IS GAMMA-BAND ACTIVITY AN INDICATOR OF COGNITIVE PROCESSING?
12. Gamma-band responses have been observed in various mammals (including humans) using different methods, such as single and multiple unit recordings or local field potential, ECoG, EEG and MEG recordings. Gamma-band activity can be elicited by viewing moving bars (Eckhorn et al., 1988; Engel et al., 1992), by simple auditory stimuli such as tones (Pantev et al., 1991), by somatosensory stimuli (Ahissar and Vaadia, 1990) and by odors (Bressler and Freeman, 1980; Freeman, 1991). They also accompany manipulative movements (Murthy and Fetz, 1992). However, this does not imply a specifically cognitive function for gamma-band responses. Very simple stimuli, such as bars or tones, are unlikely to elicit cognitive processing. Such stimulation triggers perception processes, but it is unclear whether additional processes will follow. 13. To determine whether synchronized and/or repetitive activity of neurons serves a specifically cognitive function, one must compare brain responses in two para
