Evidence of peripheral auditory activity modulation by the auditory cortex in humans

• Published in: Neuroscience 2001-01, Vol.104 (2), p.347-358
• Main Authors: Khalfa, S, Bougeard, R, Morand, N, Veuillet, E, Isnard, J, Guenot, M, Ryvlin, P, Fischer, C, Collet, L
• Format: Article
• Language: English
• Subjects: Adult; Audiometry; Auditory Cortex - cytology; Auditory Cortex - physiology; Auditory Cortex - surgery; auditory descending pathways; Auditory Pathways - cytology; Auditory Pathways - physiology; Auditory Perception - physiology; Biological and medical sciences; Cochlea - cytology; Cochlea - physiology; Denervation - adverse effects; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Efferent Pathways - cytology; Efferent Pathways - physiology; Epilepsy - pathology; Epilepsy - physiopathology; Epilepsy - surgery; Evoked Potentials, Auditory - physiology; Feedback - physiology; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Humans; Magnetic Resonance Imaging; Male; medial olivary nucleus; medial olivocochlear system; Middle Aged; Neural Inhibition - physiology; temporal lobe; Vertebrates: nervous system and sense organs
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(01)00072-0

At the auditory periphery, the medial olivocochlear system is assumed to be involved in complex sound processing and may be influenced by feedback from higher auditory nuclei. Indeed, the descending auditory pathway includes fibers coming from the auditory cortex that are anatomically well positioned to influence the superior olivary complex, and thus the medial efferent system. The aim of the present study was to verify the hypothesis of an implied influence of the auditory cortex on the peripheral auditory system. In three rare cases of patients presenting with intractable temporal lobe epilepsy, Heschl’s gyrus (i.e. the temporal superior gyrus) was surgically removed in the right hemisphere in two patients and in the left hemisphere in a third patient, in order to minimize epilepsy attacks, as preoperative stereoencephalography had shown the epileptic focus or tumor to be situated in those locations. In all three cases, several weeks after the operation the medial olivocochlear system was clearly less functional on both sides, but especially on the side contralateral to the resection. In healthy controls, no such pattern was obtained. In four other epileptic patients, who were operated unilaterally at the anterior temporal pole, amygdala and hippocampus with the temporal gyrus partially spared, efferent suppression grew stronger in the ear ipsilateral to surgery. These results revealed that, in humans, the primary and secondary auditory cortex play a role in modulating auditory periphery activity through direct or indirect efferent fibers. In accordance with previous findings, this descending influence may improve the auditory afferent message by adapting the hearing function according to cortical analysis of the ascending input.