Abstract
Functional neuroimaging studies have implicated the left lateral occipitotemporal cortex (LOTC) in both tool and hand perception but the functional role of this region is not fully known. Here, by using a task manipulation, we tested whether tool-/hand-selective LOTC contributes to the discrimination of tool-associated hand actions. Participants viewed briefly presented pictures of kitchen and garage tools while they performed one of two tasks: in the action task, they judged whether the tool is associated with a hand rotation action (e.g., screwdriver) or a hand squeeze action (e.g., garlic press), while in the location task they judged whether the tool is typically found in the kitchen (e.g., garlic press) or in the garage (e.g., screwdriver). Both tasks were performed on the same stimulus set and were matched for difficulty. Contrasting fMRI responses between these tasks showed stronger activity during the action task than the location task in both tool- and hand-selective LOTC regions, which closely overlapped. No differences were found in nearby object- and motion-selective control regions. Importantly, these findings were confirmed by a TMS study, which showed that effective TMS over the tool-/hand-selective LOTC region significantly slowed responses for tool action discriminations relative to tool location discriminations, with no such difference during sham TMS. We conclude that left LOTC contributes to the discrimination of tool-associated hand actions.
Highlights
Tools physically and functionally extend our body, allowing us to achieve a wide range of goals that would not be possible with our bodies alone
No differences were found in nearby object- and motion-selective control regions. These findings were confirmed by a transcranial magnetic stimulation (TMS) study, which showed that effective TMS over the tool-/hand-selective lateral occipitotemporal cortex (LOTC) region significantly slowed responses for tool action discriminations relative to tool location discriminations, with no such difference during sham TMS
In a subsequent TMS study, we found that effective TMS over hand/tool-selective left LOTC differentially affected performance on tool action as compared to tool location discriminations, such that effective TMS significantly slowed responses on the action task relative to the location task, with no such difference during sham TMS
Summary
Tools physically and functionally extend our body, allowing us to achieve a wide range of goals that would not be possible with our bodies alone. It remains possible that toolselective activity in LOTC reflects shape differences between tools and other objects (e.g., elongated tool shape; Sakuraba et al, 2012), or the small size of tools relative to typically used control categories (Konkle and Oliva, 2012) These properties are not strictly visual and might still account for tool-selective LOTC activity in the congenitally blind. Recent fMRI evidence sheds new light on the putative role of left LOTC in tool perception by showing that tool-selective regions closely overlap with hand-selective regions (Bracci et al, 2012) This finding raises the possibility that left LOTC contributes to tool action discrimination by accessing tool-associated hand action or hand posture representations
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