Connectionists: World wide VVTNS series: Wednesday, February 14 at 11am (ET), Nader Nikbakht, MIT

[David Hansel]

[image: VVTNS.png]
https://www.wwtns.online - on twitter: wwtns at TheoreticalWide

You are cordially invited to the lecture  given by

Nader Nikbakht

MIT

on the topic of

*"*Thalamocortical dynamics in a complex learned behavior*"*

The lecture will be held on zoom on *February 14, 2024*, at *11:00 am ET *

Register on our website - https://www.wwtns.online  -to receive the zoom
link

*Abstract:* Performing learned behaviors requires animals to produce
precisely timed motor sequences. The underlying neuronal circuits must
convert incoming spike trains into precisely timed firing to indicate the
onset of crucial sensory cues or to carry out well-coordinated muscle
movements. Birdsong is a remarkable example of a complex, learned and
precisely timed natural behavior which is controlled by a
brainstem-thalamocortical feedback loop. Projection neurons within the
zebra finch cortical nucleus HVC (used as a proper name), produce precisely
timed, highly reliable and ultra-sparse neural sequences that are thought
to underlie song dynamics. However, the origin of short timescale dynamics
of the song is debated. One model posits that these dynamics reside in HVC
and are mediated through a synaptic chain mechanism. Alternatively, the
upstream motor thalamic nucleus Uveaformis (Uva), could drive HVC bursts as
part of a brainstem-thalamocortical distributed network. Using focal
temperature manipulation we found that the song dynamics reside chiefly in
HVC. We then characterized the activity of thalamic nucleus Uva, which
provides input to HVC. We developed a lightweight (~1 g) microdrive for
juxtacellular recordings and with it performed the very first extracellular
single unit recordings in Uva during song. Recordings revealed
HVC-projecting Uva neurons contain timing information during the song, but
compared to HVC neurons, fire densely in time and are much less reliable.
Computational models of Uva-driven HVC neurons estimated that a high degree
of synaptic convergence is needed from Uva to HVC to overcome the
inconsistency of Uva firing patterns. However, axon terminals of single Uva
neurons exhibit low convergence within HVC such that each HVC neuron
receives input from 2-7 Uva neurons. These results suggest that thalamus
maintains sequential cortical activity during song but does not provide
unambiguous timing information. Our observations are consistent with a
model in which the brainstem-thalamocortical feedback loop acts at the
syllable timescale (~100 ms) and does not support a model in which the
brainstem-thalamocortical feedback loop acts at fast timescale (~10 ms) to
generate sequences within cortex.

*About VVTNS : Created as the World Wide Neuroscience Seminar (WWTNS) in
November 2020 and renamed in homage to Carl van Vreeswijk in Memoriam
(April 20, 2022), its aim is to be a platform to exchange ideas among
theoreticians. Speakers have the occasion to talk about theoretical aspects
of their work which cannot be discussed in a setting where the majority of
the audience consists of experimentalists. The seminars, **held on
Wednesdays at 11 am ET,**  are 45-50 min long followed by a discussion. The
talks are recorded with authorization of the speaker and are available to
everybody on our YouTube channel.*
ᐧ
ᐧ
ᐧ
ᐧ

ᐧ


-- 
'Life is good ..' (Carl van Vreeswijk, 1962-2022)
---------------------------------------
David Hansel
Directeur de Recherche  au CNRS
Co-Group leader
Cerebral Dynamics Plasticity and Learning lab., CNRS
45 rue des Saints Peres 75270 Paris Cedex 06
Tel (Cell):   +33 607508403 - Fax (33).1.49.27.90.62



ᐧ
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.srv.cs.cmu.edu/pipermail/connectionists/attachments/20240211/85180b94/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: VVTNS.png
Type: image/png
Size: 41084 bytes
Desc: not available
URL: <http://mailman.srv.cs.cmu.edu/pipermail/connectionists/attachments/20240211/85180b94/attachment.png>