Representational content in visual ventral stream is modulated by level of specificity M Andreas, B Devereux, A Clarke, L Tyler |
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Centre for Speech, Language and the Brain, University of Cambridge, United Kingdom
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| People can process objects in a variety of different ways. This study focused on where and by what extent are object representations in the ventral stream modulated by specific task-demands. Using fMRI we ran two one-back tasks: 1) a perceptual identity version where subjects judged if successive objects were identical images, and 2) a category version where successive objects had to be from the same category (e.g. animal). We then used representational similarity analysis (Kriegeskorte et al, 2008, Frontiers in Systems Neuroscience, 2(4)) to investigate how object representations were modulated by the cognitive demands of the two different tasks. Model-based similarity matrices, encoding semantic and perceptual information about the stimuli, were correlated with fMRI similarity matrices. We found that: a) both tasks shared information content within posterior portions of ventral stream and b) lingual gyrii and anteromedial portions of the ventral stream exhibited information content reflecting semantic structure for the category task whereas the same regions exhibited information content encoding visual information (i.e. shape and orientation) for the perceptual identity task. These results suggest that the ventral stream system of object processing is flexible and dynamic, being modulated by the visuo-semantic demands of the task at hand. |
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