PubMed · 4350843
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Y Katsuki. 1972. [Information processing in the auditory system].. https://pubmed.ncbi.nlm.nih.gov/4350843/
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This part of the paper deals with the neurophysiological background of speech analysis and hearing of music. Single vowel- and consonant-detector cells could be clearly separated at the colliculus and geniculate level (Kallert, Keidel). Musical stimulation is decoded at three levels: hair cells, geniculate, and auditory cortex. Human cortical evoked potentials represent rhythm, consonance, and (as DC-shift) the emotional content of music. Marked harmonics, even of single hair-cell vibrations and in single units of medial geniculate in combination with clock-cell networks, are the physiological basis of "harmony" in music. Dissonant stimuli are detectable at the cortical level in man (Finkenzeller, Keidel).
A 14-channel SQUID (superconducting quantum interference device) system has been used to record the magnetic signal from the human brain in response to an auditory stimuli (750, 1,000, 1,250 and 1,500 Hz, 70, 76 and 82 dB SPL, 500 ms duration). Three individuals with normal hearing were studied. The locations of magnetic response at the latency of 70 ms (P70), 100 ms (N100) and 160 ms (P160) from the onset of the auditory stimulus were identified. The location for N100 response corresponded to the primary auditory cortex (area 41), where a clear tonotopic organization was demonstrated. The amplitopic organization was less evident. These results suggest a flow of auditory signals in the temporal lobe and tonotopic organization in the auditory cortex.
Auditory evoked magnetic fields were recorded with a 24-SQUID magnetometer on a patient with a vascular lesion in the right auditory cortex and its vicinity. The contralateral transient 100 ms response (N100m) was absent over the damaged side, with no recovery within 16 months. Responses were normal over the healthy side. The responses to a binaural click train where interaural delays caused the perception of a shifting sound source; responses were again normal over the left side. Ipsilateral tones elicited N100m over the normal hemisphere but with smaller amplitude and longer latency than in healthy subjects. We suggest that ipsilateral responses are triggered by ipsilateral afferents but are significantly modified by excitatory callosal connections which did not work in our patient.