Cerebral Cortex Advance Access published online on October 29, 2009
Cerebral Cortex, doi:10.1093/cercor/bhp213
Projection from Visual Areas V2 and Prostriata to Caudal Auditory Cortex in the Monkey
1 Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA, 2 Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA, 3 Department of Hearing and Speech Sciences, Vanderbilt University, Nashville, TN 37203, USA, 4 Departamento de Neurobiologia, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Bloco G, CCS, Ilha do Fundaõ, Rio de Janeiro, RJ 21941-900, Brazil, 5 Institute for Psychology, Hungarian Academy of Sciences, Budapest 1083, Hungary, 6 Faculty of Information Technology, Péter Pázmány Catholic University, Budapest 1083, Hungary
Address correspondence to Charles E. Schroeder, PhD, Cognitive Neuroscience & Schizophrenia Program, Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA. Email: schrod{at}nki.rfmh.org.
Studies in humans and monkeys report widespread multisensory interactions at or near primary visual and auditory areas of neocortex. The range and scale of these effects has prompted increased interest in interconnectivity between the putatively "unisensory" cortices at lower hierarchical levels. Recent anatomical tract-tracing studies have revealed direct projections from auditory cortex to primary visual area (V1) and secondary visual area (V2) that could serve as a substrate for auditory influences over low-level visual processing. To better understand the significance of these connections, we looked for reciprocal projections from visual cortex to caudal auditory cortical areas in macaque monkeys. We found direct projections from area prostriata and the peripheral visual representations of area V2. Projections were more abundant after injections of temporoparietal area and caudal parabelt than after injections of caudal medial belt and the contiguous areas near the fundus of the lateral sulcus. Only one injection was confined to primary auditory cortex (area A1) and did not demonstrate visual connections. The projections from visual areas originated mainly from infragranular layers, suggestive of a "feedback"-type projection. The selective localization of these connections to peripheral visual areas and caudal auditory cortex suggests that they are involved in spatial localization.
Key Words: auditory cortex • connectivity • monkey • multisensory • V1