Delayed hemodynamic responses in schizophrenia.

While there are many reports of reduced amplitude of hemodynamic responses in schizophrenia, there are no reports of delayed hemodynamic responses, in spite of event-related brain potential (ERP) evidence of slowed neural responses. Recently, Henson et al. (2002) [Henson, R.

Acquiring and inhibiting prepotent responses in schizophrenia: event-related brain potentials and functional magnetic resonance imaging.

Background: Schizophrenia is associated with deficits in using context to establish prepotent responses in complex paradigms and failures to inhibit prepotent responses once established.

Objective: To assess prepotent response establishment and inhibition in patients with schizophrenia using event-related brain potential (ERP) and functional magnetic resonance imaging (fMRI) in a simple NoGo task. To combine fMRI and ERP data to focus on fMRI activations associated with the brief (approximately 200 ms) moment of context updating reflected in the NoGo P300 ERP component.

Anatomy of an error: ERP and fMRI.

Successful inhibition of pre-potent responses involves conflict; failed inhibition involves both conflict and errors, complicating the study of errors. Event-related potential (ERP) and functional magnetic resonance imaging (fMRI) data were collected while ten subjects (26-55 years old) performed a Go/NoGo task, with pre-potent responses (88% Go) and inhibition of responses (12% NoGo). We measured error-related negativity (ERN) to false alarms (FA), correct-related negativity (CRN) to hits, NoGo N2 to correct rejections (CR) and Go N2 to hits.