Visual input dynamically changes responses to spatiotemporal tactile input patterns in S1 neurons

To understand how sensory events are represented in and perceived by the brain, one must understand how varying internal brain states affect neuronal decoding of sensory input. Recent studies indicate global state changes in the brain impact the representation of haptic events in neurons of the primary somatosensory cortex (S1). It could be argued that the manipulations used so far to alter the cortical circuitry behavior were artificial and not reflective of normal information processing in the neocortex. In the present study we therefore wanted to explore if natural visual stimulation also could impact the interpretation of given tactile input patterns. We recorded the unitary extracellular responses to a set of spatiotemporal tactile input patterns presented either alone or together with simultaneously multicolor flashing lights from a large number of neurons in parallel in the rat primary somatosensory cortex (S1). We found that the visual input, mildly but consistently altered the temporal spike outputs to tactile input patterns in S1 neurons. We argue that the visual input change the global cortical state to an extent that it affects the cortical representation of haptic events even within the S1 and that this is an indication that the cortical network in its information processing may be far more reliant on globally distributed network dynamics than traditionally thought.