Early stage vision in schizophrenia and schizotypal personality disorder

Previous studies of visual perception have reported deficits in contrast sensitivity and dot motion discrimination in schizophrenia. We tested whether these deficits also appear in schizotypal personality disorder (SPD). SPD appears to be genetically and symptomatically related to schizophrenia, but without the marked psychosocial impairment associated with psychotic disorders. The present study investigated contrast sensitivity for moving and static gratings, form discrimination and dot motion discrimination in 24 patients with schizophrenia or schizoaffective disorder (SZ), 16 individuals with SPD, and 40 control subjects. SZ, but not SPD subjects, showed impairments on tests of contrast sensitivity for static and moving gratings, form discrimination in noise, and dot motion discrimination. Visual performance did not differ between medicated SZ patients and patients withdrawn from medication. These results confirm early stage visual deficits in schizophrenia regardless of medication status. SPD subjects, in contrast, show intact early stage visual processing despite the presence of marked schizotypal symptoms.     

Color discrimination deficits in Parkinson's disease are related to cognitive impairment and white‐matter alterations

Color discrimination deficit is a common nonmotor manifestation of Parkinson's disease (PD). However, the pathophysiology of this dysfunction remains poorly understood. Although retinal structure changes found in PD have been suggested to cause color discrimination deficits, the impact of cognitive impairment and cortical alterations remains to be determined. We investigated the contribution of cognitive impairment to color discrimination deficits in PD and correlated them with cortical anomalies. Sixty‐six PD patients without dementia and 20 healthy controls performed the Farnsworth–Munsell 100 hue test and underwent a comprehensive neuropsychological assessment for mild cognitive impairment diagnosis. In a subgroup of 26 PD patients, we also used high‐definition neuroanatomical magnetic resonance imaging for cortical thickness and diffusion tensor analysis. PD patients with mild cognitive impairment performed poorly on the Farnsworth–Munsell 100 hue test compared with PD patients without mild cognitive impairment and controls. In PD patients, performance on the Farnsworth–Munsell 100 hue test was correlated with measures of visuospatial abilities and executive functions. Neuroimaging analysis revealed higher mean and radial diffusivity values in right posterior white‐matter structures that correlated with poor performance on the Farnsworth–Munsell 100 hue test. No cortical thickness correlation reached significance. This study showed that cognitive impairment makes a major contribution to the color discrimination deficits reported in PD. Thus, performance on the Farnsworth–Munsell 100 hue test may reflect cognitive impairment more than color discrimination deficits in PD. Poor performance on the Farnsworth–Munsell 100 hue test was also associated with white‐matter alterations in right posterior brain regions. © 2012 Movement Disorder Society     

Aging and visual motion discrimination in normal adults and schizophrenia patients

Motion perception is impaired in many neuropathological conditions, including schizophrenia. Motion perception also declines in the course of normal aging. In this study, we ask whether aging is an additive factor in the motion-discrimination deficits of schizophrenia patients. We examined motion perception in schizophrenia patients (n=44) and non-psychiatric controls (n=40) whose ages ranged from 18 to 55. The tasks included velocity discrimination and contrast detection. Thresholds for each of the two tasks were determined for each subject using psychophysical methods. Schizophrenia patients showed significantly increased thresholds (degraded performance) for velocity discrimination compared with the controls. Degraded performance in patients was not related to age. In controls, however, velocity discrimination thresholds were significantly increased beginning by age 45. Performance on a contrast-detection task, which does not require precise discrimination of motion signals, was not significantly affected by age in either group. Aging, even in its early stages, degrades motion discrimination in normal adults. Aging, however, does not adversely affect motion-discrimination deficits in schizophrenia patients through age 55. A similar motion-discrimination deficit in schizophrenia patients and aging normal adults suggests that the mechanisms underlying motion processing in schizophrenia and normal aging may be associated.     

Cognitive deficits in early-onset schizophrenia spectrum patients and their non-psychotic siblings: a comparison with ADHD

BACKGROUND: Previous research has shown cognitive deficits in patients with schizophrenia spectrum disorders in the areas of executive function, verbal memory and attention. Subtle deficits have been shown in healthy first-degree relatives of patients, suggesting that they may be trait markers. The specificity of these markers for schizophrenia compared with another neurodevelopmental disorder, Attention Deficit Hyperactivity Disorder (ADHD) has not been reliably established. METHODS: The Rey Auditory Verbal Learning Test (RAVLT), Hayling Sentence Completion Test (HSCT), FAS Test of orthographic verbal fluency (FAS) and Continuous Performance Test-Identical Pairs (CPT-IP) were administered to adolescent schizophrenia spectrum patients (SZ; n=30), adolescent siblings of schizophrenia spectrum patients (SZ-SIB; n=36), healthy control participants (HC; n=72); a neurodevelopmental comparison group of adolescents with ADHD (n=27). RESULTS: The SZ group were impaired on all measures. The SZ-SIB group were impaired on IQ, immediate recall (RAVLT), target sensitivity (CPT-IP), response initiation (HSCT); error rates for the FAS and HSCT. There were no significant differences between the SZ-SIB and ADHD groups on individual measures of cognitive function. Principal Components Analysis revealed four factors on which further analyses were conducted. The SZ-SIB and ADHD groups showed different profiles of impairment on components related to response initiation and sustained attention/vigilance when each was compared with the HC group. CONCLUSIONS: Deficits in intellectual function, verbal memory and response initiation/inhibition were found in the SZ-SIB group indicating that these are markers of risk for schizophrenia. Subtle differences in profiles of impairment in the SZ-SIB and ADHD groups on composite measures of attention and response initiation require further investigation.     

Progressive worsening of spatial and chromatic processing deficits in Parkinson disease

CONTEXT: Impairments of color discrimination (CD) and contrast sensitivity are established signs of Parkinson disease (PD), but their temporal evolution has not been studied. OBJECTIVE: To determine whether there is progressive, longitudinal deterioration of color discrimination (CD) and contrast sensitivity (CS) in PD. DESIGN: A prospective study. SETTING: Tertiary care center-based sample of PD patients without dementia with normal visual acuity (Snellen fraction >0.6 in the best eye). MAIN OUTCOME MEASURES: With a mean +/- SD interval of 19.8 +/- 2.8 months, the following tests were applied twice in 28 patients: the Lanthony D15 test and the Farnsworth Munsell 100 Hue test as tests of CD and the monocular and binocular Pelli-Robson test and the binocular Vistech tables as tests of CS. RESULTS: There was deterioration of both CD (Farnsworth Munsell 100 hue test: P =.002) and CS (binocular Vistech test at a spatial frequency of 6 cycles per degree, P<.001). Both deficits correlated with age, and the chromatic deficit additionally correlated with higher impairment of motor function (Unified Parkinson's Disease Rating Scale motor section, P =.04) and activities of daily life (Unified Parkinson's Disease Rating Scale activities of daily living section, P =.006). Patients with the highest pathologic psychiatric rating score (Brief Psychiatric Rating Scale) performed worse on both CS (P =.02) and CD (P =.01) at the second examination. CONCLUSIONS: Impairments of CD and CS in PD are progressive over time. Visual deficits may influence overall motor function and lead to enhanced motor impairment.     

Metacognition in psychosis: Comparison of schizophrenia with bipolar disorder

While deficits in metacognition have been observed in schizophrenia (SZ), it is less clear whether these are specific to the disorder. Accordingly, this study compared metacognitive abilities of patients with schizophrenia and bipolar disorder (BD) and examined the degree to which neurocognition contributed to metacognitive deficits in both groups. Participants were 30 patients with SZ and 30 with BD. Metacognitive capacity was measured using the Metacognition Assessment Scale Abbreviated (MAS-A). This scale comprises four domains: self-reflectivity, understanding others? minds, decentration and mastery. Verbal memory, executive functioning and symptoms were concurrently assessed. Group comparisons revealed that SZ patients had greater deficits in metacognitive self-reflectivity, which correctly classified 85.2% of patients with SZ in a logistic regression. Self-reflectivity and understanding others? minds were related to verbal memory and executive functioning in the SZ group, but not in the BD group. Furthermore, greater positive and general psychotic symptoms were associated with poorer metacognition in SZ. Results suggest SZ involves unique deficits in the ability to self-reflect and that these deficits may be uniquely linked with neurocognition.     

Schizophrenia patients show task switching deficits consistent with N-methyl-d-aspartate system dysfunction but not global executive deficits: implications for pathophysiology of executive dysfunction in schizophrenia

Schizophrenia is associated with cognitive processing deficits, including deficits in executive processing, that represent a core component of the disorder. In the Task Switching Test, subjects view ambiguous stimuli and must alternate between competing rules to generate correct responses. Subjects show worse performance (prolonged response time and/or increased error rates) on the first response after a switch than on subsequent responses ("switch costs"), as well as performing worse when stimuli are incongruent as opposed to congruent ("congruence costs"). Finally, subjects show worse performance in the dual vs single task condition ("mixing costs"). In monkeys, the N-methyl-D-aspartate (NMDA) antagonist ketamine has been shown to increase congruence but not switch costs. Here, subjects viewed colored letters and had to respond alternately based upon letter (X vs O) or color (red vs blue). Switch, congruence and mixing costs were calculated. Patients with schizophrenia (n = 16) and controls (n = 17) showed similar switch costs, consistent with prior literature. Patients nevertheless showed increased congruence and mixing costs. In addition, relative to controls, patients showed worse performance across conditions in the letter vs color tasks, suggesting deficits in form vs color processing. Overall, while confirming executive dysfunction in schizophrenia, this study indicates that not all aspects of executive control are impaired and that the task switching paradigm may be useful for evaluating neurochemical vs neuroanatomic hypotheses of schizophrenia.     

Spatiotemporal visual processing in schizophrenia

Studies examining visual processing in schizophrenia have provided inconsistent results. In this study, the authors measured static and dynamic visual contrast sensitivity (CS) in patients with schizophrenia (n=20) and control subjects (n=15). Extrapyramidal symptoms were evaluated with the Simpson-Angus scale. In the static condition, the patients with schizophrenia showed reduced CS in the spatial frequency range of 2.9-14.4 cycles per degree of visual angle (c/d). In the dynamic condition, CS loss was present over the whole range tested (0.5-14.4 c/d). Higher Simpson-Angus scores and higher doses of antipsychotic medication were associated with more severe CS deficits. These results suggest that the hypodopaminergic state induced by antipsychotic medication may produce parkinsonian visual impairments in schizophrenia patients.     

Distinct facial processing in schizophrenia and schizoaffective disorders

Although schizophrenia and schizoaffective disorders have both similar and differing clinical features, it is not well understood whether similar or differing pathophysiological processes mediate patients' cognitive functions. Using psychophysical methods, this study compared the performances of schizophrenia (SZ) patients, patients with schizoaffective disorder (SA), and a healthy control group in two face-related cognitive tasks: emotion discrimination, which tested perception of facial affect, and identity discrimination, which tested perception of non-affective facial features. Compared to healthy controls, SZ patients, but not SA patients, exhibited deficient performance in both fear and happiness discrimination, as well as identity discrimination. SZ patients, but not SA patients, also showed impaired performance in a theory-of-mind task for which emotional expressions are identified based upon the eye regions of face images. This pattern of results suggests distinct processing of face information in schizophrenia and schizoaffective disorders.     

Cognition in young schizophrenia outpatients: comparison of first-episode with multiepisode patients

Cognitive impairments are recognized as a central feature of schizophrenia (SZ), largely independent of other symptoms, and a major cause of poor functioning. Studies indicate cognitive deterioration in the first years after the onset of SZ. These studies, however, have been criticized for using a small sample size, for having limited monitoring of confounding variables, and for the inclusion of cohorts of different ages. The current study compared the cognitive profile of first-episode schizophrenia patients, multi-episode schizophrenia patients and healthy controls (n = 44, n = 39, and n = 44; respectively). The study focused on the early stages of the disorder, recruiting only young patients. All subjects underwent an extensively validated computerized cognitive assessment (Cambridge Neuropsychological Test Automated Battery). The results revealed widespread cognitive impairments in SZ patients, compared with healthy control subjects. The multiepisode SZ patients were significantly more impaired than the first-episode ones, with deficits mainly related to psychomotor speed, pattern memory, and executive functioning. The functioning in other cognitive domains (ie, attention and spatial memory) was deficient even at an early stage of the disorder. These findings can help clarify the course of cognitive decline in young-aged SZ patients and aid in the development of phase-appropriate interventions.     

Cannabis use is associated with schizotypy and attentional disinhibition

While most neurochemical research into the pathogenesis of schizophrenia (SZ) has focused on the dopaminergic, glutamatergic, and serotonergic systems, the exact nature and cause of this disorder have proven intractable. Given the recent discovery and elucidation of the endogenous cannabinioid system, a re-examination of the cannabis-induced exacerbation hypothesis of SZ is warranted. The purpose of the present study was to assess whether current cannabis users exhibit personality correlates and neurocognitive deficits similar to those observed in SZ patients. 15 current cannabis users, 15 drug-free controls, and 10 past cannabis users were assessed on tasks which assess attentional inhibition, spatial working memory, olfactory identification, and schizotypal personality. Current cannabis users demonstrated deficits in attentional inhibition, decreased reaction time, and significantly higher scores on the schizotypal personality questionnaire (SPQ) compared with the non-using and past cannabis using groups. No group differences were found on the working memory or olfactory identification tasks. These results suggest that cannabis use can mimic attentional deficits seen in acute schizophrenia and is associated with schizotypal personality, thus setting the stage for a possible cannabinoid model of SZ.     

Auditory cortex responsiveness during talking and listening: early illness schizophrenia and patients at clinical high-risk for psychosis

Objective: The corollary discharge mechanism is theorized to dampen sensations resulting from our own actions and distinguish them from environmental events. Deficits in this mechanism in schizophrenia may contribute to misperceptions of self-generated sensations as originating from external stimuli. We previously found attenuated speech-related suppression of auditory cortex in chronic patients, consistent with such deficits. Whether this abnormality precedes psychosis onset, emerges early in the illness, and/or progressively worsens with illness chronicity, is unknown. Methods: Event-related potentials (ERPs) were recorded from schizophrenia patients (SZ; n = 75) and age-matched healthy controls (HC; n = 77). A subsample of early illness schizophrenia patients (ESZ; n = 39) was compared with patients at clinical high-risk for psychosis (CHR; n = 35) and to a subgroup of age-matched HC (n = 36) during a Talk-Listen paradigm. The N1 ERP component was elicited by vocalizations as subjects talked (Talk) and heard them played back (Listen). Results: As shown previously, SZ showed attenuated speech-related N1 suppression relative to HC. This was also observed in ESZ. N1 suppression values in CHR were intermediate to HC and ESZ and not statistically distinguishable from either comparison group. Age-corrected N1 Talk-Listen difference z scores were not correlated with illness duration in the full SZ sample. Conclusions: Putative dysfunction of the corollary discharge mechanism during speech is evident early in the illness and is stable over its course. The intermediate effects in CHR patients may reflect the heterogeneity of this group, requiring longitudinal follow-up data to address if speech-related N1 suppression abnormalities are a risk marker for conversion to psychosis.     

White matter organization and neurocognitive performance variability in schizophrenia

BackgroundWhite matter alterations in schizophrenia are associated with deficits in neurocognitive performance. Recently, across task within-individual variability (WIV) has emerged as a useful construct for assessing the profile in cognitive performance in schizophrenia. However, the neural basis of WIV has not been studied in patients with schizophrenia.MethodsTwenty-five patients with schizophrenia (SZ) and 27 healthy comparison subjects (HC) performed a computerized neurocognitive battery (CNB) and underwent diffusion tensor imaging (DTI). WIV for performance accuracy and speed on the CNB was calculated across-tasks. Voxel-wise group comparisons of white matter fractional anisotropy (FA) were performed using tract-based spatial statistics (TBSS). The relationship between accuracy and speed WIV on the CNB and white matter FA was examined within the regions that differentiated patients and healthy comparison subjects.ResultsSZ had higher WIV for performance accuracy and speed as compared to HC. FA in SZ compared to HC was reduced in bilateral frontal, temporal and occipital white matter including a large portion of the corpus callosum. In white matter regions that differed between patients and comparison subjects, higher FA in the left cingulum bundle and left fronto-occipital fasciculus were associated with lower CNB speed WIV for HC, but not SZ. Accuracy WIV was not associated with differences in white matter FA between SZ and HC.ConclusionsWe provide evidence that WIV is greater in patients with SZ and that this greater within-individual variability in performance in patients is associated with disruptions of WM integrity in specific brain regions.     

Neurocognition, symptomatology, and functional skills in older alcohol-abusing schizophrenia patients

Deficits in neurocognitive functioning are common to both schizophrenia and alcoholism. Recent studies suggest that neurocognitive functioning is the most significant predictor of social-adaptive functioning in schizophrenia. Cognitive impairment induced by alcoholism may result in more impaired functional outcome for comorbid patients. Past research examining alcohol-abusing schizophrenia patients has not examined correlates with functional outcome and has generally been limited to relatively younger patients. This study examined neurocognitive functioning and its correlates in alcohol-abusing schizophrenia patients between the ages of 40 and 80. Outpatients with schizophrenia (SZ; n = 17) or both schizophrenia and alcohol abuse or dependence (SZ + ETOH; n = 18) were tested on a neurocognitive battery, rated for symptomatology, and assessed for functional abilities. The results suggest that alcohol abuse in schizophrenia is associated with more impaired functioning across many domains, including memory impairment, negative and general psychopathology symptoms, and adaptive functions. The only significant predictor of impaired functional status in the overall sample and the SZ + ETOH group was neurocognitive functioning.     

Magnocellular contributions to impaired motion processing in schizophrenia

Patients with schizophrenia show impairments in motion processing, along with deficits in lower level processing primarily involving the magnocellular visual pathway. The present study investigates potential magnocellular contributions to impaired motion processing in schizophrenia using a combined neurophysiological and behavioral approach. As compared to prior motion studies in schizophrenia, thresholds were determined for both incoherent and coherent visual motion. In this study, velocity discrimination thresholds were measured for schizophrenia patients (n=14) and age-matched normal control subjects (n=16) using a staircase procedure. Early visual processing was evaluated using steady-state visual evoked potentials (ssVEP), with stimuli biased toward activation of either the magnocellular or parvocellular visual pathways through luminance contrast manipulation. Patients with schizophrenia showed poor velocity discrimination for both incoherent and coherent motion, with no significant group x task interaction. Further, when coherent motion performance was measured at individually determined incoherent motion thresholds, accuracy levels for patients were similar to controls, also indicating similarity of deficit for incoherent vs. coherent motion discrimination. Impairments in velocity discrimination correlated significantly with reduced amplitude of ssVEP elicited by magnocellular -- but not parvocellular -- selective stimuli. This study demonstrates that deficits in motion processing in schizophrenia are significantly related to reduced activation of the magnocellular visual system. Further, this study supports and extends prior reports of impaired motion processing in schizophrenia, and indicates significant bottom-up contributions to higher-order cognitive impairments.     

Fractionation of verbal memory impairment in schizophrenia and schizophreniform psychosis

OBJECTIVES: The characterization, aetiology, and course of verbal memory deficits in schizophrenia remain ill defined. The impact of antipsychotic medications is also unclear. The purpose of the present paper was to investigate verbal memory performance in established schizophrenia (SZ) and first-episode schizophreniform psychosis (FE). METHOD: Performances of 32 SZ and 33 FE patients were compared to those of 47 healthy volunteers on measures of verbal working memory, verbal associative learning and story recall. RESULTS: Story recall deficits, but not deficits in working memory or paired associate learning, were demonstrated by both patient groups. Patients treated with typical neuroleptics had more impairment in associative learning with arbitrary word pairings than those treated with atypicals, regardless of patient group. CONCLUSIONS: The results are consistent with the notion that some neuropsychological impairment is present at the time of psychosis onset and that this impairment is non-progressive. However, deficits may be specific to subclasses of memory function.     

The impact of familial risk for schizophrenia or bipolar disorder on cognitive control during episodic memory retrieval

Episodic memory impairment is a robust correlate of familial risk for schizophrenia (SZ) and bipolar disorder (BD); still much is unknown about the processes that underlie this deficit and how they may be implicated in BD and SZ. We examined the possibility that (a) episodic memory impairment may arise from abnormalities in the cognitive control of interference between task-relevant and task-irrelevant memories during retrieval; inability to suppress task-irrelevant representations could give rise to intrusions of inappropriate memories and increased rate of forgetting, (b) cognitive control deficits during retrieval may be differentially affected by familial predisposition to SZ or BD. We examined episodic memory in relatives of patients with SZ (SZ-R) (n=15) or BD (BD-R) (n=17) compared to healthy controls (n=23) using the California Verbal Learning Test (CVLT) and the Doors and People Test (DPT). All relatives were free of any psychiatric morbidity and were matched to controls on age, sex, educational achievement and general intellectual ability. During the CVLT, both relatives' groups made significantly more perseverative recall errors than controls. However, intrusion errors were significantly increased in SZ-R only. SZ-R also showed increased rate of forgetting in the DPT while BD-R were comparable to controls. Familial predisposition to SZ, compared to that of BD, was associated with significantly greater impairment in cognitive control processes during episodic memory retrieval with some evidence of specificity for SZ in connection with mechanisms relating to increased forgetting.     

How specific are deficits in mismatch negativity generation to schizophrenia?

BACKGROUND: Mismatch negativity (MMN) is an auditory event-related potential that provides an index of auditory sensory memory. Deficits in MMN generation have been repeatedly demonstrated in chronic schizophrenia. Their specificity to schizophrenia has not been established. METHODS: Mismatch negativity to both duration and frequency deviants was investigated in gender- and age-matched patients with schizophrenia or schizoaffective disorder (n = 26), bipolar disorder (n = 16), or major depression (n = 22) and healthy control subjects (n = 25). RESULTS: Only patients with schizophrenia demonstrated significantly smaller mean MMN than did healthy control subjects. Detailed analyses showed significantly smaller MMN to both duration and frequency deviants in patients with schizophrenia than in healthy control subjects; however, the reduction of frequency MMN in patients with schizophrenia was not significant in the comparison across all groups. Mismatch negativity topography did not differ among groups. No consistent correlations with clinical, psychopathologic, or treatment variables were observed. CONCLUSIONS: Mismatch negativity deficits, and by extension deficits in early cortical auditory information processing, appear to be specific to schizophrenia. Animal and human studies implicate dysfunctional N-methyl-D-aspartate receptor functioning in MMN deficits. Thus MMN deficits may become a useful endophenotype to investigate the genetic underpinnings of schizophrenia, particularly with regard to the N-methyl-D-aspartate receptor.     

Wisconsin Card Sorting deficits in the offspring of schizophrenics in the New York High-Risk Project

It has been suggested that performance on the Wisconsin Card Sorting Test (WCST) may be an indicator of vulnerability to schizophrenia. WCST deficits have been demonstrated in schizophrenic patients and their relatives, but not as yet in their offspring. This study aimed to further establish the indicator potential of WCST deficits by analyzing data collected as part of the New York High-Risk Project (NYHRP), a longitudinal study of attention, cognition and clinical functioning in the offspring of schizophrenic (HRSz, n=73), affective disordered (HRAff, n=61) and normal comparison (NC, n=120) parents. Parental Research Diagnostic Criteria diagnoses were established by semi-structured interview (SADS-L). WCST testing was carried out when offspring were in their mid-20s. HRSz subjects performed significantly more poorly on the WCST than HRAff and NC subjects. High-risk subjects who developed psychotic symptoms prior to or shortly after testing did not differ significantly from HRSz subjects who did not become ill. Thus, WCST performance in the offspring of schizophrenics resembles that of schizophrenic patients and may distinguish HRSz from offspring at risk for nonschizophrenic illness. WCST deficits may be a specific familial indicator of vulnerability, but appear not to distinguish between those subjects at risk for schizophrenia who do or do not become ill.