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Intracortical generators of auditory ERP
- Multielectrode study in an animal model

George Karmos

Institute for Psychology, Hungarian Academy of Sciences, 1394 Budapest, Hungary

The aim of the present study was to investigate the intracortical processes responsible for the generation of event related potentials (ERPs). Adult cats were chronically implanted with a matrix of 30 epidural electrodes or with 16 - 23 contact intracortical multielectrodes which made possible the recording of field potentials and multiple unit activity (MUA) from consecutive depths of the auditory cortex. Intracortical generators of two characteristic auditory ERP phenomena, the mis-match negativity (MMN) and the auditory steady state response (SSR) were anal-ysed. Surface mapping revealed that the MMN appears with greatest amplitude in the AII area. Intracortical records proved that in the latency range of the surface MMN, a disinhibitory process appears in the middle layers. This is manifested by a decrease of the source strength, representing neuronal hyperpolarization and an in-crease of the MUA activity. The analysis of the intracortical generation of the SSR indicated that it cannot be explained by the summation of the middle latency com-ponents. When the stimulus repetition rate increased above 20 Hz, the early surface positive component ceased while the input sink in layer IV remained unchanged. Stimuli in the range of 30 - 40 Hz, which elicited the surface SSR, induced a new supra-granular sink-source oscillation, which seemed to be responsible for the si-nu-soid pattern of SSR. The data indicate that intracortical studies in animal models can help to understand neuronal processes of ERP generation.

Supported by OTKA (T18452), HFSP (RG25/96B), by and MAKA (J.F.444)

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Temporal Aspects of Human Cortical Information Processing
Proceedings of the Finnish Japanese Symposium, Otaniemi, June 14 - 17, 1998
Edited by O.V. Lounasmaa
Internet page created Fri, Sep 18, 1998 at 07:28:19 with Frontier. Peter Berglund, peter@neuro.hut.fi