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.     

Compromised late-stage motion processing in schizophrenia.

BACKGROUND: Visual motion processing is compromised in schizophrenia, as shown in deficient velocity discrimination. Processing of motion signals comprises progressive stages along the geniculate-striate-extrastriate-cortex pathway. Based on neurophysiologic and brain lesion studies, a velocity discrimination deficit can implicate early-stage motion processing if it is contrast-dependent or late-stage motion processing if it is contrast-independent. METHODS: To determine which stage underlies the deficient velocity discrimination in schizophrenia, we examined the effects of visual contrast on velocity discrimination. We measured velocity discrimination thresholds in schizophrenia patients (n = 34) and normal control subjects (n = 17) at both low and high contrasts, using each subject's contrast detection threshold to equate contrast levels. RESULTS: Schizophrenia patients showed poor velocity discrimination that improved little with high contrast, whereas normal control subjects showed enhanced velocity discrimination with increased contrast. CONCLUSIONS: The finding that the velocity discrimination deficit in schizophrenia is independent of contrast modulation implicates the later, rather than the earlier, stages of motion processing, which is mediated in the extrastriate cortex.     

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.     

Dependence of impaired eye tracking on deficient velocity discrimination in schizophrenia

BACKGROUND: Abnormal smooth pursuit eye movements have been found in many schizophrenic patients and in about 40% of their first-degree biological relatives. A velocity discrimination deficit has also been demonstrated in schizophrenic patients. In this study, we address the relation between deficient velocity discrimination and impaired smooth pursuit eye movements, inasmuch as the brain regions responsible for processing velocity signals are implicated in generating and maintaining smooth pursuit. METHODS: Horizontal eye movements of 15 schizophrenic patients and 8 normal controls were recorded in response to sine wave (predictable) and step-ramp (nonpredictable) targets. Smooth pursuit eye movements were assessed during both the initiation and maintenance periods. Correlations were computed between measures of smooth pursuit (qualitative rating, peak gain, saccade frequency, and initial acceleration) and contrast sensitivity for velocity discrimination. RESULTS: Contrast sensitivity for fine velocity discrimination was significantly correlated both with initial acceleration of smooth pursuit and with peak gain, but was not significantly correlated with saccade frequency and qualitative ratings of pursuit integrity. No significant correlations were found within the normal control group. CONCLUSION: Deficient processing of velocity information seems to be one component that contributes to a dysfunction in the initiation and maintenance of smooth pursuit in schizophrenia.     

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.     

Bipolar and schizophrenic patients differ in patterns of visual motion discrimination

BACKGROUND: Since Kraepelin's early distinction between bipolar disorder and schizophrenia, it has been assumed that these disorders represent two different pathophysiological processes, although they share many clinical symptoms. Previous studies showed that velocity discrimination, a sensitive psychophysiological measure of the visual motion system, is deficient in schizophrenia. Here we examined whether the motion processing impairment found in schizophrenia also occurs in bipolar disorder. METHODS: We compared 16 bipolar patients, 25 schizophrenic patients, and 25 normal controls on a velocity discrimination task. We measured the psychophysical threshold for velocity discrimination and contrast detection (as a control task) in all subjects. RESULTS: Bipolar patients showed normal velocity discrimination thresholds at intermediate velocities, the range in which velocity cues dominate velocity discrimination, and at low velocities. Schizophrenic patients, however, showed elevated velocity discrimination thresholds at intermediate and low velocities. At higher velocities, both bipolar and schizophrenic patients showed elevated thresholds. All subjects showed normal contrast detection thresholds. CONCLUSIONS: Normal velocity discrimination in the intermediate range of velocity indicates unimpaired motion processing in bipolar disorder. The abnormal velocity discrimination of both schizophrenic and bipolar patients at higher velocities may reflect impaired temporal processing rather than impaired motion processing per se. These results suggest that the pathophysiological processes of bipolar disorder and schizophrenia diverge at the stage of visual motion processing, a sensory component mediated primarily in the extrastriate cortex.     

Bipolar and schizophrenic patients differ in patterns of visual motion discrimination

BackgroundSince Kraepelin's early distinction between bipolar disorder and schizophrenia, it has been assumed that these disorders represent two different pathophysiological processes, although they share many clinical symptoms. Previous studies showed that velocity discrimination, a sensitive psychophysiological measure of the visual motion system, is deficient in schizophrenia. Here we examined whether the motion processing impairment found in schizophrenia also occurs in bipolar disorder.MethodsWe compared 16 bipolar patients, 25 schizophrenic patients, and 25 normal controls on a velocity discrimination task. We measured the psychophysical threshold for velocity discrimination and contrast detection (as a control task) in all subjects.ResultsBipolar patients showed normal velocity discrimination thresholds at intermediate velocities, the range in which velocity cues dominate velocity discrimination, and at low velocities. Schizophrenic patients, however, showed elevated velocity discrimination thresholds at intermediate and low velocities. At higher velocities, both bipolar and schizophrenic patients showed elevated thresholds. All subjects showed normal contrast detection thresholds.ConclusionsNormal velocity discrimination in the intermediate range of velocity indicates unimpaired motion processing in bipolar disorder. The abnormal velocity discrimination of both schizophrenic and bipolar patients at higher velocities may reflect impaired temporal processing rather than impaired motion processing per se. These results suggest that the pathophysiological processes of bipolar disorder and schizophrenia diverge at the stage of visual motion processing, a sensory component mediated primarily in the extrastriate cortex.     

Object versus spatial visual mental imagery in patients with schizophrenia

OBJECTIVE: Recent research has revealed a larger impairment of object perceptual discrimination than of spatial perceptual discrimination in patients with schizophrenia. It has been suggested that mental imagery may share processing systems with perception. We investigated whether patients with schizophrenia would show greater impairment regarding object imagery than spatial imagery. METHODS: Forty-four patients with schizophrenia and 20 healthy control subjects were tested on a task of object visual mental imagery and on a task of spatial visual mental imagery. Both tasks included a condition in which no imagery was needed for adequate performance, but which was in other respects identical to the imagery condition. This allowed us to adjust for nonspecific differences in individual performance. RESULTS: The results revealed a significant difference between patients and controls on the object imagery task (F(1,63) = 11.8, p = 0.001) but not on the spatial imagery task (F(1,63) = 0.14, p = 0.71). To test for a differential effect, we conducted a 2 (patients v. controls) small ha, Cyrillic 2 (object task v. spatial task) analysis of variance. The interaction term was statistically significant (F(1,62) = 5.2, p = 0.026). CONCLUSIONS: Our findings suggest a differential dysfunction of systems mediating object and spatial visual mental imagery in schizophrenia.     

Selective impairment in visual perception of biological motion in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is associated with a variety of well-documented cognitive deficits such as deficits in memory and executive functioning, but little is known about basic perceptual concomitants of OCD. This study investigated global, configural processing in OCD using dynamic (moving) and static stimuli with minimal demands on cognitive function. Twenty OCD patients and 16 age- and education-matched healthy control subjects were tested on four perceptual tasks: two motion tasks involved detection and discrimination of human activity portrayed by point-light animations ("biological" motion). The other two tasks involved detection of coherent, translational motion defined by random-dot cinematograms and detection of static global shape defined by spatially distributed contours. OCD patients exhibited impaired performance on biological motion tasks; in contrast, their performance on tasks of coherent motion detection and global form perception were comparable to those of healthy controls. These results indicate that OCD patients have a specific deficit in perceiving biological motion signals, whereas their perception of non-biological coherent motion and static global shape is intact. Because efficient social interactions depend on accurate and rapid perception of subtle socially relevant cues, deficits in biological motion perception may compromise social functioning in people with OCD.     

Abnormal visual motion processing in schizophrenia: a review of research progress

Motion processing represents a perceptual domain in which dynamic visual information is encoded to support the perception of movement. Research over the last decade has found a variety of abnormalities in the processing of motion information in schizophrenia. The abnormalities span from discrimination of basic motion features (such as speed) to integration of spatially distributed motion signals (such as coherent motion). Motion processing involves visual signals across space and time and thus presents a special opportunity to examine how spatial and temporal information is integrated in the visual system. This article surveys the behavioral and neuroimaging studies that probe into the spatial integration of motion information in schizophrenia. An emerging theme from these studies points to an imbalanced regulation of spatial interaction processes as a potential mechanism mediating different levels of abnormal motion processing in schizophrenia. The synthesis of these mechanism-driven studies suggests that further investigation of the neural basis and functional consequences of this abnormal motion processing are needed in order to render a basic biomarker for assessment and intervention of cognitive dysfunction in this mental disorder.     

Language processing and human voice perception in schizophrenia: a functional magnetic resonance imaging study.

BACKGROUND: Neuroimaging studies have demonstrated either reduced left-lateralized activation or reversed language dominance in schizophrenia. These findings of left hemispheric dysfunction could be attributed to language processing tasks, which activate mainly left hemispheric function. Recent functional magnetic resonance imaging studies reported right-lateralized temporal activation by human voice perception, but few studies have investigated activation by human voice in schizophrenia. We aimed to clarify the cerebral function of language processing in schizophrenia patients by considering cerebral activation of human voice perception. METHODS: Fourteen right-handed schizophrenia patients and 14 right-handed controls with matched handedness, sex, and education level were scanned by functional magnetic resonance imaging while listening to sentences (SEN), reverse sentences (rSEN), and identifiable non-vocal sounds (SND). RESULTS: Under the SEN-SND and SEN-rSEN contrasts including language processing, patients showed less activation of the left hemisphere than controls in the language-related fronto-tempo-parietal region, hippocampus, thalamus and cingulate gyrus. Under the rSEN-SND contrast including human voice perception, patients showed less activation than controls in the right-lateralized temporal cortices and bilateral posterior cingulate. CONCLUSIONS: Our results indicate that schizophrenia patients have impairment of broader bilateral cortical-subcortical regions related to both the semantic network in the left hemisphere and the voice-specific network in the right hemisphere.     

Smooth pursuit eye movements to extra-retinal motion signals: deficits in patients with schizophrenia

In order to understand mechanisms underlying the smooth pursuit abnormality(ies) in schizophrenia, new methods, which independently evaluated predictive smooth pursuit responses to extra-retinal motion signals, were developed and tested. The study compared responses to only extra-retinal motion signals in normal volunteers (n = 25), and individuals with a chronic (n = 21) and a recent onset (n = 18) schizophrenia. Subject groups with chronic schizophrenia and recent onset schizophrenia had significantly poorer predictive pursuit than normal subjects in response to only extra-retinal motion signals. The poor predictive pursuit was evident even at low target velocity when the closed-loop pursuit gain was normal in patients with schizophrenia. Ten of the 18 recent onset patients were drug-free at the time of testing and had no or minimum previous exposure to anti-psychotic medications. Re-analyses of the data showed that on most measures of predictive pursuit, drug-free patients were not significantly different from patients who received anti-psychotic drug treatment. Both patient groups had significantly poorer predictive pursuit than normal subjects. These results suggest that a deficit in processing extra-retinal motion may underlie the abnormal smooth pursuit response in schizophrenia. At low target velocities, patients with schizophrenia were able to compensate for the low extra-retinal gain by increasing the gain of response to the retinal slip velocity. This indicates that patients were able to process retinal slip velocity and generate smooth pursuit eye movements, but experienced a specific deficit in processing and/or integrating extra-retinal motion information for the smooth pursuit response.     

Right lateral fusiform gyrus dysfunction during facial information processing in schizophrenia.

BACKGROUND: Patients with schizophrenia exhibit facial information processing deficits that likely contribute to their social dysfunction. Whether the deficits involve facial affect and/or identity processing or result from other cognitive abnormalities in schizophrenia remains controversial, and a brain dysfunction specifically related to them has never been reported. If such dysfunction existed, it should be consistently observed across groups of patients and during performance of different facial information processing tasks, independently of whether such tasks demand working memory (WM), semantic, or other cognitive processes. We hypothesized that the right lateral fusiform gyrus (rLFG), one of several human brain areas involved in facial information processing, would consistently show activation abnormalities during both facial affect and identity discrimination in schizophrenia. METHODS: We used functional magnetic resonance imaging to measure brain activation in two groups of six chronic, stable schizophrenic outpatients and two of six age- and gender-matched healthy controls. One group of patients and one of controls performed facial affect-with or without semantic processing-and identity discrimination tasks, and the other two groups WM tasks with facial expression cues and varying attentional demands. RESULTS: Patients from either group failed to activate the rLFG when compared to controls in any task. Other activation abnormalities were task-specific (i.e., seen only during performance of one set of tasks) and not consistently observed in both groups of patients, and thus could not be directly and solely linked to facial information discrimination. CONCLUSIONS: These results indicate a specific rLFG dysfunction during early facial information--identity or affect--processing, independent from other cognitive deficits, in schizophrenia.     

Visual perception and working memory in schizotypal personality disorder

OBJECTIVE: Patients affected by schizophrenia show deficits in both visual perception and working memory. The authors tested early-stage vision and working memory in subjects with schizotypal personality disorder, which has been biologically associated with schizophrenia. METHOD: Eleven subjects who met DSM-III-R criteria for schizotypal personality disorder and 12 normal comparison subjects were evaluated. Performance thresholds were obtained for tests of visual discrimination and working memory. Both form and trajectory processing were evaluated for each task. RESULTS: Subjects with schizotypal personality disorder showed intact discrimination of form and trajectory but were impaired on working memory tasks. CONCLUSIONS: These data suggest that subjects with schizotypal personality disorder, unlike patients affected by schizophrenia, have relatively intact visual perception. Subjects with schizotypal personality disorder do show specific deficits on tasks of comparable difficulty when working memory demands are imposed. Schizotypal personality disorder may be associated with a more specific visual processing deficit than schizophrenia, possibly reflecting disruption of frontal lobe systems subserving visual working memory operations.     

Facial emotion perception in Chinese patients with schizophrenia and non-psychotic first-degree relatives

Although there is a consensus that patients with schizophrenia have certain deficits in perceiving and expressing facial emotions, previous studies of facial emotion perception in schizophrenia do not present consistent results. The objective of this study was to explore facial emotion perception deficits in Chinese patients with schizophrenia and their non-psychotic first-degree relatives. Sixty-nine patients with schizophrenia, 56 of their first-degree relatives (33 parents and 23 siblings), and 92 healthy controls (67 younger healthy controls matched to the patients and siblings, and 25 older healthy controls matched to the parents) completed a set of facial emotion perception tasks, including facial emotion discrimination, identification, intensity, valence, and corresponding face identification tasks. The results demonstrated that patients with schizophrenia performed significantly worse than their siblings and younger healthy controls in accuracy in a variety of facial emotion perception tasks, whereas the siblings of the patients performed as well as the corresponding younger healthy controls in all of the facial emotion perception tasks. Patients with schizophrenia also showed significantly reduced speed than younger healthy controls, while siblings of patients did not demonstrate significant differences with both patients and younger healthy controls in speed. Meanwhile, we also found that parents of the schizophrenia patients performed significantly worse than the corresponding older healthy controls in accuracy in terms of facial emotion identification, valence, and the composite index of the facial discrimination, identification, intensity and valence tasks. Moreover, no significant differences were found between the parents of patients and older healthy controls in speed after controlling the years of education and IQ. Taken together, the results suggest that facial emotion perception deficits may serve as potential endophenotypes for schizophrenia.     

Age-associated differences in cognitive performance in older community dwelling schizophrenia patients: differential sensitivity of clinical neuropsychological and experimental information processing tests

Cognitive dysfunction is a common feature of schizophrenia and deficits are present before the onset of psychosis, and are moderate to severe by the time of the first episode. Controversy exists over the course of cognitive dysfunction after the first episode. This study examined age-associated differences in performance on clinical neuropsychological (NP) and information processing tasks in a sample of geriatric community living schizophrenia patients (n=172). Compared to healthy control subjects (n=70), people with schizophrenia did not differ on NP tests across age groups but showed evidence for age-associated cognitive worsening on the more complex components of an information-processing test. Age-related changes in cognitive function in schizophrenia may be a function of both the course of illness and the processing demands of the cognitive measure of interest. Tests with fixed difficulty, such as clinical NP tests, may differ in their sensitivity from tests for which parametric difficulty manipulations can be performed.     

Sensory contributions to impaired prosodic processing in schizophrenia.

BACKGROUND: Deficits in affect recognition are prominent features of schizophrenia. Within the auditory domain, patients show difficulty in interpreting vocal emotional cues based on intonation (prosody). The relationship of these symptoms to deficits in basic sensory processing has not been previously evaluated. METHODS: Forty-three patients and 34 healthy comparison subjects were tested on two affective prosody measures: voice emotion identification and voice emotion discrimination. Basic auditory sensory processing was measured using a tone-matching paradigm and the Distorted Tunes Test (DTT). A subset of subjects was also tested on facial affect identification and discrimination tasks. RESULTS: Patients showed significantly impaired performance on all emotion processing tasks. Within the patient group, a principal components analysis demonstrated significant intercorrelations between basic pitch perception and affective prosodic performance. In contrast, facial affect recognition deficits represented a distinct second component. Prosodic affect measures correlated significantly with severity of negative symptoms and impaired global outcome. CONCLUSIONS: These results demonstrate significant relationships between basic auditory processing deficits and impaired receptive prosody in schizophrenia. The separate loading of auditory and visual affective recognition measures suggests that within-modality factors may be more significant than cross-modality factors in the etiology of affect recognition deficits in schizophrenia.     

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.     

Impaired visual recognition of biological motion in schizophrenia

BACKGROUND: Motion perception deficits have been suggested to be an important feature of schizophrenia but the behavioral consequences of such deficits are unknown. Biological motion refers to the movements generated by living beings. The human visual system rapidly and effortlessly detects and extracts socially relevant information from biological motion. A deficit in biological motion perception may have significant consequences for detecting and interpreting social information. METHODS: Schizophrenia patients and matched healthy controls were tested on two visual tasks: recognition of human activity portrayed in point-light animations (biological motion task) and a perceptual control task involving detection of a grouped figure against the background noise (global-form task). Both tasks required detection of a global form against background noise but only the biological motion task required the extraction of motion-related information. RESULTS: Schizophrenia patients performed as well as the controls in the global-form task, but were significantly impaired on the biological motion task. In addition, deficits in biological motion perception correlated with impaired social functioning as measured by the Zigler social competence scale [Zigler, E., Levine, J. (1981). Premorbid competence in schizophrenia: what is being measured? Journal of Consulting and Clinical Psychology, 49, 96-105.]. CONCLUSION: The deficit in biological motion processing, which may be related to the previously documented deficit in global motion processing, could contribute to abnormal social functioning in schizophrenia.     

Impaired emotion perception in schizophrenia: a differential deficit

We investigated previously reported contradictory findings regarding the nature of deficits in emotion perception among patients with schizophrenia. Some studies have concluded that such deficits are due to a generalized impairment in visual processing of faces, while others have found it to be restricted to facial emotional expressions. We examined 37 patients and 32 healthy controls, matched on age and education, using three computerized tests: matching facial identity, matching facial emotional expressions, and discrimination of subtle differences in the valence of facial emotional expressions. Our results showed impaired matching of emotions in patients with schizophrenia. This impairment did not manifest on tasks that depended on perceiving the identity of faces or cues of the relative valence of facial emotional expressions. Our findings support the differential deficit hypothesis of emotion perception in schizophrenia.