The auditory-visual multisensory neurons and auditory-visual information integration in rat cortex

Conventional electrophysiological technique was used to determine the distribution of auditory-visual multisensory neurons and to study the auditory-visual information integration in rat cortex. 130 auditory-visual bimodal neurons including 65 A-V neurons, 28 v-A neurons and 37 a-A neurons were isolated. These bimodal neurons located in the boundary area between auditory and visual cortex were mainly in the dorsal bank of auditory cortex. There are divided strip trends in the distribution of different types of bimodal neurons that most of v-A neurons were recorded in the cortex close to auditory cortex, a-V neurons were mostly appeared in the part adjacent to visual cortex and a majority of A-V neurons were between of them. One point must be pointed out that bimodal neurons were presented not uniformly but in the way of patchy distribution. According to the different integration effects, all bimodal neurons were divided into three types: enhancement, modulation and depression. The temporal disparity among combinations of two stimuli was showed to be a critical factor influencing the integration of auditory and visual information. At the same time the best interstimulus interval time under which the strongest interaction can be evoked has been thoroughly studied and found that it has somewhat regular arrangement that 98 of the 130 (75%) auditory-visual bimodal neurons in this experiment have the best integration among the 30-50 ms interval time. The results suggest that the auditory-visual bimodal neurons exist in the rat cortex having the similar multisensory and auditory-visual integration characteristics of the multimodal neurons in the other animals' analogy cortex.