The aim of the present research was to investigate the effect of peripheral (ambient) stimulation on focal visual processing using the far-out jerk effect in normal observers and subgroups with positive- and negative-symptoms in schizophrenia. The far-out jerk effect refers to a reduction in sensitivity of a briefly presented stimulus in central vision in the presence of a sudden movement or oscillation of a stimulus in peripheral vision. In order to measure the far-out jerk effect the focal contrast sensitivity of 5.0Hz modulated sinusoidal target gratings (0.5, 1.0, 2.0, 4.0, and 8.0 number of cycles per degree (c/°)) was measured in the presence of three kinds of peripheral surround: a blank field, a stationary 0.75 c/° grating, and a 5.0Hz drifting 0.75 c/° grating (far-out jerk effect). The findings showed that there were no significant differences in focal contrast sensitivity between the control and positive-symptom group with a blank field and stationary grating surround. However, a 5.0Hz drifting grating surround resulted in a significant reduction in contrast sensitivity at 0.5, 1.0 and 2.0 c/° in the positive-symptom group. In comparison with the control group the negative-symptom group showed a generalised reduction in focal contrast sensitivity, a significantly smaller far-out jerk effect, and a significant reduction in contrast sensitivity at 0.5 c/° with a stationary grating surround. The finding that both stationary and moving peripheral surrounds have an inhibitory effect on focal contrast sensitivity suggests that there is a dispersion in the visual demarcation between stationary and temporal events in the perception of visual motion in the negative-symptom group. © 2003 Elsevier Science Ltd. All rights reserved.

Item Type:	Refereed Article
Research Division:	Psychology
Research Group:	Cognitive and computational psychology
Research Field:	Sensory processes, perception and performance
Objective Division:	Health
Objective Group:	Public health (excl. specific population health)
Objective Field:	Mental health
UTAS Author:	Slaghuis, WL (Dr Walter Slaghuis)
UTAS Author:	Thompson, AK (Ms Alanda Katie Thompson)
ID Code:	26247
Year Published:	2003
Web of Science® Times Cited:	25
Deposited By:	Psychology
Deposited On:	2003-08-01
Last Modified:	2004-04-21
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