40-Hz steady state response in awake cats after bilateral chronic lesions in auditory cortices or inferior colliculi.
To reveal the generators of 40-Hz steady state response, the following investigations in awake cat were performed: (i) analyses of 40-Hz SSR without any lesions, and study of stimulus rate; (ii) effect of chronic lesions in the bilateral auditory cortex; (iii) effect of chronic lesions in the bilateral inferior colliculus. The maximum amplitudes were obtained at stimulus rates of 40-50 Hz. In cat with lesions in the bilateral auditory cortex, the wave configurations and the phase were retained but the amplitude was reduced to 90%. In cat with lesions in the inferior colliculus, the wave configurations and the phase were retained but the amplitude was reduced to 60%. These data suggest the following conclusions: (i) cat was a suitable animal model for human's 40-Hz SSR; (ii) the auditory cortex could be one of the generators of 40-Hz SSR; (iii) the inferior colliculus could be an important generator of 40-Hz SSR; (iv) 40-Hz SSR seems to be generated through not only primary auditory pathways, but also nonspecific auditory pathways, which receive auditory information in parallel from the brainstem, thalamus, and cerebrum.
Tsuzuku
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Department of Otolaryngology, Teikyo University School of Medicine, Tokyo, Japan.
D000818:Animals; D001303:Auditory Cortex / Q000166:cytology / Q000503:physiopathology*; D001306:Auditory Pathways; D002415:Cats; D004558:Electric Stimulation; D005072:Evoked Potentials, Auditory; D016057:Evoked Potentials, Auditory, Brain Stem; D007245:Inferior Colliculi / Q000166:cytology / Q000503:physiopathology*; D010784:Photomicrography; D014851:Wakefulness