Development Of Auditory-visual Multisensory Neurons And Multisensory Integration In Rat Cortex

Conventional electrophysiology techniques were applied to study the development of auditory-visual multisensory neurons in 2-week, 3-week, 4-week, 6-week postnatal and adult rat cortex.It was found that, at the auditory-visual associated cortex that represents the boundary area of parietal-occipital-temporal cortex, most of the neurons encountered in 2-week-old rats' cortex were auditory-responsive ones, which account for 81.73% (85/104); while only 11 visual-responsive neurons were recorded, that is 10.58% (11/104) of the total. However, auditory-visual multisensory neurons could be found at this postnatal age, despite their scarce (7.69%, 8/104). Gradually, as the development processes, the number and the percentage of auditory-visual multisensory neurons increases, from 13.04% (18/138 ) at 3-week postnatal, up to 18.18% (24/132) at 4-week postnatal, reaching 18.80% (25/133) at 6-week postnatal, and the approaching the adult level (19.31%, 28/145 ) .There was regular and territorial distribution of auditory-visual multisensory neurons: v-A neurons typically were encountered around the dorsal auditory cortex, a-V neurons mainly appeared in areas adjacent to visual cortex, while most A-V neurons lied between the former two kinds of neurons.A great deal of postnatal maturation is necessary before these newborn multisensory neurons are capable of adult-like response. Response latencies of newborn neurons are remarkbly long at early development stage, and then gradually decrease with the increasing age. And the minimum thresholds of auditory-visual multisensory neurons show development-dependent decrease as well. While the...