How a single nerve cell can multiply

Date:
February 24, 2022
Source:
Max-Planck-Gesellschaft
Summary:
Neurons are constantly performing complex calculations to process
sensory information and infer the state of the environment. For
example, to localize a sound or to recognize the direction of
visual motion, individual neurons are thought to multiply two
signals. However, how such a computation is carried out has been a
mystery for decades. Researchers have now discovered in fruit flies
the biophysical basis that enables a specific type of neuron to
multiply two incoming signals. This provides fundamental insights
into the algebra of neurons -- the computations that may underlie
countless processes in the brain.



FULL STORY ========================================================================== Neurons are constantly performing complex calculations to process
sensory information and infer the state of the environment. For example,
to localize a sound or to recognize the direction of visual motion,
individual neurons are thought to multiply two signals. However, how such
a computation is carried out has been a mystery for decades. Researchers
at the Max Planck Institute for Biological Intelligence, in foundation
(i.f.), have now discovered in fruit flies the biophysical basis that
enables a specific type of neuron to multiply two incoming signals. This provides fundamental insights into the algebra of neurons -- the
computations that may underlie countless processes in the brain.


==========================================================================
We easily recognize objects and the direction in which they move. The
brain calculates this information based on local changes in light
intensity detected by our retina. The calculations occur at the level
of individual neurons. But what does it mean when neurons calculate? In
a network of communicating nerve cells, each cell must calculate its
outgoing signal based on a multitude of incoming signals. Certain types
of signals will increase and others will reduce the outgoing signal -- processes that neuroscientists refer to as 'excitation' and 'inhibition'.

Theoretical models assume that seeing motion requires the multiplication
of two signals, but how such arithmetic operations are performed at
the level of single neurons was previously unknown. Researchers from
Alexander Borst's department at the Max Planck Institute for Biological Intelligence, i.f., have now solved this puzzle in a specific type
of neuron.

Recording from T4 cells The scientists focused on so-called T4 cells in
the visual system of the fruit fly. These neurons only respond to visual
motion in one specific direction. The lead authors Jonatan Malis and Lukas Groschner succeeded for the first time in measuring both the incoming and
the outgoing signals of T4 cells. To do so, the neurobiologists placed the animal in a miniature cinema and used minuscule electrodes to record the neurons' electrical activities. Since T4 cells are among the smallest of
all neurons, the successful measurements were a methodological milestone.

Together with computer simulations, the data revealed that the activity of
a T4 cell is constantly inhibited. However, if a visual stimulus moves in
a certain direction, the inhibition is briefly lifted. Within this short
time window, an incoming excitatory signal is amplified: Mathematically, constant inhibition is equivalent to a division; removing the inhibition results in a multiplication.

"We have discovered a simple basis for a complex calculation in a single neuron," explains Lukas Groschner. "The inverse operation of a division is
a multiplication. Neurons seem to be able to exploit this relationship,"
adds Jonatan Malis.

Relevance for behavior The T4 cell's ability to multiply is linked
to a certain receptor molecule on its surface. "Animals lacking this
receptor misperceive visual motion and fail to maintain a stable course in behavioral experiments," explains co-author Birte Zuidinga, who analyzed
the walking trajectories of fruit flies in a virtual reality setup. This illustrates the importance of this type of computation for the animals' behavior. "So far, our understanding of the basic algebra of neurons was
rather incomplete," says Alexander Borst. "However, the comparatively
simple brain of the fruit fly has allowed us to gain insight into this seemingly intractable puzzle." The researchers assume that similar
neuronal computations underlie, for example, our abilities to localize
sounds, to focus our attention, or to orient ourselves in space.

special promotion Explore the latest scientific research on sleep and
dreams in this free online course from New Scientist -- Sign_up_now_>>> ========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Lukas N. Groschner, Jonatan G. Malis, Birte Zuidinga, Alexander
Borst. A
biophysical account of multiplication by a single neuron. Nature,
2022; DOI: 10.1038/s41586-022-04428-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220224112628.htm

--- up 11 weeks, 5 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)