How does the brain keep track of things moving around us? A new piece of
the puzzle
Findings resolve long-standing questions about brain function, opening up
new avenues of research into memory disorders

Date:
February 22, 2022
Source:
University of California - Los Angeles Health Sciences
Summary:
A new study has found that hippocampal neurons in rats accurately
map the position of a moving object even while the rat is
stationary. The results challenge the idea that the hippocampus,
a region of the brain involved in learning and memory, only encodes
a map of space based on movement.



FULL STORY ========================================================================== Understanding how the brain creates a map of the space around us has implications for research into learning and memory disorders ranging from autism to Alzheimer's disease, where subjects often have an incorrect perception of space-time and events. Previously, it was thought that
only neurons in the visual cortex were able to map the position of moving objects, and that the hippocampus, the memory-making part of the brain, required spatial exploration or a cognitive task in order to contribute.


==========================================================================
A new UCLA study has found that hippocampal neurons in rats accurately
map the position of a moving object even while the rat is stationary. The results challenge the idea that the hippocampus, a region of the brain
involved in learning and memory, only encodes a map of space based
on movement.

Panel a) shows the rat seated in the midst of augmented reality setup with
a green bar of light moving around him. Panel b) shows the top down view
of the maze. Panel c) shows the activity of four different neurons as a function of the position of the bar. Neurons encode the angular position
of the bar of light even when the rat is not moving, thus challenging
the prevailing hypothesis that the hippocampus requires exploration to
create an abstract map of space. (Graphic courtesy of Dr. Mayank Mehta).

These new findings resolve long-standing puzzles about hippocampal
function and open up many new avenues to develop early diagnosis and
treatment for memory disorders, says Mayank R. Mehta, PhD, head of
the W. M. Keck Center for Neurophysics at UCLA and a professor in the departments of physics, neurology, and electrical and computer engineering
at UCLA.

"For example," he said, "it allows scientists to study cognitive deficits
such as a subject's memory of events around them -- the most common
deficit in Alzheimer's." The study, published in Nature, was conducted
by scientists from the W. M. Keck Center for Neurophysics at UCLA,
including lead authors Chinmay Purandare, PhD, and Shonali Dhingra, PhD.

A VR experiment Using a modified virtual reality maze for rats developed
to probe the hippocampus's memory function, researchers created a
single bar of light on the VR screen that moved all around the rat --
"as if a person was walking around you while you're seated," Dr. Mehta explained. Previous studies had found that such simple stimuli did not
trigger the hippocampus. UCLA researchers, hypothesizing that the reason
for that was the size of the stimuli, made the size of the bar large
from the rat's perspective.

By measuring neural signals, they found a majority of neurons in the rat's hippocampus responded to the bar of light, logging its exact position,
the direction in which it was moving, and even its distance and angular
degree from the rat. The neurons also encoded identifying characteristics
of the bar of light, such as its color and texture.

The results overturn the idea that the hippocampus requires movement in
space to create a spatial map. The neural response "is quite similar
to activity patterns in the visual cortices," Dr. Mehta said. "That
makes sense since the visual cortex is a major source of input to
the hippocampus." The team plans to continue using the VR system for experiments into understanding the neural activity of patients, including
those with memory deficits such as Alzheimer's disease.

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dreams in this free online course from New Scientist -- Sign_up_now_>>> ========================================================================== Story Source: Materials provided by University_of_California_-_Los_Angeles_Health_Sciences.

Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Photo_of_a_rat_and_charts_of_data ========================================================================== Journal Reference:
1. Chinmay S. Purandare, Shonali Dhingra, Rodrigo Rios, Cliff Vuong,
Thuc
To, Ayaka Hachisuka, Krishna Choudhary, Mayank R. Mehta. Moving
bar of light evokes vectorial spatial selectivity in the
immobile rat hippocampus. Nature, 2022; 602 (7897): 461 DOI:
10.1038/s41586-022-04404- x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220222135328.htm

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