Functional microarchitecture underlying target selection and saccade generation in the primate frontal eye field

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Whether we look for a friend in the crowd or try to find a pen on our messy desk, our brain has to constantly distinguish between many different visual objects. To examine a visual object in detail, we generally look towards it so that the object falls on the region of our retina that has the highest resolution. However, as we all know from daily experience, we can also shift our attention to the periphery of our visual field while keeping our eyes still. This form of attention is thought to be a neural process that enhances the signals from a particular part of the visual field. The current view is that the brain areas that control eye movements also perform shifts of attention. According to this hypothesis, shifts of attention are thought to be planned eye movements. This view has been supported by functional brain imaging studies in humans. These studies have shown that a brain area in the frontal part of the brain, called the frontal eye field, is active both for eye movements and shifts of attention. However, studies in monkeys that recorded the activity of single nerve cells in the frontal eye field have suggested that separate groups of nerve cells may be involved in eye movements and shifts of attention. To directly test whether frontal eye field nerve cells send the same type of signal to the neural machinery in the brain stem that controls eye movements and to brain areas in the back of the brain that are involved in vision, we will identify and record these signals in monkeys. These experiments will directly test whether shifts of attention involve the groups of nerve cells in the frontal eye field that also control eye movements.