Cognitive subprocesses and schizophrenia. A. Reaction-time decomposition

Comparable repetition blindness effect in patients with schizophrenia

BACKGROUND AND OBJECTIVES

Repetition blindness (RB) refers to the difficulty to report repetitions of stimuli visually presented in a rapid list. To date only two studies have examined RB in patients with schizophrenia and the results are not clear-cut. The current study was designed to employ a task with reduced memory load, more trials in each experimental condition, and more participants to obtain a more reliable RB effect.

METHODS

A 2x2x3x2 mixed factor repeated measure design was used, with stimulus repetition, lag, and presentation rate as within-subject factors, and group (patient or control) as a between-subject factor. A rapid serial visual presentation (RSVP) procedure was used. Twenty eight inpatients with schizophrenia and 28 healthy controls participated in the experiment.

RESULTS

The patient group showed significantly impaired performance when compared tothe control group in every experimental condition. Nevertheless, the patient group demonstrated similar RB effect as the control group. Furthermore, the overall RB effect observed in patients did not relate to their illness severity or psychotic symptoms. Neither was it related to their age or education.

LIMITATIONS

It was difficult to match the age and education of the control group to that of the inpatient group.

CONCLUSIONS

Patients with schizophrenia performed worse than healthy controls in each experimental condition. Both the control and patient group showed robust RB effect in the short lag with faster rates. In addition, RB effect seemed to be irrelevant to patients' illness severity and clinical symptoms.

Fine Detection of Human Motion During Activities of Daily Living as a Clinical Indicator for the Detection and Early Treatment of Chronic Diseases: The E-Mob Project

Methods to measure physical activity and sedentary behaviors typically quantify the amount of time devoted to these activities. Among patients with chronic diseases, these methods can provide interesting behavioral information, but generally do not capture detailed body motion and fine movement behaviors. Fine detection of motion may provide additional information about functional decline that is of clinical interest in chronic diseases. This perspective paper highlights the need for more developed and sophisticated tools to better identify and track the decomposition, structuration, and sequencing of the daily movements of humans. The primary goal is to provide a reliable and useful clinical diagnostic and predictive indicator of the stage and evolution of chronic diseases, in order to prevent related comorbidities and complications among patients.

Divided Attention in Schizophrenia: A Dual Task Paradigm

Schizophrenia is known to be associated with attentional deficits. Few studies have examined whether the disorder is also associated with a deficit in the ability to divide attention, and they have given contradictory results. Some have reported that patients show greater loss of performance than healthy controls when moving from single tasks to dual tasks, and others have reported that performance loss is similar in both groups or even that patients perform the dual task better than either task on its own. To help resolve this controversy, we performed a first study in which we designed a dual task paradigm with a group of 36 healthy participants. This dual task involves 2 tasks of equivalent difficulty that make use of different sensory modalities. In the second study, we gave this dual task to 23 patients with schizophrenia and 25 healthy participants. Both groups decreased similarly their performance in dual tasks, but the patients showed lower baseline performance in the single task. Our findings suggest that patients with schizophrenia and healthy participants use similar strategies to divide their attention, but in a high-degrading stimuli condition patients perform below the controls in a single task.

Effects of different types of sensory signals on reaching performance in persons with chronic schizophrenia

Previous studies have reported movement abnormalities in persons with schizophrenia. This study aimed to examine the differences between persons with chronic schizophrenia and healthy control participants in reaching movement and the effects of sensory signals on reaching performance in persons with chronic schizophrenia. A counter-balanced repeated-measures design was employed. Twenty persons with schizophrenia and 20 age- and gender-matched control participants were recruited in this study. Reaching performance was measured in three types of sensory signal conditions (visual, auditory, and no signal), i.e., two externally triggered and one self-initiated movement were assessed in reaction time/inter-response interval, movement time, peak velocity, percentage of time in which peak velocity occurred, and movement units. The results revealed significant main effects of group in reaction time/inter-response interval (p = 0.003), movement time (p < 0.001), peak velocity (p < 0.001), and movement units (p < 0.001). The persons with chronic schizophrenia demonstrated slower response to signals and in self-initiated movement, increased movement time, and less forceful and less smooth movement compared to healthy control participants when performing the reaching task. The interaction effect between group and signal in reaction time/inter-response interval was also significant (p < 0.001). The inter-response interval for self-initiated reaching was the shortest in healthy controls. Conversely, the inter-response interval for self-initiated reaching was the longest in persons with schizophrenia. The main effect of the signal on movement time was significant (p < 0.001). The movement time of reaching was longer in response to the auditory signal than in response to visual or self-initiated. The differences in percentages of time in which peak velocity occurred between persons with schizophrenia and healthy controls (p > 0.01) and across the three conditions (p > 0.01) were non-significant. Neither duration of illness nor antipsychotic dosage was significantly associated with reaching performance (all p > 0.01). In conclusion, these findings indicate that reaching movement in persons with chronic schizophrenia is slower, less forceful, and less coordinated compared to healthy control participants. In addition, persons with chronic schizophrenia also had shorter inter-response interval for self-initiated movement and shorter movement time in auditory signal condition, independent of duration of illness and antipsychotic dosage.

Emotional Recognition in Schizophrenia: An Analysis of Response Components in Middle-Aged Adults

Ageing seems to present a bias towards positive stimuli that might be reflected in response times. However, this process is more complex for middle-aged adults, and even more in schizophrenia. In order to examine this issue, an experimental study was carried out in which 48 participants were divided into two groups: an experimental group of 24 participants diagnosed with schizophrenia and a control group of 24 subjects with no disorders. The main objective of the study was to evaluate response time components according to the emotional valence of the stimulus, to test recognition and discrimination in both groups. A battery of 120 images from the International Affective Picture System (IAPS), representing positive, negative and neutral emotional valences, was employed. Response times were evaluated in terms of analysis of variance, as well as its inherent response times components. The results showed slower responses in the group with schizophrenia than in the control one. Moreover, a poorer performance was depicted in the latency components this group. Finally, a differential deficit pattern for emotion between groups was not found.

Not All Differences between Patients with Schizophrenia and Healthy Subjects Are Pathological: Performance on the Conners' Continuous Performance Test

OBJECTIVE

This study analyzed attentional performance in patients with schizophrenia during a continuous performance task requiring a high response rate.

METHOD

The Conners' Continuous Performance Test-II (CPT-II) was administered to 64 patients with schizophrenia and 64 healthy comparison subjects. A cross-sectional design was used in order to allow analysis of the means between patients and healthy subjects. Differences in performance were assessed for significance using ANCOVA. Percentiles were also analyzed in order to determine whether a participant showed normal or pathological performance. Pearson's correlation was used to detect possible relationships between attentional performance and psychopathology.

RESULTS

Of the 12 CPT-II measures, response style and slowing of reaction time (RT) between targets increased to similar extents between patients and healthy comparison subjects. Patients performed significantly less well than non-patient group on all other measures. Nevertheless, patient's performance on four of these measures remained within the normal range, and patient's performance on the remaining measures qualified as pathological only in the case of variability in hit RT. No significant correlations between attention performance and symptoms were found.

CONCLUSIONS

These results suggest that although patients may show lower attentional functioning than non-patients on tasks requiring a high response rate, their attentional performance remains within the normal range on most dimensions.

Cognitive deficits characterization using the CogState Research Battery in first-episode psychosis patients

The computer-based CogState Research Battery (CSRB) proposes a test structure which follows MATRICS recommended cognitive domains but lacks direct comparison to pen and paper batteries in first-episode psychosis (FEP). The aim of this study was to compare performances obtained with the CSRB and a pen and paper battery in a historical cohort of FEP patients. Among patients entering an early intervention program between 2003 and 2014, separate cohorts completed the traditional pen and paper cognitive battery (n = 182) and the CSRB (n = 97). Composite z-scores were derived using normative data of matched controls (n = 64 pen and paper, n = 69 CSRB) and were compared between the two batteries for the 7 cognitive domains. The cohort tested using the CSRB performed better on the domains of processing speed, attention, visual memory, and verbal memory than the cohort tested using the pen and paper battery (all p < 0.001). Performance did not differ between the two types of batteries for the working memory, executive functions, and social cognition domains. Cognitive profiles identified in the two patient cohorts were similar, with verbal memory being the most impaired domain. Better performances on the CSRB may be primarily due to the minimal demand of the computerized tests on graphomotor abilities and reading speed compared to the pen and paper tests. Our investigation offers a better understanding on how the results obtained with computerized batteries may compare to earlier work done with traditional tests.

Response selection impairment in schizophrenia transcends sensory and motor modalities

Response selection dysfunction contributes to processing speed impairment in schizophrenia. However, it is unclear if response selection impairment transcends sensory and motor modalities or is modality specific. To address this question, healthy subjects and individuals with schizophrenia completed reaction time (RT) experiments with different combinations of sensory cues (i.e. visual, auditory) and motor response (i.e. manual, vocal). We found that response selection impairment in schizophrenia was present regardless of the sensory and motor modality of the tasks and correlated with performance on neuropsychological tests of processing speed. These results implicate dysfunction of amodal response selection brain regions in schizophrenia. Interventions that reduce the length of response selection stage processing may improve processing speed in schizophrenia.

Executive functions in borderline personality disorder

Different domains of executive function such as working memory and response inhibition were investigated together with elementary cognitive processes in borderline personality disorder (BPD). Patients with BPD (N=28) were compared to nonpatient controls (NP, N=28) on eight tasks (e.g. n-back, Go/NoGo, CPT-AX). In order to separate impairments in different cognitive domains and to assess the influence of more elementary cognitive processes on executive functioning, tasks were embedded in a reaction-time-decomposition approach. BPD patients solved tasks with accuracies comparable to those of nonpatients. The only exception was the n-back task, for which working memory is required: here, error rates were higher and increased more prominently in BPD patients depending on working memory load. In most tasks, movement times were shorter for BPD patients than for nonpatients, while the quality of task-solving was comparable. The faster processing in the BPD group was observable starting with the simplest task, i.e. a simple reaction-time task. These findings suggest that domains of executive functioning are differentially affected in BPD. In contrast to load-dependent deficits in working memory, response inhibition processes were unimpaired. Faster action-related processes could be observed in BPD patients in a variety of tasks; however, these did not influence executive functioning.

Prefrontal cortex activity during response selection predicts processing speed impairment in schizophrenia

Processing speed is the most impaired neuropsychological domain in schizophrenia and a robust predictor of functional outcome. Determining the specific cognitive operations underlying processing speed dysfunction and identifying their neural correlates may assist in developing pro-cognitive interventions. Response selection, the process of mapping stimuli onto motor responses, correlates with neuropsychological tests of processing speed and may contribute to processing speed impairment in schizophrenia. This study investigated the relationship between behavioral and neural measures of response selection, and a neuropsychological index of processing speed in schizophrenia. Twenty-six patients with schizophrenia and 21 healthy subjects underwent functional magnetic resonance imaging scanning during performance of two- and four-choice reaction time (RT) tasks and completed the Wechsler Adult Intelligence Scale-III (WAIS) Processing Speed Index (PSI). Response selection, defined as RT slowing between two- and four-choice RT, was impaired in schizophrenia and correlated with psychometric processing speed. Greater activation of the dorsolateral prefrontal cortex (PFC) was observed in schizophrenia and correlated with poorer WAIS PSI scores. Deficient response selection and abnormal recruitment of the dorsolateral PFC during response selection contribute to processing speed impairment in schizophrenia. Interventions that improve response selection and normalize dorsolateral PFC function may improve processing speed in schizophrenia.

Confirmation for a delayed inhibition of return by systematic sampling in schizophrenia

Inhibition of return (IOR) is a phenomenon thought to reflect a mechanism to protect the organism from redirecting attention to previously scanned insignificant locations. A number of studies reported altered IOR in schizophrenia patients with a reduction of its amplitude. However, incomplete sampling of stimulus onset asynchronies (SOAs) makes data on IOR time course incomplete. We examined 14 stabilized young patients with recent onset schizophrenia and 16 healthy controls matched for gender, age, and years of education. Schizophrenia patients (13 males, 1 female) had a mean age of 26.3+/-5.8 years and a mean number of years of study of 9.6+/-3.6. Their illness had a mean duration of 147 weeks. Patients displayed moderate overall slow reaction times (387 ms) in comparison with controls (322 ms). Onset of IOR was found to be delayed in schizophrenia patients appearing between 700 and 800 ms following the cue onset while it appeared at 300 ms in controls. In patients, IOR was constant up to 1100 ms; however, its amplitude was weak with an average of 6 ms. Validity effects (overall and at each SOA value) were uncorrelated to age, years of study, duration of illness, or total or subscale scores on the Positive and Negative Syndrome Scale.

Attention and visual orienting in siblings, schizophrenic patients, and controls: impairment in attentional disengagement

Visual orienting tasks reveal an impaired disengagement of attention in schizophrenia. We explored visual orientation in 20 schizophrenia patients (SZ), 20 full siblings (FS), and 20 controls (C) using a cued target detection (gap vs. no gap) and a choice reaction time task. SZ but not FS had longer reaction time with comparable reactions to warning. In contrast to C, SZ and FS did not display a significant gap effect. The disengagement deficit in schizophrenia patients and their siblings provides arguments for altered early attention mechanisms (in schizophrenic patients and their nonpsychotic relatives).

Abnormal prefrontal cortical activity and connectivity during response selection in first episode psychosis, chronic schizophrenia, and unaffected siblings of individuals with schizophrenia

The search for genes conferring liability for schizophrenia may be aided by the identification of endophenotypes. Response selection is a heritable cognitive function that is impaired in patients with schizophrenia and their unaffected siblings. The abnormalities in cerebral function that presumably underlie the deficit in patients and unaffected siblings remain to be elucidated. Cerebral neurophysiology during performance of a 4-choice reaction time (CRT) task in 25 patients with schizophrenia (15 medication free first episode (FEP) and 10 chronic patients), 32 controls, and 12 unaffected siblings of individuals with schizophrenia was investigated using fMRI. CRT was impaired in both medication free FEP and chronic patients with schizophrenia, and unaffected siblings. FEP patients, chronic patients, and unaffected siblings demonstrated greater BOLD response in the right dorsolateral prefrontal cortex (dlPFC) during CRT task blocks. The nature of the altered activation in the dlPFC was further examined using functional connectivity analysis. This revealed marked reductions in connectivity between the right dlPFC and multiple brain regions in both patient groups and, to a lesser degree, unaffected siblings. The magnitude of connectivity between right dlPFC and inferior parietal lobule correlated with task performance in the combined patient/unaffected siblings group, but not controls suggesting that the network of brain regions recruited to perform the task differed as a function of genetic liability for schizophrenia. The findings suggest that altered activity and connectivity of the right dlPFC appears to be related to genetic vulnerability for schizophrenia and may represent a potential endophenotype of the disorder.

Executive functions and cognitive subprocesses in patients with obstructive sleep apnoea

In recent years, special interest has been focused on impairments of executive functions in patients with obstructive sleep apnoea syndrome (OSAS). However, the majority of studies have not clearly separated deficits in executive functions from impairments in other cognitive processes involved in task solving. In the present study, working memory (WM) functions of 20 patients with OSAS were compared with those of 10 age-, sex- and education-matched healthy subjects. Cognitive functions were measured four times a day; each of these measurements was accompanied by an assessment of subjective and objective daytime sleepiness. To separate dysfunctions of WM from those of additionally involved processes, n-back tasks were applied embedded in a reaction-time-decomposition approach. Deficits in n-back tasks could be observed in OSAS patients in accuracy and reaction times. However, the slowing could already be observed in simple reaction time tasks. The drop in 1-back accuracy in the morning was related to daytime sleepiness. During the afternoon, accuracy of OSAS patients dropped in 2-back tasks, an effect which correlated neither with sleepiness nor with the extent of sleep apnoea or oxygen desaturation. In conclusion, our data reflect a complex perspective upon cognitive deficits in OSAS. Cross-group differences in processing time on the higher level WM task appeared to be attributable to slowing at a more elementary cognitive processing level. In contrast, reduced accuracy during the WM task in the OSAS group could not be explained by deficits in more elementary cognitive processes.

Reaction time and sustained attention in schizophrenia and its genetic predisposition

Sustained attention is affected by schizophrenia. The simplest form of Continuous Performance Test (CPT-X) is a purer test of vigilance than more demanding variants but widely thought too insensitive to detect abnormalities in those with genetic predisposition to schizophrenia. We used a 7-minute CPT to compare 61 patients diagnosed with schizophrenia, 45 of their never-psychotic relatives, and 47 control subjects. We found a significant impairment in stimulus discrimination in both patients (p=0.001) and their relatives (p=0.006). There was no difference in stimulus discrimination between relatives of patients with impaired and unimpaired stimulus discrimination. Relatives of patients with unimpaired stimulus discrimination were still inferior to controls (p=0.02). Reactions slowed in all groups equally as the test progressed. Patients showed increased mean reaction time (p<0.0001) and interquartile range (p=0.003). Relatives showed slower reaction times (p=0.01) but normal interquartile range. Groups did not differ in respect of individuals' fastest reaction times. We conclude that genetic predisposition to schizophrenia reduces performance even during a task placing minimal cognitive load on working memory and perceptual processing, suggesting impaired vigilance. Increased reaction time in the disease and its predisposition appear to be due to changes in response distribution rather than by a limitation of maximum speed. Our results raise the possibility of separating the cognitive components of vigilance, working memory and perceptual processing tapped by more demanding variants of the CPT, and draw attention to the need for consideration of dynamic neurocognitive processes in schizophrenia.

Motor response selection in children with fetal alcohol spectrum disorders

Previous work has reported timing delays in motor response selection in children with prenatal exposure to alcohol when the information load involved responding to two stimulus choices. The present study examined whether the delay in response selection extends to conditions in which the information load is increased to four and eight stimulus choices. Twenty children aged between 12 and 17 years with fetal alcohol spectrum disorders (FASD) were compared to 17 non-alcohol-exposed controls (NC) on a reaction time (RT) task involving 1, 2, 4 or 8 visual stimulus choices. The task demands required the participant to release a response key as fast as possible when the stimulus light electronically paired with the response key was activated. With the number of stimulus choices expressed on a logarithmic scale, there was a significant and linear increase in RT for the FASD children as predicted by information processing theory. Additionally, the increase in RT for the FASD group was comparable to that observed for the NC children at each level of stimulus choice examined. It was concluded that FASD adolescents require additional time to process increasing amount of information, but that the time required for motor response selection is not delayed relative to control group performance.

Schizophrenia: etiology and course

Decades of research on schizophrenia have not produced major breakthroughs, but gradual progress has been made in identifying risk factors and clarifying the nature of the etiologic process. This article provides an overview of trends in research findings as well as current assumptions about the interplay between environmental and genetic factors in the etiology of schizophrenia. Based on the cumulative findings, it appears that both genetic and prenatal factors can give rise to constitutional vulnerability. Subsequent neuromaturational processes, especially those that occur during adolescence, and exposure to stressful events can trigger the behavioral expression of this vulnerability.

Reaction-times and bioelectrical brain signals of drug-naive schizophrenic first-onset patients in identification and classification tasks

OBJECTIVE

The question of the present study is whether disturbances of response-selection in schizophrenic patients are discernible only if overt motor-actions are required, or also if covert cognitive actions are necessary.

METHOD

Visual identification (digits) and classification (dot-enumeration) tasks were presented to 18 drug-naive, first-onset schizophrenic patients and healthy controls. It is assumed that enumeration of more than three dots requires additional cognitive processes as buffering and re-focusing of attention. Reaction-times and 21-channel-EEG were measured. For eye-movement artefact-elimination a new non-parametric regression approach was applied.

RESULTS

Reaction-times revealed that in the patient group response selection is lengthened in both tasks. Perception of dot numbers is not affected. Bioelectrical data depicted a left-lateralization of posterior P100 and N 100 in the patient group as well as an enhanced fronto-central P200.

CONCLUSION

Whereas in reaction-times of patients only a disturbance of response selection is discernible, bioelectrical measurements also point to an altered organization of perceptive processes.

Cognitive subprocesses and schizophrenia. B. Maze tasks

OBJECTIVE

In a companion paper we demonstrated that in reaction-time tasks the response selection stage is selectively disturbed in schizophrenia. The aim of the present study is the investigation of subprocesses, which are incorporated into repeatedly activated loops of cognitive processes and need additional information from working memory.

METHOD

Maze tasks of varying complexity (with and without bifurcations) were presented to drug-naive and treated first-onset schizophrenic patients. The tasks had to be solved under easy and difficult motor-conditions. Both patient samples were compared with healthy control groups matched by age, sex, education and experience with the experimental setting.

RESULTS

In mazes with alternative routes patients exhibited the expected decrease of performance. However, untreated patients improved under difficult motor conditions. This improvement is smaller after neuroleptic treatment.

CONCLUSION

Under difficult motor conditions attention is focused on the execution of movements and thus withdrawn from perceiving irrelevant response alternatives, i.e. the effects of disturbed response selection are reduced.