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Katherine Bettencourt, Yaoda Xu; The impact of distractors on visual short-term memory representation in early visual areas. Journal of Vision 2013;13(9):2. doi: https://doi.org/10.1167/13.9.2.
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Visual short-term memory (VSTM) has been shown to recruit a network of brain regions, including frontal, parietal, and posterior sensory regions. Among these brain regions, the fMRI response amplitude of human parietal cortex has been shown to track the amount of visual information held in VSTM, indicating that this brain region plays a role in VSTM information storage. Separately, recent studies using fMRI multivariate pattern analysis (MVPA) have revealed that delay period activity within early visual cortex reflects the contents of VSTM, showing that early visual areas can also contribute to VSTM information storage. However, the results from early visual areas have been obtained, thus far, in the absence of visual distraction. Given the ubiquitous presence of distractors in everyday visual perception, it is crucial to understand whether early visual areas still retain visual information in VSTM under distraction. Here, in an fMRI study using MVPA, we show that while a particular orientation held in VSTM can be successfully decoded from early visual areas in the absence of distractors, decoding performance drops to chance levels when distractors are introduced during the delay period. Importantly, behavioral performance is equally good with and without distractors, showing that the failure to decode in early visual areas under distraction cannot be attributed to poor task performance. In contrast, decoding performance in parietal regions is significantly above chance regardless of whether distractors are present or not. These results indicate that parietal regions likely play a central role in VSTM information storage across a variety of stimulus conditions. In the absence of distraction, early visual areas can be recruited to aid the maintenance of memory representations, likely via a visual rehearsal mechanism. However, such contributions may not be essential for VSTM information storage, especially in the real world where observers typically receive constant visual input.
Meeting abstract presented at VSS 2013
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