Gamma-band responses in the brain: a short review of psychophysiological correlates and functional significance.

The present study shows that gamma-band (40 Hz) activities exist in a number of brain structures of different species, with seemingly different functional/behavioral correlates. This rhythm has also different dynamics in various structures and under different experimental conditions: it exists spontaneously and/or can be evoked, induced or emitted with different latencies and relations to sensory-cognitive events. Recent measurements of gamma-band activity at the cellular level stress high level functional correlates such as binding of features. In contrast, field potential measurements in both humans and animals demonstrate that gamma-band responses may have multifold functions both in 'obligatory' sensory and in cognitive processing. With respect to the generators of gamma activity, experimental data hint at the existence of a distributed gamma system in the brain. Furthermore, an interpretation of gamma rhythms as universal functional building blocks is suggested.