The Mechanism of Central Deafness

Abstract

The author evaluated a central deafness by audiometric methods in the patients whose auditory area of the temporal cortex had been damaged by head trauma or tumor. The auditory dysfunction was characterised only by a marked loss of word discrimination while the sensation for pure tones and difference limen for frequency were found intact.
The same findings were also observed in the conditioned auditory behavior reflex of the cat after ablation of the total auditory areas of the bilateral temporal cortexes as reported by Diamond et al (1957, 1962). Moreover, they found degeneration of the nerve fibers descending from the nerve cells in the auditory area to the nerve cells in the dorsal division of the medical geniculate body after ablation of the auditory area in the cat. From this fact, the author started to trace the tracks of the nerve fibers between the auditory area and the medical geniculate body by making reference to Harrison & Howe (1974) and Aitkins & Webster (1972). Finally, a closed circuit of the neurons between the auditory area and the medical geniculate body were found.
This model appears to show the neural mechanism of word discrimination in central deafness.