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キーワード:
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要旨:
Neuropsychological and functional imaging studies have associated the conceptual processing
of numbers with bilateral parietal regions (including the intraparietal sulcus, IPS). However, the processes
driving these effects remain unclear because both left and right posterior parietal regions are activated by
many other conceptual, perceptual, attention and response-selection processes. To dissociate parietal activation
that is number-selective from parietal activation related to other stimulus or response-selection processes,
we used fMRI to compare numbers and object names during exactly the same conceptual and
perceptual tasks while factoring out activations correlating with response times. We found that right parietal
activation was higher for conceptual decisions on numbers relative to the same tasks on object names,
even when response-time effects were fully factored out. In contrast, left parietal activation for numbers
was equally involved in conceptual processing of object names. We suggest that left parietal activation for
numbers reflects a range of processes, including the retrieval of learnt facts that are also involved in conceptual
decisions on object names. In contrast, number-selectivity in the right parietal cortex reflects processes
that are more involved in conceptual decisions on numbers than object names. Our results generate
a new set of hypotheses that have implications for the design of future behavioural and functional imaging
studies of patients.
