UW Eye Research Institute
Alfred Yarbus’ seminal study in 1967 illustrated that eye movement patterns correspond to the underlying structure in an image. In one test, subjects were asked to determine the ages of the people in the painting “An Unexpected Visitor,” by I.E. Repin, while their eye movements were tracked. The lines in the image under the painting represent the saccades – eye sweeps – made by the viewer, and the dots were the points where gaze rested. The most intense areas of line tracings clearly overlap the faces and bodies of the people depicted in the images, showing that the eye movement patterns clearly correspond to the task given to the subject.Tracking saccades, rapid eye movements from one position to another, is key to learning about the neural mechanisms linking vision and action. The sudden appearance of a bright light initiates a saccade that draws our eyes reflexively toward that target; or, we may volitionally direct our gaze to a remembered point. By manipulating visual tasks that induce different types of saccades, Basso can focus on cognitive processes such as target selection, memory and learning.
“Each task has different demands, allowing for the assessment of the integrity of brain pathways in health and disease,” explains Basso. “In a saccade task that requires memory, for example, an illuminated point appears in the center of a screen and the subject maintains gaze on its location. A second point briefly appears at another screen location, while the subject is instructed to retain eye focus on the first point. After a short delay, the first point disappears, signaling the subject to make a saccade to the location of the second flashed target point. This task provides a test of spatial working memory.” During this simple task, Basso takes electrophysiological recordings of neuron activity in non-human primates, monitoring responses in brain locations such as the superior colliculus and the basal ganglia, brain areas involved in transforming visual signals into internal representations that ultimately become commands to move the eyes.
What is it that allows patients with Parkinson’s disease to move in response to visual cues but prevents movement in the absence of visual stimulus to guide them? To unravel this paradox, Basso uses her study of healthy animal subjects as a baseline to advance knowledge of neural processing behind basic eye movement behaviors in conjunction with clinicians Karl Sillay, MD, UW Neurological Surgery and Ming Cheng, MD, Brown University Neurosurgery Foundation. Together they investigate how the transformation of visual information to movement goes awry in humans with neurological diseases. (Next)(Previous)