Palix J, Hauert C-A, Leonards U, 2006, "Brain oscillations--indicators for serial processing in inefficient visual search?" Perception 35 ECVP Abstract Supplement
Brain oscillations--indicators for serial processing in inefficient visual search?
J Palix, C-A Hauert, U Leonards
The electroencephalographic (EEG) N2pc component, originally suggested as neurophysiological correlate of visuospatial shifts of attention, seems rather related to target detection and distractor suppression. This reopens the debate whether a shifting focus of attention, and thus serial processing, exists in inefficient visual search. Reasoning that search rate for target-absent trials should indicate the speed with which attention can be shifted for a given search type, we here investigated whether repetitive EEG frequency components correlate with search rate in an inefficient search task. Search rate was about 67 ms/item for target-present (TP) trials and 186 ms/item for target-absent (TA) trials. Wavelet analysis of response-locked EEGs revealed significant differences in EEG beta-frequency bands (12 - 21 Hz) between TP and TA conditions, moving in time from frontal to central electrodes, presumably related to decision-making. More importantly, low-frequency modulations (~17 Hz) of response-locked EEG gamma-frequency bands (44 - 75 Hz) over posterior electrodes correlated with search rate for TA trials. Given that gamma-oscillations are thought to be related to visual processing and attention, such EEG modulations might indeed reflect a shifting focus of attention, and thus serial processing, in inefficient visual search; alternative interpretations are also discussed.
[Supported by the Faculty of Psychology and Sciences of Education, University of Geneva, Switzerland.]
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