Differential activation patterns of occipital and prefrontal cortices during motion processing: evidence from normal and schizophrenic brains

Disrupted third visual pathway function in schizophrenia: Evidence from real and implied motion processing

Impaired motion perception in schizophrenia has been associated with deficits in social-cognitive processes and with reduced activation of visual sensory regions, including the middle temporal area (MT+) and posterior superior temporal sulcus (pSTS). These findings are consistent with the recent proposal of the existence of a specific 'third visual pathway' specialized for social perception in which motion is a fundamental component. The third visual pathway transmits visual information from early sensory visual processing areas to the STS, with MT+ acting as a critical intermediary. We used functional magnetic resonance imaging to investigate functioning of this pathway during processing of naturalistic videos with explicit (real) motion and static images with implied motion cues. These measures were related to face emotion recognition and motion-perception, as measured behaviorally. Participants were 28 individuals with schizophrenia (Sz) and 20 neurotypical controls. Compared to controls, individuals with Sz showed reduced activation of third visual pathway regions (MT+, pSTS) in response to both real- and implied-motion stimuli. Dysfunction of early visual cortex and pulvinar were also associated with aberrant real-motion processing. Implied-motion stimuli additionally engaged a wide network of brain areas including parietal, motor and frontal nodes of the human mirror neuron system. The findings support concepts of MT+ as a mediator between visual sensory areas and higher-order brain and argue for greater focus on MT+ contributions to social-cognitive processing, in addition to its well-documented role in visual motion processing.

A neural mechanism underlying predictive visual motion processing in patients with schizophrenia

Psychotic symptoms may be traced back to sensory sensitivity. Thereby, visual motion (VM) processing particularly has been suggested to be impaired in schizophrenia (SCZ). In healthy brains, VM underlies predictive processing within hierarchically structured systems. However, less is known about predictive VM processing in SCZ. Therefore, we performed fMRI during a VM paradigm with three conditions of varying predictability, i.e., Predictable-, Random-, and Arbitrary motion. The study sample comprised 17 SCZ patients and 23 healthy controls. We calculated general linear model (GLM) analysis to assess group differences in VM processing across motion conditions. Here, we identified significantly lower activity in right temporoparietal junction (TPJ) for SCZ patients. Therefore, right TPJ was set as seed for connectivity analyses. For patients, across conditions we identified increased connections to higher regions, namely medial prefrontal cortex, or paracingulate gyrus. Healthy subjects activated sensory regions as area V5, or superior parietal lobule. Reduced TPJ activity may reflect both a failure in the bottom-up flow of visual information and a decrease of signal processing as consequence of increased top-down input from frontal areas. In sum, these altered neural patterns provide a framework for future studies focusing on predictive VM processing to identify potential biomarkers of psychosis.

Automatic Schizophrenia Detection Using Multimodality Media via a Text Reading Task

Schizophrenia is a crippling chronic mental disease that affects people worldwide. In this work, an automatic schizophrenia detection algorithm is proposed based on the reading deficit of schizophrenic patients. From speech and video modalities, the automatic schizophrenia detection algorithm illustrates abnormal speech, head movement, and reading fluency during the reading task. In the speech modality, an acoustic model of speech emotional flatness in schizophrenia is established to reflect the emotional expression flatness of schizophrenic speech from the perspective of speech production and perception. In the video modality, the head-movement-related features are proposed to illustrate the spontaneous head movement caused by repeated reading and unconscious movement, and the reading-fluency-related features are proposed to convey the damaged degree of schizophrenic patients' reading fluency. The experimental data of this work are 160 segments of speech and video data recorded by 40 participants (20 schizophrenic patients and 20 normal controls). Combined with support vector machines and random forest, the accuracy of the proposed acoustic model, the head-movement-related features, and the reading-fluency-related features range from 94.38 to 96.50%, 73.38 to 83.38%, and 79.50 to 83.63%, respectively. The average accuracy of the proposed automatic schizophrenia detection algorithm reaches 97.50%. The experimental results indicate the effectiveness of the proposed automatic detection algorithm as an auxiliary diagnostic method for schizophrenia.

Heightened perception of illusory motion is associated with symptom severity in schizophrenia patients

Abnormal perceptual processing in schizophrenia may contribute to the development of positive symptoms such as hallucinations. Experimental findings suggest that such abnormalities result from impaired processing of local signals into complex cortical representations. Because complex processing is needed to generate the perception of illusory motion from local signals, deteriorated perception of illusory motion would be expected in schizophrenia. However, findings are mixed, and the relationship between complex motion processing and symptoms is unclear. Illusions with multiple flow components (e.g. rotation/expansion) are known to strongly engage specialized complex processing mechanisms that may be abnormal in schizophrenia, but have not yet been investigated. We used a recently constructed paradigm based on the Pinna-Brelstaff illusion to manipulate complex-flow illusory perception in a quantitative manner and probe associations with dimensional symptoms. In 102 patients and 90 controls, perceived speed and perceptual variability for the PBF were measured across a range of parameters. Meanwhile, eye movement was recorded and gaze parameters were analysed to examine effects on illusory perception. Our results showed that patients experienced faster illusory rotation than controls, while they made fewer eye fixations. This heightened illusory perception was significantly correlated with positive and general, but not negative, symptom scores. Our results indicate that unusual processing of complex-flow motion in patients may be specifically related to dimensional symptoms, which could provide a promising strategy for parsing heterogeneity in the schizophrenia syndrome. This further highlights the role of motion perception abnormalities in the pathophysiology of schizophrenia, thus encouraging future investigation into visual remediation therapeutics.

The neural correlates of the visual consciousness in schizophrenia: an fMRI study

In the current literature, two distinct and opposite models are suggested to explain the consciousness disorders in schizophrenia. The first one suggests that consciousness disorders rely on a low-level processing deficit, when the second model suggests that consciousness disorders rely on disruption in the ability to consciously access information, with preserved unconscious processing. The current study aims to understand the mechanisms associated with visual consciousness disorder in order to pave the road that will settle the debate regarding these hypotheses. During a functional magnetic resonance imaging session, 19 healthy participants (HC) and 15 patients with schizophrenia (SCZ) performed a visual detection task to compare the neural substrates associated with the conscious access to the visual inputs. The visual detection threshold was significantly higher in SCZ than in HC [t(32) = 3.37, p = 0.002]. Whole-brain ANOVA demonstrated that around the visual detection threshold patients with SCZ failed to activate a large network of brain areas compared to HC. (1) During conscious vision, HC engaged more the left cuneus and the right occipital cortex than patients with SCZ, (2) during unconscious vision, HC engaged a large network that patients with SCZ failed to activate, and finally, (3) during the access to consciousness process, patients with SCZ failed to activate the anterior cingulate cortex. These results suggest that the consciousness disorders in schizophrenia rely on specific dysfunctions depending on the consciousness stage. The disorders of the conscious vision are associated with dysfunction of occipital areas while the ones associated with unconscious vision rely on a large widespread network. Finally, the conscious access to the visual inputs is impaired by a dysfunction of the anterior cingulate cortex. The current study suggests that none of the two suggested models can explain consciousness disorders in schizophrenia. We suggest that there is an alternative model supporting that the conscious access to visual inputs is due to a disengagement of the supragenual anterior cingulate during the unconscious processing of the visual inputs associated with a sensory deficit.

Examining motion speed processing in schizophrenia using the flash lag illusion

Research on visual perception in schizophrenia suggests a deficit in motion processing. Specifically, difficulties with discriminating motion speed are commonly reported. However, speed discrimination tasks typically require participants to make judgments about the difference between two stimuli in a two-interval forced choice (2IFC) task. Such tasks not only tap into speed processing mechanisms, but also rely on higher executive functioning including working memory and attention which has been shown to be compromised in schizophrenia. We used the Flash Lag illusion to examine speed processing in patients with schizophrenia. Based on previous research showing a strong dependence between motion speed and the illusion magnitude, we expected a deficit in speed processing to alter this relationship. A motion processing deficit in patients would also predict overall reductions in perceived lag. We found the magnitude and speed dependence of the Flash Lag illusion to be similar in patients and controls. Together, the findings suggest no general abnormality in motion speed processing in schizophrenia.

No evidence for abnormal priors in early vision in schizophrenia

The predictive coding account of psychosis postulates the abnormal formation of prior beliefs in schizophrenia, resulting in psychotic symptoms. One domain in which priors play a crucial role is visual perception. For instance, our perception of brightness, line length, and motion direction are not merely based on a veridical extraction of sensory input but are also determined by expectation (or prior) of the stimulus. Formation of such priors is thought to be governed by the statistical regularities within natural scenes. Recently, the use of such priors has been attributed to a specific set of well-documented visual illusions, supporting the idea that perception is biased toward what is statistically more probable within the environment. The Predictive Coding account of psychosis proposes that patients form abnormal representations of statistical regularities in natural scenes, leading to altered perceptual experiences. Here we use classical vision experiments involving a specific set of visual illusions to directly test this hypothesis. We find that perceptual judgments for both patients and control participants are biased in accordance with reported probability distributions of natural scenes. Thus, despite there being a suggested link between visual abnormalities and psychotic symptoms in schizophrenia, our results provide no support for the notion that altered formation of priors is a general feature of the disorder. These data call for a refinement in the predictions of quantitative models of psychosis.

Dysfunction of Magnocellular/dorsal Processing Stream in Schizophrenia

Background:

Patients with schizophrenia show not only cognitive, but also perceptual deficits. Perceptual deficits may affect different sensory modalities. Among these, the impairment of visual information processing is of particular relevance as demonstrated by the high incidence of visual disturbances. In recent years, the study of neurophysiological mechanisms that underlie visuo-perceptual, -spatial and -motor disorders in schizophrenia has increasingly attracted the interest of researchers.

Objective:

The study aims to review the existent literature on magnocellular/dorsal (occipitoparietal) visual processing stream impairment in schizophrenia. The impairment of relatively early stages of visual information processing was examined using experimental paradigms such as backward masking, contrast sensitivity, contour detection, and perceptual closure. The deficits of late processing stages were detected by examining visuo-spatial and -motor abilities.

Results:

Neurophysiological and behavioral studies support the existence of deficits in the processing of visual information along the magnocellular/dorsal pathway. These deficits appear to affect both early and late stages of visual information processing.

Conclusion:

The existence of disturbances in the early processing of visual information along the magnocellular/dorsal pathway is strongly supported by neurophysiological and behavioral observations. Early magnocellular dysfunction may provide a substrate for late dorsal processing impairment as well as higher-level cognition deficits.

Mechanisms Underlying Visuospatial Working Memory Impairments in Schizophrenia

Working memory deficits are observed in the vast majority of individuals diagnosed with schizophrenia and those at risk for the disorder. Working memory impairments are present during the prodromal stage and persist throughout the course of schizophrenia. Given the importance of cognition in functional outcome, working memory deficits are an important therapeutic target for schizophrenia. This chapter examines mechanisms underlying working memory deficits in schizophrenia, focusing on the roles of perception and attention in the encoding process. Lastly, we present a comprehensive discussion of neural oscillation and internal noise in the context of the etiology of working memory deficits in schizophrenia and introduce noninvasive treatment strategies that could improve encoding processes.

Reading deficits in schizophrenia and their relationship to developmental dyslexia: A review

Although schizophrenia and developmental dyslexia are considered distinct disorders in terms of clinical presentation and functional outcome, they both involve disruption in the processes that support skilled reading, including language, auditory perception, visual perception, oculomotor control, and executive function. Further, recent work has proposed a common neurodevelopmental basis for the two disorders, as suggested by genetic and pathophysiological overlap. Thus, these lines of research suggest that reading may be similarly impacted in schizophrenia and dyslexia. In this review, we survey research on reading abilities in individuals with schizophrenia, and review the potential mechanisms underlying reading deficits in schizophrenia that may be shared with those implicated in dyslexia. Elucidating the relationship between reading impairment in schizophrenia and dyslexia could allow for a better understanding of the pathophysiological underpinnings of schizophrenia, and could facilitate remediation of cognitive deficits that impact day-to-day functioning.

Dopamine Activation Preserves Visual Motion Perception Despite Noise Interference of Human V5/MT

When processing sensory signals, the brain must account for noise, both noise in the stimulus and that arising from within its own neuronal circuitry. Dopamine receptor activation is known to enhance both visual cortical signal-to-noise-ratio (SNR) and visual perceptual performance; however, it is unknown whether these two dopamine-mediated phenomena are linked. To assess this, we used single-pulse transcranial magnetic stimulation (TMS) applied to visual cortical area V5/MT to reduce the SNR focally and thus disrupt visual motion discrimination performance to visual targets located in the same retinotopic space. The hypothesis that dopamine receptor activation enhances perceptual performance by improving cortical SNR predicts that dopamine activation should antagonize TMS disruption of visual perception. We assessed this hypothesis via a double-blinded, placebo-controlled study with the dopamine receptor agonists cabergoline (a D2 agonist) and pergolide (a D1/D2 agonist) administered in separate sessions (separated by 2 weeks) in 12 healthy volunteers in a William's balance-order design. TMS degraded visual motion perception when the evoked phosphene and the visual stimulus overlapped in time and space in the placebo and cabergoline conditions, but not in the pergolide condition. This suggests that dopamine D1 or combined D1 and D2 receptor activation enhances cortical SNR to boost perceptual performance. That local visual cortical excitability was unchanged across drug conditions suggests the involvement of long-range intracortical interactions in this D1 effect. Because increased internal noise (and thus lower SNR) can impair visual perceptual learning, improving visual cortical SNR via D1/D2 agonist therapy may be useful in boosting rehabilitation programs involving visual perceptual training.

SIGNIFICANCE STATEMENT

In this study, we address the issue of whether dopamine activation improves visual perception despite increasing sensory noise in the visual cortex. We show specifically that dopamine D1 (or combined D1/D2) receptor activation enhances the cortical signal-to-noise-ratio to boost perceptual performance. Together with the previously reported effects of dopamine upon brain plasticity and learning (Wolf et al., 2003; Hansen and Manahan-Vaughan, 2014), our results suggest that combining rehabilitation with dopamine agonists could enhance both the saliency of the training signal and the long-term effects on brain plasticity to boost rehabilitation regimens for brain injury.

The Core Brain Region for Face Processing in Schizophrenia Lacks Face Selectivity

BACKGROUND

Face perception impairment in schizophrenia has long been recognized. However, brain mechanisms underlying this socially important perceptual deficit are not well understood. Previous magnetic resonance imaging (MRI) studies have shown that patients have altered structure in brain regions responsible for processing face information, but functional properties of these brain regions are not clearly determined. A key functional property of the face-processing system--face selectivity--has yet to be evaluated in schizophrenia.

METHODS

We used functional MRI (fMRI) to examine face selectivity of 3 core face-processing regions--fusiform face area (FFA), occipital face area (OFA), and superior temporal sulcus (STS)--in schizophrenia patients (n = 24) and healthy controls (n = 23). To disassociate face-specific processing from general perceptual processing, we compared cortical activations during performance of perceptually equated face and tree detection tasks.

RESULTS

Activation levels of the 3 putative face-processing regions during face detection did not differ between patients and controls, being similar for FFA and OFA and absent for STS. However, face selectivity, indexed by the difference in cortical activation between face and tree detection, was significantly reduced in patients for FFA, especially for low-contrast stimuli. FFA activation and perceptual performance during face detection were associated in patients.

CONCLUSIONS

These results show a lack of face-specific processing in the schizophrenic brain region presumably subserving face perception. This finding suggests boosting visual salience of face images as a potential therapeutic venue for improving face perception in this psychiatric disorder.

Greater sensitivity of the cortical face processing system to perceptually-equated face detection

Face detection, the perceptual capacity to identify a visual stimulus as a face before probing deeper into specific attributes (such as its identity or emotion), is essential for social functioning. Despite the importance of this functional capacity, face detection and its underlying brain mechanisms are not well understood. This study evaluated the roles that the cortical face processing system, which is identified largely through studying other aspects of face perception, play in face detection. Specifically, we used functional magnetic resonance imaging (fMRI) to examine the activations of the fusifom face area (FFA), occipital face area (OFA) and superior temporal sulcus (STS) when face detection was isolated from other aspects of face perception and when face detection was perceptually-equated across individual human participants (n=20). During face detection, FFA and OFA were significantly activated, even for stimuli presented at perceptual-threshold levels, whereas STS was not. During tree detection, however, FFA and OFA were responsive only for highly salient (i.e., high contrast) stimuli. Moreover, activation of FFA during face detection predicted a significant portion of the perceptual performance levels that were determined psychophysically for each participant. This pattern of result indicates that FFA and OFA have a greater sensitivity to face detection signals and selectively support the initial process of face vs. non-face object perception.

Impaired visual cortical processing of affective facial information in schizophrenia

Facial emotion perception impairment in schizophrenia is currently viewed as abnormal affective processing. Facial emotion perception also relies on visual processing. Yet, visual cortical processing of facial emotion is not well understood in this disorder. We measured perceptual thresholds for detecting facial fear and happiness in patients (n=23) and controls (n=23), and adjusted emotion intensity of facial stimuli (via morphing between images of neutral and emotive expressions) for each subject. We then evaluated activations of the visual cortex and amygdala during the performance of perceptually-equated facial emotion detection tasks. Patients had significantly lower fear- and happiness-induced activations in the visual cortex and amygdala. Activations between the visual cortex and amygdala were largely correlated, but the correlations in patients occurred abnormally early in response time course during fear perception. In schizophrenia, visual processing of facial emotion is deficient and visual and affective processing of negative facial emotion may be prematurely associated.

Pursuit eye movements as an intermediate phenotype across psychotic disorders: Evidence from the B-SNIP study

Smooth pursuit eye tracking deficits are a promising intermediate phenotype for schizophrenia and possibly for psychotic disorders more broadly. The Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) consortium investigated the severity and familiality of different pursuit parameters across psychotic disorders. Probands with schizophrenia (N=265), schizoaffective disorder (N=178), psychotic bipolar disorder (N=231), their first-degree relatives (N=306, N=217, N=273, respectively) and healthy controls (N=305) performed pursuit tracking tasks designed to evaluate sensorimotor and cognitive/predictive aspects of pursuit. Probands from all diagnostic groups were impaired on all pursuit measures of interest compared to controls (p<0.001). Schizophrenia probands were more impaired than other proband groups on both early pursuit gain and predictive gain. Relatives with and without enhanced psychosis spectrum personality traits were impaired on initial eye acceleration, the most direct sensorimotor pursuit measure, but not on pursuit gain measures. This suggests that alterations in early sensorimotor function may track susceptibility to psychosis even in the absence of psychosis related personality traits. There were no differences in pursuit measures between relatives of the three proband groups. Familiality estimates of pursuit deficits indicate that early pursuit gain was more familial than predictive gain, which has been the most widely used measure in previous family studies of psychotic disorders. Thus, while disease-related factors may induce significant impairments of pursuit gain, especially in schizophrenia, the pattern of deficits in relatives and their familiality estimates suggest that alterations in sensorimotor function at pursuit onset may indicate increased susceptibility across psychotic disorders.

Abnormalities in personal space and parietal-frontal function in schizophrenia

Schizophrenia is associated with subtle abnormalities in day-to-day social behaviors, including a tendency in some patients to “keep their distance” from others in physical space. The neural basis of this abnormality, and related changes in social functioning, is unknown. Here we examined, in schizophrenic patients and healthy control subjects, the functioning of a parietal–frontal network involved in monitoring the space immediately surrounding the body (“personal space”). Using fMRI, we found that one region of this network, the dorsal intraparietal sulcus (DIPS), was hyper-responsive in schizophrenic patients to face stimuli appearing to move towards the subjects, intruding into personal space. This hyper-responsivity was predicted both by the size of personal space (which was abnormally elevated in the schizophrenia group) and the severity of negative symptoms. In contrast, in a second study, the activity of two lower-level visual areas that send information to DIPS (the fusiform face area and middle temporal area) was normal in schizophrenia. Together, these findings suggest that changes in parietal–frontal networks that support the sensory-guided initiation of behavior, including actions occurring in the space surrounding the body, contribute to social dysfunction and negative symptoms in schizophrenia.

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A parietal–frontal network in the primate brain monitors the space near the body.

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“Personal space”, a person's “comfort zone”, is influenced by this network.

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Patients with schizophrenia show an abnormal enlargement of personal space.

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This enlargement correlates with negative symptom levels.

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This enlargement also correlates with parietal responses to personal space intrusions.

Absent activation in medial prefrontal cortex and temporoparietal junction but not superior temporal sulcus during the perception of biological motion in schizophrenia: a functional MRI study

BACKGROUND

Patients with schizophrenia show disturbances in both visual perception and social cognition. Perception of biological motion (BM) is a higher-level visual process, and is known to be associated with social cognition. BM induces activation in the "social brain network", including the superior temporal sulcus (STS). Although deficits in the detection of BM and atypical activation in the STS have been reported in patients with schizophrenia, it remains unclear whether other nodes of the "social brain network" are also atypical in patients with schizophrenia.

PURPOSE

We aimed to explore whether brain regions other than STS were involved during BM perception in patients with schizophrenia, using functional magnetic resonance imaging (fMRI).

METHODS AND PATIENTS

Seventeen patients with schizophrenia, and 17 age- and sex- matched healthy controls, underwent fMRI scanning during a one-back visual task, containing three experimental conditions: (1) BM, (2) scrambled motion (SM), and (3) static condition. We used one-sample t-tests to examine neural responses selective to BM versus SM within each group, and two-sample t-tests to directly compare neural patterns to BM versus SM in schizophrenics versus controls.

RESULTS

We found significant activation in the STS region when BM was contrasted with SM in both groups, with no significant difference between groups. On the contrary, significant activation in the medial prefrontal cortex (MPFC) and bilateral temporoparietal junction (TPJ) was found only in the control group. When we directly compared the two groups, the healthy controls showed significant greater activation in left MPFC and TPJ to BM versus SM than patients with schizophrenia.

CONCLUSION

Our findings suggest that patients with schizophrenia show normal activation to biologically and socially relevant motion stimuli in the STS, but atypical activation in other regions of the social brain network, specifically MPFC and TPJ. Moreover, these results were not due to atypical processing of motion, suggesting that patients with schizophrenia lack in the recruitment of neural circuits needed for the visual perception of social cognition.

Windows to the soul: vision science as a tool for studying biological mechanisms of information processing deficits in schizophrenia

Cognitive and information processing deficits are core features and important sources of disability in schizophrenia. Our understanding of the neural substrates of these deficits remains incomplete, in large part because the complexity of impairments in schizophrenia makes the identification of specific deficits very challenging. Vision science presents unique opportunities in this regard: many years of basic research have led to detailed characterization of relationships between structure and function in the early visual system and have produced sophisticated methods to quantify visual perception and characterize its neural substrates. We present a selective review of research that illustrates the opportunities for discovery provided by visual studies in schizophrenia. We highlight work that has been particularly effective in applying vision science methods to identify specific neural abnormalities underlying information processing deficits in schizophrenia. In addition, we describe studies that have utilized psychophysical experimental designs that mitigate generalized deficit confounds, thereby revealing specific visual impairments in schizophrenia. These studies contribute to accumulating evidence that early visual cortex is a useful experimental system for the study of local cortical circuit abnormalities in schizophrenia. The high degree of similarity across neocortical areas of neuronal subtypes and their patterns of connectivity suggests that insights obtained from the study of early visual cortex may be applicable to other brain regions. We conclude with a discussion of future studies that combine vision science and neuroimaging methods. These studies have the potential to address pressing questions in schizophrenia, including the dissociation of local circuit deficits vs. impairments in feedback modulation by cognitive processes such as spatial attention and working memory, and the relative contributions of glutamatergic and GABAergic deficits.

Neural intersections of the phonological, visual magnocellular and motor/cerebellar systems in normal readers: implications for imaging studies on dyslexia

We used fMRI to explore the extent of the anatomical overlap of three neural systems that the literature on developmental dyslexia associates with reading: the auditory phonological, the visual magnocellular, and the motor/cerebellar systems. Twenty-eight normal subjects performed four tasks during fMRI scans: word and pseudoword reading, auditory rhyming for letter names, visual motion perception, and a motor sequence learning task. We found that the left occipitotemporal cortex (OTC), which previous studies reported to be dysfunctional in dyslexia, can be fractionated into different functional areas: an anterior and lateral area that was activated by both reading and auditory rhyming tasks; a posterior area that was commonly activated by both the reading and the motion perception task and a medial/intermediate area, including the so-called Visual Word Form Area, which was specifically activated by the reading task. These results show that the left OTC is an area of segregated convergence of different functional systems. We compared our results with the hypoactivation pattern reported for reading in a previous cross-cultural PET study on 36 dyslexic subjects from three countries. The region of decreased activation in dyslexia overlapped with regions that are specific for reading and those activated during both the auditory rhyming task and the single word and pseudoword reading task described in the present fMRI study. No overlap was found with the activation patterns for the visual motion perception task or for the motor sequence learning task. These observations challenge current theories of dyslexia.

Efference copy failure during smooth pursuit eye movements in schizophrenia

Abnormal smooth pursuit eye movements in patients with schizophrenia are often considered a consequence of impaired motion perception. Here we used a novel motion prediction task to assess the effects of abnormal pursuit on perception in human patients. Schizophrenia patients (n = 15) and healthy controls (n = 16) judged whether a briefly presented moving target ("ball") would hit/miss a stationary vertical line segment ("goal"). To relate prediction performance and pursuit directly, we manipulated eye movements: in half of the trials, observers smoothly tracked the ball; in the other half, they fixated on the goal. Strict quality criteria ensured that pursuit was initiated and that fixation was maintained. Controls were significantly better in trajectory prediction during pursuit than during fixation, their performance increased with presentation duration, and their pursuit gain and perceptual judgments were correlated. Such perceptual benefits during pursuit may be due to the use of extraretinal motion information estimated from an efference copy signal. With an overall lower performance in pursuit and perception, patients showed no such pursuit advantage and no correlation between pursuit gain and perception. Although patients' pursuit showed normal improvement with longer duration, their prediction performance failed to benefit from duration increases. This dissociation indicates relatively intact early visual motion processing, but a failure to use efference copy information. Impaired efference function in the sensory system may represent a general deficit in schizophrenia and thus contribute to symptoms and functional outcome impairments associated with the disorder.

Contribution of coherent motion to the perception of biological motion among persons with Schizophrenia

People with schizophrenia (SCZ) are impaired in several domains of visual processing, including the discrimination and detection of biological motion. However, the mechanisms underlying SCZ-related biological motion processing deficits are unknown. Moreover, whether these impairments are specific to biological motion or represent a more widespread visual motion processing deficit is unclear. In the current study, three experiments were conducted to investigate the contribution of global coherent motion processing to biological motion perception among patients with SCZ. In Experiments 1 and 2, participants with SCZ (n = 33) and healthy controls (n = 33) were asked to discriminate the direction of motion from upright and inverted point-light walkers in the presence and absence of a noise mask. Additionally, participants discriminated the direction of non-biological global coherent motion. In Experiment 3, participants discriminated the direction of motion from upright scrambled walkers (which contained only local motion information) and upright random position walkers (which contained only global form information). Consistent with previous research, results from Experiment 1 and 2 showed that people with SCZ exhibited deficits in the direction discrimination of point-light walkers; however, this impairment was accounted for by decreased performance in the coherent motion control task. Furthermore, results from Experiment 3 demonstrated similar performance in the discrimination of scrambled and random position point-light walkers.

Apparent motion perception in patients with paranoid schizophrenia

Impaired perceptual inference has been suggested to be at the core of positive symptoms in schizophrenia. Apparent motion (AM) is a visual illusion in which perceptual inference gives rise to the experience of a single object moving back and forth when two spatially separated objects are flashed in alternation. Here, we investigated the strength of AM perception in patients with paranoid schizophrenia. Patients were less susceptible to the illusion as indicated by a lower probability of motion perception at the individual's optimal presentation frequency for AM. In addition, the probability of AM perception was inversely related to delusional conviction in the patient group. These results suggest that schizophrenia may be associated with a reduced susceptibility to visual phenomena that commonly rely on perceptual inference.

Crowding deficits in the visual periphery of schizophrenia patients

Accumulating evidence suggests that basic visual information processing is impaired in schizophrenia. However, deficits in peripheral vision remain largely unexplored. Here we hypothesized that sensory processing of information in the visual periphery would be impaired in schizophrenia patients and, as a result, crowding - the breakdown in target recognition that occurs in cluttered visual environments - would be stronger. Therefore, we assessed visual crowding in the peripheral vision of schizophrenia patients and healthy controls. Subjects were asked to identify a target letter that was surrounded by distracter letters of similar appearance. Targets and distracters were displayed at 8° and 10° of visual angle from the fixation point (eccentricity), and target-distracter spacing was 2°, 3°, 4°, 5°, 6°, 7° or 8° of visual angle. Eccentricity and target-distracter spacing were randomly varied. Accuracy was defined as the proportion of correctly identified targets. Critical spacing was defined as the spacing at which target identification accuracy began to deteriorate, and was assessed at viewing eccentricities of 8° and 10°. Schizophrenia patients were less accurate and showed a larger critical spacing than healthy individuals. These results indicate that crowding is stronger and sensory processing of information in the visual periphery is impaired in schizophrenia. This is in line with previous reports of preferential magnocellular dysfunction in schizophrenia. Thus, deficits in peripheral vision may account for perceptual alterations and contribute to cognitive dysfunction in schizophrenia.

Detection of visual events along the apparent motion trace in patients with paranoid schizophrenia

Dysfunctional prediction in sensory processing has been suggested as a possible causal mechanism in the development of delusions in patients with schizophrenia. Previous studies in healthy subjects have shown that while the perception of apparent motion can mask visual events along the illusory motion trace, such motion masking is reduced when events are spatio-temporally compatible with the illusion, and, therefore, predictable. Here we tested the hypothesis that this specific detection advantage for predictable target stimuli on the apparent motion trace is reduced in patients with paranoid schizophrenia. Our data show that, although target detection along the illusory motion trace is generally impaired, both patients and healthy control participants detect predictable targets more often than unpredictable targets. Patients had a stronger motion masking effect when compared to controls. However, patients showed the same advantage in the detection of predictable targets as healthy control subjects. Our findings reveal stronger motion masking but intact prediction of visual events along the apparent motion trace in patients with paranoid schizophrenia and suggest that the sensory prediction mechanism underlying apparent motion is not impaired in paranoid schizophrenia.

Hippocampal temporal-parietal junction interaction in the production of psychotic symptoms: a framework for understanding the schizophrenic syndrome

A framework is described for understanding the schizophrenic syndrome at the brain systems level. It is hypothesized that over-activation of dynamic gesture and social perceptual processes in the temporal-parietal occipital junction (TPJ), posterior superior temporal sulcus (PSTS) and surrounding regions produce the syndrome (including positive and negative symptoms, their prevalence, prodromal signs, and cognitive deficits). Hippocampal system hyper-activity and atrophy have been consistently found in schizophrenia. Hippocampal activity is highly correlated with activity in the TPJ and may be a source of over-excitation of the TPJ and surrounding regions. Strong evidence for this comes from in-vivo recordings in humans during psychotic episodes. Many positive symptoms of schizophrenia can be reframed as the erroneous sense of a presence or other who is observing, acting, speaking, or controlling; these qualia are similar to those evoked during abnormal activation of the TPJ. The TPJ and PSTS play a key role in the perception (and production) of dynamic social, emotional, and attentional gestures for the self and others (e.g., body/face/eye gestures, audiovisual speech and prosody, and social attentional gestures such as eye gaze). The single cell representation of dynamic gestures is multimodal (auditory, visual, tactile), matching the predominant hallucinatory categories in schizophrenia. Inherent in the single cell perceptual signal of dynamic gesture representations is a computation of intention, agency, and anticipation or expectancy (for the self and others). Stimulation of the TPJ resulting in activation of the self representation has been shown to result a feeling of a presence or multiple presences (due to heautoscopy) and also bizarre tactile experiences. Neurons in the TPJ are also tuned, or biased to detect threat related emotions. Abnormal over-activation in this system could produce the conscious hallucination of a voice (audiovisual speech), a person or a touch. Over-activation could interfere with attentional/emotional gesture perception and production (negative symptoms). It could produce the unconscious feeling of being watched, followed, or of a social situation unfolding along with accompanying abnormal perception of intent and agency (delusions). Abnormal activity in the TPJ would also be predicted to create several cognitive disturbances that are characteristic of schizophrenia, including abnormalities in attention, predictive social processing, working memory, and a bias to erroneously perceive threat.

Perceptual measurement in schizophrenia: promising electrophysiology and neuroimaging paradigms from CNTRICS

The sixth meeting of the Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) focused on selecting promising imaging paradigms for each of the cognitive constructs selected in the first CNTRICS meeting. In the domain of perception, the 2 constructs of interest were "gain control" and "visual integration." CNTRICS received 6 task nominations for imaging paradigms for gain control and 3 task nominations for integration. The breakout group for perception evaluated the degree to which each of these tasks met prespecified criteria. For gain control, the breakout group believed that one task (mismatch negativity) was already mature and was being incorporated into multisite clinical trials. The breakout group recommended that 1 visual task (steady-state visual evoked potentials to magnocellular- vs parvocellular-biased stimuli) and 2 auditory measures (an event-related potential (ERP) measure of corollary discharge and a functional magnetic resonance imaging (fMRI) version of prepulse inhibition of startle) be adapted for use in clinical trials in schizophrenia research. For visual integration, the breakout group recommended that fMRI and ERP versions of a contour integration test and an fMRI version of a coherent motion test be adapted for use in clinical trials. This manuscript describes the ways in which each of these tasks met the criteria used in the breakout group to evaluate and recommend tasks for further development.

Altered transfer of visual motion information to parietal association cortex in untreated first-episode psychosis: implications for pursuit eye tracking

Visual motion processing and its use for pursuit eye movement control represent a valuable model for studying the use of sensory input for action planning. In psychotic disorders, alterations of visual motion perception have been suggested to cause pursuit eye tracking deficits. We evaluated this system in functional neuroimaging studies of untreated first-episode schizophrenia (N=24), psychotic bipolar disorder patients (N=13) and healthy controls (N=20). During a passive visual motion processing task, both patient groups showed reduced activation in the posterior parietal projection fields of motion-sensitive extrastriate area V5, but not in V5 itself. This suggests reduced bottom-up transfer of visual motion information from extrastriate cortex to perceptual systems in parietal association cortex. During active pursuit, activation was enhanced in anterior intraparietal sulcus and insula in both patient groups, and in dorsolateral prefrontal cortex and dorsomedial thalamus in schizophrenia patients. This may result from increased demands on sensorimotor systems for pursuit control due to the limited availability of perceptual motion information about target speed and tracking error. Visual motion information transfer deficits to higher-level association cortex may contribute to well-established pursuit tracking abnormalities, and perhaps to a wider array of alterations in perception and action planning in psychotic disorders.

Perceptual training strongly improves visual motion perception in schizophrenia

Schizophrenia patients exhibit perceptual and cognitive deficits, including in visual motion processing. Given that cognitive systems depend upon perceptual inputs, improving patients' perceptual abilities may be an effective means of cognitive intervention. In healthy people, motion perception can be enhanced through perceptual learning, but it is unknown whether this perceptual plasticity remains in schizophrenia patients. The present study examined the degree to which patients' performance on visual motion discrimination can be improved, using a perceptual learning procedure. While both schizophrenia patients and healthy controls showed decreased direction discrimination thresholds (improved performance) with training, the magnitude of the improvement was greater in patients (47% improvement) than in controls (21% improvement). Both groups also improved moderately but non-significantly on an untrained task-speed discrimination. The large perceptual training effect in patients on the trained task suggests that perceptual plasticity is robust in schizophrenia and can be applied to develop bottom-up behavioral interventions.

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.

Eye tracking performance and the boundaries of the schizophrenia spectrum

In order to investigate the nature of the eye tracking impairment in schizophrenia spectrum we measured pursuit gain with a constant velocity target using a quantitative (RMS error in pursuit gain) and, on an exploratory basis, a qualitative (quality of tracking) measure. We utilized a sample consisting of three clinically characterized groups: patients with schizophrenia (SZ), their first degree non-psychotic relatives, subjects with schizotypal personality disorder (SPD), and healthy volunteers (HV). Thirty three SZ patients, 19 SPD subjects, 66 non-psychotic relatives (all clinically assessed for schizophrenia spectrum psychopathology--DSM-IIIR) and 18 HV were evaluated using an infrared eye tracking system. Targets were constant velocity trapezoids at 5°/s (slow) and 16°/s (fast). The quality of the eye tracking was independently evaluated by at least two raters (ICC: 0.92). The RMS measures at the two velocities (quantitative measure) and the quality of the tracking obtained for each velocity were entered separately into a two factor repeated measures ANOVA, with velocity and diagnosis as the independent measures. For the quantitative ratings (RMS error), a significant effect for velocity was found, with all subjects performing worse at the higher velocity, but there was no significant velocity by diagnosis interaction. In addition, an overall significant effect for diagnosis was found in the four-group ANOVA. In post hoc multiple comparison tests, SZ subjects performed significantly worse from the HV and the relatives. SPD subjects were not different from patients with schizophrenia (or from any group--and their performance was intermediate between the HV and the SZ). Relatives of the patients with schizophrenia were different from SZ subjects, but not different from SPD or HV subjects. Similar results were obtained in the exploratory qualitative ratings. Clinical symptoms did not correlate significantly with quantitative or qualitative performance in any group. We have found that the performance of SPD subjects is intermediate between that of patients with schizophrenia and the healthy volunteers in both qualitative and quantitative (exploratory) measures. Indeed, SPD subjects comprise the only group not statistically different from schizophrenic patients in quantitative or qualitative ratings.

Reinforcement ambiguity and novelty do not account for transitive inference deficits in schizophrenia

The capacity for transitive inference (TI), a form of relational memory organization, is impaired in schizophrenia patients. In order to disambiguate deficits in TI from the effects of ambiguous reinforcement history and novelty, 28 schizophrenia and 20 nonpsychiatric control subjects were tested on newly developed TI and non-TI tasks that were matched on these 2 variables. Schizophrenia patients performed significantly worse than controls on the TI task but were able to make equivalently difficult nontransitive judgments as well as controls. Neither novelty nor reinforcement ambiguity accounted for the selective deficit of the patients on the TI task. These findings implicate a disturbance in relational memory organization, likely subserved by hippocampal dysfunction, in the pathophysiology of schizophrenia.

Schizophrenia patients show augmented spatial frame illusion for visual and visuomotor tasks

Previous research has identified several key processes of visual perception and visually guided action that are implicated in schizophrenia. Yet, it is not well understood whether similar or different brain mechanisms mediate the abnormalities in these two processes. To explore this issue, we examined visual and visuomotor processing in schizophrenia, utilizing an illusion known as the Roelofs effect. This illusion refers to the spatial mislocalization of an object within an off-centered frame, with the object appearing to be shifted towards the opposite direction of the frame offset. In this study, localization of the object was measured either by a direct visual response or by an immediate or delayed visuomotor (reaching-to-touch) response. Patients demonstrated significantly greater magnitudes of the Roelofs effect in all response modes, indicating the existence of excessive spatial contextual effects of the frame during the processing of visual and visuomotor information, and when the two types of information are integrated over a delayed visuomotor response condition. These results provide evidence for a hypothesis of improper inhibitory control as a common mechanism underpinning abnormal visual and visuomotor processes in this mental disorder.

Differential roles of low and high spatial frequency content in abnormal facial emotion perception in schizophrenia

While schizophrenia patients are impaired at facial emotion perception, the role of basic visual processing in this deficit remains relatively unclear. We examined emotion perception when spatial frequency content of facial images was manipulated via high-pass and low-pass filtering. Unlike controls (n=29), patients (n=30) perceived images with low spatial frequencies as more fearful than those without this information, across emotional salience levels. Patients also perceived images with high spatial frequencies as happier. In controls, this effect was found only at low emotional salience. These results indicate that basic visual processing has an amplified modulatory effect on emotion perception in schizophrenia.

Regional brain activity during early visual perception in unaffected siblings of schizophrenia patients

BACKGROUND

Visual masking paradigms assess the early part of visual information processing, which may reflect vulnerability measures for schizophrenia. We examined the neural substrates of visual backward performance in unaffected sibling of schizophrenia patients using functional magnetic resonance imaging (fMRI).

METHODS

Twenty-one unaffected siblings of schizophrenia patients and 19 healthy controls performed a backward masking task and three functional localizer tasks to identify three visual processing regions of interest (ROI): lateral occipital complex (LO), the motion-sensitive area, and retinotopic areas. In the masking task, we systematically manipulated stimulus onset asynchronies (SOAs). We analyzed fMRI data in two complementary ways: 1) an ROI approach for three visual areas, and 2) a whole-brain analysis.

RESULTS

The groups did not differ in behavioral performance. For ROI analysis, both groups increased activation as SOAs increased in LO. Groups did not differ in activation levels of the three ROIs. For whole-brain analysis, controls increased activation as a function of SOAs, compared with siblings in several regions (i.e., anterior cingulate cortex, posterior cingulate cortex, inferior prefrontal cortex, inferior parietal lobule).

CONCLUSIONS

The study found: 1) area LO showed sensitivity to the masking effect in both groups; 2) siblings did not differ from controls in activation of LO; and 3) groups differed significantly in several brain regions outside visual processing areas that have been related to attentional or re-entrant processes. These findings suggest that LO dysfunction may be a disease indicator rather than a risk indicator for schizophrenia.

An intercalation mechanism as a mode of action exerted by psychotropic drugs: results of altered phospholipid substrate availabilities in membranes?

Patients respond differently to psychotropic drugs, and this is currently a controversial theme among psychiatrists. The effects of 16 psychotropics on cell membrane parameters have been reported. These drugs belong to three major groups used in therapeutic psychiatry: antipsychotics, antidepressants, and anxiolytic/hypnotics. Human platelets, lacking dopamine (D(2)) receptors (proposed targets of most psychotropics), have been used as a cell model. Here we discuss the effects of these drugs on three metabolic phenomena and also results from Langmuir experiments. Diazepam, in contrast to the remaining drugs, had negligible effects on metabolic phenomena and had no effects in Langmuir experiments. Psychotropic drugs may work through intercalation in membrane phospholipids. It is possible that the fluidity of membranes, rich in essential fatty acids, the content being influenced by diet, could be a contributing factor to the action of psychotropics. This might in turn explain the observed major differences in therapeutic response among patients.

Eye tracking dysfunction in schizophrenia: characterization and pathophysiology

Eye tracking dysfunction (ETD) is one of the most widely replicated behavioral deficits in schizophrenia and is over-represented in clinically unaffected first-degree relatives of schizophrenia patients. Here, we provide an overview of research relevant to the characterization and pathophysiology of this impairment. Deficits are most robust in the maintenance phase of pursuit, particularly during the tracking of predictable target movement. Impairments are also found in pursuit initiation and correlate with performance on tests of motion processing, implicating early sensory processing of motion signals. Taken together, the evidence suggests that ETD involves higher-order structures, including the frontal eye fields, which adjust the gain of the pursuit response to visual and anticipated target movement, as well as early parts of the pursuit pathway, including motion areas (the middle temporal area and the adjacent medial superior temporal area). Broader application of localizing behavioral paradigms in patient and family studies would be advantageous for refining the eye tracking phenotype for genetic studies.

Timing is everything: neural response dynamics during syllable processing and its relation to higher-order cognition in schizophrenia and healthy comparison subjects

Successful linguistic processing requires efficient encoding of successively-occurring auditory input in a time-constrained manner, especially under noisy conditions. In this study we examined the early neural response dynamics to rapidly-presented successive syllables in schizophrenia participants and healthy comparison subjects, and investigated the effects of noise on these responses. We used magnetoencephalography (MEG) to reveal the time-course of stimulus-locked activity over bilateral auditory cortices during discrimination of syllable pairs that differed either in voice onset time (VOT) or place of articulation (POA), in the presence or absence of noise. We also examined the association of these early neural response patterns to higher-order cognitive functions. The M100 response, arising from auditory cortex and its immediate environs, showed less attenuation to the second syllable in patients with schizophrenia than healthy comparison subjects during VOT-based discrimination in noise. M100 response amplitudes were similar between groups for the first syllable during all three discrimination conditions, and for the second syllable during VOT-based discrimination in quiet and POA-based discrimination in noise. Across subjects, the lack of M100 attenuation to the second syllable during VOT-based discrimination in noise was associated with poorer task accuracy, lower education and IQ, and lower scores on measures of Verbal Learning and Memory and Global Cognition. Because the neural response to the first syllable was not significantly different between groups, nor was a schizophrenia-related difference obtained in all discrimination tasks, early linguistic processing dysfunction in schizophrenia does not appear to be due to general sensory input problems. Rather, data suggest that faulty temporal integration occurs during successive syllable processing when the signal-to-noise ratio is low. Further, the neural mechanism by which the second syllable is suppressed during noise-challenged VOT discrimination appears to be important for higher-order cognition and provides a promising target for neuroscience-guided cognitive training approaches to schizophrenia.

Perception measurement in clinical trials of schizophrenia: promising paradigms from CNTRICS

The third meeting of the Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) focused on selecting promising measures for each of the cognitive constructs selected in the first CNTRICS meeting. In the domain of perception, the 2 constructs of interest were gain control and visual integration. CNTRICS received 5 task nominations for gain control and three task nominations for visual integration. The breakout group for perception evaluated the degree to which each of these tasks met prespecified criteria. For gain control, the breakout group for perception believed that 2 of the tasks (prepulse inhibition of startle and mismatch negativity) were already mature and in the process of being incorporated into multisite clinical trials. However, the breakout group recommended that steady-state visual-evoked potentials be combined with contrast sensitivity to magnocellular vs parvocellular biased stimuli and that this combined task and the contrast-contrast effect task be recommended for translation for use in clinical trial contexts in schizophrenia research. For visual integration, the breakout group recommended the Contour Integration and Coherent Motion tasks for translation for use in clinical trials. This manuscript describes the ways in which each of these tasks met the criteria used by the breakout group to evaluate and recommend tasks for further development.

Can persons with schizophrenia appreciate visual art?

The way schizophrenia patients perceive the world is largely mysterious. Understanding and appreciating the visual world begins with the perception of basic visual features, which is altered in this mental disorder. Yet, the roles basic visual features play in functional activities such as appreciation of art are unclear. This study examined the effects of visual feature manipulation on beauty perception of art in schizophrenia patients (n=29) and in normal controls (n=30). Three pieces of art--The Starry Night (Van Gogh), Mona Lisa (Da Vinci) and a natural landscape photograph (anonymous)--were manipulated in terms of their coloration (removal of color), spatial frequency content (low or high-frequency pass) and visual noise level (with added noise). Subjects judged the beauty of the original and visual-feature-manipulated artworks by rating each piece individually (1 to 7) and by ranking all pieces from most to least beautiful. For the three original art pieces, averaged ratings and rankings were similar in patients and controls. However, when the visual features of the original pieces were manipulated, changes in the beauty ratings were significantly smaller in patients. The reduced sensitivity to visual feature manipulations suggests that the modulation of basic visual signals, often used for vivid and dynamic expressions in art, may be under-appreciated in schizophrenia.