Traveling brain waves help detect hard-to-see objects
Scientists discover patterns of neural waves in the awake brain that help detect objects

Date:
October 7, 2020
Source:
Salk Institute
Summary:
A team of scientists has uncovered details of the neural mechanisms
underlying the perception of objects. They found that patterns of
neural signals, called traveling brain waves, exist in the visual
system of the awake brain and are organized to allow the brain to
perceive objects that are faint or otherwise difficult to see.



FULL STORY ========================================================================== Imagine that you're late for work and desperately searching for your
car keys.

You've looked all over the house but cannot seem to find them
anywhere. All of a sudden you realize your keys have been sitting right
in front of you the entire time. Why didn't you see them until now?

==========================================================================
Now, a team of Salk Institute scientists led by Professor John Reynolds
has uncovered details of the neural mechanisms underlying the perception
of objects. They found that patterns of neural signals, called traveling
brain waves, exist in the visual system of the awake brain and are
organized to allow the brain to perceive objects that are faint or
otherwise difficult to see. The findings were published in Nature on
October 7, 2020.

"We've discovered that faint objects are much more likely to be seen if visualizing the object is timed with the traveling brain waves. The waves actually facilitate perceptual sensitivity, so there are moments in time
when you can see things that you otherwise could not," says Reynolds,
senior author of the paper and holder of the Fiona and Sanjay Jha Chair
in Neuroscience. "It turns out that these traveling brain waves are an information-gathering process leading to the perception of an object." Scientists have studied traveling brain waves during anesthesia
but dismissed the waves as an artifact of the anesthesia. Reynolds'
team, however, wondered if these waves exist in the visual part of the
brain while awake and if they play a role in perception. They combined recordings in the visual cortex with cutting-edge computational techniques
that enabled them to detect and track traveling brain waves.

"In order to understand the neural mechanisms of perception, we needed
to develop new computational techniques to track neuronal activity in
the visual cortex moment by moment," says co-first author Lyle Muller, BrainsCAN-funded assistant professor in the Department of Applied
Mathematics and the Brain and Mind Institute at Western University in
Ontario, Canada, and previously a postdoctoral fellow in the Sejnowski
lab at Salk. "We then used these computational methods to uncover
what change was occurring in the nervous system to suddenly allow
for object recognition." The scientists recorded the activity of the
neurons from an area of the brain that contained a complete map of the
visual world. They then tracked the trajectories of the traveling brain
waves during a visual perception task. The scientists held an onscreen
target at the threshold of visibility, so that observers could only
detect the object 50 percent of the time, and recorded when the target
was spotted. Since the target was not changing, the researchers reasoned
that the observer's ability to perceive the object only half of the time
had to be due to some change in the neural signals inside the brain.

They found that the brain's ability to recognize targets was directly
related to when and where the traveling brain waves occurred in the visual system: when the traveling waves aligned with the stimulus, the observer
could detect the target more easily. These traveling brain waves, which occurred several times per second, were similar to a stadium of sports
fans successively standing up and raising their arms, then lowering them
and sitting down again. It appears that the visual system is actively
sensing the external environment, according to the team.

"There is a spontaneous level of activity in the brain that appears to
be regulated by these traveling waves," says Salk Professor Terrence
Sejnowski, an author of the paper and holder of the Francis Crick
Chair. "We think the waves are the product of the activity that
is propagating around the brain, driven by local neurons firing."
"We go about our everyday lives thinking that we are accurately seeing
the world, but, in fact, our brains are filling in details that are
difficult to see," says Zac Davis, co-first and corresponding author
of the paper and a Salk postdoctoral fellow in the Reynolds lab. "Now,
we have discovered how the brain weaves together hard-to-see information
to perceive an object." In the future, the scientists plan to examine
whether these brain waves are coordinated across different brain regions devoted to vision. The researchers theorize that the brain waves could
serve as a gate between the sensory processing and conscious perception
that emerges from the brain as a whole.


========================================================================== Story Source: Materials provided by Salk_Institute. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Zachary W. Davis, Lyle Muller, Julio Martinez-Trujillo, Terrence
Sejnowski, John H. Reynolds. Spontaneous travelling cortical
waves gate perception in behaving primates. Nature, 2020; DOI:
10.1038/s41586-020- 2802-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201007123114.htm

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