Spatial frequency masking in positive- and negative-symptom schizophrenia.

The role of transient and sustained channels in masking was investigated in groups with positive and negative symptoms in schizophrenia and in a control group. The target stimulus was a 3.0 c/deg sinusoidal grating, which was masked at 11 stimulus-onset asynchronies between -40 to 360 ms by a 1.0 c/deg mask or an 11.0 c/deg mask. The results showed that there was no difference between the control and positive-symptom groups in the perception of the 3 c/deg target stimulus, nor was there a difference when the target was masked by 1 or 11 c/deg masking stimuli. In comparison with the control and positive-symptom groups, the negative-symptom group showed a significantly higher threshold for the perception of the 3 c/deg target stimulus and more masking with a 1 c/deg mask, but not with an 11 c/deg mask. The results provide evidence for distinguishable differences in visual masking between groups with positive and negative symptoms in schizophrenia.