Crossmodal stimulation influences communication in visual-somatosensory cortical networks of the Brown Norway rat

Abstract

Processing of most action goals and complete perception of the environment, like spatial localization of events, require integration of information from different sensory systems. The classical idea of a hierarchical sensory organization is challenged by recent evidence from both human and primate work showing that multisensory processing is already taking place in primary sensory cortices. However, the mechanisms underlying this multisensory processing and the role of primary sensory cortices in crossmodal communication and oscillatory coupling remain largely unknown. Congruent and incongruent uni- and bimodal visual (light spot) and tactile (whisker deflection) stimulation was performed simultaneously with extracellular multielectrode recordings in the primary visual (V1) and somatosensory (S1, barrel field) neocortices of adolescent Brown Norway rats in vivo. Tactile stimulation led after 10–30 ms to a phase-locked, large amplitude response in the contralateral S1 that is accompanied by prominent, layer-specific sinks and sources. Additionally, non-phase-locked oscillations were induced in different frequency ranges. Visual stimulation alone did not change the amplitude of oscillations compared to baseline activity in the contralateral S1, but reset the phase of ongoing oscillatory activity. Because of the visual impact in the S1, bimodal congruent stimulation led to an increase of the evoked response and changed the timing of amplitude enhancement of oscillations. These data indicate that networks in the barrel cortex are modulated by crossmodal visual input.