Neuronal mechanisms and perceptual significance of somatoauditory interactions in primate A1.

Abstract

Recent anatomical, physiological, and neuroimaging findings indicate multisensory convergence at early, putatively unisensory stages of cortical processing. We sought to confirm somatosensory‐auditory interaction in AI, and to define both its physiological mechanisms and its consequences for auditory information processing. Laminar current source density and multiunit activity were sampled during multielectrode penetrations of primary auditory area AI in awake macaques revealed clear somato‐auditory interactions, with a novel mechanism: Somatosensory inputs appear to reset the phase of ongoing neuronal oscillations, so that accompanying auditory inputs arrive during an ideal, high excitability phase, and produce amplified neuronal responses. In contrast, responses to auditory inputs arriving during the opposing low‐excitability phase tend to be suppressed. We speculate that these effects are likely mirrored by corresponding changes in the gain of the perceptual representation. Our findings underscore the instrumental role of neuronal oscillations in sensory operations. The timing and laminar profile of the multisensory interactions in AI indicate that nonspecific thalamic systems may play a key role in the effect.