Visual masking by object substitution in schizophrenia

BackgroundSchizophrenia patients demonstrate impairment on visual backward masking, a measure of early visual processing. Most visual masking paradigms involve two distinct processes, an early fast-acting component associated with object formation and a later component that acts through object substitution. So far, masking paradigms used in schizophrenia research have been unable to separate these two processes.MethodWe administered three visual processing paradigms (location masking with forward and backward masking, four-dot backward masking and a cuing task) to 136 patients with schizophrenia or schizoaffective disorder and 79 healthy controls. A psychophysical procedure was used to match subjects on identification of an unmasked target prior to location masking. Location masking interrupts object formation, four-dot masking task works through masking by object substitution and the cuing task measures iconic decay.ResultsPatients showed impairment on location masking after being matched for input threshold, similar to previous reports. After correcting for age, patients showed lower performance on four-dot masking than controls, but the groups did not differ on the cuing task.ConclusionsPatients with schizophrenia showed lower performance when masking was specific to object substitution. The difference in object substitution masking was not due to a difference in rate of iconic decay, which was comparable in the two groups. These results suggest that, despite normal iconic decay rates, individuals with schizophrenia show impairment in a paradigm of masking by object substitution that did not also involve disruption of object formation.

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Regional Brain Activity Associated with Visual Backward Masking

Journal of Cognitive Neuroscience ◽

10.1162/0898929052880011 ◽

2005 ◽

Vol 17 (1) ◽

pp. 13-23 ◽

Cited By ~ 34

Author(s):

Michael F. Green ◽

David Glahn ◽

Stephen A. Engel ◽

Keith H. Nuechterlein ◽

Fred Sabb ◽

...

Keyword(s):

Visual Processing ◽

Visual Masking ◽

Anterior Cingulate ◽

Data Driven ◽

Motion Processing ◽

Backward Masking ◽

Imaging Data ◽

Neural Basis ◽

Data Driven Approach ◽

Visual Backward Masking

In visual backward masking, the visibility of a briefly presented visual target is disrupted by a mask that is presented shortly thereafter. The goal of the current study was to identify regions in the human cortex that may provide the neural basis of visual masking. We searched for areas whose activity correlated with perception as we systematically varied the strength of masking. A total of 13 subjects performed a backward masking task during functional magnetic resonance imaging. Target and mask were presented at three delay intervals (34, 68, and 102 msec) and behavioral measures confirmed that the targets were more visible at longer masking intervals. Two sets of regions of interest were identified: Distinct regions in the visual cortex (V1/V2, LO, hMT+) were segregated using scans to localize visual processing drawn from the existing literature. Additional cortical regions were selected in a data-driven approach based on their activity during the backward masking task. For each set, we determined the regions whose magnitude of activation increased at longer masking intervals. Nine of the subjects provided valid behavioral performance data on the visual masking task and imaging data from these subjects were used for subsequent analysis. The scans of visual processing areas identified four regions, including: early visual areas (V1 and V2), the motion-sensitive regions in the lateral occipital (LO) lobe (hMT+), and two components (dorsal and ventral) of the object-sensitive region, LO. Of these, the ventral and dorsal LO regions were sensitive to the strength of the mask. For the data-driven approach, six regions were identified on the basis of a difference map in which all masking intervals were contrasted with rest. These included the inferior parietal, anterior cingulate, precentral, insula, thalamic, and occipital areas. The predicted effects of more activity with weaker masking were seen in the thalamus, inferior parietal, and anterior cingulate. This study isolated three types of visual processing areas. The first included regions that subserve key stages of vision (including object and motion processing). The second type responded to the presentation of briefly presented visual stimuli, regardless of masking interval. The third type (selected from the first two) included regions sensitive to the interval between the target and mask. These latter regions (including ventral LO, inferior parietal, anterior cingulate, and thalamus) may form the neural substrate of backward masking.

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The Neurophysiology of Backward Visual Masking: Information Analysis

Journal of Cognitive Neuroscience ◽

10.1162/089892999563409 ◽

1999 ◽

Vol 11 (3) ◽

pp. 300-311 ◽

Cited By ~ 127

Author(s):

Edmund T. Rolls ◽

Martin J. Tovée ◽

Stefano Panzeri

Keyword(s):

Visual Processing ◽

Visual Information ◽

Computational Models ◽

Direct Evidence ◽

Visual Masking ◽

Neuronal Response ◽

Short Soas ◽

Stimulus Onset ◽

Backward Masking ◽

Neuronal Responses

Backward masking can potentially provide evidence of the time needed for visual processing, a fundamental constraint that must be incorporated into computational models of vision. Although backward masking has been extensively used psychophysically, there is little direct evidence for the effects of visual masking on neuronal responses. To investigate the effects of a backward masking paradigm on the responses of neurons in the temporal visual cortex, we have shown that the response of the neurons is interrupted by the mask. Under conditions when humans can just identify the stimulus, with stimulus onset asynchronies (SOA) of 20 msec, neurons in macaques respond to their best stimulus for approximately 30 msec. We now quantify the information that is available from the responses of single neurons under backward masking conditions when two to six faces were shown. We show that the information available is greatly decreased as the mask is brought closer to the stimulus. The decrease is more marked than the decrease in firing rate because it is the selective part of the firing that is especially attenuated by the mask, not the spontaneous firing, and also because the neuronal response is more variable at short SOAs. However, even at the shortest SOA of 20 msec, the information available is on average 0.1 bits. This compares to 0.3 bits with only the 16-msec target stimulus shown and a typical value for such neurons of 0.4 to 0.5 bits with a 500-msec stimulus. The results thus show that considerable information is available from neuronal responses even under backward masking conditions that allow the neurons to have their main response in 30 msec. This provides evidence for how rapid the processing of visual information is in a cortical area and provides a fundamental constraint for understanding how cortical information processing operates.

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Forward and backward visual masking in schizophrenia: influence of age

Psychological Medicine ◽

10.1017/s003329170200716x ◽

2003 ◽

Vol 33 (5) ◽

pp. 887-895 ◽

Cited By ~ 30

Author(s):

M. F. GREEN ◽

K. H. NUECHTERLEIN ◽

B. BREITMEYER ◽

J. TSUANG ◽

J. MINTZ

Keyword(s):

Visual Processing ◽

Visual Masking ◽

Target Identification ◽

High Energy ◽

Forward Masking ◽

Backward Masking ◽

Staircase Method ◽

Patients Âgés ◽

Age Related ◽

Age Range

Background. Visual masking tasks assess the earliest stages of visual processing. This study was conducted to address: (1) whether schizophrenia patients show masking deficits after controlling for sensory input factors; (2) whether patients have relatively intact forward masking (when the mask precedes the target) compared with backward masking (when the mask follows the target); and (3) whether the masking deficits in schizophrenia reflect an accelerated age-related decline in performance.Method. A staircase method was used to ensure that the unmasked target identification was equivalent across subjects to eliminate any confounding due to differences in discrimination of simple perceptual inputs. Three computerized visual masking tasks were administered to 120 schizophrenia patients (ages 18–56) and 55 normal comparison subjects (ages 19–54) under both forward and backward masking conditions. The tasks included: (1) locating a target; (2) identifying a target with a high-energy mask; and (3) identifying a target with a low-energy mask.Results. Patients showed deficits across all three masking tasks. Interactions of group by forward versus backward masking were not significant, suggesting that deficits in forward and backward masking were comparable. All three conditions showed an age-related decline in performance and rates of decline were comparable between patients and controls. Two of the masking conditions showed increased rates of decline in backward, compared to forward, masking.Conclusions. We found age-related decline in performance that was comparable for the two groups. In addition, we failed to find evidence of a relative sparing of forward masking in schizophrenia. These results suggest that: (1) early visual processing deficits in schizophrenia are not due to a simple perceptual input problem; (2) sustained channels are involved in the masking deficit (in addition to transient channels); and (3) for the age range in this study, these deficits in schizophrenia are not age-related.

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The Neural Basis of Perceptual Hypothesis Generation and Testing

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2006.18.2.258 ◽

2006 ◽

Vol 18 (2) ◽

pp. 258-266 ◽

Cited By ~ 18

Author(s):

R. Weidner ◽

N. J. Shah ◽

G. R. Fink

Keyword(s):

Spatial Attention ◽

Visual Processing ◽

Visual Information ◽

Visual Masking ◽

Target Location ◽

Blood Oxygenation ◽

Neural Basis ◽

Object Substitution Masking ◽

Signal Changes ◽

Object Substitution

Four-dot masking is a new form of visual masking that does not involve local contour interactions or spatial superimposition of the target stimulus and the mask (as, e.g., in pattern or metacontrast masking). Rather, the effective masking mechanism is based on object substitution. Object substitution masking occurs when low-level visual information representations are altered before target identification through iterative interaction with high-level visual processing stages has been completed. Interestingly, object substitution interacts with attention processes: Strong masking effects are observed when attentional orientation toward the target location is delayed. In contrast, no masking occurs when attention can be rapidly shifted to and engaged onto the target location. We investigated the neural basis of object substitution masking by studying the interaction of spatial attention and masking processes using functional magnetic resonance imaging. Behavioral data indicated a two-way interaction between the factors Spatial Attention (valid vs. invalid cueing) and Masking (four-dot vs. pattern masking). As expected, spatial attention improved performance more strongly during object substitution masking. Functional correlates of this interaction were found in the primary visual cortex, higher visual areas, and left intraparietal sulcus. A region-of-interest analysis in these areas revealed that the largest blood oxygenation level-dependent signal changes occurred during effective four-dot masking. In contrast, the weakest signal changes in these areas were observed when target visibility was highest. The data suggest that these areas represent an object substitution network dedicated to the generation and testing of a perceptual hypotheses as described by the object substitution theory of masking of Di-Lollo et al. [Competition for consciousness among visual events: The psychophysics of reentrant visual processes. Journal of Experimental Psychology: General, 129, 481–507, 2000].

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Measuring and modeling selective attention in early visual processing

PsycEXTRA Dataset ◽

10.1037/e536982012-174 ◽

1997 ◽

Cited By ~ 1

Author(s):

George Sperling ◽

Shui-I. Shih

Keyword(s):

Selective Attention ◽

Visual Processing ◽

Early Visual Processing

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Facilitation of visual backward masking by increasing target duration: A methodological extension

Psychonomic Science ◽

10.3758/bf03335281 ◽

1969 ◽

Vol 17 (6) ◽

pp. 360-361 ◽

Cited By ~ 6

Author(s):

Dean G. Purcell ◽

Alan L. Stewart

Keyword(s):

Target Duration ◽

Backward Masking ◽

Visual Backward Masking

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Visual masking during the attentional blink: Tests of the object substitution hypothesis.

Journal of Experimental Psychology Human Perception & Performance ◽

10.1037/0096-1523.29.1.238 ◽

2003 ◽

Vol 29 (1) ◽

pp. 238-258 ◽

Cited By ~ 18

Author(s):

Barry Giesbrecht ◽

Walter F. Bischof ◽

Alan Kingstone

Keyword(s):

Attentional Blink ◽

Visual Masking ◽

Object Substitution

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Directional selectivity and its use in early visual processing

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1981.0001 ◽

1981 ◽

Vol 211 (1183) ◽

pp. 151-180 ◽

Cited By ~ 348

Keyword(s):

Visual Processing ◽

Visual Motion ◽

Time Derivative ◽

Receptive Fields ◽

Specific Model ◽

Zero Crossings ◽

Second Stage ◽

Early Visual Processing ◽

Local Direction ◽

Zero Values

The construction of directionally selective units, and their use in the processing of visual motion, are considered. The zero crossings of ∇ 2 G(x, y) ∗ I(x, y) are located, as in Marr & Hildreth (1980). That is, the image is filtered through centre-surround receptive fields, and the zero values in the output are found. In addition, the time derivative ∂[∇ 2 G(x, y) ∗ l(x, y) ]/∂ t is measured at the zero crossings, and serves to constrain the local direction of motion to within 180°. The direction of motion can be determined in a second stage, for example by combining the local constraints. The second part of the paper suggests a specific model of the information processing by the X and Y cells of the retina and lateral geniculate nucleus, and certain classes of cortical simple cells. A number of psychophysical and neurophysiological predictions are derived from the theory.

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