Andy Dykstra HST.722 November 1, 2007 The role of gamma oscillations in perceptual binding and scene analysis. Andy Dykstra HST.722 November 1, 2007

Perceptual Binding? Objects have features However, we perceive them as whole entities How does one associate the various features with each other to form the representation of the object? How does one assign features to objects when multiple objects are present? How do different neuronal patterns, each representing a feature, “bind” together to bring about unified percepts and meaningful action? Von der Malsburg (1981), Roskies (1999), Tallon-Baudry and Bertrand (1999)

Gamma Oscillations? 30 – 80 Hz fluctuations in neuronal signals measured at varying levels (units, local field potentils, EEG, MEG) Three types: Steady-state response Evoked (synchronized with stimulus) Induced (brought about by stimulus, but not synchronous with stimulus) Epiphenomena or fundamental role in perception and cognition? Gray (1994), Buzsáki (2006), Buzsáki and Draguhn (2004), Tallon-Baudry and Bertrand (1999)

Are they related? Gamma oscillations may provide mechanism of synchronizing neuronal populations representing different features This, when observed, could bind features

Results from the Auditory System. Joilot et al. (1994) Evoked responses @ ~40Hz track perception of one or two clicks

Results from the Auditory System. Ross et al. (2005) Stimulus induced reset of 40-Hz ASSR

Results from the Auditory System. Lakatos et al. (2005) Hierarchy of oscillatory activity in primary auditory cortex Delta (1-4Hz) modulates theta (4-10Hz), which modulates gamma (30-50Hz) Suggests that auditory cortex is optimized to process rhythmic inputs and provides possible mechanism for rhythmic expectation

Questions?