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?