Origins of thalamic and cortical projections to the posterior auditory field in congenitally deaf cats.
Crossmodal plasticity takes place following sensory loss, such that areas that normally process the missing modality are reorganized to provide compensatory function in the remaining sensory systems. For example, congenitally deaf cats outperform normal hearing animals on localization of visual stimuli presented in the periphery, and this advantage has been shown to be mediated by the posterior auditory field (PAF). In order to determine the nature of the anatomical differences that underlie this phenomenon, we injected a retrograde tracer into PAF of congenitally deaf animals and quantified the thalamic and cortical projections to this field. The pattern of projections from areas throughout the brain was determined to be qualitatively similar to that previously demonstrated in normal hearing animals, but with twice as many projections arising from non-auditory cortical areas. In addition, small ectopic projections were observed from a number of fields in visual cortex, including areas 19, 20a, 20b, and 21b, and area 7 of parietal cortex. These areas did not show projections to PAF in cats deafened ototoxically near the onset of hearing, and provide a possible mechanism for crossmodal reorganization of PAF. These, along with the possible contributions of other mechanisms, are considered.
Department of Physiology and Pharmacology, University of Western Ontario, Canada; Brain and Mind Institute, University of Western Ontario, Canada. Electronic address: bbutler9@uwo.ca.
Blake E
BE
Butler
Department of Physiology and Pharmacology, University of Western Ontario, Canada; Brain and Mind Institute, University of Western Ontario, Canada.
Nicole
N
Chabot
Department of Experimental Otology, Medical University Hannover, Germany; AudioNeuroTechnology, Medical University Hannover, Germany.
Andrej
A
Kral
Department of Physiology and Pharmacology, University of Western Ontario, Canada; Department of Psychology, University of Western Ontario, Canada; Brain and Mind Institute, University of Western Ontario, Canada; National Centre for Audiology, University of Western Ontario, Canada.
Stephen G
SG
Lomber
D000222:Adaptation, Physiological; D000223:Adaptation, Psychological; D000818:Animals; D001303:Auditory Cortex / Q000503:physiopathology*; D001306:Auditory Pathways / Q000503:physiopathology; D001307:Auditory Perception; D001522:Behavior, Animal; D002415:Cats; D003638:Deafness / Q000151:congenital / Q000503:physiopathology* / Q000523:psychology; D004195:Disease Models, Animal; D005260:Female; D006309:Hearing; D056347:Neuroanatomical Tract-Tracing Techniques; D009473:Neuronal Plasticity; D013788:Thalamus / Q000503:physiopathology*; D014793:Visual Cortex / Q000503:physiopathology; D014796:Visual Perception
Anatomical connectivity; Auditory cortex; BDA; Crossmodal plasticity