as personal facts of their lives. These recordings were then played back to the volunteers while their brains were being scanned with fMRI. The results showed that the two types of autobiographical memory engaged different parts of the brain, even when the memories concerned the same contents. Recall of personal episodic memories more strongly engaged parts of the frontal lobes involved in self-awareness, as well as areas involved in visual memory.
Levine, B., Turner, G.R., Tisserand, D., Hevenor, S.J., Graham, S.J. & McIntosh, A.R. 2004. The Functional Neuroanatomy of Episodic and Semantic Autobiographical Remembering: A Prospective Functional MRI Study. Journal of Cognitive Neuroscience, 16(9), 1633-1646.
New technique sheds light on autobiographical memory
A new technique for studying autobiographical memory has revealed new findings about autobiographical memory, and may prove useful in studying age-related cognitive impairment. Previous inconsistencies between controlled laboratory studies of memory (typically, subjects are asked to remember items they have previously seen in the laboratory, such as words presented on a computer screen) and studies of autobiographical memory have seemed to indicate that the brain may function differently in the two processes. However, such differences might instead reflect how the memories are measured. In an effort to provide greater control over the autobiographical memories, volunteer subjects were given cameras and instructed to take pictures of campus scenes. The subjects were also instructed to remember the taking of each picture as an individual event, noting the physical conditions and their psychological state, such as their mood and associations with the subject of the images. The subjects were then shown a selection of campus photos they had not taken. While their brains were scanned, they were then shown a mix of their own photos with those they had not taken, and asked to indicate whether each photo was new, seen earlier in the lab, or one they had taken themselves. The researchers found that recalling the autobiographical memories activated many of the same brain areas as laboratory memories (the medial temporal lobe and the prefrontal cortex); however, they also activated brain areas associated with "self-referential processing" (processing information about one's self), and regions associated with retrieval of visual and spatial information, as well as showing a higher level of activity in the recollection areas in the hippocampus.
Cabeza, R., Prince, S. E., Daselaar, S. M., Greenberg, D. L., Budde, M., Dolcos, F., … Rubin, D. C. (2004). Brain Activity during Episodic Retrieval of Autobiographical and Laboratory Events: An fMRI Study using a Novel Photo Paradigm. Journal of Cognitive Neuroscience, 16(9), 1583–1594. doi:10.1162/0898929042568578
The chunking of our lives: the brain "sees" life in segments
We talk about "chunking" all the time in the context of memory. But the process of breaking information down into manageable bits occurs, it seems, right from perception. Magnetic resonance imaging reveals that when people watched movies of common, everyday, goal-directed activities (making the bed, doing the dishes, ironing a shirt), their brains automatically broke these continuous events into smaller segments. The study also identified a network of brain areas that is activated during the perception of boundaries between events. "The fact that changes in brain activity occurred during the passive viewing of movies indicates that this is how we normally perceive continuous events, as a series of segments rather than a dynamic flow of action."
Zacks, J.M., Braver, T.S., Sheridan, M.A., Donaldson, D.I., Snyder, A.Z., Ollinger, J.M., Buckner, R.L. & Raichle, M.E. 2001. Human brain activity time-locked to perceptual event boundaries. Nature Neuroscience, 4(6), 651-5.
Amygdala may be critical for allowing perception of emotionally significant events despite inattention
We choose what to pay attention to, what to remember. We give more weight to some things than others. Our perceptions and memories of events are influenced by our preconceptions, and by our moods. Researchers at Yale and New York University have recently published research indicating that the part of the brain known as the amygdala is responsible for the influence of emotion on perception. This builds on previous research showing that the amygdala is critically involved in computing the emotional significance of events. The amygdala is connected to those brain regions dealing with sensory experiences, and the theory that these connections allow the amygdala to influence early perceptual processing is supported by this research. Dr. Anderson suggests that “the amygdala appears to be critical for the emotional tuning of perceptual experience, allowing perception of emotionally significant events to occur despite inattention.”
Anderson, A.K. & Phelps, E.A. 2001. Lesions of the human amygdala impair enhanced perception of emotionally salient events. Nature, 411, 305-309.
Why some people remember events better than others
Gene linked to poor episodic memory
Brain derived neurotrophic factor (BDNF) plays a key role in neuron growth and survival and, it now appears, memory. We inherit two copies of the BDNF gene - one from each parent - in either of two versions. Slightly more than a third inherit at least one copy of a version nicknamed "met," which the researchers have now linked to poorer memory. Those who inherit the “met” gene appear significantly worse at remembering events that have happened to them, probably as a result of the gene’s effect on hippocampal function. Most notably, those who had two copies of the “met” gene scored only 40% on a test of episodic (event) memory, while those who had two copies of the other version scored 70%. Other types of memory did not appear to be affected. It is speculated that having the “met” gene might also increase the risk of disorders such as Alzheimer’s and Parkinson's.
Egan, M.F., Kojima, M., Callicott, J.H., Goldberg, T.E., Kolachana, B.S., Bertolino, A., Zaitsev, E., Gold, B., Goldman, D., Dean, M., Lu, B. & Weinberger, D.R. 2003. The BDNF val66met Polymorphism Affects Activity-Dependent Secretion of BDNF and Human Memory and Hippocampal Function. Cell, 112, 257-269.
Childhood "amnesia" linked to vocabulary
"Childhood amnesia" is the term given to the well-known phenomenon of our almost complete lack of memory for the experiences of our very early childhood. Exactly why it occurs is long been a subject of debate. New research suggests the answer may lie in the very limited vocabulary of very young children. A study of 2- and 3-year-old children found that children can only describe memories of events using words they knew when the experience occurred. When asked about the experimental situation (involving a "magic shrinking machine") a year later, the children easily remembered how to operate the device, but were only able to describe the machine in words they knew when they first learned how to operate it.
Simcock, G. & Hayne, H. 2002. Breaking the Barrier? Children Fail to Translate Their Preverbal Memories Into Language. Psychological Science, 13 (3), 225-231.
Left-handers may be better at remembering events
A recent study that compared episodic memory (for events) and implicit memory (for facts) concluded that the two hemispheres of the brain work together to help us remember events, while facts are processed in one hemisphere alone. It seems that people whose brains' halves work together more actively (people with left-handedness in their families - although not necessarily left-handed themselves) remember events better than they remember facts. These findings also help explain why children don't remember events until about age 4, when the fibers connecting the hemispheres fully develop.
Christman, S.D. & Propper, R.E. (2001). Superior Episodic Memory Is Associated With Interhemispheric Processing. Neuropsychology, 15 (4), 607–616.
Cultural differences in autobiographical memory
American adults and preschool children recall their personal memories in a way that is consistently different from the way indigenous Chinese do, according to recent study. "Americans often report lengthy, specific, emotionally elaborate memories that focus on the self as a central character. Chinese tend to give brief accounts of general routine events that center on collective activities and are often emotionally neutral."From an earlier study (published in Memory, Vol. 8, 2000), it is thought that these differences in remembering (with their implications for sense of self) reflect the different conversational styles between mother and child found in these two cultures.
Wang, Q. (2001). Culture effects on adults’ earliest childhood recollection and self-description: Implications for the relation between memory and the self. Journal of Personality and Social Psychology, 81(2), 220–233. doi:10.1037/0022-3522.214.171.124
People remember prices more easily if they have fewer syllables
The phonological loop — an important component of working memory —can only hold 1.5 to 2 seconds of spoken information. For that reason, faster speakers have an advantage over slower speakers. Now a consumer study reveals that every extra syllable in a product's price decreases its chances of being remembered by 20%. Thus, people who shorten the number of syllables (e.g. read 5,325 as 'five three two five' as opposed to 'five thousand three hundred and twenty five') have better recall. However, since we store information both verbally and visually, it’s also the case that unusual looking prices, such as $8.88, are recalled better than typical looking prices.
Vanhuele, M., Laurent, G., Dreze, X. & Calder, B. 2006. Consumers' Immediate Memory for Prices. Journal of Consumer Research, in press.
Increasing consumer preferences by manipulating memory
In two experiments, people who had to solve an anagram before seeing a target brand, they were more likely to claim to have seen the brand before, and to prefer it over competing brands.
Kronlund, A. & Bernstein, D.M. 2006. Unscrambling words increases brand name recognition and preference. Applied Cognitive Psychology, 20(5), 681–687.
Older adults more likely to "remember" misinformation
In a study involving older adults (average age 75) and younger adults (average age 19), participants studied lists of paired related words, then viewed new lists of paired words, some the same as before, some different, and some with only one of the two words the same. In those cases, the "prime" word, which was presented immediately prior to the test, was plausible but incorrect. The older adults were 10 times more likely than young adults to accept the wrong word and falsely "remember" earlier studying that word. This was true even though older adults had more time to study the list of word pairs and attained a performance level equal to that of the young adults. Additionally, when told they had the option to "pass" when unsure of an answer, older adults rarely used the option. Younger adults did, greatly reducing their false recall. The findings reflect real-world reports of a rising incidence of scams perpetrated on the elderly, which rely on the victim’s poor memory and vulnerability to the power of suggestion.
Jacoby, L.L., Bishara, A.J., Hessels, S. & Toth, J.P. 2005. Aging, Subjective Experience, and Cognitive Control: Dramatic False Remembering by Older Adults. Journal of Experimental Psychology: General, 134 (2)
Repeated product warnings are remembered as product recommendations
Warnings about particular products may have quite the opposite effect than intended. Because we retain a familiarity with encountered items far longer than details, the more often we are told a claim about a consumer item is false, the more likely we are to accept it as true a little further down the track. Research also reveals that older adults are more susceptible to this error. It is relevant to note that in the U.S. at least, some 80% of consumer fraud victims are over 65.
Skurnik, I., Yoon, C., Park, D.C. & Schwarz, N. 2005. How Warnings About False Claims Become Recommendations. Journal Of Consumer Research, 31
You may not be able to recall it, but it influences you anyway
“Forgetting” doesn’t mean the memory is erased from your brain. “Forgotten” information may in fact influence you more than it would if it hadn’t been forgotten — because you’re unaware of the influence. This somewhat alarming possibility has been raised by a recent study in which college students studied lists of nonfamous and famous names. Some participants were told to remember the nonfamous names, while the others were told to forget them. Later, both groups were asked to judge whether or not a name was famous from a mixed list of famous and nonfamous names. Those who were told to forget misidentified more nonfamous names as famous than those who had been told to remember.
Such a judgment is of course made on the basis of the familiarity of the name. It is exposure to an item that affects its familiarity – not whether or not you consciously remember it. By telling the participants to “forget” what they’d seen, the experimenters were removing the participants’ awareness of the source of the familiarity, not the familiarity itself.
Bjork, E.L. & Bjork, R.A. 2003. Intentional Forgetting Can Increase, Not Decrease, Residual Influences of To-Be-Forgotten Information. Journal of Experimental Psychology: Learning, Memory, and Cognition, 29 (4), 524–531.