Early-stage Visual Processing Research Articles

Correlates of clinical variables on early-stage visual processing in schizophrenia and bipolar disorder

The use of noninvasive tools can help understand mental states and changes that are caused by medications, symptom severity, and other clinical variables. We investigated low-level visual processing using the contrast sensitivity function (CSF), a reliable, robust, and widely used approach. Our main purpose was (1) to evaluate visual impairments in schizophrenia (SCZ) and bipolar disorder (BPD) patients and (2) to investigate associations between clinical variables and visual function in both diseases. Fifty-six healthy controls (HCs; mean age = 31.04 years), 42 BPD patients (mean age = 32.84 years) who took only lithium, and 39 SCZ patients who took only olanzapine (mean age = 32.80 years) were recruited for this study. CSF differed between groups. Both groups of patients exhibited lower discrimination at low, mid-, and high spatial frequencies compared with HCs. No differences were observed between patients, with the exception of high spatial frequency. These impairments were also related to clinical variables, revealed by a strong effect in the mediation analyses. These findings may aid investigations of other clinical variables and the role of state- and trait-like effects on visual and cognitive processing in these patient populations. This study underscores the need for visual remediation interventions.

Early Visual Processing Is Associated With Social Cognitive Performance in Recent-Onset Schizophrenia.

BackgroundEarly-stage visual processing deficits are evident in chronic schizophrenia. Consistent with a cascade model of information processing, whereby early perceptual processes have downstream effects on higher-order cognition, impaired visual processing is associated with deficits in social cognition in this clinical population. However, the nature of this relationship in the early phase of illness is unknown. Here, we present data from a study of early visual processing and social cognitive performance in recent-onset schizophrenia (ROSz).MethodThirty-two people with ROSz and 20 healthy controls (HC) completed a visual backward masking task using stimuli of real world objects (Object Masking) to assess early-stage (i.e., 0–125 ms post-stimulus onset) visual processing. Subjects also completed two tasks of social cognition, one assessing relatively low-level processes of emotion identification (Emotion Biological Motion, EmoBio), and another assessing more complex, higher-order theory of mind abilities (The Awareness of Social Inference Test, TASIT). Group differences were tested with repeated measures ANOVAs and t-tests. Bivariate correlations and linear regressions tested the strength of associations between early-stage visual processing and social cognitive performance in ROSz.ResultsFor Object Masking, the mask interfered with object identification over a longer interval for ROSz than for HC [F (3.19, 159.35) = 8.51, p < 0.001]. ROSz were less accurate on the EmoBio task [t (50) = −3.36, p = 0.001] and on the TASIT compared to HC [F (1, 50) = 38.37, p < 0.001]. For the TASIT ROSz were disproportionately impaired on items assessing sarcasm detection [F (1, 50) = 4.30, p = 0.04]. In ROSz, better Object Masking performance was associated with better social cognitive performance [r EmoBio = 0.45, p < 0.01; r TASIT = 0.41, p < 0.02]. Regression analyses did not provide significant support for low-level social cognition mediating the relationship between visual processing and high-level social cognition.ConclusionEarly-stage visual processing, low-level social cognition, and high-level social cognition were all significantly impaired in ROSz. Early-stage visual processing was associated with performance on the social cognitive tasks in ROSz, consistent with a cascade model of information processing. However, significant cascading effects within social cognition were not supported. These data suggest that interventions directed at early visual processing may yield downstream effects on social cognitive processes.

Localization of Early-Stage Visual Processing Deficits in First-Episode Psychosis

Impairments in sensory-perceptual visual processing are observed in long-term psychosis. However, their presence and contribution to symptoms remain less well established early in disease course. We used magnetoencephalography (MEG) to examine sensory responses within primary visual cortex (V1) in individuals at their first psychotic episode in the schizophrenia spectrum (FESz).

Localization of Early-Stage Visual Processing Deficits at Schizophrenia Spectrum Illness Onset Using Magnetoencephalography.

Impairments in early-stage visual processing are observed in chronic psychosis. However, their presence, localization within the brain, and contribution to cognitive symptoms remain less well established early in disease course. The present study utilized magnetoencephalography (MEG) to examine sensory responses within primary visual cortex (V1). MEG was recorded from 38 individuals diagnosed with a schizophrenia spectrum illness at first psychotic episode (FESz) and 38 matched healthy controls (HC) during visual search tasks. The inverse solution for cortical activity contributing to the M100 visual evoked field was derived. Task performance and V1 activation were compared between groups. FESz exhibited a reduced V1 response relative to HC. This group deficit, however, was selective for the left hemisphere (LH). A similar interaction was observed for response time with FESz exhibiting slower responses to right visual field targets, a difference not observed among HC. Among FESz, larger LH V1 activity was associated with larger hallucination subscale scores on the Scale for the Assessment of Positive Symptoms. Early-stage visual processing deficits localized to V1 are present at disease onset in the schizophrenia spectrum. This impairment appears to be restricted to the LH, consistent with previous reports detailing a predominantly LH disease process in early psychosis, and activity within this region was associated with an increased experience of hallucinations. These findings detail the cortical responses contributing to visual processing impairments and their relationship with symptoms at disease onset, advancing our understanding of their developmental trajectory over the course of psychotic illness.

Tobacco Use Decreases Visual Sensitivity in Schizophrenia.

Smoking prevalence in patients who are diagnosed with schizophrenia (SCZ) is higher than in the general population. Chronic tobacco use in SCZ patients may reduce the side effects of antipsychotic drugs, thus serving as a self-medication for such side effects. Understanding the ways in which chronic tobacco use influences visual sensitivity has clinical implications, which may serve as a tool for non-invasively diagnosing early-stage visual processing deficits. The present study evaluated the effects of chronic tobacco use on visual sensitivity in SCZ patients. Our purpose was to provide new directions for future research, mainly psychophysical and electrophysiological studies. In the present study, 40 smoker controls (SC), 20 SCZ tobacco users, and 20 SCZ tobacco nonusers were recruited from the Psychosocial Care Center. Visual sensitivity was compared between both SCZ groups and the SC group. Patients with SCZ who were chronic tobacco users presented lower visual sensitivity for chromatic (p < 0.001) and achromatic (p < 0.001) stimuli compared with the other groups. Our findings highlight the need to evaluate possible addictive behavior in patients with SCZ, which may contribute to public policies that seek to improve the quality of life of SCZ patients and their families.

Parkinson bradykinesia correlates with EEG background frequency and perceptual forward projection.

To deal with processing-time in the nervous system, visuomotor control requires anticipation. An index for such anticipation is provided by the 'flash-lag illusion' in which moving objects are perceived ahead of static objects while actually being in the same place. We investigated the neurophysiological relation between visuomotor anticipation and motor velocity in Parkinson's disease (PD) and controls. Motor velocity was assessed by the number of keystrokes in 30s ('kinesia score') and visuomotor anticipation in a behavioural flash-lag paradigm while electroencephalography data was obtained. PD patients (n = 24) were divided in a 'PDslow' and a 'PDfast' group based on kinesia score. The PDslow group had a lower kinesia score than controls (resp. 40.3 ± 1.7 and 64.9 ± 4.6, p < 0.001). The flash-lag illusion was weaker in the PDslow group than in controls (resp. fractions 0.32 ± 0.04 and 0.50 ± 0.09 of the responses indicating perceived lagging, p = 0.03). Furthermore, the magnitude of the flash-lag illusion correlated with the kinesia score (cc = 0.45, p = 0.02). Finally, electroencephalography background frequency was lower in the PDslow group than in controls (resp 8.24 ± 0.24 and 9.1 ± 0.32 Hz, p = 0.01) and background frequency correlated with the kinesia score (cc = 0.58, p = 0.001). The decreased flash-lag illusion and lower electroencephalography background frequency in more bradykinetic PD patients provides support for disturbed visuomotor anticipations, putatively caused by reduced, sub-cortically mediated, network efficiency. This suggests a link between anticipation in early-stage visual motion processing and motor preparation.

The hierarchical sparse selection model of visual crowding.

Because the environment is cluttered, objects rarely appear in isolation. The visual system must therefore attentionally select behaviorally relevant objects from among many irrelevant ones. A limit on our ability to select individual objects is revealed by the phenomenon of visual crowding: an object seen in the periphery, easily recognized in isolation, can become impossible to identify when surrounded by other, similar objects. The neural basis of crowding is hotly debated: while prevailing theories hold that crowded information is irrecoverable – destroyed due to over-integration in early stage visual processing – recent evidence demonstrates otherwise. Crowding can occur between high-level, configural object representations, and crowded objects can contribute with high precision to judgments about the “gist” of a group of objects, even when they are individually unrecognizable. While existing models can account for the basic diagnostic criteria of crowding (e.g., specific critical spacing, spatial anisotropies, and temporal tuning), no present model explains how crowding can operate simultaneously at multiple levels in the visual processing hierarchy, including at the level of whole objects. Here, we present a new model of visual crowding—the hierarchical sparse selection (HSS) model, which accounts for object-level crowding, as well as a number of puzzling findings in the recent literature. Counter to existing theories, we posit that crowding occurs not due to degraded visual representations in the brain, but due to impoverished sampling of visual representations for the sake of perception. The HSS model unifies findings from a disparate array of visual crowding studies and makes testable predictions about how information in crowded scenes can be accessed.

A new theoretical approach to improving face recognition in disorders of central vision: Face caricaturing

Damage to central vision, of which age-related macular degeneration (AMD) is the most common cause, leaves patients with only blurred peripheral vision. Previous approaches to improving face recognition in AMD have employed image manipulations designed to enhance early-stage visual processing (e.g., magnification, increased HSF contrast). Here, we argue that further improvement may be possible by targeting known properties of mid- and/or high-level face processing. We enhance identity-related shape information in the face by caricaturing each individual away from an average face. We simulate early- through late-stage AMD-blur by filtering spatial frequencies to mimic the amount of blurring perceived at approximately 10° through 30° into the periphery (assuming a face seen premagnified on a tablet computer). We report caricature advantages for all blur levels, for face viewpoints from front view to semiprofile, and in tasks involving perceiving differences in facial identity between pairs of people, remembering previously learned faces, and rejecting new faces as unknown. Results provide a proof of concept that caricaturing may assist in improving face recognition in AMD and other disorders of central vision.

Evaluation of magnocellular pathway abnormalities in schizophrenia: a frequency doubling technology study and clinical implications

Visual processing deficits have been reported for patients with schizophrenia. Previous studies demonstrated differences in early-stage processing of schizophrenics, although the nature, extent, and localization of the disturbance are unknown. The magnocellular and parvocellular visual pathways are associated with transient and sustained channels, but their respective contributions to schizophrenia-related visual deficits remains controversial. The aim of this study was to evaluate magnocellular dysfunction in schizophrenia using frequency doubling technology. Thirty-one patients with schizophrenia and 34 healthy volunteers were examined. Frequency doubling technology testing was performed in one session, consisting of a 15-minute screening strategy followed by the C-20 program for frequency doubling technology. Schizophrenic patients showed lower global mean sensitivity (30,97 ± 2,25 dB) compared with controls (32,17 ± 3,08 dB), p<0.009. Although there was no difference in the delta sensitivity of hemispheres, there was a difference in sensitivity analysis of the fibers crossing the optic chiasm, with lower mean sensitivity in the patient group (28,80 dB) versus controls (30,66 dB). The difference was higher in fibers that do not cross the optic chiasm, with lower mean sensitivity in patients (27,61 dB) versus controls (30,26 dB), p<0.005. Our results suggest that there are differences between global sensitivity and fiber sensitivity measured by frequency doubling technology. The different sensitivity of fibers that do not cross the optic chiasm is consistent with most current etiological hypotheses for schizophrenia. The decreased sensitivity responses in the optic radiations may significantly contribute to research assessing early-stage visual processing deficits for patients with schizophrenia.

Visual field loss in schizophrenia: evaluation of magnocellular pathway dysfunction in schizophrenic patients and their parents

Purpose:We sought to evaluate the visual pathway deficits in schizophrenic patients, compared with their parents and healthy controls, using Matrix frequency doubling technology (FDT) perimetry. Matrix FDT is an ophthalmic test used to detect visual field loss.Method:A total of 13 patients, 13 parents, and 12 healthy controls were enrolled in the study. Participants were subjected to Matrix FDT perimetry in a single test session. We analyzed the mean deviation for each eye and used a generalized estimated equation to evaluate differences among the groups and correct the dependency between the eyes.Results:The global mean deviation (presented as the mean of both eyes) was significantly lower in the schizophrenic patients than in their parents or controls. Analysis of the general sensitivity of the fibers crossing the optic chiasm showed a difference between the groups (P = 0.006), indicating that the sensitivity of the fibers crossing the optic chiasm was lower than those which did not cross. But when we analyzed the specific groups, the difference between the fibers was not considerable. Comparison of the right and left hemispheres showed that general sensitivity was lower for the left hemisphere, but when we analyzed specific groups, the difference was not significant (P = 0.29).Conclusion:These findings are suggestive of a lower global sensitivity in schizophrenic patients and their parents compared with controls. This difference may be an endophenotype of schizophrenia. The present study adds to a growing body of research on early-stage visual processing deficits in schizophrenia.

Early-stage visual processing abnormalities in high-functioning autism spectrum disorder (ASD)

It has been reported that individuals with autism spectrum disorder (ASD) have abnormal responses to the sensory environment. For these individuals sensory overload can impair functioning, raise physiological stress, and adversely affect social interaction. Early-stage (i.e. within 200ms of stimulus onset) auditory processing abnormalities have been widely examined in ASD using event-related potentials (ERP), while ERP studies investigating early-stage visual processing in ASD are less frequent. We wanted to test the hypothesis of early-stage visual processing abnormalities in ASD by investigating ERPs elicited in a visual oddball task using illusory figures. Our results indicate that individuals with ASD have abnormally large cortical responses to task irrelevant stimuli over both parieto-occipital and frontal regions-of-interest (ROI) during early stages of visual processing compared to the control group. Furthermore, ASD patients showed signs of an overall disruption in stimulus discrimination, and had a significantly higher rate of motor response errors.

Sensory Contributions to Impaired Emotion Processing in Schizophrenia

Both emotion and visual processing deficits are documented in schizophrenia, and preferential magnocellular visual pathway dysfunction has been reported in several studies. This study examined the contribution to emotion-processing deficits of magnocellular and parvocellular visual pathway function, based on stimulus properties and shape of contrast response functions. Experiment 1 examined the relationship between contrast sensitivity to magnocellular- and parvocellular-biased stimuli and emotion recognition using the Penn Emotion Recognition (ER-40) and Emotion Differentiation (EMODIFF) tests. Experiment 2 altered the contrast levels of the faces themselves to determine whether emotion detection curves would show a pattern characteristic of magnocellular neurons and whether patients would show a deficit in performance related to early sensory processing stages. Results for experiment 1 showed that patients had impaired emotion processing and a preferential magnocellular deficit on the contrast sensitivity task. Greater deficits in ER-40 and EMODIFF performance correlated with impaired contrast sensitivity to the magnocellular-biased condition, which remained significant for the EMODIFF task even when nonspecific correlations due to group were considered in a step-wise regression. Experiment 2 showed contrast response functions indicative of magnocellular processing for both groups, with patients showing impaired performance. Impaired emotion identification on this task was also correlated with magnocellular-biased visual sensory processing dysfunction. These results provide evidence for a contribution of impaired early-stage visual processing in emotion recognition deficits in schizophrenia and suggest that a bottom-up approach to remediation may be effective.

BET differences among simultaneous evoked frequency band responses during early-stage visual processing distinguish schizophrenia from healthy subjects

In this work, we attempt to extend to the schizophrenia's research the evidence that different frequency bands may emerge from different sources during early-stage visual processing, in a mental state-specific manner, while subjects are passively viewing a visual stimulus. We applied standard pattern reversal stimulation (checker-board), a task with low cognitive demands, coupled to a dense EEG recording system to estimate the neural correlates of the evoked θ, α, β, β1, and γ frequency band responses by means of brain electrical tomography (BET). After filtering the evoked activity using different bandpasses, a very different picture about the current sources during P100 will emerge. The results showed notable differences between the two groups. In healthy subjects we localized the significances in the anterior cingulate, caudate nucleus, thalamus, precuneous region, and superior parietal that were more active for γ band. In patients with schizophrenia differences occupy the hippocampus, parahippocampus, thalamus, midbrain, precuneus, and superior parietal regions. Most areas were more active for γ band except precuneous and superior parietal region more active for θ and α frequency band. These sets of regions, in both groups, reflect events that are parallel to and partly independent of the P100 component, while in the schizophrenia, these regions have been previous linked to the major symptoms of the disease. We concluded that this result provides important evidence indicating that the proposed method is able to differentiate electrophysiological patterns in healthy subjects from those in patients with schizophrenia.

Regions with different evoked frequency band responses during early-stage visual processing distinguish mild Alzheimer dementia from mild cognitive impairment and normal aging

Although diagnostic procedures have been developed for detection of mild cognitive impairment (MCI) and mild Alzheimer dementia (AD), more valid noninvasive tools are needed. In this work, we apply a procedure based on the evidences that different evoked frequency band responses may emerge from different sources during early-stage visual processing in a mental state-specific manner, while subjects were passively viewing a visual stimulus. In this case, spatial differences should arise across mental conditions such as mild Alzheimer dementia, mild cognitive impairment, and normal aging. With the use of EEG source image we found three different neural patterns in aged individuals: (1) left hippocampus and midbrain in mild AD, (2) left lateral orbitofrontal gyrus, left nucleus accumbens, caudate nucleus, thalamus, posterior cinguli, right precuneous, right superior parietal lobe in MCI, and (3) right lateral-medial orbitofrontal gyrus, caudate nucleus, thalamus, right lateral occipitotemporal gyrus in elderly controls. Although preliminary, these results show remarkably robust differences that distinguish between an age-matched control group, a group with MCI, and a group with mild AD. Because the method applied in this work differentiates among clinical entities with varying severity of cognitive decline, it may eventually serve as an electrophysiological marker in the early detection of neurodegeneration.

What's in a face? Effects of stimulus duration and inversion on face processing in schizophrenia

A number of studies show deficits in early-stage visual processing in schizophrenia. Deficits are also seen at more complex levels, such as ability to discriminate faces. This study investigated the “face inversion” effect, which reflects intrinsic cortical processing within the ventral visual stream, as well as contrast sensitivity, which reflects low-level visual processing, in order to evaluate integrity of specific stages of face processing in schizophrenia. Patients with schizophrenia and controls discriminated between pairs of upright or inverted faces or houses that had been manipulated to differ in the shape of the parts or the spatial distance among parts. The duration threshold for above chance performance on upright stimuli was obtained for patients using a house discrimination task. Contrast sensitivity was assessed for gratings of three spatial frequencies ranging from 0.5 to 21 cycles/degree. Patients needed significantly longer time to obtain 70% correct for upright stimuli and showed decreased contrast sensitivity. Increased duration threshold correlated with reduced contrast sensitivity to low (magnocellular-biased) but not medium or high spatial frequency stimuli. Using increased durations, patients showed significant inversion effects that were equivalent to those of controls on the face part and spacing tasks. Like controls, patients did not show inversion effects on the house tasks. These findings show that patients have difficulty integrating visual information as shown by increased duration thresholds. However, when faces were presented at these longer duration thresholds, patients showed the same relative processing ability for upright vs. inverted faces as controls, suggesting preserved intrinsic processing within cortical face processing regions. Similar inversion effects for face part and spacing for both groups suggest that they are using the same holistic face processing mechanism.

Attentional modulation of early-stage visual processing in schizophrenia

This study shows that paying attention to the color of a visual stimulus is manifested by an early endogenous scalp-positive event-related brain potential (ERP) component, referred to as “selection positivity”, that emerges within the first 100 ms after stimulus onset in healthy observers. In contrast, recently ill and chronically ill schizophrenia patients as well as patients at high risk for schizophrenia all failed to show this early ERP component while attending to color. These results suggest that a relatively early stage of visual-selective processing in posterior extrastriate cortex is disrupted in schizophrenia.

Scotopic sensitivity in schizophrenia

Among participants with schizophrenia there is evidence for early-stage visual processing deficits, which may arise in the rod pathways. Input to the earliest level of this pathway, however, has not been tested in this population. It has been widely hypothesized that schizophrenia participants have magnocellular deficits that occur at the pre-cortical level. To address this hypothesis, we studied absolute scotopic (dark-adapted) sensitivity in fifteen schizophrenia and fifteen matched control participants. Scotopic thresholds were assessed using a 1.85-deg, 510-nm circular test stimulus located at 10° eccentricity in the left visual field and presented in Maxwellian-view. Thresholds were obtained using a two-alternative forced-choice paradigm (an average of 200 trials per participant was obtained). Threshold estimates were derived using probit analysis. In this procedure the transformed binomial data (the inverse of the normal probability integral) is fit with a weighted linear regression. Noise was defined as the average deviation from this line. Lens optical density was also assessed by comparing absolute scotopic thresholds to the extinction spectrum of rhodopsin. Scotopic thresholds and lens density values of the two groups were evaluated using independent samples t-tests. The scotopic thresholds, and associated noise, did not differ between the schizophrenia and control participants. Lens density was also nearly identical between groups. These results suggest that magnocellular deficits in schizophrenia may not be due to problems at the level of the rods but are more likely to occur later in the visual pathway.

Global–Local Visual Processing in Schizophrenia: Evidence for an Early Visual Processing Deficit

Abnormalities in early-stage visual processing might contribute to observed higher neurocognitive deficits in schizophrenia, but to date no clear link has been established. Schizophrenia has been associated with deficits in the magnocellular visual pathway, suggesting a relative bias for processing elemental (local) as opposed to configural (global) aspects of a hierarchical stimulus; however, global-local paradigm studies in schizophrenia have yielded mixed results. In the current study, global-local and event-related potential (ERP) procedures were concomitantly used to assess temporal and spatial characteristics of hierarchical visual stimulus processing abnormalities. Patients (n = 24) had slower and less accurate responses to global stimuli than a healthy comparison group (n = 29). They exhibited a marked decrement in N150 ERP amplitude, which correlated with speed of response to global stimuli. They also failed to show an augmented P300 response to local stimuli. Behavioral and physiological data are consistent and support a global visual processing deficit in schizophrenia. This is manifest at a relatively early stage of visual processing and might relate to physiological disturbances in areas V3/V3a of the extrastriate cortex.

Impairments in generation of early-stage transient visual evoked potentials to magno- and parvocellular-selective stimuli in schizophrenia

Objective Patients with schizophrenia demonstrate significant impairments of early visual processing, potentially implicating dysfunction of the magnocellular visual pathway. The present study evaluates transient visual evoked potential (tVEP) responses to stimuli biased toward the magnocellular (M) or parvocellular (P) systems in patients with schizophrenia vs. normal volunteers first to evaluate relative contributions of M and P systems to specific tVEP components in schizophrenia and, second, to evaluate integrity of early M and P processing in schizophrenia. Methods Seventy-four patients with schizophrenia and schizoaffective disorder were compared with 59 control subjects using separate stimuli to assess the tVEP response to M, P and mixed M/P conditions. Stimuli were biased toward M vs. P processing by manipulation of chromatic and achromatic contrast. C1, P1, N1 and P2 components were compared between patients and controls. All subjects showed 20/32 vision or better. Results Waveforms were obtained to low contrast (M), chromatic contrast (P) and high contrast (mixed M/P) stimuli in both patients and controls. C1 was present to P and mixed M/P stimuli. Patients showed a significant reduction in amplitude and an increase in latency of the C1 component. P1 was elicited primarily by M and mixed M/P stimuli, whereas N1 was elicited primarily by P and mixed M/P stimuli. Patients showed reductions in both P1 and N1 amplitudes across conditions. However, only reductions in P1 amplitude survived covariation for between group differences in visual acuity. Further, P1 amplitude reductions in the M condition correlated with a proxy measure of global outcome. Conclusions M- and P-selective stimuli elicit differential components of the tVEP. Patients with schizophrenia show significant reductions in response even to simple visual stimuli. Deficits, particularly within the M system, may correlate significantly with global outcome and level of community functioning. Significance Whereas deficits in high-order cognitive processing have been extensively documented in schizophrenia, integrity of early-stage sensory processing has been studied to a lesser degree. The present findings suggest that deficits in early-stage visual processing are significantly related to overall clinical outcome in schizophrenia. Further, between-group differences in visual acuity may influence VEP results, even for subjects with ‘normal’ vision (20/32 or better).

Early-stage visual processing deficits in schizophrenia

While cognitive dysfunction including memory and attentional deficits are well known in schizophrenia, recent work has also shown basic sensory processing deficits. Deficits are particularly prominent in the visual system and may be related to cognitive deficits and outcome. This article reviews studies of early-stage visual processing in schizophrenia published during the past year. These studies reflect the growing interest and importance of sensory processing deficits in schizophrenia. The visual system is divided into magnocellular and parvocellular pathways which project to dorsal and ventral visual areas. Recent electrophysiological and behavioral investigations have found preferential magnocellular/dorsal stream dysfunction, with some deficits in parvocellular function as well. These early-stage deficits appear to be related to higher level cognitive, social, and community function. Structural studies of occipital cortex and particularly optic radiations provide anatomical support for early visual processing dysfunction. These findings highlight the importance of sensory processing deficits, in addition to higher cognitive dysfunction, for understanding the pathophysiology of schizophrenia. Understanding the nature of sensory processing deficits may provide insight into mechanisms of pathology in schizophrenia, such as N-methyl-D-aspartate dysfunction or impaired signal amplification, and could lead to treatment strategies including sensory processing rehabilitation that may improve outcome.