2 results
Visual masking by object substitution in schizophrenia
- M. F. Green, J. K. Wynn, B. Breitmeyer, K. I. Mathis, K. H. Nuechterlein
-
- Journal:
- Psychological Medicine / Volume 41 / Issue 7 / July 2011
- Published online by Cambridge University Press:
- 16 November 2010, pp. 1489-1496
-
- Article
- Export citation
-
Background
Schizophrenia 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.
Forward and backward visual masking in schizophrenia: influence of age
- M. F. GREEN, K. H. NUECHTERLEIN, B. BREITMEYER, J. TSUANG, J. MINTZ
-
- Journal:
- Psychological Medicine / Volume 33 / Issue 5 / July 2003
- Published online by Cambridge University Press:
- 26 June 2003, pp. 887-895
-
- Article
- Export citation
-
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.