Cognitive impairments in psychotic disorders: common mechanisms and measurement

Decades of research have provided robust evidence of cognitive impairments in psychotic disorders. Individuals with schizophrenia appear to be impaired on the majority of neuropsychological tasks, leading some researchers to argue for a "generalized deficit", in which the multitude of cognitive impairments are the result of a common neurobiological source. One such common mechanism may be an inability to actively represent goal information in working memory as a means to guide behavior, with the associated neurobiological impairment being a disturbance in the function of the dorsolateral prefrontal cortex. Here, we provide a discussion of the evidence for such impairment in schizophrenia, and how it manifests in domains typically referred to as cognitive control, working memory and episodic memory. We also briefly discuss cognitive impairment in affective psychoses, reporting that the degree of impairment is worse in schizophrenia than in bipolar disorder and psychotic major depression, but the profile of impairment is similar, possibly reflecting common mechanisms at the neural level. Given the recent release of the DSM-5, we end with a brief discussion on assessing cognition in the context of diagnosis and treatment planning in psychotic disorders.

A female advantage in basic face recognition is absent in schizophrenia

Healthy females outperform males on face recognition tasks. Relative to healthy individuals, schizophrenia patients are impaired at face perception. Yet, it is unclear whether the female advantage found in healthy controls is preserved in females with schizophrenia. In the present study, we compared male and female patients and healthy controls on two basic face perception tasks - detection and identity discrimination. In the detection task, subjects located an upright or inverted line-drawn face (or tree) embedded within a larger line-drawing. In the identity discrimination task, subjects determined which of two side-by-side face images matched an earlier presented face image. Healthy females were significantly more accurate than healthy males on face detection, but not on identity discrimination. However, female patients were not more accurate than male patients on either task. On both upright face detection and face identity discrimination, healthy controls significantly outperformed patients. Patients' performance on face detection was closely associated with tree detection and IQ scores, as well as level of psychosis. This pattern of results suggests that a female advantage in basic face perception is no longer available in schizophrenia, and that this absence may be related to a generalized deficit factor which acts to level performance across sexes, and putative changes in sex-related neurobiological differences associated with schizophrenia.

Building a clinically relevant cognitive task: case study of the AX paradigm

Tasks developed for basic cognitive neuroscience are often ill suited for experimental psychopathology. The development of the expectancy variant of AX continuous performance task to test theories about context processing in schizophrenia is used as an illustration of how this has been done in one research program. Four design principles are recommended: tasks should (1) have a foundation in existing literature and therefore stay as close as possible to an existing task; (2) be simple, which is frequently accomplished by paring down a task to evaluate the function of interest; (3) probe a mechanism of interest, with conditions that selectively manipulate this mechanism; and (4) have the potential to distinguish a specific deficit on the mechanism of interest from a generalized impairment. Data from a number of studies support several aspects of context-processing theory; however unpredicted results have also been reported. The development of the expectancy AX paradigm continues, and future developments that may enhance its usefulness are also described.