Visual Psychophysics

Ivan Bodis-Wollner, MD, DSc, who is board certified in both neurology and ophthalmology, has conducted studies looking at eye movements and visual stability impairment in neurodegenerative disorders. Quick, darting eye movements, called saccades, and blinks are executed constantly when one is awake. Yet one is neither aware of their occurrence, nor of a shifting visual scene by S, nor of an interruption of vision by B. While much has been recently learned concerning how frontal and parietal cortical mechanisms ensure visual stability and continuity associated with saccades and blinks, the role of the occipital cortex remains an enigma. Recent data suggest occipital participation during saccades and blinks even without visual input.

Dr. Bodis-Wollner uses techniques of functional MRI (fMRI), transcranial magnetic stimulation (TMS) and discrete wavelet transformation of the perisaccadic EEG to allow both frequency and time resolution. Although different, these techniques converge to determine intrinsic occipital neuronal mechanisms.

Saccadic eye movement and blink-related occipital responses are compared to the effect of visual stimulation without eye movement. Furthermore the potential differential processing of so-called isoluminant color and luminance contrast stimuli will be evaluated during saccades and blinks.

The studies have a significance to the physiology of eye movements, blink and vision, and to short-term, activity-dependent plasticity as one early step in sensorimotor coordination. Potentially they may contribute to clinical neurology in neurodegenerative disorders in which saccades and visual perception suffer, and to research and diagnosis in schizophrenia.