Posterior Parietal Cortex Encoding of Dynamic Hand Force Underlying Hand-Object Interaction

Abstract

Major achievements of primate evolution are skilled hand-object interaction and tool use, both in part dependent on parietal cortex expansion. We recorded spiking activity from macaque inferior parietal cortex during directional manipulation of an isometric tool, which required the application of hand forces to control a cursor's motion on a screen. In areas PFG/PF, the activity of ϳ70% neurons was modulated by the hand force necessary to implement the desired target motion, reflecting an inverse model, rather than by the intended motion of the visual cursor (forward model). The population vector matched the direction and amplitude of the instantaneous force increments over time. When exposed to a new force condition, that obliged the monkey to change the force output to successfully bring the cursor to the final target, the activity of a consistent subpopulation of neurons changed in an orderly fashion and, at the end of a "Wash-out" session, retained memory of the new learned association, at the service of predictive control of force. Our findings suggest that areas PFG/PF represent a crucial node of the distributed control of hand force, by encoding instantaneous force variations and serving as a memory reservoir of hand dynamics required for object manipulation and tool use. This is coherent with previous studies in humans showing the following: (1) impaired adaptation to a new force field under TMS parietal perturbation; (2) defective control of direction of hand force after parietal lesion; and (3) fMRI activation of parietal cortex during object manipulation requiring control of fine hand forces.

Saliency Detection as a Reactive Process: Unexpected Sensory Events Evoke Corticomuscular Coupling

“…The force pattern we observed is also different from the unipolar increases of exerted force during voluntary goal-directed isometric contractions ( Desmedt and Godaux, 1978 ; Ferrari-Toniolo et al, 2015 ). Instead, the alternating patterns of force decreases and increases are reminiscent of the earliest stage of voluntary ballistic movements, when agonists and antagonists muscles alternate bursts of activity to trigger a goal-directed action ( Marsden et al, 1983 ; Berardelli et al, 1996 ).…”

Computational Architecture of the Parieto-Frontal Network Underlying Cognitive-Motor Control in Monkeys

“…PFG is composed of neurons active during the execution of object-oriented hand actions ( Gardner et al, 2007 ; Rozzi et al, 2008 ), often showing selectivity for grip type ( Bonini et al, 2012 ). Concerning hand dynamics, neural activity in PFG encodes instantaneous force variation and retains memory of force signals for guiding hand action ( Ferrari-Toniolo et al, 2015 ). These data suggest an involvement of this area in the cortical network for fine control of object grasping and manipulation.…”

Visual experiences during letter production contribute to the development of the neural systems supporting letter perception

“…Real‐time visual cues that point to online changes in the action, such as a curve that went a bit too far to the right while making an ‘R’, may invoke these parietal responses in expert writers who have acquired their own stereotyped movement patterns for each letter as well as a large amount of experience with them. Several recent neurophysiological studies have suggested that the left intraparietal sulcus does, in fact, store some memory of a past experience of visual‐motor coordination (Ferrari‐Toniolo, Visco‐Comandini, Papazachariadis, Caminiti, & Battaglia‐Mayer, 2015; Haar, Donchin, & Dinstein, 2015; Kastner, Chen, Jeong, & Mruczek, 2017), perhaps accumulating evidence for potential motor movements (Tosoni, Galati, Romani, & Corbetta, 2008), and this same region has been associated with visual‐motor coordination during letter production in adults (Haar et al, 2015; Kadmon Harpaz, Flash, & Dinstein, 2014; Vinci‐Booher et al, 2019).…”