Cognition and the inhibitory control of saccades in schizophrenia and Parkinson's disease.

Historically, various lines of evidence have converged on the view that the brain expends much of its neural resources on inhibiting its own activity in a critical step towards the cognitive control of behaviour. The loss of inhibitory control is widely reported in neurological and psychiatric disorders; however, the consequences of reduced inhibition in terms of wider cognitive effects on cognitive control operations such as planning, abstract thought, working memory and the ability to appreciate the perspective of others ('theory of mind') has been widely overlooked. The antisaccade paradigm examines the conflict between a prepotent stimulus that produces a powerful urge to fixate the target, and the overriding goal to 'look' in the opposite direction. In this chapter we illustrate how this paradigm is increasingly used to explore the relationship of inhibitory control and cognition in Parkinson's disease, schizophrenia and healthy participants. Evidence is presented that is consistent with the theory of cognitive inhibition as a distinct process that can be dissociated from working memory. We conclude that the inhibitory control of saccadic eye movement should be studied in the wider context of cognitive operations.