Event Details:
Synchronous coupling between fast neural oscillations has been proposed as a powerful mechanism of sensory binding and communication between neural populations. Coupled oscillations in thalamo-cortical circuits may even serve for long distance brain communication.
Noninvasive recordings of brain activity in human using electroencephalography (EEG) or magnetoencephalography (MEG) capture mass activity generated in thousands or even hundreds of thousands of synchronously activated neurons. Thus, a wide gap exists between models of synchrony in small scale networks and the large scale level of EEG and MEG recording.
This talk presents a series of experiments in the auditory system which taken together support the model of communication via cortico-thalamo-cortical connections.
Auditory stimulus driven cortical oscillations show resonance like frequency specificity at 40 Hz. The temporal dynamics of amplitude and phase reveal a characteristic time constant of around 200 ms for temporal integration. Concurrent stimuli reset ongoing 40-Hz oscillation and initiate a subsequent rebound with same 200-ms time constant. Such temporal dynamics are interpreted as representing a change in the binding network according to changes in the sensory environment. With somatosensory stimulation we demonstrated that properties of the oscillatory 40-Hz system are common across sensory modalities. With an auditory masking study we separated 40-Hz oscillations in the sensory and higher-order parts of a sensory binding network. The results demonstrated reduced capability of sensory binding in aging, contributing to the common problem of understanding speech in noise for older adults.