Electrophysiological correlates of motor plans and graspability via dorsal/ventral interactions
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Vision has historically been subdivided into two major systems. The vision-for-perception system is thought to be responsible for generating visual representations in service of recognition and identification. Conversely, the vision-for-action system is thought to transform visual information towards the goal of guiding motor behavior. Both systems have been linked to distinct anatomical pathways - the ventral pathway, originating in early visual cortex and terminating in the temporal lobe, is thought to mediate vision-for-perception, while the dorsal pathway, originating in early visual cortex and terminating in the parietal lobe, is thought to mediate vision-for-action. While serving as a fertile and influential theoretical framework, a growing body of evidence suggests these processing streams may not be as independent as once thought. Our current investigation is predicated on the observation that many visuomotor behaviors (mediated through the dorsal pathway), such as the manipulation of man-made tools, are contingent on the successful identification of the object (mediated through the ventral pathway). Here we investigate the nature of these interactions using High-Density Electroencephalography (HD-EEG), Multivariate Pattern analysis (MVPA) & EEG source localization. In experiment 1, participants viewed images of animate objects (birds & insects) and inanimate objects (tools & graspable objects). The frequency-tagging approach and the Fast Fourier Transform was used to examine frequency domain amplitude differences between the object categories. In experiment 2, evoked potentials from the same stimuli categories were used to explore the temporal dynamics of object processing. Next, source localization was used to explore the temporal dynamics of object processing within the dorsal and ventral pathways. Experiment 3 recapitulated the analyses used in experiment 2 on a different stimulus set (a stimulus set that controlled for the shape confound that exists between tools and graspable objects). Our results do not support the main hypothesis (i.e., we do not observe a temporal difference in the classification of tools vs. graspable objects between the dorsal and ventral pathway). Nonetheless, successful classification between the aforementioned stimulus categories is observed at the sensor level (EEG time course MVPA) as well as at the source level (source localized MVPA) in both neural pathways. These results may provide interesting implications regarding the spatiotemporal dynamics of object processing as well as the involvement of the two pathways.