Multisensory Input to the Lateral Rostral Suprasylvian Sulcus (LRSS) in Ferret

For the brain to construct a comprehensive percept of the sensory world, information from the different senses must converge onto individual neurons within the central nervous system. As a consequence, how these neurons convert convergent sensory input into multisensory information is an important question facing neuroscience today. Recent physiological studies have demonstrated the presence of a robust population of multisensory neurons in the lateral bank of the rostral suprasylvian sulcus (LRSS) in adult ferret (Keniston et al, 2008). The LRSS is a region situated between somatosensory and auditory cortices, where bimodal (somatosensory-auditory) neurons occupy the greatest percentage of the sensory-responsive cell population. The present study was designed to evaluate the anatomical connections that underlie these multisensory features. Injections of neuroanatomical tracer were first made into the LRSS. After transport and histological processing, microscopy revealed retrogradely-labeled cell bodies in identified regions of cortex and thalamus. The resultant analysis showed that the greatest number of projections to LRSS originated in auditory and somatosensory cortex. Of these, auditory cortex contributed a greater proportion of inputs. These anatomical data support the idea that LRSS is a multisensory cortex that receives primarily bimodal input from auditory and somatosensory sources