Nav: Home

Mount Sinai study reveals how learning in the present shapes future learning

April 06, 2017

Neurons in the prefrontal cortex "teach" neurons in the hippocampus to "learn" rules that distinguish memory-based predictions in otherwise identical situations, suggesting that learning in the present helps guide learning in the future, according to research conducted at the Icahn School of Medicine at Mount Sinai and published April 5 in the journal Neuron.

The study, led by Matthew Shapiro, PhD, Professor of Neuroscience at the Icahn School of Medicine at Mount Sinai, investigated memory flexibility and interference, the mechanisms by which the brain interprets events and anticipates their likely outcomes. The hippocampus is a temporal lobe brain structure needed for remembering recent events: for example, where you ate your last meal. The prefrontal cortex is where the brain uses context to switch flexibility between remembered rules, such as knowing to look left before crossing a street in North America but right before crossing in Britain. Without such rules, memories interfere with one another and predictions based on memory are inaccurate.

High-functioning individuals rapidly integrate memories with goals to choose their course of action. This cognitive flexibility requires interaction between the prefrontal cortex and hippocampus. Previous research indicates that interactions between these two brain regions are disrupted in many neuropsychiatric conditions, including schizophrenia, depression, and attention deficit disorder, but the mechanisms of these interactions have largely remained a mystery.

"We want to understand how our brains learn to think ahead and the mechanisms that use context to recall events, predict outcomes and inform decisions. For example, how does the brain know to answer a ringing telephone at home but not in someone else's house? " says Dr. Shapiro. "We found that 'rules' signaled by the medial prefrontal cortex 'teach' the hippocampus to distinguish goals, as rats learned to switch from one goal to another. We already knew that hippocampal cells predicted memory decisions through prospective coding, firing at different rates before rats chose different goals. We learned that inactivating the prefrontal cortex reduced prospective coding by the hippocampus. Furthermore, the more the prefrontal cortex altered hippocampal activity as rats learned one rule, the faster they switched to the next rule."

The research team tested spatial memory in rats using a plus-shaped maze in a task that depends on hippocampal function. The rats were trained to walk from the far end of a start arm (North or South) through a choice point to the end of one of two goal arms (West or East) to find hidden food. After the rat returned reliably to the rewarded spatial goal from each of the two start arms (e.g. "go East"), the opposite goal was rewarded and the animals had to learn a rule reversal (e.g. "go West"). The research team found that intact rats learned an initial goal and performed roughly three reversals each day, while rats with prefrontal cortex dysfunction learned only the initial goal; rats with hippocampal dysfunction learned none. This observation suggested that the prefrontal cortex might teach the hippocampus to differentiate goal-related memories.

To test this hypothesis, researchers placed micro-electrodes into both the prefrontal cortex and hippocampus and recorded the activity of ensembles of single neurons in both structures during learning and stable memory performance in the plus-shaped maze.

Because both brain regions were recorded simultaneously, the research team could test whether activity in one region changed before or at the same time as the other during different phases of learning and memory, as rats learned to approach one goal and switch to another.

"We found that neuronal activity was synchronized in the two structures, and that neurons in the prefrontal cortex modulated hippocampal place cell activity during learning," says Dr. Shapiro. "Prefrontal cortical and hippocampal cell activity predicted imminent choices, as though both structures were contributing to spatial memory retrieval."

They also found that the prefrontal cortex most strongly altered hippocampal place cell activity during reversals, just before a rat learned to reliably select a new goal. Moreover, the strength of the prefrontal modulation of hippocampal activity predicted how quickly the rats learned the next reversal. In other words, the more that the hippocampus "learned" what the prefrontal cortex "taught," the faster the rat learned the next rule.

Functional magnetic resonance imaging studies show how specific structures within the prefrontal cortex interact to use contextual information and modify emotional responses. These prefrontal dynamics are reduced in people suffering from depression and recover when depressive symptoms remit.

The new mechanisms uncovered by this study will likely improve our understanding of and inform new treatments for psychiatric conditions that involve hippocampal and prefrontal cortex interactions. Ongoing research is investigating whether the same mechanisms described in this study are at play between the hippocampus and other prefrontal structures.
-end-
About the Mount Sinai Health System

The Mount Sinai Health System is an integrated health system committed to providing distinguished care, conducting transformative research, and advancing biomedical education. Structured around seven member hospital campuses and a single medical school, the Health System has an extensive ambulatory network and a range of inpatient and outpatient services--from community?based facilities to tertiary and quaternary care.

The System includes approximately 6,600 primary and specialty care physicians, 12?minority?owned free?standing ambulatory surgery centers, over 45 ambulatory practices throughout the five boroughs of New York City, Westchester, and Long Island, as well as 31 affiliated community health centers. Physicians are affiliated with the Icahn School of Medicine at Mount Sinai, which is ranked among the top 20 medical schools both in National Institutes of Health funding and by U.S. News & World Report.

For more information, visit http://www.mountsinai.org, or find Mount Sinai on Facebook, Twitter and YouTube.

The Mount Sinai Hospital / Mount Sinai School of Medicine

Related Neurons Articles:

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.
Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.
How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.
A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.
Shaping the social networks of neurons
Identification of a protein complex that attracts or repels nerve cells during development.
With these neurons, extinguishing fear is its own reward
The same neurons responsible for encoding reward also form new memories to suppress fearful ones, according to new research by scientists at The Picower Institute for Learning and Memory at MIT.
How do we get so many different types of neurons in our brain?
SMU (Southern Methodist University) researchers have discovered another layer of complexity in gene expression, which could help explain how we're able to have so many billions of neurons in our brain.
These neurons affect how much you do, or don't, want to eat
University of Arizona researchers have identified a network of neurons that coordinate with other brain regions to influence eating behaviors.
Mood neurons mature during adolescence
Researchers have discovered a mysterious group of neurons in the amygdala -- a key center for emotional processing in the brain -- that stay in an immature, prenatal developmental state throughout childhood.
Connecting neurons in the brain
Leuven researchers uncover new mechanisms of brain development that determine when, where and how strongly distinct brain cells interconnect.
More Neurons News and Neurons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.