Brains Are Different in People With Highly Superior Autobiographical Memory

ScienceDaily (July 30, 2012) — UC Irvine scientists have discovered intriguing differences in the brains and mental processes of an extraordinary group of people who can effortlessly recall every moment of their lives since about age 10.

UC Irvine scientists have discovered intriguing differences in the brains and mental processes of an extraordinary group of people who can effortlessly recall every moment of their lives since about age 10. (Credit: © James Steidl / Fotolia)

The phenomenon of highly superior autobiographical memory — first documented in 2006 by UCI neurobiologist James McGaugh and colleagues in a woman identified as “AJ” — has been profiled on CBS’s “60 Minutes” and in hundreds of other media outlets. But a new paper in the peer-reviewed journal Neurobiology of Learning & Memory‘s July issue offers the first scientific findings about nearly a dozen people with this uncanny ability.

All had variations in nine structures of their brains compared to those of control subjects, including more robust white matter linking the middle and front parts. Most of the differences were in areas known to be linked to autobiographical memory, “so we’re getting a descriptive, coherent story of what’s going on,” said lead author Aurora LePort, a doctoral candidate at UCI’s Center for the Neurobiology of Learning & Memory.

Surprisingly, the people with stellar autobiographical memory did not score higher on routine laboratory memory tests or when asked to use rote memory aids. Yet when it came to public or private events that occurred after age 10½, “they were remarkably better at recalling the details of their lives,” said McGaugh, senior author on the new work.

“These are not memory experts across the board. They’re 180 degrees different from the usual memory champions who can memorize pi to a large degree or other long strings of numbers,” LePort noted. “It makes the project that much more interesting; it really shows we are homing in on a specific form of memory.”

She said interviewing the subjects was “baffling. You give them a date, and their response is immediate. The day of the week just comes out of their minds; they don’t even think about it. They can do this for so many dates, and they’re 99 percent accurate. It never gets old.”

The study also found statistically significant evidence of obsessive-compulsive tendencies among the group, but the authors do not yet know if or how this aids recollection. Many of the individuals have large, minutely catalogued collections of some sort, such as magazines, videos, shoes, stamps or postcards.

UCI researchers and staff have assessed more than 500 people who thought they might possess highly superior autobiographical memory and have confirmed 33 to date, including the 11 in the paper. Another 37 are strong candidates who will be further tested.

“The next step is that we want to understand the mechanisms behind the memory,” LePort said. “Is it just the brain and the way its different structures are communicating? Maybe it’s genetic; maybe it’s molecular.”

McGaugh added: “We’re Sherlock Holmeses here. We’re searching for clues in a very new area of research.”



Journal Reference:

  1. Aurora K.R. LePort, Aaron T. Mattfeld, Heather Dickinson-Anson, James H. Fallon, Craig E.L. Stark, Frithjof Kruggel, Larry Cahill, James L. McGaugh. Behavioral and neuroanatomical investigation of Highly Superior Autobiographical Memory (HSAM). Neurobiology of Learning and Memory, 2012; 98 (1): 78 DOI: 10.1016/j.nlm.2012.05.002


University of California – Irvine (2012, July 30). Brains are different in people with highly superior autobiographical memory. ScienceDaily. Retrieved August 1, 2012, from­ /releases/2012/07/120730170341.htm

When Rules Change, Brain Falters

ScienceDaily (July 30, 2012) — For the human brain, learning a new task when rules change can be a surprisingly difficult process marred by repeated mistakes, according to a new study by Michigan State University psychology researchers.

A cap worn by subjects in a Michigan State University experiment picks up EEG signals at the scalp; the signals are then transmitted via optical cable to a computer where the data is stored for analysis. (Credit: Photo by G.L. Kohuth)

Imagine traveling to Ireland and suddenly having to drive on the left side of the road. The brain, trained for right-side driving, becomes overburdened trying to suppress the old rules while simultaneously focusing on the new rules, said Hans Schroder, primary researcher on the study.

“There’s so much conflict in your brain,” said Schroder, “that when you make a mistake like forgetting to turn on your blinker you don’t even realize it and make the same mistake again. What you learned initially is hard to overcome when rules change.”

The study, in the research journal Cognitive, Affective & Behavioral Neuroscience, is one of the first to show how the brain responds to mistakes that occur after rules change.

Study participants were given a computer task that involved recognizing the middle letter in strings such as “NNMNN” or “MMNMM.” If “M” was in the middle, they were to press the left button; if “N” was in the middle, they were to press the right. After 50 trials, the rules were reversed so the participants had to press the right button if “M” was in the middle and the left if “N” was in the middle.

Participants made more repeated errors when the rules were reversed, meaning they weren’t learning from their mistakes. In addition, a cap measuring brain activity showed they were less aware of their errors. When participants did respond correctly after the rules changed, their brain activity showed they had to work harder than when they were given the first set of rules.

“We expected they were going to get better at the task over time,” said Schroder, a graduate student in MSU’s Department of Psychology. “But after the rules changed they were slower and less accurate throughout the task and couldn’t seem to get the hang of it.”

Continually making these mistakes in the work environment can lead to frustration, exhaustion and even anxiety and depression, said Jason Moser, assistant professor of psychology and director of MSU’s Clinical Psychophysiology Lab.

“These findings and our past research suggest that when you have multiple things to juggle in your mind — essentially, when you are multitasking — you are more likely to mess up,” Moser said. “It takes effort and practice for you to be more aware of the mistakes you are missing and stay focused.”

In addition to Schroder and Moser, co-researchers include Erik Altmann, associate professor of psychology, and master’s student Tim Moran.



Journal Reference:

  1. Hans S. Schroder, Tim P. Moran, Jason S. Moser, Erik M. Altmann. When the rules are reversed: Action-monitoring consequences of reversing stimulus–response mappings. Cognitive, Affective, & Behavioral Neuroscience, 2012; DOI: 10.3758/s13415-012-0105-y


Michigan State University (2012, July 30). When rules change, brain falters. ScienceDaily. Retrieved August 1, 2012, from­ /releases/2012/07/120730124239.htm

Mindreading Hormone? A Better Judge of Character With Nasal Spray?

ScienceDaily (July 30, 2012) — Ingesting the hormone oxytocin via nasal spray improves the ability to read people’s facial expressions. These findings hold great promise for treatment of mental health disorders and drug addiction.

An instrument was used to measure dilation of the pupils and how test subjects focused their gaze while solving tasks on a computer screen in front of them. (Credit: Olga Chelnokova)

In other contexts, oxytocin is already well-known as the “bliss hormone.” The hormone is secreted upon stimulation by touch and is known to result in a feeling of calm and physical relaxation. It is also used to induce labour in childbirth and as an aid for women experiencing difficulties in breastfeeding.

Oxytocin has also been referred to as a “mindreading” hormone. Recent research findings show that there may be some truth to these claims — although the mindreading component may have a more down-to-earth explanation.

Angry people seemed angrier

As part of a research project carried out by Siri Leknes, a research fellow at the Department of Psychology at the University of Oslo, 40 healthy students were administered nasal spray containing a dose of either saltwater or oxytocin. They were subsequently shown photographs of faces displaying angry, happy or neutral expressions. Some of the photos showed individuals displaying more “hidden” emotional expressions which tend to be picked up at a more subconscious level.

“We found that oxytocin intensified test subjects’ awareness of the emotions present in the photos. Faces expressing anger stood out as angrier and less happy, and correspondingly, faces expressing happiness were happier,” explains Dr Leknes.

“We know that people express feelings in other ways than through facial expression alone, for example, by means of body language and vocalisation. We presume that our findings also apply for these modes of expression,” she adds.

The study receives funding under the Research Council of Norway’s Alcohol and Drug Research Programme (RUSMIDDEL).

Greatest effect on those who need it the most

There were two rounds to the experiment to ensure that all student subjects were tested using both salt water and oxytocin — without letting them know which dose they would be receiving each time.

“It turns out that those with the lowest aptitude for judging emotional expression properly — that is, those with the poorest scores during the saltwater round — were the ones who showed the greatest improvement using oxytocin. This is really fascinating; the people who need it the most are thus the ones who get the most out of using the hormone,” Dr Leknes points out.

Based on previous research along with her own findings, Dr Leknes believes in oxytocin’s potential as a supplementary treatment for people suffering from mental health disorders or drug-dependency. In fact, nearly all mental health disorders involve a diminished ability to recognise the feelings of others. The same applies for drug abusers.

“Oxytocin will not be a cure-all for mental illness or drug addiction, but it may be of use as a supplementary treatment. It may make individuals better equipped to interpret the signals of others around them, which may improve how they function in social settings,” Dr Leknes explains.

Testing for treatment of drug abuse up next

Oxytocin nasal spray is available via prescription and is relatively safe when used as directed. Side effects are extremely rare. According to Dr Leknes, doctors are already allowed to prescribe oxytocin for the treatment of various problems associated with social functionality such as autism.

“In such cases, however, it’s a matter of isolated treatments which are not evaluated as a whole. It is important that we research this to gain greater insight into the effect,” she points out.

Siri Leknes and her colleagues are now hoping to take their efforts a step further and examine how well oxytocin works as a supplementary treatment for drug abusers.

“If it turns out that our assumptions are correct, then we may be able to come up with a simple treatment that would mean a great deal for people who find it difficult to pick up on the social cues of their peers,” says Dr Leknes.




The Research Council of Norway (2012, July 30). Mindreading hormone? A better judge of character with nasal spray?. ScienceDaily. Retrieved July 31, 2012, from­ /releases/2012/07/120730094909.htm

Smell the Potassium: New Understanding of Trigger for Compulsive Mating and Male-On-Male Death Matches

ScienceDaily (July 29, 2012) — The vomeronasal organ (VNO) is one of evolution’s most direct enforcers. From its niche within the nose in most land-based vertebrates, it detects pheromones and triggers corresponding basic-instinct behaviors, from compulsive mating to male-on-male death matches. A new study from the Stowers Institute for Medical Research, published online in Nature Neuroscience on July 29, 2012, extends the scientific understanding of how pheromones activate the VNO, and has implications for sensory transduction experiments in other fields.

“We found two new ion channels — both of them potassium channels — through which VNO neurons are activated in mice,” says Associate Investigator C. Ron Yu, Ph.D., senior author of the study. “This is quite unusual; potassium channels normally don’t play a direct role in the activation of sensory neurons.”

Humans have shrunken, seemingly vestigial VNOs, but still exhibit instinctive, pre-programmed behaviors relating to reproduction and aggression. Scientists hope that an understanding of how the VNO works in mice and other lower mammals will provide clues to how these innate behaviors are triggered in humans.

The VNO works in much the same way as the main olfactory organ that provides the sense of smell. Its neurons and their input stalks, known as dendrites, are studded with specialized receptors that can be activated by contact with specific messenger-chemicals called pheromones, found mostly in body fluids. When activated, VNO receptors cause adjacent ion channels to open or close allowing ions to flood into or out of a neuron. These inflows and outflows of electric charge create voltage surges that can activate a VNO neuron, so that it signals to the brain to turn on a specific behavior.

In 2002, as a postdoctoral researcher at Columbia University, Yu was a member of one of the first teams to find that VNO receptors rely heavily on a calcium channel called TRPC2. But there were hints that VNO neurons use other ion channels too; and in a study reported last November in Nature Communications, Yu’s team at Stowers, including first author SangSeong Kim, Ph.D., a postdoctoral researcher, found evidence for the role of a chloride-specific channel, CACC.

In the new study, Yu, Kim and their colleagues looked for VNO potassium channels, which admit positively charged potassium ions. They began by setting up whole-cell patch clamp tests, in which tiny electrodes measure the net flow of charged ions through the membranes of neurons in a slice of mouse VNO tissue. To determine the contribution of potassium ions to these currents, they replaced the potassium ions in the neurons with chemically similar cesium ions, which cannot get through potassium channels. When these potassium-depleted VNO neurons were exposed to pheromone-containing mouse urine, the usual net inward flow of positive charge was significantly greater than it had been when the neurons contained potassium.

That and other experiments with the VNO tissue slices suggested that potassium ions normally flow out of VNO neurons through potassium channels when a VNO receptor is activated. This was not completely unexpected; neurons typically have a greater concentration of potassium ions inside than outside, leading to an outward flow when potassium channels are opened. The outward flow originates mostly from the main bodies of neurons and helps reset neurons to a resting state voltage. However, in the VNO neurons a strong outward flow of potassium also occurred within the dendrites, directly countering the inward flow of positive ions that would activate the neurons. “It seemed a bit bizarre that such an important system would work against itself in this way,” Yu says.

The team was able to zero in on the two potassium channels responsible, which are known as SK3 and GIRK. But when they set up experiments to evaluate these channels not in VNO tissue slices but “in vivo” — in the working VNOs of live mice — they found a very different result: On balance the potassium channels now sent potassium ions in the inward direction. In fact, these two newly discovered channels seemed to account for more than half of the VNO-activating current.

This inflowing-potassium phenomenon is known to occur in another type of sensory neuron, the sound-sensitive cochlear hair cell, whose external environment contains relatively high levels of potassium. “This made us wonder whether the VNO also has a high level of potassium in the fluid surrounding its dendrites,” says Kim.

It does. It turns out that the standard preparation of tissue slices for the initial patch-clamp experiments had washed away that naturally high concentration. The resulting low concentration had misleadingly caused potassium ions to be sucked out of VNO neuron dendrites when the SK3 and GIRK potassium channels were opened. “It’s a cautionary tale that shows the importance of doing in vivo experiments,” Yu says.

The finding that potassium channels contribute to the primary activation of the VNO could be a clue to the origins of the organ. “We speculate that the VNO may have evolved to have a high extracellular concentration of ions, as well as multiple ion channels, so that it remains functional even when it comes into contact with various ion-rich bodily fluids,” Yu says. “The diversity of signaling pathways perhaps make it more robust in triggering innate behaviors.”

Other researchers who contributed to the research include Limei Ma, Ph.D. and Kristi L. Jensen, of Yu’s laboratory at the Stowers Institute; Michelle M. Kim, Ph.D., of Columbia University; and Chris T. Bond, Ph.D., and John P. Adelman, Ph.D., of Oregon Health & Science University.

The study was supported by funding from the Stowers Institute and the National Institute on Deafness and Other Communication Disorders, which is part of the National Institutes of Health.


Journal Reference:

  1. SangSeong Kim, Limei Ma, Kristi L Jensen, Michelle M Kim, Chris T Bond, John P Adelman, C Ron Yu. Paradoxical contribution of SK3 and GIRK channels to the activation of mouse vomeronasal organ. Nature Neuroscience, 2012; DOI: 10.1038/nn.3173


Stowers Institute for Medical Research (2012, July 29). Smell the Potassium: New understanding of trigger for compulsive mating and male-on-male death matches. ScienceDaily. Retrieved July 30, 2012, from­ /releases/2012/07/120729142133.htm

The Longer You’re Awake, the Slower You Get

ScienceDaily (July 27, 2012) — Anyone that has ever had trouble sleeping can attest to the difficulties at work the following day. Experts recommend eight hours of sleep per night for ideal health and productivity, but what if five to six hours of sleep is your norm? Is your work still negatively affected? A team of researchers at Brigham and Women’s Hospital (BWH) have discovered that regardless of how tired you perceive yourself to be, that lack of sleep can influence the way you perform certain tasks.


This finding is published in the July 26, 2012 online edition of The Journal of Vision.

“Our team decided to look at how sleep might affect complex visual search tasks, because they are common in safety-sensitive activities, such as air-traffic control, baggage screening, and monitoring power plant operations,” explained Jeanne F. Duffy, PhD, MBA, senior author on this study and associate neuroscientist at BWH. “These types of jobs involve processes that require repeated, quick memory encoding and retrieval of visual information, in combination with decision making about the information.”

Researchers collected and analyzed data from visual search tasks from 12 participants over a one month study. In the first week, all participants were scheduled to sleep 10-12 hours per night to make sure they were well-rested. For the following three weeks, the participants were scheduled to sleep the equivalent of 5.6 hours per night, and also had their sleep times scheduled on a 28-hour cycle, mirroring chronic jet lag. The research team gave the participants computer tests that involved visual search tasks and recorded how quickly the participants could find important information, and also how accurate they were in identifying it. The researchers report that the longer the participants were awake, the more slowly they identified the important information in the test. Additionally, during the biological night time, 12 a.m. -6 a.m., participants (who were unaware of the time throughout the study) also performed the tasks more slowly than they did during the daytime.

“This research provides valuable information for workers, and their employers, who perform these types of visual search tasks during the night shift, because they will do it much more slowly than when they are working during the day,” said Duffy. “The longer someone is awake, the more the ability to perform a task, in this case a visual search, is hindered, and this impact of being awake is even stronger at night.”

While the accuracy of the participants stayed the fairly constant, they were slower to identify the relevant information as the weeks went on. The self-ratings of sleepiness only got slightly worse during the second and third weeks on the study schedule, yet the data show that they were performing the visual search tasks significantly slower than in the first week. This finding suggests that someone’s perceptions of how tired they are do not always match their performance ability, explains Duffy.

This research was supported by NIH grant P01 AG09975 and was conducted in the BWH CCI, part of the Harvard Catalyst Clinical and Translational Science Center (UL1 RR025758-01), formerly a GCRC (M01RR02635). Development and implementation of the visual search task was supported in part by NIH grant R21 AT002571. JFD was supported in part by the BWHBRI Fund to Sustain Research Excellence; MM was supported by fellowships from the La-Roche and Novartis Foundations (Switzerland) and Jazz Pharmaceuticals (USA); SWC was supported in part by a fellowship from the Natural Sciences and Engineering Research Council of Canada.



Journal Reference:

  1. Marc Pomplun,    Edward J. Silva,    Joseph M. Ronda,    Sean W. Cain,    Mirjam Y. Münch,    Charles A. Czeisler,    and Jeanne F. Duffy. The effects of circadian phase, time awake, and imposed sleep restriction on performing complex visual tasks: Evidence from comparative visual search. The Journal of Vision, July 26, 2012 DOI: 10.1167/12.7.14


Brigham and Women’s Hospital (2012, July 27). The longer you’re awake, the slower you get. ScienceDaily. Retrieved July 29, 2012, from­ /releases/2012/07/120727111317.htm

Lucid Dreamers Help Scientists Locate the Seat of Meta-Consciousness in the Brain

ScienceDaily (July 27, 2012) — Studies of lucid dreamers show which centers of the brain become active when we become aware of ourselves in dreams.

Which areas of the brain help us to perceive our world in a self-reflective manner is difficult to measure. During wakefulness, we are always conscious of ourselves. In sleep, however, we are not. But there are people, known as lucid dreamers, who can become aware of dreaming during sleep. Studies employing magnetic resonance tomography (MRT) have now been able to demonstrate that a specific cortical network consisting of the right dorsolateral prefrontal cortex, the frontopolar regions and the precuneus is activated when this lucid consciousness is attained. All of these regions are associated with self-reflective functions. This research into lucid dreaming gives the authors of the latest study insight into the neural basis of human consciousness.

The human capacity of self-perception, self-reflection and consciousness development are among the unsolved mysteries of neuroscience. Despite modern imaging techniques, it is still impossible to fully visualize what goes on in the brain when people move to consciousness from an unconscious state. The problem lies in the fact that it is difficult to watch our brain during this transitional change. Although this process is the same, every time a person awakens from sleep, the basic activity of our brain is usually greatly reduced during deep sleep. This makes it impossible to clearly delineate the specific brain activity underlying the regained self-perception and consciousness during the transition to wakefulness from the global changes in brain activity that takes place at the same time.

Scientists from the Max Planck Institutes of Psychiatry in Munich and for Human Cognitive and Brain Sciences in Leipzig and from Charité in Berlin have now studied people who are aware that they are dreaming while being in a dream state, and are also able to deliberately control their dreams. Those so-called lucid dreamers have access to their memories during lucid dreaming, can perform actions and are aware of themselves – although remaining unmistakably in a dream state and not waking up. As author Martin Dresler explains, “In a normal dream, we have a very basal consciousness, we experience perceptions and emotions but we are not aware that we are only dreaming. It’s only in a lucid dream that the dreamer gets a meta-insight into his or her state.”

By comparing the activity of the brain during one of these lucid periods with the activity measured immediately before in a normal dream, the scientists were able to identify the characteristic brain activities of lucid awareness.

“The general basic activity of the brain is similar in a normal dream and in a lucid dream,” says Michael Czisch, head of a research group at the Max Planck Institute of Psychiatry. “In a lucid state, however, the activity in certain areas of the cerebral cortex increases markedly within seconds. The involved areas of the cerebral cortex are the right dorsolateral prefrontal cortex, to which commonly the function of self-assessment is attributed, and the frontopolar regions, which are responsible for evaluating our own thoughts and feelings. The precuneus is also especially active, a part of the brain that has long been linked with self-perception.” The findings confirm earlier studies and have made the neural networks of a conscious mental state visible for the first time.



Journal Reference:

  1. Martin Dresler, Renate Wehrle, Victor I. Spoormaker, Stefan P. Koch, Florian Holsboer, Axel Steiger, Hellmuth Obrig, Philipp G. Sämann, Michael Czisch. Neural Correlates of Dream Lucidity Obtained from Contrasting Lucid versus Non-Lucid REM Sleep: A Combined EEG/fMRI Case Study. Sleep, 2012;35(7):1017-1020


Max-Planck-Gesellschaft (2012, July 27). Lucid dreamers help scientists locate the seat of meta-consciousness in the brain. ScienceDaily. Retrieved July 29, 2012, from­ /releases/2012/07/120727095555.htm



Do Ovaries Continue to Produce Eggs During Adulthood?

ScienceDaily (July 26, 2012) — A compelling new genetic study tracing the origins of immature egg cells, or ‘oocytes’, from the embryonic period throughout adulthood adds new information to a growing controversy. The notion of a “biological clock” in women arises from the fact that oocytes progressively decline in number as females get older, along with a decades-old dogmatic view that oocytes cannot be renewed in mammals after birth.


After careful assessment of data from a recent study published in PLoS Genetics, scientists from Massachusetts General Hospital and the University of Edinburgh argue that the findings support formation of new eggs during adult life; a topic that has been historically controversial and has sparked considerable debate in recent years.

Eggs are formed from progenitor germ cells that exit the mitotic cycle, thereby ending their ability to proliferate through cell division, and subsequently enter meiosis, a process unique to the formation of eggs and sperm which removes one half of the genetic material from each type of cell prior to fertilization.

While traditional thinking has held that female mammals are born with all of the eggs they will ever have, newer research has demonstrated that adult mouse and human ovaries contain a rare population of progenitor germ cells called oogonial stem cells capable of dividing and generating new oocytes. Using a powerful new genetic tool that traces the number of divisions a cell has undergone with age (its ‘depth’) Shapiro and colleagues counted the number of times progenitor germ cells divided before becoming oocytes; their study was published in PLoS Genetics in February this year.

If traditional thinking held true, all divisions would have occurred prior to birth, and thus all oocytes would exhibit the same depth regardless of age. However, the opposite was found — eggs showed a progressive increase in depth as the female mice grew older.

In their assessment of the work by Shapiro and colleagues — published recently in a PLoS Genetics Perspective article — reproductive biologists Dori Woods, Evelyn Telfer and Jonathan Tilly conclude that the most plausible explanation for these findings is that progenitor germ cells in ovaries continue to divide throughout reproductive life, resulting in production of new oocytes with greater depth as animals age.

Although these investigations were performed in mice, there is emerging evidence that oogonial stem cells are also present in the ovaries of reproductive-age women, and these cells possess the capacity, like their mouse counterparts, to generate new oocytes under certain experimental conditions. While more work is needed to settle the debate over the significance of oocyte renewal in adult mammals, Woods and colleagues emphasize that “the recent work of Shapiro and colleagues is one of the first reports to offer experimental data consistent with a role for postnatal oocyte renewal in contributing to the reserve of ovarian follicles available for use in adult females as they age.”


Journal Reference:

  1. Woods DC, Telfer EE, Tilly JL. Oocyte Family Trees: Old Branches or New Stems? PLOS Genet, 2012 DOI: 10.1371/journal.pgen.1002848


Public Library of Science (2012, July 26). Do ovaries continue to produce eggs during adulthood?. ScienceDaily. Retrieved July 28, 2012, from­ /releases/2012/07/120726180259.htm

One Act of Remembering Can Influence Future Acts

ScienceDaily (July 26, 2012) — Can the simple act of recognizing a face as you walk down the street change the way we think? Or can taking the time to notice something new on our way to work change what we remember about that walk? In a new study published in the journal Science, New York University researchers show that remembering something old or noticing something new can bias how you process subsequent information.

This novel finding suggests that our memory system can adaptively bias its processing towards forming new memories or retrieving old ones based on recent experiences. For example, when you walk into a restaurant or for the first time, your memory system can both encode the details of this new environment as well as allow you to remember a similar one where you recently dined with a friend. The results of this study suggest that what you did right before walking into the restaurant can determine which process is more likely to occur.

Previous scholarship has demonstrated that both encoding new memories and retrieving old ones depend on the same specific brain region — the hippocampus. However, computational models suggest that encoding and retrieval occur under incompatible network processes. In other words, how can the same part of the brain perform two tasks that are at odds with each other?

At the heart of this paradox is distinction between encoding, or forming a new memory, and memory retrieval, or recalling old information. Specifically, encoding is thought to rely on pattern separation, a process that makes overlapping, or similar, representations more distinct, whereas retrieval is thought to depend on pattern completion, a process that increases overlap by reactivating related memory traces.

With this in mind, the researchers saw a potential resolution to this neurological paradox — that the hippocampus can be biased towards either pattern completion or pattern separation, depending on the current context?

To address this question, the researchers conducted an experiment in which participants rapidly switched between encoding novel objects and retrieving recently presented ones. The researchers hypothesized that processing the novel objects would bias participants’ memory systems towards pattern separation while processing the old ones would evoke pattern completion biases.

Specifically, they were shown a series of objects that fell into three categories: novel objects (i.e., an initial presentation of an image, such as an apple or a face), repeated objects, or objects that were similar but not identical to previously presented ones (e.g., an apple with slightly different shape from the initial image). Participants were then asked to identify each as new (first presentation), old (exact repetition), or similar (not exact repetition). The similar items were the critical study items since they contained a little old and little new information. Thus, participants could either notice the novel details or incorrectly identify these stimuli as old.

The researchers found that participants’ ability to notice the new details and correctly label those stimuli as ‘similar’ depended on what they did on the previous trial. Specifically, if they encountered a new stimulus on the preceding trial, participants were more likely to notice the similar trials were similar, but not old, items.

By contrast, in another experiment, the researchers demonstrated that the same manipulation can also influence how we form new memories. In this study, the researchers tested how well participants were able to form links between overlapping memories. They found that participants were more likely to construct these links when the overlapping memories were formed immediately after retrieving an unrelated old object as compared to identifying a new one. This suggests that after processing old objects, participants were more likely to retrieve the associated memories and link them to an ongoing experience.

“We’ve all had the experience of seeing an unexpected familiar face as we walk down the street and much work has been done to understand how it is that we can come to recognize these unexpected events,” said Lila Davachi, an associate professor in NYU’s Department of Psychology and the study’s senior author. “However, what has never been appreciated is that simply seeing that face can have a substantial impact on your future state of mind and can allow you, for example, to notice the new café that just opened on the corner or the new flowers in the garden down the street.”

“We spend most of our time surrounded by familiar people, places, and objects, each of which has the potential to cue memories,” added Katherine Duncan, the study’s first author who was an NYU doctoral student at the time of the study and is now a postdoctoral researcher at Columbia University. “So why does the same building sometimes trigger nostalgic reflection but other times can be passed without notice? Our findings suggest that one factor maybe whether your memory system has recently retrieved other, even unrelated, memories or if it was engaged in laying down new ones.”

Co-author Arhanti Sadanand assisted with the research as an NYU undergraduate. She begins medical school at Virginia Commonwealth University this fall.


Journal Reference:

  1. K. Duncan, A. Sadanand, L. Davachi. Memory’s Penumbra: Episodic Memory Decisions Induce Lingering Mnemonic Biases. Science, 2012; 337 (6093): 485 DOI: 10.1126/science.1221936


New York University (2012, July 26). One act of remembering can influence future acts. ScienceDaily. Retrieved July 28, 2012, from­ /releases/2012/07/120726142045.htm

Biological Mechanism for Growing Massive Animal Weapons, Ornaments Discovered

ScienceDaily (July 26, 2012) — In the animal kingdom, huge weapons such as elk antlers or ornaments like peacock feathers are sexy. Their extreme size attracts potential mates and warns away lesser rivals.


Now researchers led by scientists at the University of Montana and Washington State University have discovered a developmental mechanism they think may be responsible for the excessive growth of threatening horns or come-hither tail feathers. Published in the July 26 online edition of Science, the research reveals a mechanism to explain both the size of these traits, and the incredible variation among males of the same species — why some beetles, for instance, grow massive horns while their fellows grow nothing but nubbins.

“Our research explains how these enormous traits get to be so enormous,” said Doug Emlen, a professor and evolutionary biologist in UM’s Division of Biological Sciences. “People have known for 100 years that the best males produce the biggest structures, but nobody has really understood how. Our work looks under the hood to explain why so many sexually selected structures get so massive.”

The researchers discovered when they disturbed the insulin-signaling pathway in Japanese rhinoceros beetles — big insects that can grow horns two-thirds the length of their bodies — the horns were far less likely to grow. In fact, horn growth was stunted eight times as much as growth of the wings, or the rest of the body. They interpret this to mean that the exaggerated structures — the horns — are more sensitive to signaling through this physiological pathway than are other traits.

“If you have a lot of food, you have a lot of insulin,” said Laura Corley Lavine, a Washington State University entomologist and co-principle investigator with Emlen. “You respond to that by making a really giant, exaggerated horn. Then the female can tell she wants to mate with you because you are truthfully advertising your condition.”

The researchers injected a cocktail of double-stranded RNA into the beetle larvae to shut down the desired insulin pathway gene. Within 72 hours normal insulin signaling had resumed, but by then horn growth was stunted. Genitalia grew normally despite the shutdown, and the wings and bodies were slightly affected. The horns, however, experienced major changes.

The experiment confirmed what the researchers thought the insulin pathway was doing to the beetles. “We’re the first ones to make the link by explicitly tying the insulin pathway to the evolution of these kinds of male weapons,” Lavine said. “The discovery of the actual mechanism might now open new avenues of study for how exaggerated traits evolved, their genetic basis and the evolution of animal signals.”

“There is a hormone signal secreted by the brain that circulates through the whole animal,” Emlen said. “It communicates to the different cells and tissues and essentially tells them how much to grow.” Hormone levels reflect the physiological condition of each animal, with high circulating levels in well-fed, dominant individuals and lower levels in poorly fed or less-fit individuals. When tissues are sensitive to these signals, as most tissues are, their final sizes scale with the overall quality and size of the animal. Because of this mechanism, big beetles have larger eyes, legs and wings than smaller beetles.

Emlen said the horns are exquisitely sensitive to these insulin signals — more sensitive than other structures. Developing horns in big, fit, well-fed males are drenched with the hormone, spurring exaggerated horn growth. On the flip side, a small, less-fit male receive less of the horn-boosting hormone, stunting growth of its weapon.

Emlen said this process explains how horns can range from massive to nonexistent among male beetles of the same species and why the size of such exaggerated, showy traits accurately reflects the overall quality of the males who wield them. He said the results likely are applicable to other species beyond rhinoceros beetles, since additional studies have tied this same physiological pathway to growth of red deer antlers and crab pincer claws.

“Horns and antlers matter,” Emlen said. “Animals pay attention to them when they size each other up for battle. And females pay attention to horns or are attracted to males with really big tails. Why? Because only the best of the best can have really big horns or tails.”



Journal Reference:

  1. Douglas J. Emlen,    Ian A. Warren,    Annika Johns,    Ian Dworkin,    and Laura Corley Lavine. A Mechanism of Extreme Growth and Reliable Signaling in Sexually Selected Ornaments and Weapons. Science, 26 July 2012 DOI: 10.1126/science.1224286


Washington State University (2012, July 26). Biological mechanism for growing massive animal weapons, ornaments discovered. ScienceDaily. Retrieved July 28, 2012, from­ /releases/2012/07/120726142202.htm

Connectomics: Mapping the Neural Network Governing Male Roundworm Mating

ScienceDaily (July 26, 2012) — In a study published July 26 online in Science, researchers at Albert Einstein College of Medicine of Yeshiva University have determined the complete wiring diagram for the part of the nervous system controlling mating in the male roundworm Caenorhabditis elegans, an animal model intensively studied by scientists worldwide.


The study represents a major contribution to the new field of connectomics — the effort to map the myriad neural connections in a brain, brain region or nervous system to find the specific nerve connections responsible for particular behaviors. A long-term goal of connectomics is to map the human “connectome” — all the nerve connections within the human brain.

Because C. elegans is such a tiny animal- adults are one millimeter long and consist of just 959 cells — its simple nervous system totaling 302 neurons make it one of the best animal models for understanding the millions-of-times-more-complex human brain.

The Einstein scientists solved the structure of the male worm’s neural mating circuits by developing software that they used to analyze serial electron micrographs that other scientists had taken of the region. They found that male mating requires 144 neurons — nearly half the worm’s total number — and their paper describes the connections between those 144 neurons and 64 muscles involving some 8,000 synapses. A synapse is the junction at which one neuron (nerve cell) passes an electrical or chemical signal to another neuron.

“Establishing the complete structure of the synaptic network governing mating behavior in the male roundworm has been highly revealing,” said Scott Emmons, Ph.D., senior author of the paper and professor in the department of genetics and in the Dominick P. Purpura Department of Neuroscience at Einstein. “We can see that the structure of this network has spatial characteristics that help explain how it exerts neural control over the multi-step decision-making process involved in mating.”

In addition to determining how the neurons and muscles are connected, Dr. Emmons and his colleagues for the first time accurately measured the weights of those connections, i.e., an estimate of the strength with which one neuron or muscle communicates with another.

The research was supported by the Medical Research Council (U.K.); the National Institute of Mental Health (R21MH63223) and the Office of Behavioral and Social Sciences Research (OD010943), both of the National Institutes of Health; and the G. Harold and Leila Y. Mathers Charitable Foundation.


Journal Reference:

  1. T. A. Jarrell, Y. Wang, A. E. Bloniarz, C. A. Brittin, M. Xu, J. N. Thomson, D. G. Albertson, D. H. Hall, S. W. Emmons. The Connectome of a Decision-Making Neural Network. Science, 2012; 337 (6093): 437 DOI: 10.1126/science.1221762


Albert Einstein College of Medicine of Yeshiva University (2012, July 26). Connectomics: Mapping the neural network governing male roundworm mating. ScienceDaily. Retrieved July 28, 2012, from­ /releases/2012/07/120726142043.htm