Toward a spatiotemporal neurocognitive framework of manipulable object processing.

The neural processing of small handheld manipulable objects (henceforth tools) involves a series of brain regions that have been well characterized over the last decades, both anatomically and functionally. But neural processing unfolds over time, requiring the static spatial descriptions that emerged from this research to be accompanied by temporal dynamics between the nodes of the tool network. Temporally-resolved techniques (such as M/EEG) are critical in this endeavor. Yet, to date, studies using such techniques have not been integrated with this spatial depiction. We analyzed M/EEG temporal findings in light of the current knowledge of the tool network, to clarify the type of framework the field should aim for to reach a spatiotemporal understanding of tool processing. Our integrative analysis revealed that (1) there are tool-specific M/EEG responses starting as early as ∼60 ms and extending until ∼600 ms; (2) tools can be differentiated from non-manipulable inanimate objects based on their M/EEG visuomotor-related responses, as indexed by mu rhythm desynchronization; and (3) these M/EEG visuomotor-related responses can be further decomposed into the visuomotor preparatory computation of separate tool-directed actions (reach, grasp, and use). These findings frame a novel account of spatiotemporal dynamics underlying the visuomotor preparation of tool-directed actions. This spatiotemporal account highlights the temporal dynamics between tool-network nodes while processing different tool features, which can then feed visuomotor hubs for the generation of functional visuomotor representations of tool-directed actions.