Auditory projections to extrastriate visual cortex: connectional basis for multisensory processing in 'unimodal' visual neurons.
Neurophysiological studies have recently documented multisensory properties in 'unimodal' visual neurons of the cat posterolateral lateral suprasylvian (PLLS) cortex, a retinotopically organized area involved in visual motion processing. In this extrastriate visual area, a region has been identified where both visual and auditory stimuli were independently effective in activating neurons (bimodal zone), as well as a second region where visually-evoked activity was significantly facilitated by concurrent auditory stimulation but was unaffected by auditory stimulation alone (subthreshold multisensory region). Given their different distributions, the possible corticocortical connectivity underlying these distinct forms of crossmodal convergence was examined using biotinylated dextran amine (BDA) tracer methods in 21 adult cats. The auditory cortical areas examined included the anterior auditory field (AAF), primary auditory cortex (AI), dorsal zone (DZ), secondary auditory cortex (AII), field of the rostral suprasylvian sulcus (FRS), field anterior ectosylvian sulcus (FAES) and the posterior auditory field (PAF). Of these regions, the DZ, AI, AII, and FAES were found to project to the both the bimodal zone and the subthreshold region of the PLLS. This convergence of crossmodal inputs to the PLLS suggests not only that complex auditory information has access to this region but also that these connections provide the substrate for the different forms (bimodal versus subthreshold) of multisensory processing which may facilitate its functional role in visual motion processing.
Clemo
H Ruth
HR
Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298-0709, USA. rclemo@vcu.edu
Sharma
Giriraj K
GK
Allman
Brian L
BL
Meredith
M Alex
MA
D000818:Animals; D001303:Auditory Cortex / Q000166:cytology* / Q000502:physiology*; D001710:Biotin / Q000031:analogs & derivatives; D001931:Brain Mapping; D002415:Cats; D003911:Dextrans; D005456:Fluorescent Dyes; D009039:Motion Perception / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology; D014793:Visual Cortex / Q000166:cytology* / Q000502:physiology*
D003911:Dextrans; D005456:Fluorescent Dyes; C076397:biotinylated dextran amine; D001710:Biotin