Absence of cross-modal reorganization in the primary auditory cortex of congenitally deaf cats.

To investigate possible cross-modal reorganization of the primary auditory cortex (field A1) in congenitally deaf cats, after years of auditory deprivation, multiunit activity and local field potentials were recorded in lightly anesthetized animals and compared with responses obtained in hearing cats. Local field potentials were also used for current source-density analyses. For visual stimulation, phase-reversal gratings of three to five different spatial frequencies and three to five different orientations were presented at the point of central vision. Peripheral visual field was tested using hand-held stimuli (light bar-shaped stimulus of different orientations, moved in different directions and flashed) typically used for neurophysiological characterization of visual fields. From 200 multiunit recordings, no response to visual stimuli could be found in A1 of any of the investigated animals. Using the current source-density analysis of local field potentials, no local generators of field potentials could be found within A1, despite of the presence of small local field potentials. No multiunit responses to somatosensory stimulation (whiskers, face, pinna, head, neck, all paws, back, tail) could be obtained. In conclusion, there were no indications for a cross-modal reorganization (visual, somatosensory) of area A1 in congenitally deaf cats.