Goal-directed visual processing differentially impacts human ventral and dorsal visual representations.

Published Date: 
August 14, 2017

Vaziri-Pashkam M, Xu Y.

Recent studies have challenged the ventral/"what" and dorsal/"where" two-visual-processing-pathway view by showing the existence of "what" and "where" information in both pathways. Is the two-pathway distinction still valid? Here, we examined how goal-directed visual information processing may differentially impact visual representations in these two pathways. Using fMRI and MVPA, in three experiments on human participants (57% females), by manipulating whether color or shape were task relevant and how they were conjoined, we examined shape-based object category decoding in occipito-temporal and parietal regions. We found that object category representations in all the regions examined were influenced by whether or not object shape was task relevant. This task effect, however, tended to decrease as task relevant and irrelevant features were more integrated, reflecting the well-known object-based feature encoding. Interestingly, task relevance played a relatively minor role in driving the representational structures of early visual and ventral object regions. They were driven predominantly by variations in object shapes. In contrast, the effect of task was much greater in dorsal than ventral regions, with object category and task relevance both contributing significantly to the representational structures of the dorsal regions. These results showed that whereas visual representations in the ventral pathway are more invariant and reflect "what an object is", those in the dorsal pathway are more adaptive and reflect "what we do with it". Thus, despite the existence of "what" and "where" information in both visual processing pathways, the two pathways may still differ fundamentally in their roles in visual information representation.SIGNIFICANCE STATEMENTVisual information is thought to be processed in two distinctive pathways: the ventral pathway that processes "what" an object is and the dorsal pathway that processes "where" it is located. This view has been challenged by recent studies revealing the existence of "what" and "where" information in both pathways. Here, we found that goal-directed visual information processing differentially modulates shape-based object category representations in the two pathways. While ventral representations are more invariant to the demand of the task, reflecting what an object is, dorsal representations are more adaptive, reflecting what we do with the object. Thus, despite the existence of "what" and "where" information in both pathways, visual representations may still differ fundamentally in the two pathways.