Somatosensory processing in the biological relatives of schizophrenia patients: a signal detection analysis of two-point discrimination

This study examined 2-point discrimination performance in 1 st-degree biological relatives (n = 39) of individuals with schizophrenia and normal adult control participants (n = 30) recruited from the community. They completed an objective 2-point discrimination task, adapted for use with a signal detection approach to permit separation of discriminability (i.e., sensitivity, d') from response bias/ criterion (or motivation, lnbeta). Relatives revealed poorer performance on the d' index compared with controls. The 2 groups did not differ on lnbeta, suggesting a genuine difference in sensitivity but not response bias. The sensitivity deficit might reflect decreased spatial acuity and/or impaired intensity cue processing of tactile stimuli. Poor performance on the d' index was most closely associated with 2 schizotypic features, namely "odd beliefs/magical thinking."     

The relationship of clinical, cognitive and social measures in schizophrenia: a preliminary finding combining measures in probands and relatives

This study examines performance of schizophrenia patients, unaffected relatives and controls in social cognition, cognitive and psychiatric scales looking for possible markers of vulnerability in schizophrenia. Performance of schizophrenia patients from multiplex families, first-degree relatives, and matched controls was compared and, subsequently, discriminant analysis method was used for identifying the best predictors for group membership. By using Multigroup Discriminant Analyses on the three groups, the best predictors were PANSS, Premorbid Adjustment Scale, Faux Pas test, and a face/emotion categorizing task. This model obtained 82% correct global classification, suggesting that the combination of psychiatric scales and neuropsychological/social cognition tasks are the best approach for characterizing this disease. Although preliminary, our results suggest that social cognition tasks are robust markers of schizophrenia family impairments, and that combining clinical, social and neuropsychological measures is the best approach to asses patients and relatives vulnerability.     

Response inhibition and interference control: Effects of schizophrenia,genetic risk,and schizotypy

The ability to inhibit inappropriate responses and suppress irrelevant information is a core feature of executive control. In this study, we provide a detailed analysis of prepotent response inhibition and interference in patients with schizophrenia. To further test the role of genetic factors and subclinical schizophrenia‐like traits, we additionally studied clinically unaffected, first‐degree relatives of schizophrenia patients and assessed dimensions of schizotypy in both relatives and healthy controls. Inhibition and interference control were assessed using a battery comprising the antisaccade, Stroop, stop signal, go/no‐go, flanker, and Simon tasks. Schizophrenia patients differed from both relatives and controls in making more errors on the antisaccade task and having longer response times on the Stroop task, especially the incongruent condition. Patients also had general, that is, condition independent, increases in reaction times on the go/no‐go and flanker tasks and made more errors on the flanker and Simon tasks, suggesting general performance impairments independent of inhibitory demand. Relatives were characterized by hypometric antisaccade amplitude gain despite normal prosaccades, suggesting a selective deficit in non‐standard sensorimotor transformations. Schizotypy was correlated with inhibitory performance across a number of tasks in both relatives and controls. Generally, these effects were independent of verbal intelligence levels. Overall, the findings point to rather selective impairments of inhibitory control in the schizophrenia spectrum and confirm a previously observed deficit in antisaccade spatial accuracy as an endophenotype of schizophrenia.     

The contribution of metamemory deficits to schizophrenia

A number of recent studies have demonstrated that individuals with schizophrenia display knowledge corruption; that is, they hold false information with strong conviction. This aberration in metamemory is thought to stem from poor memory accuracy in conjunction with impaired discrimination of correct and incorrect judgments in terms of confidence. Thirty-one participants with schizophrenia, along with 61 healthy control participants and 48 control participants with other psychiatric conditions, participated in a computerized source memory task. Whereas no differences in memory accuracy were observed between the group with schizophrenia and the group with other psychiatric diagnoses, knowledge corruption was specifically impaired in those with schizophrenia. Schizophrenia participants showed a significantly decreased confidence gap: They were more confident in errors and less confident in correct responses relative to those in the control groups. Knowledge corruption is theorized to be a potential risk factor for the emergence of delusions.     

Maintenance of grip-induced muscle tension: a behavioral marker of schizophrenia.

A grip-induced muscle tension maintenance task distinguished between schizophrenic patients, regardless of medication or hospitalization status, and both normals and controls with affective (unipolar and bipolar) disorders. Unaffected first-degree relatives of schizophrenic patients also showed a grip deficit. Coupling the grip task with a visual discrimination task that divided attention through instruction or reinforcement contingency, increased grip error times for all groups. No group differences appeared on the discrimination task, regardless of difficulty level, and the tone used to provide corrective feedback was not implicated in the grip deficit. The results suggest that the grip task is tapping, in a systematic and reliable manner, a motor-control abnormality that may be useful as a behavioral marker of schizophrenia.     

Common and specific cognitive deficits in schizophrenia: relationships to function

The goals of the present study were to assess the interrelationships among tasks from the MATRICS and CNTRACS batteries, to determine the degree to which tasks from each battery capture unique variance in cognitive dysfunction in schizophrenia, and to determine the ability of tasks from each battery to predict functional outcome. Subjects were 104 schizophrenia patients and 132 healthy control subjects recruited as part of the CNTRACS initiative. All subjects completed four CNTRACS tasks and two tasks from the MATRICS battery: Brief Assessment of Cognition in Schizophrenia Symbol Coding and the Hopkins Verbal Learning Test. Functional outcome was also assessed in the schizophrenia subjects. In both the patient and control groups, we found significant intercorrelations between all higher order cognitive tasks (episodic memory, goal maintenance, processing speed, verbal learning) but minimal relationships with the visual task. For almost all tasks, scores were significantly related to measures of functional outcome, with higher associations between CNTRACS tasks and performance-based measures of function and between one of the MATRICS tasks and self-reported functioning, relative to the other functioning measures. After regressing out variance shared by other tasks, we continued to observe group differences in performance among task residuals, particularly for measures of episodic memory from both batteries, although these residuals did not correlate as robustly with functional outcome as raw test scores. These findings suggest that there exists both shared and specific variance across cognitive tasks related to cognitive and functional impairments in schizophrenia and that measures derived from cognitive neuroscience can predict functional capacity and status in schizophrenia.     

Mentalising, schizotypy, and schizophrenia.

Despite accumulating evidence that patients with schizophrenia perform poorly in mentalising tasks, doubts remain about the primacy of the role played by defective mentalising in schizophrenia. This study investigated the relationship between mentalising ability and self-reported schizotypal traits in non-clinical adults who reported no history of psychiatric illness in order to test two counter-proposals: (1) defective mentalising is a primary cause of psychotic symptoms in schizophrenia; and (2) defective mentalising in schizophrenia is a secondary consequence of the chronic asociality that is typical of general psychiatric illness. Mentalising ability was tested using a false-belief picture sequencing task that has been used elsewhere to demonstrate poor mentalising in patients with schizophrenia. Evidence of selective mentalising deficits in high schizotypal non-clinical subjects discounted the view that defective mentalising is restricted to psychiatric illness and strengthened the case for continuity models of psychosis-proneness. Furthermore, evidence that poor mentalisers in the normal population are more likely to self-report psychotic-like traits, as well as asocial or idiosyncratic behaviours, refuted suggestions that defective mentalising is linked solely to asocial symptomatology and supported the view that defective mentalising may have a fundamental role to play in the explanation of psychotic symptoms. In order to specify what that role might be, alternative theoretical accounts of defective mentalising were tested. Neither executive planning deficits nor failure to inhibit cognitively salient inappropriate information could adequately explain the pattern of selective mentalising deficits found in high schizotypal non-clinical subjects. Our findings suggest that there exists a domain-specific cognitive module that is dedicated to inferring and representing mental states which, when dysfunctional, causes defective mentalising that manifests phenomenologically in psychotic-like traits and impoverished social awareness of variable expression and ranging severity.     

Oculomotor delayed response abnormalities in young offspring and siblings at risk for schizophrenia

Individuals with schizophrenia are know to demonstrate cognitive and behavioral difficulties, particularly alterations in executive functions, including working memory. It is unclear whether these deficits reflect trait-related vulnerability to schizophrenia indicators and can be assessed by studying nonpsychotic relatives of patients with schizophrenia. In this study, we used an oculomotor delayed response (ODR) paradigm to examine spatial working memory in 37 "high-risk" child and adolescent offspring and siblings (age range=6-25 years) of patients with schizophrenia or schizoaffective disorder. Compared with 37 age- and sex-matched healthy controls (age range=6-23 years), high-risk subjects showed nonsignificantly greater errors in the ODR task at longer delay intervals. Statistical analyses suggested that performance improved with age in healthy control subjects, whereas it worsened with age in high-risk subjects. In both groups, the ODR errors were generally associated with poorer sustained attention (Continuous Performance Test: visuospatial d prime), somewhat poorer executive function (Wisconsin Card Sorting Test), and elevated Heinrichs-Buchanan neurological soft signs scores. These findings indicate the presence of spatial working memory abnormalities in individuals at risk for schizophrenia. Furthermore, these abnormalities may be progressive in nature. The ODR task is a valuable indicator of prefrontal cortical function and spatial working memory and may be a potentially valuable marker for familial risk of schizophrenia.     

Psychometrically matched visual-processing tasks in schizophrenia spectrum disorders

Patients with schizophrenia show deficits in visual perception and working memory, but the relationship between these deficits has not been characterized with psychometrically matched tasks. The authors administered 2 visual discrimination and 6 recognition tasks to 43 schizophrenia spectrum patients and 22 nonpsychiatric subjects. When performing difficulty-matched tasks, spectrum subjects showed more severe impairments for motion compared with form processing. When tasks were matched on true score variance, spectrum subjects exhibited worse performance on both form and motion discrimination, and a differential deficit in motion recognition with a short display duration and long interstimulus interval. These results provide evidence of differential deficits in visual processing in schizophrenia that appear to be dependent on the temporal characteristics of the tasks.     

Quality of life assessment in Turkish patients with schizophrenia and their relatives

Quality of life of first-degree relatives living in the same household with patients having schizophrenia has not been sufficiently explored. 30 patients with schizophrenia (16 women, 14 men), diagnosed using DSM-IV criteria, 31 of their relatives (15 women, 16 men), and 34 control subjects (21 women, 13 men) were included in the study. The mean age of the patients, their relatives, and the control subects were 39.8 +/- 10.9, 58.1 +/- 12.5 and 37.3 +/- 17.0, respectively. The World Health Oranization Quality of Life-Brief Form was administered to all subjects. Quality of life was worse for the patient group than for their relatives and control subjects, but relatives of the patients and control subjects were not significantly different on Quality of life. Quality of life was negatively correlated with the severity of psychopathology and extrapyramidal side effects induced by antipsychotic drugs in the patients.     

Impaired control of visual attention in schizophrenia

To investigate attentional impairment in schizophrenia, the authors examined the performance of 22 patients with schizophrenia and 16 healthy control subjects in 4 visual search tasks that varied in perceptual requirements and in the need for precise attentional control. The rate of search was slowed in the patients in all tasks. However, the degree of slowing was largest in tasks requiring precise attentional control and smallest in tasks that were perceptually difficult but required less attentional control. This pattern of results indicates that the primary impairment of attention in schizophrenia lies in the control of attention and not in the selection processes that operate once attention has been directed to an object.     

Identification of tone duration, line length, and letter position: an experimental approach to timing and working memory deficits in schizophrenia

Patients with schizophrenia display numerous cognitive deficits, including problems in working memory, time estimation, and absolute identification of stimuli. Research in these fields has traditionally been conducted independently. We examined these cognitive processes using tasks that are structurally similar and that yield rich error data. Relative to healthy control participants (n = 20), patients with schizophrenia (n = 20) were impaired on a duration identification task and a probed-recall memory task but not on a line-length identification task. These findings do not support the notion of a global impairment in absolute identification in schizophrenia. However, the authors suggest that some aspect of temporal information processing is indeed disturbed in schizophrenia.     

The role of recollection in source memory: an examination of schizophrenia patients and their first-degree relatives

Source recognition memory deficits have repeatedly been observed in people with schizophrenia (SZ), and have also recently been observed in their first-degree relatives. These deficits have been hypothesized to result, at least in part, from impairments in the conscious recollection process. Although other processes are clearly also affected in SZ, it has been proposed that impairments in the conscious recollection process could be a parsimonious explanation for the source memory deficits observed in their relatives. Here, we tested 25 patients with SZ and 34 of their non-affected parents, as well as two groups of matched healthy controls, on a short-term associative memory task that shares the characteristics of standard source recognition tasks but minimizes the need for recollection of stored information from memory. This task was administered in order to determine if deficits can still be observed in these people when involvement of the conscious recollection process is minimized. We observed deficits on our short-term source memory task in people with SZ, but their first-degree relatives did not share this deficit. These results support the idea that multiple memory processes supporting associative/source memory are affected in SZ, whereas the source memory deficits previously observed in relatives of SZ seem specific to tasks that rely on the conscious recollection process.     

Reaction time slowing during high-load, sustained-attention task performance in relation to psychometrically identified schizotypy

Prior research has demonstrated a reliable deficit in performance accuracy (e.g., d') on sustained-attention tasks in relation to psychometrically identified schizotypy and clinically diagnosed schizotypal psychopathology. The present study sought to expand the understanding of sustained-attention performance in relation to psychometric schizotypy through a study of reaction time (RT) performance. In this study, the author examined performance accuracy and RT on a high-load, sustained-attention task, the Continuous Performance Test-Identical Pairs (CPT-IP) version, in 31 high Perceptual Aberration Scale (PAS) and 26 normal control (control PAS) subjects from a large university population. High PAS (psychometric schizotypy) subjects displayed significantly longer RT performance on the CPT-IP relative to controls. The RT slowing was not explained by mental state or general intellectual ability factors. Contrary to expectation, a difference in performance accuracy (e.g., d') was not observed between the groups; however, power and other considerations cloud the interpretation of this finding. The meaning of the observed RT slowing is examined and its relation to current models of the development of schizophrenia is discussed.     

Facilitation of word recognition by semantic priming in schizophrenia

Schizophrenic (n = 21), bipolar (n = 18), and normal control subjects (n = 21) were compared on a word recognition measure of semantic priming. The task involved the presentation of related, neutral, and unrelated word pairs; the second word (target word) in each pair was presented in a degraded form. Facilitation was defined as the accuracy of target word recognition for the related word pairs minus accuracy for the neutral word pairs. Titration, achieved by manipulating the degradation of the target word, was used to maintain each subject's overall accuracy for related and neutral items at approximately 50%. This procedure minimized the artifactual effects of overall accuracy on the difference score. Schizophrenics exceeded both normal control subjects and bipolar subjects on facilitation. Bipolar subjects did not differ from control subjects. The results support Maher's hypothesis that semantic priming effects are heightened in schizophrenia.     

Spatial frequency discrimination in schizophrenia

Pathways within the visual system can be distinguished on the basis of selectivity for low or high spatial frequencies. Spatial frequency discrimination was evaluated in 17 medicated male patients with schizophrenia and 19 male control subjects. Subjects were required to discriminate whether pairs of high contrast, sinusoidally modulated gratings were the same or different in spatial frequency. Accuracy performance was compared at high, medium, and low spatial frequencies on tasks matched for control performance. Patients showed a greater performance decrement of 12% on low as compared with 4% on high spatial frequencies. These findings suggest a disturbance of right hemisphere mechanisms involved in spatial perception and attention in schizophrenia.     

Revisiting the suitability of antisaccade performance as an endophenotype in schizophrenia

Poor performance on the antisaccade task has been proposed as a candidate endophenotype in schizophrenia. Caveats to this proposal, however, include inconsistent findings in first-degree relatives of individuals with schizophrenia, and substantial heterogeneity in individuals with the disorder. In this study, we examined antisaccade performance in patients and relatives, and sought to establish whether antisaccade measures could differentiate between two patients clusters identified in the Western Australian Family Study of Schizophrenia with either pervasive cognitive deficits (CD) or cognitively spared (CS). Ninety-three patients (CD = 47, CS = 46), 99 relatives and 62 healthy controls carried out a standard antisaccade task. Results showed: (i) significantly greater error rate, and prolonged latencies to correct responses and self-correction saccades in patients compared with controls; (ii) high error rates in relatives of poorly performing patients; (iii) longer latencies of self-correction saccades in relatives compared to controls; and (iv) higher error rate and longer latencies of self-correction saccades in the CD subgroup compared with CS. Unaffected relatives as a group were unimpaired in error rate as compared to healthy controls. These findings suggest that the antisaccade error rate and latency of self-correction saccades are useful measures in specific applications of genetic research in schizophrenia, without fully meeting endophenotype co-familiality requirements.     

Un déficit de mémoire de la source spécifique chez les patients schizophrènes comparés à des volontaires sains et des patients présentant un épisode dépressif majeur

One of the main cognitive models of positive symptoms in schizophrenia proposes that they arise through impaired self-monitoring. The most replicated findings is that, compared to healthy volunteers, schizophrenics patients have impairment in source monitoring tasks required to distinguish between memories of their self-generated material and externally generated events, generally words, as a consequence of a malfunction in either a central monitor or in a reality discrimination process. However, only few studies have investigated the specificity of those tasks. The aim of this study was to compare performances in 2 source monitoring tasks of 3 groups: 30 schizophrenic patients with positive symptoms, 22 patients presenting a major depressive disorder and 24 healthy volunteers. Tasks were built using current French words extracted from a verbal fluency task. We reported a specific significant deficit in source monitoring task in patients with schizophrenia, no difference was observed between healthy volunteers and major depressive disorder patients.     

Exaggerated leftward bias in the mental number line of patients with schizophrenia

Several visuo-motor tasks can be used to demonstrate biases towards left hemispace in schizophrenic patients, suggesting a minor right hemineglect. Recent studies in neglect patients used a new number bisection task to highlight a lateralized defect in their visuo-spatial representation of numbers. To test a possible lateralized representational deficit in schizophrenia, we used the number bisection task in 11 schizophrenic patients compared to 11 healthy controls. Participants were required to orally indicate the central number of an interval orally presented. Whereas healthy subjects showed no significant bias, schizophrenic patients presented a significant leftward bias. Therefore, these results suggest an impairment in higher order representations of the number space in patients with schizophrenia, an impairment that is qualitatively similar to the deficit described in neglect patients.     

Performance of schizophrenia and bipolar patients on verbal and figural working memory tasks

Working memory (WM) was studied in 82 healthy volunteers, 43 schizophrenia patients, and 81 bipolar patients. Schizophrenia patients were impaired on verbal and figural WM tasks that possessed similar test discriminating power. Bipolar patients performed similarly to healthy volunteers. A mathematical model of WM performance revealed a primary role for reduced WM span in accounting for the impaired verbal WM of schizophrenia patients and a primary role for diminished attention in accounting for impaired figural WM. Although WM impairment in schizophrenia is due neither to the general effects of severe mental illness nor to the specific type of material studied, the microarchitecture of abnormal WM in schizophrenia may depend on the stimulus material presented.