Adult plasticity of spatiotemporal receptive fields of multisensory superior colliculus neurons following early visual deprivation.

PURPOSE Previous work has established that the integrative capacity of multisensory neurons in the superior colliculus (SC) matures over a protracted period of postnatal life (Wallace and Stein, 1997), and that the development of normal patterns of multisensory integration depends critically on early sensory experience (Wallace et al., 2004). Although these studies demonstrated the importance of early sensory experience in the creation of mature multisensory circuits, it remains unknown whether the reestablishment of sensory experience in adulthood can reverse these effects and restore integrative capacity. METHODS The current study tested this hypothesis in cats that were reared in absolute darkness until adulthood and then returned to a normal housing environment for an equivalent period of time. Single unit extracellular recordings targeted multisensory neurons in the deep layers of the SC, and analyses were focused on both conventional measures of multisensory integration and on more recently developed methods designed to characterize spatiotemporal receptive fields (STRF). RESULTS Analysis of the STRF structure and integrative capacity of multisensory SC neurons revealed significant modifications in the temporal response dynamics of multisensory responses (e.g., discharge durations, peak firing rates, and mean firing rates), as well as significant changes in rates of spontaneous activation and degrees of multisensory integration. CONCLUSIONS These results emphasize the importance of early sensory experience in the establishment of normal multisensory processing architecture and highlight the limited plastic potential of adult multisensory circuits.