Spontaneous selective attention in schizophrenia

The use of working memory for task prediction: What benefits accrue from different types of foreknowledge?

The assumption that the deployment of executive processes invariably improves task performance is implicit to cognitive theory. In particular, working memory can be used to retain and update historical information about predictable trial sequences (foreknowledge) so that subjects can anticipate and prepare for the upcoming trial more effectively. We review the effects of different types of foreknowledge on response accuracy and latency, particularly in relation to experiments investigating saccadic eye movements in humans. While it is possible to make all aspects of an impending trial predictable, varying the predictability of different components of the trial independently can reveal which cognitive operations are potentially modifiable by foreknowledge. These operations include stimulus processing, retrieval of task-set rules, and response preparation, among others. The available data suggest that, while response preparation can be completed and the response even executed before the stimulus appears (i.e. anticipation) when the subject possesses complete task-foreknowledge (knowing both the stimulus to appear and the response required), foreknowledge of the task-set alone does not permit advance configuration of the task-set rules. A taxonomy for foreknowledge is proposed, including foreknowledge for timing, stimulus, set, response, and task. Work on differentiating these effects in neurophysiology, neuroimaging, and neuropsychology is still in the early stages.

A Meta-Analysis of Cognitive Deficits in Adults with a Diagnosis of Schizophrenia

This review identified 1275 studies examining cognitive deficits in people with schizophrenia, published between 1990 and 2003. Data from 113 studies (4365 patients and 3429 controls) were combined in a meta-analysis carried out on the five cognitive domains of IQ, memory, language, executive function, and attention. Studies were excluded where they lacked a suitable control group or failed to present complete information. In all five cognitive domains, analysis indicated a consistent trend for patients to perform more poorly than healthy controls, with significant heterogeneity across studies. Sources of heterogeneity were analyzed and a need to ensure more appropriate composition of patient and control groups and to adopt a more refined and methodologically correct, hypothesis-driven approach was identified.

The sensitivity of the Spontaneous Selective Attention Test (SSAT): a study of schizophrenic inpatients and outpatients versus normal controls

The Spontaneous Selective Attention Task (SSAT) is a visual word-identification task that measures the type of selective attention that occurs spontaneously when there are multiple stimuli, all potentially relevant, and insufficient time to process each of them fully. The present study was designed to examine the sensitivity of the SSAT by comparing the performance of 40 schizophrenic inpatients and 30 schizophrenic outpatients to that of 70 normal controls. The pattern of results reported previously for schizophrenic inpatients versus normals was replicated, and these findings were extended to include schizophrenic outpatients in partial symptom remission. Schizophrenic inpatients and outpatients were just as accurate in identifying words as normals, but spontaneous selective attention under conditions of predictability was abnormal in both patient groups. Furthermore, the ability of the SSAT to discriminate between schizophrenic patients and controls was confirmed. A ratio measure of spontaneous selective attention had a sensitivity of 77% and a base rate of 9% in a normal population (when a cutoff value was set to minimize false positives and false negatives). Thus, the SSAT is a sensitive measure of an attentional phenotype that may be useful in genetic studies of schizophrenia.

Genetic and developmental factors in spontaneous selective attention: a study of normal twins

The Spontaneous Selective Attention Task (SSAT) is a visual word identification task designed to measure the type of selective attention that occurs spontaneously when there are multiple stimuli, all potentially relevant, and insufficient time to process each of them fully. These are conditions which are common in everyday life. SSAT performance is measured by word identification accuracy, first under a baseline divided attention condition with no predictability, then under a selective attention condition with partial predictability introduced via word repetition. Accuracy to identify novel words in the upper location which becomes partially predictable (P words) vs. the lower location which remains non-predictable (N words) can be used to calculate a baseline performance index and a P/N ratio measure of selective attention. The SSAT has been shown to identify an attentional abnormality that may be useful in the development of an attentional endophenotype for family-genetic studies of schizophrenia. This study examined age and genetic effects on SSAT performance in normal children in order to evaluate whether the SSAT has the potential to qualify as a candidate endophenotype for schizophrenia in studies of at-risk children. A total of 59 monozygotic twin pairs and 33 same-sex dizygotic twin pairs ranging from 10 to 18 years of age were tested on the SSAT, a Continuous Performance Test. (CPT), a Span of Apprehension Test (SPAN) and a full-scale IQ test. Baseline performance on the SSAT, which was correlated with verbal IQ and SPAN performance, improved with age but showed no significant heritability. The P/N selectivity ratio was stable over the 10-18-year age range, was not significantly correlated with IQ, CPT, or SPAN performance, and its heritability was estimated to be 0.41. These findings suggest that the P/N selectivity ratio measured by the SSAT may be useful as a vulnerability marker in studies of children born into families segregating schizophrenia.