One ubiquitous finding in functional magnetic resonance imaging studies is that repeated stimuli elicit lower responses than novel stimuli. In apparent contradiction, some studies have reported the exact opposite effect - greater responses to repeated than novel stimuli - in many of the same brain regions. Interestingly, these latter enhancement effects are typically obtained when stimuli have been degraded. To explore this observation, the present study examines the degree to which visual quality mediates repetition effects in a stimulus-selective ventral visual area. Subjects were presented with grayscale photographs of scenes that were either near or substantially above visual threshold, as determined by calibrating image contrast to behavioral performance. The presentation of 2 identical high-contrast scenes elicited lower blood oxygen level-dependent (BOLD) responses than the presentation of 2 different high-contrast scenes (repetition attenuation). Conversely, the presentation of 2 identical low-contrast scenes elicited greater BOLD responses than the presentation of 2 different low-contrast scenes (repetition enhancement). Neurophysiological studies suggest that repetition attenuation in ventral visual areas may reflect the reactivation of perceptual representations that have become sparse and selective as a result of prior experience, whereas repetition enhancement may reflect spared access to existing representations by severely degraded input.
Bibliographical noteFunding Information:
This work was supported by National Institutes of Health (NIH) Grant EY014193 to MMC. NBTB was further supported by a foreign Natural Sciences and Engineering Research Council of Canada Postgraduate
Scholarship. ABL was also supported by an NIH National Research Service Award. The authors would like to thank David Widders for his assistance in data collection and 3 anonymous reviewers for helpful comments. Conflict of Interest: None declared.
All Science Journal Classification (ASJC) codes
- Cognitive Neuroscience
- Cellular and Molecular Neuroscience