Research objectives and content
Information about a single visual object is spread over many cortical areas: it must be integrated into a coherent perception. This feature binding problem could be solved if the neurons responding to the same object synchronized their discharges in the gamma-band (30-70 Hz). Stimulus-specific gamma-band activity was observed in cats and monkeys areas V1, V2 and MT. Still, if oscillatory synchronization reflects the existence of a distributed cell assembly coding for an object, a larger number of areas should get synchronized. Human EEG data suggest it is so, but do not allow to precise which areas are involved.
We aim at understanding better how synchronized oscillatory activity is set up within the ventral stream of the visual brain. We wish to determine what is the spatial extent of gamma-band activity and how synchrony between sites is varying with time. We shall first define and test in humans an experimental protocol where a strong and reproducible gamma-band response can be recorded, and use the same paradigm in the awake monkey. Multi-channels recordings from the cortical surface of the ventral stream should enable us to precise, without any a priori, which areas are involved in oscillatory synchronization. We shall then refine the recording levels to study the spatial and dynamic properties of oscillatory synchronization within and between these areas.
Training content (objective, benefit and expected impact)
The Center for Cognitive Sciences in Bremen combines two rare advantages: 1- it is one of the few places that offers multi-channels recording facilities both in humans and awake monkeys. I shall acquire the technique of electrophysiological recordings in behaving monkeys, supervised in this work by Dr. A. Kreiter who has a strong experience in this field. 2- Researchers with different scientific backgrounds share a common interest in visual integration and synchronized oscillatory activity. This should bring me into a multi-disciplinary approach of these issues (awake monkey electrophysiology, visual psychophysics, cognitive psychophysiology). Links with industry / industrial relevance (22)