The latest research has implications for understanding sensory disorders
and building better prosthetics and robots that can fine-tune their movements based on what they touch

Date:
October 14, 2021
Source:
Salk Institute
Summary:
Researchers have discovered how neurons in a small area of the
mammalian brain help filter distracting or disruptive signals
-- specifically from the hands -- to coordinate dexterous
movements. Their results may hold lessons in how the brain filters
other sensory information as well.



FULL STORY ==========================================================================
As you read this article, touch receptors in your skin are sensing your environment. Your clothes and jewelry, the chair you're sitting on, the computer keyboard or mobile device you're using, even your fingers as they brush one another unintentionally -- each touch activates collections
of nerve cells. But, unless a stimulus is particularly unexpected or
required to help you orient your own movements, your brain ignores many
of these inputs.


==========================================================================
Now, Salk researchers have discovered how neurons in a small area of
the mammalian brain help filter distracting or disruptive signals -- specifically from the hands -- to coordinate dexterous movements. Their results, published in the journal Scienceon October 14, 2021, may hold
lessons in how the brain filters other sensory information as well.

"These findings have implications not only for gaining a better
understanding of how our nervous system interacts with the world, but
also for teaching us how to build better prosthetics and robots, and how
to more effectively repair neural circuitry after disease or injury,"
says Eiman Azim, assistant professor in Salk's Molecular Neurobiology Laboratory and the William Scandling Developmental Chair.

Scientists have long known that input from the hands is needed to
coordinate dexterous movements, from throwing a ball to playing a musical instrument. In one classic experiment, volunteers with anesthetized,
numb fingertips found it extremely difficult to pick up and light a match.

"There's a common misconception that the brain sends a signal and you
just perform the resulting movement," says Azim. "But in reality, the
brain is constantly incorporating feedback information about the state
of your limbs and fingers and adjusting its output in response." If the
brain responded to every signal from the body, it would quickly become overwhelmed -- as happens with some sensory processing disorders. Azim and
his colleagues wanted to identify exactly how a healthy brain manages to
pick and choose which tactile signals to take into account to coordinate dexterous movements like manipulating objects.



==========================================================================
They used a combination of tools in mice to study cells within a
small area in the brainstem called the cuneate nucleus, which is the
first area signals from the hand enter the brain. While it was known
that sensory information passes through the cuneate nucleus, the team discovered that a set of neurons in this region actually controls how
much information from the hands eventually passes on to other parts of
the brain. By manipulating those circuits to allow more or less tactile feedback through, Azim's team could influence how mice perform dexterous
tasks -- such as pulling a rope or learning to distinguish textures -
- to earn rewards.

"The cuneate nucleus is often referred to as a relay station, as
if information was just passing through it," says Staff Researcher
James Conner, first author of the new paper. "But it turns out that
sensory information is actually being modulated in this structure."
Conner and Azim went on to show how different parts of the cortex in
mice - - the region responsible for more complex, adaptive behavior --
can in turn control the neurons of the cuneate to dictate how strongly
they're filtering sensory information from the hands.

Today, despite decades of work, most prosthetics and robots struggle to
be nimble-fingered and carry out small, precise hand movements. Azim and
Conner say their work could help inform the design of better processes to integrate sensory information from artificial fingers into these kinds
of systems to improve their dexterity. It also could have implications
for understanding sensory processing disorders or troubleshooting what
goes wrong in the brain when the flow of sensory information is thrown
out of balance.

"Sensory systems have evolved to have very high sensitivity in order to maximize protective responses to external threats. But our own actions
can activate these sensory systems, thereby generating feedback signals
that can be disruptive to our intended actions," says Conner.

"We're constantly bombarded with information from the world, and the
brain needs ways to decide what comes through and what doesn't," says
Azim. "It's not just tactile feedback, but visual and olfactory and
auditory, temperature and pain -- the lessons we're learning about this circuitry likely apply in general ways to how the brain modulates these
types of feedback as well." Other authors included Andrew Bohannon,
Masakazu Igarashi, James Taniguchi and Nicholas Baltar of Salk.

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


========================================================================== Journal Reference:
1. James M. Conner, Andrew Bohannon, Masakazu Igarashi, James
Taniguchi,
Nicholas Baltar, Eiman Azim. Modulation of tactile feedback for
the execution of dexterous movement. Science, 2021 DOI: 10.1126/
science.abh1123 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211014154131.htm

--- up 6 weeks, 8 hours, 25 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)