Department of Bioengineering, Imperial College London, UK
Wednesday 7 March 2007, 16:00
Seminar Room B10 (Basement)
Alexandra House, 17 Queen Square, London, WC1N 3AR
Synchronization and sensory coding
Recent results from a number of groups have revealed the "correlation = 0.2 in the cortex" dogma to be an over-simplification: with carefully constructed stimuli, inter-neuronal synchronization can depend upon stimulus properties in interesting ways. We have been using Information Theory to study the effect of this stimulus-dependent synchronization on the neural coding of orientation and contrast in V1. We analysed pairs of simultaneously recorded neurons in the macaque primary visual cortex, whose receptive fields were carefully mapped and co-stimulated. Direction coding showed weak synergistic effects at short timescales, trailing off to informational independence at long timescales. An information component analysis revealed that this was due to a balance of a synergistic contribution due to the stimulus-dependence of synchronization, with redundancy due to the overlap of tuning. In comparison, contrast coding was dominated by redundancy due to the similarity in contrast tuning curves, showing weak synergy at only very short time scales (< 5 ms). I will discuss the significance of this result for the coding and processing of sensory information by cortical circuits, and, if there is time at the end of the talk, introduce some recent work in which are comparing sensory coding in two cortical circuits: the cerebral and the cerebellar.