Predictive coding
Does expectation affect brain responses to repeated objects?
Open access · cc by · source: Europe PMC
When people expect to see an object repeated, the brain's visual processing regions show a significantly reduced response, but only in the left hemisphere.
How this study connects
Role on claims
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Highly predictable sensory patterns or expected stimulus repetitions lead to a reduction of neural activity in early sensory processing regions.
Evidence for the claim as stated.
Hemodynamic changes in visual processing areas, such as the left lateral occipital complex, show that neural repetition suppression is strongly modulated by top-down perceptual expectations.
Evidence for the claim as stated.
Study at a glance
- Design
- Human experiment — fMRI repetition suppression in object-selective cortex as a function of perceptual expectation; localizer in a subset
- N
- N=19 · University of Salzburg undergraduates, 11 women, ages 18–30; 16 completed a functional localizer
- Population
- Healthy undergraduates with normal or corrected vision
- Outcome
- Repetition-suppression in object-selective cortex supporting perceptual expectation
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Does expectation affect brain responses to repeated objects?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
19 healthy young adults were scanned in this study
Nineteen undergraduate students (11 female) from the University of Salzburg (age 18–30 years) participated in the present study.
75% of the stimulus pairs in the high-probability context contained repeated images
In the high-probability context, images were the same in 75% of trials.
Key findings
The researchers discovered that expectation heavily modulated repetition suppression, but only in the left hemisphere of the brain. In the left lateral occipital complex, expected repetitions caused a 21% reduction in neural activity, whereas unexpected repetitions led to a 1% increase in activity. In contrast, the right hemisphere and other specialized brain regions did not show this expectation-dependent modulation.
Methodology
To see if visual expectation influences how the brain processes repeated objects, researchers scanned 19 healthy young adults using fMRI. Participants viewed pairs of object drawings where the second image was either identical or different, presented across two contexts: a high-probability context where 75% of the pairs contained repeated images, and a low-probability context where only 25% did. To identify specific brain regions of interest, 16 of the participants also completed a functional localizer scan.
Limitations
The study's results are limited by its small sample size of 19 university students, meaning these findings might not apply to more diverse age groups. Because the lateralization effect was unexpected, this study cannot explain why expectation-based modulation of repetition suppression occurred exclusively in the left hemisphere. Additionally, since participants performed a passive target-detection task, the design cannot clarify how active engagement or goal-directed attention might influence these neural responses.
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