Performance Of Schizophrenics Research Articles

Effect of Gaze Direction on Orienting of Attention in Patients with Schizophrenia: Attention or Social Cognition Deficit?

Introduction: the ability to use the gaze direction of another person to guide attention is part of a complex construct named Social Cognition. Schizophrenics showed impairments in domains of social cognition. Aim and objectives: the aim of this study was to investigate whether gaze cueing of attention is compromised in schizophrenic subjects. Materials and methods: we tested 18 schizophrenics and 18 controls who were presented with gaze and arrow cues in a modified version of the Posner’s spatial cueing paradigm. Results: The performance of schizophrenics was compromised when the cue is represented by the gaze rather than by the arrow. In fact, our results showed that two groups differ only for gaze condition both in reaction times (F1,34=61.557; p=0.0001) and number of errors (F1,34=6.39; p=0.002). Moreover, the correlation analysis showed that the Eyes Task negatively correlates with invalid condition when the cue was the gaze (r=-0.504, p=0.03). This result underlines the crucial relation between the emotional recognition capacity of the another person’s gaze and the orienting of attention capacity through the interpretation of other people’s gazes. These capacities seem to be precursors for good development of Social Cognition. Conclusion: Taken together, these findings suggest that schizophrenics showed a specific deficit in social attention, that is part of social cognition construct. Deficit in attention to gaze direction in patients with schizophrenia may contribute to interpersonal and social cognitive difficulties. Thus, the gaze interpretation ability can be considered as an important part in rehabilitation strategies for schizophrenics

Pathological Effects of Cortical Architecture on Working Memory in Schizophrenia

Neural connectivity of the prefrontal cortex is essential to working memory. Reduction of prefrontal connectivity and abnormal prefrontal dopamine modulation are common characteristics associated with schizophrenia. Two experiments separately modeled the effects of exaggerated pruning and of synaptic depression to imitate schizophrenic performance in a prefrontal neural network. In the first model, effects of cortical pruning were simulated with a set of scale-free networks of neurons and compared with empirical results from the Sternberg working memory task. The second set of simulations were based on the synaptic theory of working memory. Simulations of this model measured memory duration in relation to synaptic facilitation and depression constants and in relation to the level of neural connectivity. In the first set of simulations, modulating levels of cortical pruning resulted in a gain or loss in accuracy and speed of memory recollection. In the second set of simulations, increased facilitation time constants and decreased inhibitory time constants resulting in longer memory durations, and overly connected networks resulted in very low memory durations. In the first model, the decline in memory performance can be attributed to the emergence of pathological memory behavior brought about by the warping of the basins of attraction. Collectively, the simulations demonstrate that a reduction of prefrontal cortical hubs can lead to schizophrenia like performance in neural networks, and may account for pathological working memory in the disorder.

Nitric Oxide Synthase Mediates the Ability of Darbepoetin Alfa to Improve the Cognitive Performance of STOP Null Mice

STOP (stable tubule only polypeptide) null mice display neurochemical and behavioral abnormalities that resemble several well-recognized features of schizophrenia. Recent evidence suggests that the hematopoietic growth factor erythropoietin improves the cognitive performance of schizophrenics. The mechanism, however, by which erythropoietin is able to improve the cognition of schizophrenics is unclear. To address this question, we first determined whether acute administration of the erythropoietin analog known as darbepoetin alpha (D. alpha) improved performance deficits of STOP null mice in the novel objective recognition task (NORT). NORT performance of STOP null mice, but not wild-type littermates, was enhanced 3 h after a single injection of D. alpha (25 microg/kg, i.p.). Improved NORT performance was accompanied by elevated NADPH diaphorase staining in the ventral hippocampus as well as medial and cortical aspects of the amygdala, indicative of increased nitric oxide synthase (NOS) activity in these structures. NOS generates the intracellular messenger nitric oxide (NO) implicated in learning and memory. In keeping with this hypothesis, D. alpha significantly increased NO metabolite levels (nitrate and nitrite, NOx) in the hippocampus of both wild-type and STOP null mice. The NOS inhibitor, N (G)-nitro-L- arginine methyl ester (L-NAME; 25 mg/kg, i.p.), completely reversed the increase in hippocampal NOx levels produced by D. alpha. Moreover, L-NAME also inhibited the ability of D. alpha to improve the NORT performance of STOP null mice. Taken together, these observations suggest D. alpha enhances the NORT performance of STOP null mice by increasing production of NO.

Regional gray matter reduction and theory of mind deficit in the early phase of schizophrenia: a voxel‐based morphometric study

We tested the association between theory of mind (ToM) performance and structural changes in the brains of patients in the early course of schizophrenia. Voxel-based morphometry (VBM) data of 18 patients with schizophrenia were compared with those of 21 controls. ToM skills were assessed by computerized faux pas (FP) tasks. Patients with schizophrenia performed significantly worse in FP tasks than healthy subjects. VBM revealed significantly reduced gray matter density in certain frontal, temporal and subcortical regions in patients with schizophrenia. Poor FP performance of schizophrenics correlated with gray matter reduction in the left orbitofrontal cortex and right temporal pole. Our data indicate an association between poor ToM performance and regional gray matter reduction in the left orbitofrontal cortex and right temporal pole shortly after the onset of schizophrenia.

Widespread Cortical Dysfunction in Schizophrenia: The FBIRN Imaging Consortium

This Special Theme issue presents a series of related papers describing fMRI data collected as part of a multi-site brain imaging consortium, the Functional Imaging Biomedical Informatics Research Network (FBIRN) on the same subject population ( approximately 125 patients and approximately 125 controls), a larger sample than would have been possible from a single-site, and from a broader clinical and demographic range of patients. Potkin et al observe cortical inefficiency during retrieval of items from memory but not during encoding of those items; Brown et al showed that the lawful relationship between memory retrieval time and neural activation is decoupled in patients with schizophrenia. Wible et al analyzed the same memory data and report activations of left auditory and parietal cortices are especially abnormal in patients who tend to hallucinate. Using an auditory target detection task, Ford et al report abnormal activation of left primary auditory cortex in the hallucinators. A multivariate analysis of those auditory data by Kim et al found differences in connectivity in patients and controls. These studies on the same patient sample suggest that abnormal circuitry characterizes schizophrenic performance in both auditory target detection and memory retrieval, and that patients who hallucinate have reduced left auditory cortical activation on both tasks. Segall et al report anatomical differences between patients and controls in the largest sample yet published. Finally, Potkin et al. identified six genes that influence DLPFC activation and have functions related to forebrain development and stress responses in schizophrenia. These related publications indicate the power of multisite neuroimaging.

Context, complexity, and cognitive processing in schizophrenia

Background. Cohen et al.'s (1990, 1999) concept of context has been employed to explain various schizophrenic cognitive deficits. Braver et al.'s (2001) modified definition allows us to link context to cognitive complexity and explain a range of our experimental findings. Method. Saccadic and manual responses to experimental paradigms involving familiar and unfamiliar versions of tasks varying in stimulus–response compatibility, response familiarity, and temporal factors were used. These include comparison of acoustic and visually driven saccades and antisaccades, manual and saccadic pattern reproduction, and colour (cognitively guided) saccades with two delay intervals. Results. In one experiment, schizophrenic participants, unlike controls, made fewer errors on the auditory compared to the visual antisaccade task, suggesting that prepotent responses are more easily inhibited when stimulus–response compatibility is reduced. In a second experiment in which a left–right response sequence is reproduced manually or saccadically, schizophrenic performance is impaired when the novel and thus more complex saccadic response is required. In the third experiment, a colour signal is interpreted to determine the correct direction of a saccade. With two different blocked delay intervals, shortening the delay results in schizophrenic performance decline, suggesting difficulty adjusting to temporal context changes. Conclusion. These results, together with our previous findings (Schooler et al., 1997a; Zahn et al., 1998) suggest schizophrenic context processing deficits become increasingly evident as contexts become more complex. These results may be due to microgaps in schizophrenic individuals’ maintenance of context.

Evaluación de rasgos personales, "self", esquizofrenia y estructuras de la línea media cortical

There is no consensus about the definition of self however it is traditionally associated to identity. Many researchers are searching the neural regions that process self related information. Some studies have observed an activation of midline structures during the processing of information related to self. Self perturbations are not a part of diagnostic criteria for schizophrenia, nevertheless they are implicitly considered as part of the clinical picture. Some studies have tried to determine its perturbation using psychometric tests, but there are no studies that assess the association between brain activity and the performance of schizophrenics in tasks that require self-referential evaluations. The attempt to find a neural substrate for self is polemical. However, this model could be evaluated studying if, in schizophrenic patients, the tasks related to self processing are different from normal subjects at the psychophysiological and behavioral levels. This line of research could provide new diagnostic tools for early diagnosis and prevention in psychiatry.

A meta-analytic review of verbal fluency deficits in schizophrenia relative to other neurocognitive deficits

Introduction. A prominent view in the neuropsychological literature is that schizophrenia is particularly associated with executive dysfunction, yet in a meta-analytic review it was concluded that, relative to their general level of intellectual functioning, schizophrenics are not disproportionately impaired on a measure of this construct, the Wisconsin Card Sorting Test (WCST). However, verbal fluency tests may be more valid measures of executive functioning as they are more sensitive to the presence of focal frontal lobe injuries.Method. A meta-analysis was conducted on 84 studies comparing the performance of schizophrenics and healthy controls on tests of phonemic and semantic fluency, as well as other cognitive measures presumed to impose only minimal demands on executive functioning.Results. Neither phonemic or semantic fluency deficits qualified as differential deficits relative to general intelligence or psychomotor speed. Patients with schizophrenia were significantly more impaired on semantic relative to phonemic fluency.Conclusions. As for the WCST, deficits on tests of verbal fluency reflect a more generalised intellectual impairment and not particular difficulties with executive control processes. The larger deficit for semantic relative to phonemic fluency suggests that, in addition to general retrieval difficulties, schizophrenia is associated with compromises to the semantic store.

Predicting successful job performance of schizophrenics after discharge from hospital

Predicting the job performance of schizophrenic patients after discharge from hospital has been the focus of many studies within the last 30 years. In our own long-term study, we have started to follow-up 50 consecutively admitted schizophrenics taking their individual return on the so-called first employment market as primary target variable. To evaluate the respective predictive power, a set of different neuropsychological, psychopathological and psychosocial parameters was gathered in each patient.

Conversation with Conan Kornetsky.

Conversation with Conan Kornetsky.

Attentional dysfunction of chronic schizophrenia: No association with long-term institutionalization.

Attentional processes play a central role in information selection, which is impaired in schizophrenic patients. In the present study, we attempted to characterize the attentional performance of chronic schizophrenics using a computerized assessment of the multiple components of attentional function. Two comparable samples, consisting, respectively, of out-patients and in-patients, were tested in order to assess the effect of chronic institutionalization. Twenty-four subjects (half in-patients and half out-patients) fulfillling DSM-IV criteria for schizophrenia were examined with a standard computerized battery for the assessment of attention, namely Testbatterie zur Aufmerksamkeitsprufung (TAP). Both groups were impaired on all measures of attentional processing (in terms of both reaction times and number of errors). There were no significant differences in attentional performance between in- and out-patients. In conclusion, the present findings confirm the presence of pervasive attentional dysfunction in chronic schizophrenia; the lack of significant differences in performance between in- and out-patients supports the hypothesis that the cognitive deficits are inherently associated with the illness and cannot be attributed to environmental/social factors.

Auditory distraction and thought disorder in chronic schizophrenic inpatients: Evidence for separate contributions by incapacity and poor allocation and a subsyndrome related to the allocation deficit

This study investigated auditory attentional processes associated with schizophrenic thought disorder. Thirty-five chronically schizophrenic, state hospital inpatients were assessed for thought disorder using the Thought, Language, and Communication Disorders Scale (TLC) and tested in an attentional task. Two measures of attention were derived from the Digit Span Distraction Test (DSDT) (Oltmannns, T.F., Neale, J.M., 1975. Schizophrenic performance when distractors are present: attentional deficit or differential task difficulty. J. Abnorm. Psychol. 84, 205–209), a digit recall task in which distractor digits were interspersed with target digits. The two measures were Distractibility — the overall inaccuracy of recall — which measured attentional incapacity, and Distractible Intrusion — the number of irrelevant digits recalled — which was developed in this study to separately measure the inability to allocate attentional resources. These two measures predicted thought disorder strongly and independently. Distractibility did not significantly correlate with any TLC subscale. In contrast, Distractible Intrusions correlated with the TLC subscales Distractible Speech, Incoherence, Loss of Goal, and Word Approximations. The present findings suggest that these subtypes may comprise a distinct subsyndrome of thought disorder, characterized by a dysfunctionally low threshold for selecting appropriate speech information, and that an attentional allocation deficit is related to this language dysfunction.

A Meta-analytic Review of Wisconsin Card Sort Studies in Schizophrenia: General Intellectual Deficit in Disguise?

A majority of studies show that schizophrenics perform poorly on so-called tests of executive or frontal lobe function - the paradigmatic case being the Wisconsin Card Sort Test (WCST). Nevertheless, the specific character of this deficit in schizophrenia remains underspecified. In particular, it seems premature to assume that schizophrenia is characterised by an executive dysfunction and/or a disorder of frontal lobe function before determining whether any deficit is: selective; disproportionate to the general level of intellectual functioning; or qualitatively comparable with that of frontal lobe patients. A meta-analysis was conducted on 29 studies comparing the performance of schizophrenics and normal controls on the WCST. This showed that the mean weighted effect size was large for categories achieved (d=0.91), medium for absolute level of perseveration (d=0.53), but only small for the proportion of perseverative errors (d=0.18). By contrast, the effect size for Wechsler Adult Intelligence Scale Intelligence Quotient (WAIS IQ) in a subset of these studies (d=1.23) was significantly larger than for any WCST measures. This pattern of findings challenges notions that schizophrenia is characterised by an executive dysfunction that is: selective; disproportionate to IQ level; and analogous to that found in frontal lobe patients. Rather, the poor WCST performance of schizophrenics appears to reflect a generalised intellectual deficit.

An artificial neural network stimulating performance of normal subjects and schizophrenics on the Wisconsin card sorting test

Mental diseases such as schizophrenia are being modeled by artificial neural networks in an attempt to understand the underlying neuropathological processes. We studied hospitalized psychiatric patients that met the DSM-IIIR criteria for schizophrenia ( N=19), and normal subjects with no psychiatric history ( N=18). Performance on the Wisconsin Card Sorting Test (WCST) by schizophrenic patients was poorer than normal subjects as estimated by various scoring measurements. We then modeled an artificial neural network, motivated by biological considerations, that is able to simulate performance of normals and schizophrenics on the WCST. In order to model the complex nature of the WCST, we designed novel learning rules based on non-associative learning paradigms. We found that there must be a minimum amount of noise, or inherent synaptic instability, for our model to perform similar to schizophrenics.

On the distinction between access and store disorders in schizophrenia: a question of deficit severity?

This study documents a severe face naming impairment in schizophrenic patients. A series of twelve patients was examined further to determine whether this deficit conformed to either an access or store disorder as described originally by Warrington and Shallice [45]. This analysis of consistency across time, effects of cueing and familiarity effects revealed heterogeneous performance patterns; pointing to access disorders in some patients and store disorders in others. However, the difference between access-like and store-like patterns of performance was strongly correlated with quantitative differences in patient deficit-severity. Hence, the notion of dichotomous access and store disorders, in schizophrenic patients, may be deceptive; with the naming performance of schizophrenics varying according to the extent of their stored knowledge, rather than any qualitative differences between patients. These findings have implications for our understanding of: cognitive deficits in both schizophrenic and neurological patients; the relationship between psychotic and neurological disorders and perhaps for the underlying neurophysiological dysfunction.

Abstraction is impaired at the perceptual level in schizophrenic patients

This study investigates category learning in schizophrenia in order to evaluate abstraction abilities at the perceptual level. The participants learned about two categories of geometric shapes. The category exemplars were presented successively. In the case of schizophrenic patients, longer exposure time and more stimulus presentations were used to counterbalance attention impairments. In spite of this, the perceptual category learning was significantly impaired in the patient group. In contrast, when the training procedure involved verbal category definition and not perceptual learning, the performance of schizophrenics was similar to that of the healthy controls. These findings suggest that the perceptual learning of categories, but not free classification judgements are impaired in schizophrenia, and that this impairment is not due to pure attentional disturbances.

Planning strategies during trail-making test performance in schizophrenics and healthy relatives

Planning strategies during trail-making test performance in schizophrenics and healthy relatives

Issues concerning relative speed of processing hypotheses, schizophrenic performance deficits, and prefrontal function: Comment on Schooler et al. (1997).

Issues concerning relative speed of processing hypotheses, schizophrenic performance deficits, and prefrontal function: Comment on Schooler et al. (1997).

The Performance of Schizophrenics on Three Cognitive Tests of Malingering, Rey 15-Item Memory Test, Rey Dot Counting, and Hiscock Forced-Choice Method

The performance of individuals with severe psychiatric disturbance such as schizophrenia on tests designed to detect malingering of cognitive symptoms (e.g., Rey 15-Item Memory Test, RMT; Rey Dot Counting Test, RDC; Hiscock Forced-Choice, F-C, method) has not been formally investigated. Some malingerers feign cognitive impairment in the context of a pseudopsychotic presentation; thus, it is essential that we understand how actual psychotic individuals perform on these measures. In our sample of 30 schizophrenic patients, 13% failed the RMT, 13% failed the RDC, and 27% failed the F-C measure. The RMT performance appeared to be significantly affected by lowered educational level. In contrast, both RDC and F-C performances were related to presence of cognitive impairment, and the RDC was also significantly affected by increasing age. No test score was significantly related to psychiatric disturbance.

Schizophrenic deficits in the processing of context. A test of a theoretical model.

Schizophrenic patients show various deficits in cognitive functions that have been difficult to understand in terms of a common unifying hypothesis. Previously described neural network models of cognitive tasks suggest that several schizophrenic performance deficits may be related to a single function-an impairment in maintaining contextual information over time and in using that information to inhibit inappropriate responses. We tested first-episode schizophrenic patients and patients later in the course of their illness on a new variant of the Continuous Performance Test designed specifically to elicit deficits in the processing of contextual information. Unmedicated schizophrenic patients showed a deterioration of their signal detection performance that followed the pattern predicted by the context hypothesis, ie, they responded inappropriately when correct responding required the maintenance of context information over time to inhibit the expression of a habitual response. This deficit correlated with positive symptoms. The results also suggested that the deficit may be worse in unmedicated patients who have had a longer course of illness. Medicated patients showed a more diffuse performance deficit. These results support the view that a single deficit in the processing of context information may underlie various cognitive impairments observed in schizophrenia. They also suggest that such an impairment is associated with positive rather than negative symptoms, and that it may worsen with the course of the illness as in the kraepelinian view of schizophrenia.