Oscillatory gamma activity in humans and its role in object representation

We experience objects as whole, complete entities irrespective of whether t hey are perceived by our sensory systems or are recalled from memory. Howev er, it is also known that many of the properties of objects are encoded and processed in different areas of the brain. How then, do coherent represent ations emerge? One theory suggests that rhythmic synchronization of neural discharges in the gamma band (around 40 Hz) may provide the necessary spati al and temporal links that bind together the processing in different brain areas to build a coherent percept. In this article we propose that this mec hanism could also be used more generally for the construction of object rep resentations that are driven by sensory input or internal, top-down process es. The review will focus on the literature on gamma oscillatory activities in humans and will describe the different types of gamma responses and how to analyze them. Converging evidence that suggests that one particular typ e of gamma activity (induced gamma activity) is observed during the constru ction of an object representation will be discussed.