Nav: Home

Computer model helps make sense of human memory

October 07, 2019

Brains are a mazy network of overlapping circuits -- some pathways encourage activity while others suppress it. While earlier studies focused more on excitatory circuits, inhibitory circuits are now understood to play an equally important role in brain function. Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) and the RIKEN Center for Brain Science have created an artificial network to simulate the brain, demonstrating that tinkering with inhibitory circuits leads to extended memory.

Associative memory is the ability to connect unrelated items and store them in memory -- to associate co-occurring items as a single episode. In this study, published in Physical Review Letters, the team used sequentially arranged patterns to simulate a memory, and found that a computer is able to remember patterns spanning a longer episode when the model takes inhibitory circuits into account. They go on to explain how this finding could be applied to explain our own brains.

"This simple model of processing shows us how the brain handles the pieces of information given in a serial order," explains Professor Tomoki Fukai, head of OIST's Neural Coding and Brain Computing Unit, who led the study with RIKEN collaborator Dr. Tatsuya Haga. "By modelling neurons using computers, we can begin to understand memory processing in our own minds."

Lower Your Inhibitions

Thinking about the brain in terms of physical, non-biological phenomena is now a widely accepted approach in neuroscience -- and many ideas lifted from physics have now been validated in animal studies. One such idea is understanding the brain's memory system as an attractor network, a group of connected nodes that display patterns of activity and tend towards certain states. This idea of attractor networks formed the basis of this study.

A tenet of neurobiology is that "cells that fire together wire together" -- neurons that are active at the same time become synchronized, which partly explains how our brains change over time. In their model, the team created excitatory circuits -- patterns of neurons firing together -- to replicate the brain. The model included many excitatory circuits spread across a network.

More importantly, the team inserted inhibitory circuits into the model. Different inhibitory circuits act locally on a particular circuit, or globally across the network. The circuits block unwanted signals from interfering with the excitatory circuits, which are then better able to fire and wire together. These inhibitory circuits allowed the excitatory circuits to remember a pattern representing a longer episode.

The finding matches what is currently known about the hippocampus, a brain region involved in associative memory. It is thought that a balance of excitatory and inhibitory activity is what allows new associations to form. Inhibitory activity could be regulated by a chemical called acetylcholine, which is known to play a role in memory within the hippocampus. This model is a digital representation of these processes.

A challenge to the approach, however, is the use of random sampling. The sheer number of possible outputs, or attractor states, in the network, overworks a computer's memory capacity. The team instead had to rely on a selection of outputs, rather than a systematic review of every possible combination. This allowed them to overcome a technical difficulty without jeopardizing the model's predictions.

Overall, the study allowed for overarching inferences -- inhibitory neurons have an important role in associative memory, and this maps to what we might expect in our own brains. Fukai says that biological studies will need to be completed to determine the exact validity of this computational work. Then, it will be possible to map the components of the simulation to their biological counterparts, building a more complete picture of the hippocampus and associative memory.

The team will next move beyond a simple model toward one with additional parameters that better represents the hippocampus, and look at the relative importance of local and global inhibitory circuits. The current model comprises neurons that are either off or on -- zeros and ones. A future model will include dendrites, the branches that connect neurons in a complicated mesh. This more realistic simulation will be even better placed to make conclusions about biological brains.
-end-


Okinawa Institute of Science and Technology (OIST) Graduate University

Related Neurons Articles:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.
Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.
A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.
Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.
Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.
Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.
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.
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

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at Radiolab.org/donate.