Complementary contribution of the medial and lateral human parietal cortex to grasping: a repetitive TMS study

Abstract

The dexterous control of our grasping actions relies on the cooperative activation of many brain areas. In the parietal lobe, 2 grasp-related areas collaborate to orchestrate an accurate grasping action: dorsolateral area AIP and dorsomedial area V6A. Single-cell recordings in monkeys and fMRI studies in humans have suggested that both these areas specify grip aperture and wrist orientation, but encode these grasping parameters differently, depending on the context. To elucidate the causal role of phAIP and hV6A, we stimulated these areas, while participants were performing grasping actions (unperturbed grasping). rTMS over phAIP impaired the wrist orientation process, whereas stimulation over hV6A impaired grip aperture encoding. In a small percentage of trials, an unexpected reprogramming of grip aperture or wrist orientation was required (perturbed grasping). In these cases, rTMS over hV6A or over phAIP impaired reprogramming of both grip aperture and wrist orientation. These results represent the first direct demonstration of a different encoding of grasping parameters by 2 grasp-related parietal areas.

Visual sensitivity at the service of action control in posterior parietal cortex

“…Indeed, the error signal may be extremely useful to premotor areas, that have a direct input from V6A (Matelli et al, 1998;Galletti et al, 2004;Gamberini et al, 2009; when orchestrating successful motor control. These neuronal properties representing differences in the degree to which cells are influenced by feedback control versus feedforward planning of reaching and reachto-grasp find a parallel in the human brain with recent transcranial magnetic interference with V6A activity during reaching and grasping (Breveglieri et al, 2021;Breveglieri et al, 2022;Breveglieri et al, 2023), showing a causal involvement of human V6A in state estimation for reaching and grasping. Regarding object vision, cognitive recognition is a typical function associated with the ventral stream (Ungerleider and Mishkin, 1982;Goodale and Milner, 1992), whereas the dorsolateral visual stream is shown to be able to process shape to correctly shape the hand during grasping (Romero et al, 2014;Theys et al, 2015;Schaffelhofer and Scherberger, 2016).…”

“…Indeed, the error signal may be extremely useful to premotor areas, that have a direct input from V6A ( Matelli et al, 1998 ; Galletti et al, 2004 ; Gamberini et al, 2009 ; 2021 ) when orchestrating successful motor control. These neuronal properties representing differences in the degree to which cells are influenced by feedback control versus feedforward planning of reaching and reach-to-grasp find a parallel in the human brain with recent transcranial magnetic interference with V6A activity during reaching and grasping ( Breveglieri et al, 2021 ; Breveglieri et al, 2022 ; Breveglieri et al, 2023 ), showing a causal involvement of human V6A in state estimation for reaching and grasping.…”

Grasping with a twist: Dissociating action goals from motor actions in human frontoparietal circuits

“…While processing of object location for reaching and object shape and size for grasping have been well characterized behaviorally and neurally (Cavina-Pratesi et al, 2010), the influence of object orientation on reach-to-grasp actions has only recently been investigated in the monkey and human. These studies have suggested that object orientation and/or wrist/grip orientation rely on V6A/aSPOC (Battaglini et al, 2002; Monaco et al, 2011) and the adjacent cIPS (Rice et al, 2007; Shikata et al, 2001; Valyear et al, 2006) perhaps along with aIPS (Breveglieri et al, 2022). One fMRI study that had participants grasp a dial much like ours found that “bistable” object orientations (which equally afforded two possible grip postures) evoked greater activation in cIPS than stable orientations (which afforded only one grip posture) (Wood et al, 2017).…”