Research

Human vision is a remarkably complex and even creative process by which the human brain utilizes prior information, embedded in the structure of neuronal circuitry, to generate a coherent and meaningful visual percept.  Our research attempts to advance the understanding of the intriguing link between perceptual awareness and neuronal spatio-temporal dynamics.

Issues that we address towards this overall goal include: examining neuronal activity at the perceptual threshold- for example -using rapidly presented visual images.  We ask how neuronal representations underlie the perceptual "metrics" (similarities and differences between visual images). How do neuronal maps re-emerge during different stages of sleep?  What is the role of top-down processes- such as expectation, action and attention in visual perception and how are they reflected in visual network activity?  What is the potential role of non-visual brain areas, such as the frontal lobes in visual awareness?  In particular, we examine how models of visual perception can be fitted into global cortical frameworks of specialization such as inward ("intrinsic") and outward ("extrinsic") oriented systems.

Finally, important insights can be gained not only from considering the human visual system as an "information processing" device, but also when it is deprived of visual input- i.e. during rest.  Understanding the state changes of the visual system as it toggles between visual awareness and rest can provide important clues to the critical factors underlying perpetual awareness.  Furthermore, the dynamics of the visual system, as well as other cortical systems during rest provide a potential "window" into brain plasticity, abstract thought processes, and even various brain pathologies.

These complex issues necessitate measurements at multiple spatial and temporal scales.  Our research attempts to achieve such information by integrating slow, non-invasive brain imaging using magnetic resonance (fMRI) and fast, invasive recordings, conducted for clinical purposes in patients. This approach is providing new insights about the information flow, integration and nature of neuronal signals that ultimately results in the appearance of a vivid visual image in a person's mind.