Exploring imagined movements in patients with schizophrenia.

Patients with schizophrenia demonstrate impairments indicative of an inability to accurately monitor internally generated images. Motor imagery measures the ability to generate internal images of intended but not executed motor movements. Ten patients with schizophrenia completed actual and imagined versions of a pointing task with a well defined speed-accuracy trade-off function. For controls, movement time increases as target size decreases for both actual and imagined movements. Despite showing the expected speed-accuracy trade-off for actual movements, the imagined movements of schizophrenics showed no reliable relationship to target size. This was true for each patient and appeared to be independent of symptom profile. These results suggest that patients with schizophrenia are unable to generate accurate internal images of their own motor movements.