Huang X, Blau S, Paradiso MA. Background changes delay the perceptual availability of form information.
J Neurophysiol 2005;
94:4331-43. [PMID:
16107521 DOI:
10.1152/jn.01312.2004]
[Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In natural visual situations, unlike most psychophysical experiments, when a new stimulus appears in a portion of the visual field, the surrounding background changes simultaneously. In recordings from macaque V1, we found that a visual stimulus presented simultaneously with a background change evokes a response that is qualitatively different from the response to the same stimulus flashed on a static background. With the changing background, information about stimulus orientation and contrast is significantly delayed compared with the static-background situation. Our physiological results make several predictions that we test in the present paper with human psychophysical experiments. In a backward masking paradigm, a bar stimulus was either flashed onto a static background or presented simultaneously with a change in background luminance or pattern. Subjects discriminated bar orientation or detected that the scene changed before the mask. To achieve an equivalent contrast threshold for orientation discrimination, a longer stimulus-mask onset asynchrony (SOA) was needed in the changing than in the static-background condition; to match the orientation discrimination performance in the static and changing-background conditions at a fixed SOA, a higher bar contrast was needed when the background changed. Moreover, in the changing-background condition, a longer SOA was needed to discriminate bar orientation than to detect the scene change. These results suggest that orientation information is available more slowly when the background changes; orientation information is available earlier as stimulus contrast increases. The psychophysical findings are consistent with our physiological predictions. Compared with the common technique of flashing stimuli onto a static background, the changing-background paradigm may be more similar to natural vision in which saccades bring new stimuli and backgrounds into the visual field.
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