Lennart Verhagen (Donders Institute, Nijmegen)

When we reach for a knife we adjust our grip according to its size and shape, but also to its intended use. Similarly, when grasping a tomato we fluently incorporate its perceived ripeness in our grasp plan. Our behaviour often relies on the integration of prior perceptual and current visuospatial features of action targets. These features are primarily separately processed in the ventral and dorsal visual streams. This talk will focus on how stored perceptual target features influence motor control by serving as action priors, shaping the initial structure of a movement plan.

I will discuss results of fMRI and concurrent TMS-EEG-kinematic studies, where human subjects were preparing and performing grasping movements that required the integration of perceptual and visuospatial cues. Using fMRI, we isolated and characterized cortical regions supporting this integration in the dorso-lateral and dorso-medial parieto-frontal circuits, including the anterior intraparietal sulcus (aIPS) and the superior bank of the parieto-occipital sulcus (sPOS). Using TMS, we transiently disrupted aIPS and sPOS processing during action planning, and characterized both the cortical dynamics and behavioural consequences by EEG and kinematic recordings.

I will argue that the incorporation in action planning of object priors and current visuospatial evidence are supported by the dorso-lateral and dorso-medial circuit, respectively. This interpretation extends the role of these circuits beyond their known contribution to visuomotor processing. Moreover, it informs a reinterpretation of previous observations and resolves existing contradictory accounts of aIPS and sPOS function. The proposed mechanisms could provide a general template for understanding how and when prior and conceptual information influences sensorimotor processes.