Study of neural activities of the primary auditory cortex and middle latency auditory evoked potentials.
This study was undertaken to clarify the relationship between the neural activities of the auditory cortex and components of middle latency auditory evoked potentials (ML-AEPs) (NI and PI) in the cat. Extracellular single-unit activities in the auditory cortex AI (AC-AI) were recorded simultaneously with ML-AEPs. In addition, the effects of removal of the AC-AI and AII and the cerebral hemisphere on ML-AEPs were also studied. ML-AEPs of humans consist of Na, Pa, and Nb components with preceding VI and VII, and those of the cat consist of NI, PI and NII with preceding P6 and P7. Among the 21 unit activities obtained from the AC-AI, 14 showed time-locked responses to click stimuli. The positive and negative waves of these unit activities have a phase reversal relation to N7 and P7, respectively. They are not related in latencies to NI and PI. Recording of ML-AEPs from the surface of the AC-AI showed large negative potentials (No), which also had a phase reversal relation to P7. The amplitude of P7 and No decreased after the unilateral and the bilateral removal of the AC-AI and AII. NI and PI decreased in amplitude after the unilateral removal of the cerebral hemisphere and further decreased after the bilateral removal. The above mentioned findings indicate that the neural activities of the primary AC are the ones mostly related to P7 and that NI and PI reflect neural activities of the cerebral hemispheres.
Department of Neurosurgery, Hamamatsu University School of Medicine, Japan.
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Yokoyama
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Uemura
D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D002415:Cats; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*