Audiovisual integration in the primary auditory cortex of an awake rodent

Much is known about the behavioral and physiological aspects of multimodal integration in primates, whereas less is known about the extent of audiovisual integration in other species. This study investigated the temporal integration of audiovisual stimuli in the primary auditory cortex (A1) of a standard animal model of auditory physiology: the Mongolian gerbil (Meriones unguiculatus). We recorded single unit responses to auditory and visual stimuli in the A1 of awake gerbils. A tone burst (auditory stimulus) paired with a flashing light (visual stimulus) at differing lag times (from 0 to ±160ms) was presented contralateral to the recording site. As a result, the auditory response was altered significantly by the visual stimulus in more than 25% of the A1 units. The effect of the visual stimulus on the auditory response decreased as the time lag between the two modalities increased. The influence of the visual stimulus remained relatively greater when it preceded rather than followed the auditory stimulus. These results suggest that the A1 and earlier (subcortical) auditory structures of the rodent are capable of temporally integrating information from auditory and visual modalities.