Posts tagged memory retrieval
Articles and news from the latest research reports.
Information in brain cells’ electrical activity combines memory, environment, and state of mind
The information carried by the electrical activity of neurons is a mixture of stored memories, environmental circumstances, and current state of mind, scientists have found in a study of laboratory rats. The findings, which appear in the journal PLoS Biology, offer new insights into the neurobiological processes that give rise to knowledge and memory recall.
The study was conducted by Eduard Kelemen, a former graduate student and post-doctoral associate at the State University of New York (SUNY) Downstate Medical Center, and André Fenton, a professor at New York University’s Center for Neural Science and Downstate Medical Center. Kelemen is currently a postdoctoral fellow at University of Tuebingen in Germany.
The idea that recollection is not merely a replay of our stored experiences dates back to Plato. He believed that memory retrieval was, in fact, a much more intricate process—a view commonly accepted by today’s cognitive psychologists and couched in the theory of constructive recollection. The theory posits that during memory retrieval, information across different experiences may combine during recall to form a single experience. Such a process may explain the prevalence of false memories. For example, studies have shown that people mistakenly recalled seeing a school bus in a movie if the bus was mentioned after they watched the movie.
In addition, other scholarship has shown that a subject’s mindset can also influence the retrieved information. For example, looking at a house from the perspective of a homebuyer or a burglar leads to different recollections—potential purchasers may recall the house’s leaky roof while would-be burglars may remember where the jewelry is kept.
But while the psychological contours of retrieval are well-documented, very little is known about the neural activity that underlies this process.
With this in mind, Fenton and Kelemen centered their study on the neurophysiological processes rats employ as they solve problems that require memory retrieval. To do so, they employed techniques developed during the last two decades. These involve monitoring the electrical activity of neurons in the rats’ hippocampus—the part of the brain used to encode new memories and retrieve old ones. By spotting certain types of neuronal activity, researchers have historically been able to perform what amounts to a mind reading exercise to decode what the rat is thinking and even comprehend the specifics of the rats’ memory retrieval.
In their experiments, Fenton and Kelemen tested the viability of a concept, “cross-episode retrieval”— stimulating the brain activity in a given circumstance that was also activated in a previous, distinctive experience.
“Such cross-episode expression of past activity can create opportunities for generating novel associations and new information that was never directly experienced,” the authors wrote.
To test their hypotheses, rats were placed in a stable, circular arena, then in a rotating, circular arena of the same size, followed by a return to the stable arena. In the rotating arena condition, the surface turned slowly, making it necessary for the rat to think about its location either in terms of the rotating floor or in terms of the stationary room.
Overall, the results showed district neural activity between the stable and rotating conditions. However, during the rotating task, the researchers intermittently observed “cross-episode retrieval”—that is, at times, neurons expressed patterns of electrical activity under the rotating-arena condition that were similar to those activity patterns that were used in the stable-arena condition. Notably, cross-episode retrieval occurred more frequently when the angular position of the rotating arena was about to complete a full rotation and return to the same position as in the stable condition, demonstrating that retrieval is influenced by the environment.
To show that cross-episode retrieval was influenced by current state of mind, Fenton and Kelemen took advantage of an earlier finding from their experiments: during the arena rotation, neural activity switches between signaling the rat’s location in the stationary room and the rat’s location on the rotating arena floor. Cross-episode retrieval was also more likely when neuronal activity represented the position of the rat in the stationary room than when it represented positions that rotate with the arena. This showed that retrieval is influenced by internal cognitive variables that are encoded by hippocampal discharge—i.e., a state of mind.
“These experiments demonstrate novel, key features of constructive human episodic memory in rat hippocampal discharge,” explained Fenton, “and suggest a neurobiological mechanism for how experiences of different events that are separate in time can nonetheless comingle and recombine in the mind to generate new information that can sometimes amount to valuable, creative insight and knowledge.”
(Source: nyu.edu)
Remember the telephone game where people take turns whispering a message into the ear of the next person in line? By the time the last person speaks it out loud, the message has radically changed. It’s been altered with each retelling.
Turns out your memory is a lot like the telephone game, according to a new Northwestern Medicine study.
Every time you remember an event from the past, your brain networks change in ways that can alter the later recall of the event. Thus, the next time you remember it, you might recall not the original event but what you remembered the previous time. The Northwestern study is the first to show this.
“A memory is not simply an image produced by time traveling back to the original event — it can be an image that is somewhat distorted because of the prior times you remembered it,” said Donna Bridge, a postdoctoral fellow at Northwestern University Feinberg School of Medicine and lead author of the paper on the study recently published in the Journal of Neuroscience. “Your memory of an event can grow less precise even to the point of being totally false with each retrieval.”
Better Understanding of Memory Retrieval Between Children and Adults
ScienceDaily (July 24, 2012) — Neuroscientists from Wayne State University and the Massachusetts Institute of Technology (MIT) are taking a deeper look into how the brain mechanisms for memory retrieval differ between adults and children. While the memory systems are the same in many ways, the researchers have learned that crucial functions with relevance to learning and education differ.
The team’s findings were published on July 17, 2012, in the Journal of Neuroscience.
According to lead author Noa Ofen, Ph.D., assistant professor in WSU’s Institute of Gerontology and Department of Pediatrics, cognitive ability, including the ability to learn and remember new information, dramatically changes between childhood and adulthood. This ability parallels with dramatic changes that occur in the structure and function of the brain during these periods.
In the study, “The Development of Brain Systems Associated with Successful Memory Retrieval of Scenes,” Ofen and her collaborative team tested the development of neural underpinnings of memory from childhood to young adulthood. The team of researchers exposed participants to pictures of scenes and then showed them the same scenes mixed with new ones and asked them to judge whether each picture was presented earlier. Participants made retrieval judgments while researchers collected images of their brains with magnetic resonance imaging (MRI).
Using this method, the researchers were able to see how the brain remembers. “Our results suggest that cortical regions related to attentional or strategic control show the greatest developmental changes for memory retrieval,” said Ofen.
The researchers said that older participants used the cortical regions more than younger participants when correctly retrieving past experiences.
"We were interested to see whether there are changes in the connectivity of regions in the brain that support memory retrieval," Ofen added. "We found changes in connectivity of memory-related regions. In particular, the developmental change in connectivity between regions was profound even without a developmental change in the recruitment of those regions, suggesting that functional brain connectivity is an important aspect of developmental changes in the brain."
This study marks the first time that the development of connectivity within memory systems in the brain has been tested, and the results suggest that the brain continues to rearrange connections to achieve adult-like performance during development.
Ofen and her research team plan to continue research in this area, focused on modeling brain network connectivity, and applying these methods to study abnormal brain development.
Source: Science Daily