Removal of epileptically compromised tissue in the frontal cortex restores oculomotor selection in the antisaccade task

Abstract

The frontal cortex is heavily involved in oculomotor selection. Here, we investigated the neural correlates of eye movement selection during an antisaccade task in a young epileptic patient in whom the seizure focus included the frontal cortex and affected its function. Before resection surgery, the patient had difficulty in performing correct antisaccades towards the visual field contralateral to the seizure focus. Because the FEF is the only area in the human frontal cortex that is known to have a lateralized oculomotor function in the antisaccade task, this behavioural imbalance between the two visual fields suggests a disruption of FEF functioning by the nearby seizure focus. Electrocorticographic recordings at the seizure focus indeed showed that the seizure focus interfered with correct antisaccade performance. These results were in line with fMRI recordings revealing less task-related frontal activity for the hemisphere of the seizure focus, possibly reflecting diminished top-down engagement of the oculomotor system. Two months after removal of the compromised tissue, the seizures had disappeared, and antisaccade performance was the same for both visual hemifields. We conclude that a seizure focus in the frontal cortex can induce a dysfunction in the selection of eye movements, which is resolved after removal of interfering tissue.