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(Dis)organizational principles for neuronal responses in the whisker system| old_uid | 12141 |
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| title | (Dis)organizational principles for neuronal responses in the whisker system |
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| start_date | 2013/02/26 |
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| schedule | 12h-13h30 |
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| online | no |
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| summary | Rodents use their whiskers to perform demanding sensory discrimination
tasks. Identifying an object's position or texture requires the system
to encode temporal patterns of whisker motion fluctuations with high
precision. Accordingly, neurons in the somatosensory thalamus and
cortex are not just sensitive to spatial stimulus structure -e.g.,
motion of particular whiskers or in particular directions-, but also
have clear feature selectivity (receptive fields) in the temporal
domain. Here I will describe recent work in search of the principles
governing this feature selectivity.
Different neurons in the barrel cortex participate heterogeneously in
a given sensory task -e.g., texture discrimination. The highly
variable representation across single neurons coexists with a robust
code for texture at the level of small populations. The robustness of
the population signal is explained by synergistic interactions between
neurons carrying stronger and weaker signals; the variability across
single neurons can be partly understood in terms of neurons within a
given processing stage having highly diverse temporal feature
selectivity. This diversity appears uncoordinated with any aspect of
whisker somatotopy. As a consequence, a wide range of response
properties can be sampled within a small region of barrel cortex.
Diverse temporal feature selectivity is also found in the VPM nucleus,
the main thalamic relay to cortex: different VPM neurons respond to
distinct stimulus features. The existence of rich, diverse population
codes at both thalamic and cortical stages raises the question of how
information is successfully transmitted under conditions where the
heterogeneity of thalamic neurons manifests itself - i.e., where
thalamic responses are not overwhelmingly synchronous. I will present
ongoing work suggesting the feasibility of a mode of communication
where partially synchronous thalamic activity could suffice to
influence cortical neurons. Specifically, in slice experiments we have
found that thalamocortical synapses have strikingly heterogeneous
short-term plasticity during ongoing stimulation: each synapse
responds most strongly to particular stimulation intervals, giving
rise to a rich "synaptic population code" for dynamic stimuli. |
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| responsibles | Sackur |
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