Gamma-band MEG activity to coherent motion depends on task-driven attention

We examined gamma-band magnetoencephalographic (MEG) activity in humans manipulating attention to visual stimuli by auditory distractors. After exposure to both visual and auditory noise (a baseline), subjects attended to the first of two stimuli (either regular motion of bars or a tone sequence) presented asynchronously, and responded to its offset. A spectral power analysis revealed an increased, relative to baseline, 40 Hz MEG response to attended coherent motion. The enhancement occurred within the initial 50-250 ms from motion onset over modality-specific (occipital) cortices. The increase was not observed when attention was captured by auditory distractors. Our findings suggest that 40 Hz activity in the human visual cortex is related to integration of featural information that is supported by attention.