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 the 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. Similarly, adult alcoholics also have difficulty inhibiting context inappropriate saccades. The smooth pursuit eye movements of alcoholics are completely normal. Over the few past years, we have added several new computer-based cognitive tasks designed to assess risk-taking and impulsive behavior. One of these tasks, the Iowa Gambling Task (IGT) has been shown to be associated with damage to the ventro-mesial frontal cortex. We have found that performance on the IGT distinguishes alcoholics from controls. In this task the alcoholics engage in more high risk/high potential payoff behavior than controls. This is consistent with the idea that alcoholics are more responsive to the immediate consequences than the long-term consequences of their behavior.
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