PhD defense: Romain Brasselet

2010-12-03 at 14:00

University Pierre&Marie Curie Paris VI, Building B, room 501



Neural Coding in the Ascending Somatosensory Pathway: A Metrical Information Theory

In order to study neurotransmission, we propose an extension of Shannon information, dubbed metrical information, that explicitly embeds the metrical relations between signals through a spike train metrics. The metrics is interpreted as a projection of the properties of the decoder onto the space of spike trains. Thus, it allows to predict what are the optimal parameters of the neurons that receive these signals to transmit a maximal amout of information. We apply this new method to microneurography recordings of fingertip mechanoreceptors with the Victor-Purpura spike train metrics. We show that after a few tens of milliseconds, it is possible to reach a maximal metrical information. We then design a feedforward model of the cuneate nucleus (CN) that we connect to the cutaneous receptors according to divergence and convergence recordings in the cat. The properties of the individual CN neurons are also based on electrophysiological recordings in the cat. In order to assess the capacity of such a layer of neurons to convey information, we implemented a biologically plausible spike-time dependent plasticity rule. We show that the layer can transmit the metrical information and the high organization of the mechanoreceptors signals with a very short delay (5-10 ms). Finally, we design a new spike train distance that is inspired by the processing of signals by real neurons. We show with this distance that, with appropriate parameters, the space of the population spike trains can be isometric to the stimulus space. This metrical organization can be seen as a basis for the ability of the central nervous system to generalize.

Keywords: neural coding, spike train metrics, information theory, somatosensory system, cuneate nucleus, microneurography.
Angelo Arleo (NPA-UPMC, Paris), supervisor
Vincent Hayward (ISIR-UPMC, Paris), examiner
Roland Johansson (Umea University, Umea, Suède), examiner
Stefano Panzeri (Italian Institute of Technology, Gênes, Italie), reviewer
Simon Thorpe (CERCO, Toulouse), examiner
Jonathan Victor (Weill Cornell Medical College, NY, Etats-Unis), reviewer