Abstract
Grasping requires translating object geometries into appropriate hand shapes. How the brain computes these transformations is currently unclear. We investigated three key areas of the macaque cortical grasping circuit with microelectrode arrays and found cooperative but anatomically separated visual and motor processes. The parietal area AIP operated primarily in a visual mode. Its neuronal population revealed a specialization for shape processing, even for abstract geometries, and processed object features ultimately important for grasping. Premotor area F5 acted as a hub that shared the visual coding of AIP only temporarily and switched to highly dominant motor signals towards movement planning and execution. We visualize these non-discrete premotor signals that drive the primary motor cortex M1 to reflect the movement of the grasping hand. Our results reveal visual and motor features encoded in the grasping circuit and their communication to achieve transformation for grasping.
Highlights
Grasping objects of different shapes and sizes appears trivial in daily life
We can distinguish between thousands of objects (Biederman, 1987) and shape our hands according to their geometry in order to hold and manipulate them (Napier, 1956; Smeets and Brenner, 1999)
The results presented by Schaffelhofer and Scherberger suggest that grasping movements are generated from visual information about the object via anterior intraparietal (AIP) and F5 neurons communicating with each other
Summary
Grasping objects of different shapes and sizes appears trivial in daily life. We can distinguish between thousands of objects (Biederman, 1987) and shape our hands according to their geometry in order to hold and manipulate them (Napier, 1956; Smeets and Brenner, 1999). Neurons in AIP were shown to strongly respond to the presentation of graspable objects or 3D contours (Murata et al, 2000; Taira et al, 1990; Theys et al, 2012b), but could encode specific grip types (Baumann et al, 2009). This grasp-relevant information processed in AIP is exchanged with F5 via dense reciprocal connections (Borra et al, 2008; Gerbella et al, 2011; Luppino et al, 1999). Connections of the dorsal subdivision of F5 (F5p) to the spinal cord and to M1 provide further evidence for the important role of F5 for grasp movement preparation (Borra et al, 2010; Dum and Strick, 2005)
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