Scholastic test scores at grades 4 and 8 were nonsignificantly below average in this group of children who later developed schizophrenia. However, test scores dropped significantly between grades 8 and 11. This corresponds to ages 13-16 years, or the onset of puberty. Poor or declining scholastic performance may be a precursor to the cognitive impairment seen during the first episode of illness.

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This study reports evidence that individuals with schizophrenia (SC) demonstrate intact attentional selection for visual working memory (WM) storage. A group of 62 participants with SC and 55 control participants without SC were studied in a series of 5 experiments that examined the ability to use top-down and bottom-up cues to guide WM encoding, as well as the ability to spontaneously select a subset of representations for storage. Participants with SC exhibited a consistent and robust ability to use selective attention in the control of WM in all 5 experiments, demonstrating a remarkable island of preserved functioning given the broad spectrum of impairments of attention and WM that have been widely reported in those with SC. These findings indicate that attention is not globally impaired in SC and make it possible to delineate more precisely the nature of the specific impairment of attention in this disorder.

Reaction times (RTs) are substantially prolonged in schizophrenia patients, but the latency of the P3 component is not. This suggests that the RT slowing arises from impairments in a late stage of processing. To test this hypothesis, 20 schizophrenia patients and 20 control subjects were tested in a visual oddball paradigm that was modified to allow measurement of the lateralized readiness potential (LRP), an index of stimulus-response translation processes. Difference waves were used to isolate the LRP and the P3 wave. Patients and control subjects exhibited virtually identical P3 difference waves, whereas the LRP difference wave was reduced in amplitude and delayed in latency in the patients. These results indicate that, at least in simple tasks, the delayed RTs observed in schizophrenia are primarily a consequence of impairments in the response selection and preparation processes that follow perception and categorization.Although delusions and hallucinations are the most dramatic features of schizophrenia, this disorder is also accompanied by pervasive, debilitating, and treatment-resistant cognitive and psychomotor deficits (Gold, 2004). Of these, deficits in episodic memory and executive function have attracted the most interest in the research literature. However, a recent metaanalysis revealed that deficits in processing speed, as assessed by Digit Symbol tasks, is the most robust impairment documented in the literature (Dickinson, Ramsey, & Gold, 2007). This psychometric evidence echoes the claim made by Robert Cancro more than 3 decades ago that reaction time (RT) slowing is the "closest thing to a north star in schizophrenia research" (Cancro, Sutton, Kerr, & Sugerman, 1971, p. 351). Thus, there is abundant evidence for slowed behavioral performance in schizophrenia, but the origins of this impairment remain largely obscure despite extensive behavioral studies of reaction time in the older literature (see review by Nuechterlein, 1977). That is, it is unclear if observed behavioral slowing is the result of slowing at all stages of task processing or whether slowing at a specific stage of processing is implicated. Indeed it appears likely that the failure of this older body of research to reveal the origins of response slowing in schizophrenia led the field to largely abandon the investigation of this robust empirical finding.We have begun using event-related potentials (ERPs) to reexamine this issue. In our first study, we used the N2pc component to show that the allocation of visual attention occurs at the same speed in patients with schizophrenia and healthy control subjects, despite the fact that RT slowing was observed in the patients . The current experiment was designed to use the P3 wave and the lateralized readiness potential to determine if the categorization and response selection processes indexed by these ERP components are related to RT slowing.Correspondence from the editor and publisher should be sent to: Steven J. Luck,

Dystonia is a movement disorder considered to result from basal ganglia dysfunction. The aim of this study was to investigate the functional significance of frontal hyperactivity demonstrated in dystonia in imaging studies by examining executive function and working memory, in which the prefrontal cortex is known to be involved. We assessed 10 patients with idiopathic dystonia and 12 age- and IQ-matched normal controls. All subjects completed tests of first letter, category, and alternating category word fluency, the Wisconsin Card Sorting Test, the Stroop Colour Word Naming Test, the Missing Digit Test of working memory, a test of random number generation, a test requiring generation of self-ordered random number sequences, the Paced Serial Addition Test, a test of conditional associative learning, and finger tapping and peg insertion under unimanual, bimanual, and dual task conditions. The patients with dystonia did not differ significantly from controls on any measures of executive function or working memory used other than category word fluency and the extent of decline in tapping with one hand under dual task conditions when simultaneously inserting pegs with the other hand. For this small sample, the results suggest that unlike other movement disorders associated with fronto-striatal dysfunction such as Parkinson's disease or Huntington's disease, dystonia was not associated with deficits on the tests of executive function or working memory used. A more detailed investigation of cognitive function in a larger sample of patients is required.