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Size matters: effects of stimulus size, duration and eccentricity on the visual gamma-band response

Size matters: effects of stimulus size, duration and eccentricity on the visual gamma-band response
Size matters: effects of stimulus size, duration and eccentricity on the visual gamma-band response
Objective: The effects of stimulus size, duration and eccentricity on the visual gamma-band response (GBR) in human EEG were investigated and compared to visual evoked potentials (VEPs) in order to differentiate in future (and past) experiments whether changes in GBRs are due to stimulus-related (exogenous) or cognitive effects.
Methods: EEG was recorded from 23 subjects while they performed a simple choice reaction time task requiring discrimination of squares and circles. In separate blocks stimulus size, duration, and eccentricity were manipulated. EEG was recorded from 64 electrodes. A wavelet transform based on Morlet wavelets was employed for the analysis of gamma-band activity.
Results: Amplitude of the GBR was diminished for small and peripheral stimuli. With short stimulus durations ON and OFF responses of the GBR merged into one peak. In comparison, VEP amplitudes were less susceptible to stimulus features. In contrast to VEP latencies, however, GBR latency did not show a lateralization for eccentric stimuli.
Conclusions: In addition to previous experiments which have shown a modulation of the GBR by various cognitive processes, the present results demonstrate the susceptibility of the GBR in human EEG to exogenous factors, as numerous intracortical recordings in non-human primates have shown before. The results suggest that the human GBR resides in early visual areas.
Significance: The demonstration of the susceptibility of the GBR to stimulus properties implies that studies aimed at exploring the involvement of the GBR in information processing have to be designed carefully. It also constrains the localization of the human GBR.
gamma-band oscillations, 40 Hz, exogenous, size, duration, eccentricity
1810-1820
Busch, Niko A.
25756146-04b5-4f71-8c3d-83eaa12597a2
Debener, Stefan
e6bf9143-09a8-45c0-8536-3564885375d4
Kranczioch, Cornelia
c5d9d3fb-2b54-4ae0-85dd-fb1ae11aea4f
Engel, Andreas K.
4c9e2742-c147-46d6-b750-bcab4b5baf34
Herrmann, Christoph S.
e3edc057-1857-4a1e-81f9-dc2dbd279cf7
Busch, Niko A.
25756146-04b5-4f71-8c3d-83eaa12597a2
Debener, Stefan
e6bf9143-09a8-45c0-8536-3564885375d4
Kranczioch, Cornelia
c5d9d3fb-2b54-4ae0-85dd-fb1ae11aea4f
Engel, Andreas K.
4c9e2742-c147-46d6-b750-bcab4b5baf34
Herrmann, Christoph S.
e3edc057-1857-4a1e-81f9-dc2dbd279cf7

Busch, Niko A., Debener, Stefan, Kranczioch, Cornelia, Engel, Andreas K. and Herrmann, Christoph S. (2004) Size matters: effects of stimulus size, duration and eccentricity on the visual gamma-band response. Clinical Neurophysiology, 115 (8), 1810-1820. (doi:10.1016/j.clinph.2004.03.015).

Record type: Article

Abstract

Objective: The effects of stimulus size, duration and eccentricity on the visual gamma-band response (GBR) in human EEG were investigated and compared to visual evoked potentials (VEPs) in order to differentiate in future (and past) experiments whether changes in GBRs are due to stimulus-related (exogenous) or cognitive effects.
Methods: EEG was recorded from 23 subjects while they performed a simple choice reaction time task requiring discrimination of squares and circles. In separate blocks stimulus size, duration, and eccentricity were manipulated. EEG was recorded from 64 electrodes. A wavelet transform based on Morlet wavelets was employed for the analysis of gamma-band activity.
Results: Amplitude of the GBR was diminished for small and peripheral stimuli. With short stimulus durations ON and OFF responses of the GBR merged into one peak. In comparison, VEP amplitudes were less susceptible to stimulus features. In contrast to VEP latencies, however, GBR latency did not show a lateralization for eccentric stimuli.
Conclusions: In addition to previous experiments which have shown a modulation of the GBR by various cognitive processes, the present results demonstrate the susceptibility of the GBR in human EEG to exogenous factors, as numerous intracortical recordings in non-human primates have shown before. The results suggest that the human GBR resides in early visual areas.
Significance: The demonstration of the susceptibility of the GBR to stimulus properties implies that studies aimed at exploring the involvement of the GBR in information processing have to be designed carefully. It also constrains the localization of the human GBR.

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More information

Published date: 2004
Keywords: gamma-band oscillations, 40 Hz, exogenous, size, duration, eccentricity

Identifiers

Local EPrints ID: 27543
URI: https://eprints.soton.ac.uk/id/eprint/27543
PURE UUID: 3bfd2396-ed4e-4716-9493-ed5acb88c388

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Date deposited: 25 Apr 2006
Last modified: 15 Jul 2019 19:12

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