The following is a summary of “Weakened untuned gain control is associated with schizophrenia while atypical orientation-tuned suppression depends on visual acuity,” published in the February 2023 issue of Oncology by Pokorny, et al.
Psychosis’s defining characteristic is perceptual abnormalities. A brain mechanism causing unusual perceptual experiences has been proposed: weakened contrast surround suppression. Although earlier research examined suppression by having participants rate how much of a low-contrast target they thought to be surrounded by a high-contrast surround, it became feasible to modify perceived contrast by changing the direction of a matched-contrast center and surround. It may be possible to understand the brain mechanisms behind atypical surround suppression in psychosis by removing the bottom-up segmentation cue of contrast difference and focusing on orientation-dependent suppression.
Persons with schizophrenia (PSZ; N = 31), people with bipolar disorder (PBD; N = 29), first-degree biological relatives of these patient groups (PBDrel, PSZrel; N = 28, N = 21, respectively), and healthy controls (N = 29) were included in the study. Although group differences were negligible at the condition that caused the highest suppression, PSZ showed less surround suppression across orientations. PBD and PSZrel showed varying degrees of suppression, although PBDrel functioned most like controls.
It was interesting to note that visual acuity could mitigate group differences in the amount of orientation-dependent surround suppression. The observed pattern of results, including the absence of group differences when the orientation of the center and surround were the same, was reproduced in a simulation in which visual acuity and/or focused attention interact with untuned gain control. The findings shed more light on the perceptual mechanisms behind the poor center-surround processing in psychosis and offered new information on how visual acuity affects orientation-dependent suppression in PSZ.