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Study explores neural correlates of working memory gating

Brain imaging and behavioral tests show dual activation of prefrontal cortex, striatum

In a world in which people suffer from information overload, humans need to be able to mentally sift through data and decide what is relevant. Working memory, the capacity people have to retain information over short periods of time, provides the key to sorting through the heaps of mental data.

University neuroscientists, working to better understand this process, have identified the underlying neural mechanism for choosing which memory information to act on.

The research showed that parts of the lateral prefrontal cortex and the frontostriatal circuit were implicated in selecting information from working memory in a study published in the journal Neuron this month.

When people are attending to information, they are presented with a “double-edged problem where you want to be able to selectively attend to information, and you want to hang onto that information over time,” said Christopher Chatham, a postdoctoral scholar and the paper’s lead author.

Working memory, which helps to resolve this problem, can be understood with two complementary functional models, input and output gating, Chatham said.

Input gating allows a person to decide what is allowed into memory in the first place. Then, output gating allows the person to choose which bits of this information are relevant in a given moment of time and should be used to drive action.

“We live in a world full of potential distractions, so input and output gating helps us filter through those,” Chatham said.

The experiment focused on output gating, using behavioral and functional brain imaging versions of a task that tested participants’ ability to attend to multiple pieces of information. The participants were presented with a letter, digit or symbol and periodically asked to answer questions about what they had seen. In some trials they were told which object to attend to beforehand, and in others they were not, representing the functions of input and output gating respectively, said David Badre, an assistant professor of cognitive, linguistic and psychological sciences and the paper’s senior author.

The  imaging data suggests that two separate areas of the brain — the prefrontal cortex and the striatum — are activated together to allow a person to recall answers and respond correctly, a function of output gating. The same neural circuit fires when selecting a motor response, Badre said.

The study provides insight into a quickly growing domain of neuroscience, Justin Baker '97, instructor in psychiatry at Harvard Medical School, wrote in an email to The Herald.

“The authors are exploring the principles governing the organization of the prefrontal cortex and how it exerts control over how other brain systems process signals, which is one of the great unanswered problems in human neurobiology,” Baker wrote.

This research could also benefit the treatment of diseases, as it studies the “site of impairments found in debilitating disorders affecting cognition like schizophrenia and bipolar disorder,” Baker added.

Working memory is crucial to understanding humans’ cognitive functioning, because it supports lots of higher mental functions, such as planning, decision making and intelligence, Badre said. A person with deficient working memory will especially struggle to complete goal-directed tasks, he added.

“There’s something about (working memory capacity) that is critically predictive of intellectual abilities,” Chatham said.

This study is part of ongoing research on working memory, Chatham said, adding that the team next plans to investigate the “causal factors” in working memory.


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