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Juan Chen, Melvyn Alan Goodale, Jody C Culham, Jacqueline C Snow; fMRI activation and connectivity in the dorsal and ventral visual streams for elongated and stubby tools and non-tools. Journal of Vision 2014;14(10):189. doi: https://doi.org/10.1167/14.10.189.
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Images of tools induce stronger activation than images of non-tool objects in a left-lateralized network of areas including the superior parietal lobe (SPL) and posterior medial temporal gyrus (pMTG). Importantly, however, graspable tools tend to be elongated rather than stubby, and so the tool-selective responses in these areas may reflect sensitivity to elongation rather than 'toolness' per se. It is also unclear what the role of object identity information from lateral occipital complex (LOC) is in driving responses in dorsal 'tool' regions, such as SPL. Here we performed an fMRI study examining the extent to which 'tool-selective' areas are sensitive to the following object categories: elongated tools, elongated non-tools, stubby tools, and stubby non-tools. We used psychophysiological interactions (PPI) to measure the pattern of connectivity with dorsal tool-selective SPL during the perception of each of the different stimulus types. We observed greater activation for tool versus non-tool stimuli in the left SPL and left pMTG. The tool-selective fMRI responses in both of these areas were driven primarily by elongated rather than stubby exemplars. PPI analyses revealed a stronger connectivity between left SPL and left LOC when observers viewed stubby tools than stubby non-tools. But for elongated tool and elongated non-tools, the connectivity between left SPL and left LOC was not significantly different. Taken together, our results suggest that the SPL and pMTG are particularly sensitive to elongated tools, perhaps because of the statistical regularity of this aspect ratio within the category of tool-like objects. SPL is functionally integrated with ventrally-located object-selective cortex (LOC) during stubby tool viewing, suggesting that dorsal tool-selective areas may rely upon object information from LOC to facilitate action-related processes with stubby tools, but less so for prototypical (elongated) tool exemplars.
Meeting abstract presented at VSS 2014
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