Space and Time in the Parietal Cortex: fMRI Evidence for a Neural Asymmetry


How are space and time related in the brain? This study contrasts two proposals that make different predictions about the interaction between spatial and temporal magnitudes. Whereas ATOM implies that their relation is symmetric, Metaphor Theory claims it is asymmetric. We investigated whether space and time activate overlapping areas of the inferior parietal cortex (IPC) and whether they do so symmetrically or asymmetrically. We measured participants’ neural activity while they made temporal and spatial judgments on identical visual stimuli. The behavioral results replicated earlier observations of a space-time asymmetry: Spatial information influenced temporal judgments more than vice versa. The BOLD data indicated that space and time activated overlapping IPC clusters and that, consistent with Metaphor Theory, this activation was asymmetric: The shared region of IPC was activated more during temporal than during spatial judgments. We consider three possible interpretations of this neural asymmetry, based on 3 possible functions of IPC.

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