The study of human eye movements provides an extremely useful approach to the examination of a variety of cognitive functions. It is obvious that the latency and goal of saccadic eye movements are related to attention. What is not so obvious is that other aspects of cognition such as short-term memory, preparatory set, and inhibition of context inappropriate responses can also be assessed using eye movement techniques. Short-term memory, preparatory set, and inhibition of context inappropriate responses constitute core functions of the prefrontal cortex, the brain region most involved in the control of higher order cognitive processes. We have used a number of different tasks to elicit saccades, including Go/No Go tasks and delayed response tasks. These tasks allow us to independently assess core functions of the prefrontal cortex by measuring the accuracy and latency of memory guided saccades, as well as the frequency of context inappropriate saccades that should be inhibited. Using these tasks we have demonstrated that schizophrenics are impaired in all three core aspects of prefrontal cortex function while children with Attention Deficit Hyperactivity Disorder (ADHD) are impaired in only their ability to inhibit context inappropriate saccades. Similarilly adult alcoholics also have difficulty inhibiting context inappropriate saccades. The smooth pursuit eye movements of alcoholics are completely normal; however, preliminary evidence suggests that cerebellar volume measured by MRI is correlated with smooth pursuit performance. - behavioral research, neurosciences, electrophysiology/EEG - Human Subjects
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