Effects of picture repetition on induced gamma band responses, evoked potentials, and phase synchrony in the human EEG.

Repeated experience with an object due to prior exposure to that object is commonly referred to as perceptual or repetition priming. One possible neuronal mechanism for repetition priming is 'repetition suppression' within a cell assembly coding the stimulus. Recently, induced gamma band responses (GBRs) were discussed as a possible physiological correlate of activity in such a cell assembly. The present EEG study was designed to investigate the modulation of induced GBRs when line drawings were presented either once or consecutively two or three times. Results showed a broad distribution of spectral gamma power and synchrony after initial picture presentation. Repeated presentations of the same picture led to a decrease of induced gamma power and less synchronized activity between distant electrode sites. The decrease of induced GBRs and synchrony after repeated picture presentations may be linked to a 'neural savings' mechanism within a cell assembly representing an object. Furthermore, the visual evoked potential, which was modulated by priming, showed a topographically different distribution compared to induced GBRs.