In the split-second between first setting our eyes on something and processing what we've seen, an extraordinary amount of work has been done by the brain. In fact, the information received by the eyes has been coded several times over in the brain's pathways. I study the fascinating processes that underlie our ability to perceive things in the physical world around us.

The sequence of events along the brain's pathways was thought to be mainly feed-forward, with processing advancing from simple to increasingly complex attributes, and then converging to a common area where conscious perception occurs. But this scheme does not fit with known brain architecture.

Advances in neuroanatomy and neurophysiology have called attention to massive two-way communication pathways between individual brain modules. With my students and colleagues, I make explicit use of this pattern of reentrant connectivity in developing new theories of perception. We believe that visual perceptions emerge from iterative exchanges between high-level and low-level brain modules linked by reentrant pathways. The main objective of the reentrant signaling is to test alternative possibilities regarding the identity of the visual input and its location in space,

Guided by this conceptual framework, we are studying many aspects of visual perception. One topic relates to the distribution of visual attention across space and over time. Our studies of the "attentional blink" (see Current Projects ) were done in this context. The topic of principal interest relates to the dynamic transformations seen when visual stimuli are presented in rapid succession, as in a movie sequence. This led to a fascinating and counterintuitive form of masking which we call "object substitution" (see Current Projects). The objective of the research programme is to explore systematically the perceptual domains in which reentrant processes mediate visual perception, and how that mediation is modulated by the distribution of attention in space and time.