Regions in the brain that are selective for images of hands and tools have been suggested to be lateralised to the left hemisphere of right-handed individuals. In left-handers, many functions related to tool use or tool pantomime may also depend more on the left hemisphere. This result seems surprising, given that the dominant hand of these individuals is controlled by the right hemisphere. One explanation is that the left hemisphere is dominant for speech and language in the majority of left-handers, suggesting a supraordinate control system for complex motor sequencing that is required for skilled tool use, as well as for speech. In the present study, we examine if this left-hemispheric specialisation extends to perception of hands and tools in left- and right-handed individuals. We, crucially, also include a group of left-handers with right-hemispheric language dominance to examine their asymmetry biases. The results suggest that tools lateralise to the left hemisphere in most right-handed individuals with left-hemispheric language dominance. Tools also lateralise to the language dominant hemisphere in right-hemispheric language dominant left-handers, but the result for left-hemispheric language dominant left-handers are more varied, and no clear bias towards one hemisphere is found. Hands did not show a group-level asymmetry pattern in any of the groups. These results suggest a more complex picture regarding hemispheric overlap of hand and tool representations, and that visual appearance of tools may be driven in part by both language dominance and the hemisphere which controls the motor-dominant hand.

中文翻译：

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已知语言优势的左撇子和右撇子的手和工具感知的半球不对称

有人认为，惯用右手的人大脑中对手和工具图像有选择性的区域偏向于左半球。对于左利手来说，许多与工具使用或工具哑剧相关的功能也可能更多地依赖于左半球。鉴于这些人的优势手是由右半球控制的，这一结果似乎令人惊讶。一种解释是，在大多数左撇子中，左半球主导言语和语言，这表明有一个用于复杂运动排序的上位控制系统，这是熟练使用工具和言语所必需的。在本研究中，我们检查这种左半球的专业化是否延伸到左撇子和右撇子个体对手和工具的感知。至关重要的是，我们还纳入了一组具有右半球语言优势的左撇子，以检查他们的不对称偏见。结果表明，对于大多数具有左半球语言优势的惯用右手的人来说，工具偏向于左半球。在右半球语言占优势的左撇子中，工具也会偏向语言优势半球，但左半球语言占优势的左撇子的结果则更加多样化，并且没有发现明显偏向某一半球的情况。在任何组中，手部均未表现出组级不对称模式。这些结果表明，关于手和工具表征的半球重叠的更复杂的图景，并且工具的视觉外观可能部分由语言优势和控制运动优势手的半球驱动。