Neuronal Ensembles of thalamocortical networks mediating sensorimotor integration

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Cortical and thalamic ensembles underlying sensorimotor integration will be studied in vivo using microendoscopic and two-photon imaging techniques combined with targeted molecular perturbations.

Distinct ensembles of coherently active neurons are likely to underlie sensorimotor integration. Here, we hypothesize that such neuronal ensembles exist in thalamocortical networks connecting primary and secondary somatosensory cortices via thalamus. We aim to test this by experimentally creating controllable neuronal ensembles of layer 5B (L5B) neurons in the primary somatosensory cortex (S1) and recording corresponding neuronal ensembles in thalamus and layer 2/3/4 of the secondary somatosensory cortex (S2).

This will be achieved in vivo by microendoscopy, two-photon microscopy and electrophysiological recordings. S1 connects to S2 via a corticothalamocortical (CTC) loop operating two strong synaptic connections. The driver synapse connecting L5B neurons with thalamic relay neurons situated in the thalamic posteromedial nucleus (POm) will generate a thalamic relay cell ensemble defined by L5B to relay cell connectivity. The synapse connecting the relay cell to S2 neurons will generate a connectivity-dependent ensemble of L2/3/4 neurons. The unusual delayer and amplifier properties of the synapse formed by L5B neurons onto relay neurons could be instrumental in recruiting single neurons into ensembles. Selective genetic perturbation of the two synapses forming the CTC loop will be used to probe for the function of the loop in entraining neuronal ensemble formation in S2 cortex. As a perspective, this approach will allow addressing the behavioural function conferred by neuronal ensembles of the CTC network.
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Abraham NM, Egger V, Shimshek DR, Renden R, Fukunaga I, Sprengel R*, Seeburg PH, Klugmann M, Margrie TW, Schaefer AT, Kuner T (2010) Synaptic inhibition accelerates odor discrimination in mice. Neuron 65:399-411.

Groh A, de Kock CPJ, Wimmer VC, Sakmann B, Kuner T (2008) Driver or coincidence detector: modal switch of a corticothalamic giant synapse controlled by spontaneous activity and short-term depression. J Neurosci 28:9652-9663.

Krieger P, Kuner T, Sakmann B (2007) Synaptic connections between layer 5B pyramidal neurons in mouse somatosensory cortex are independent of apical dendrite bundling. J Neurosci 27:11473-11482.

*Principal investigators of other projects within the CRC