Abstract
Efficient object grasping requires the continuous control of arm and hand movements based on visual information. Previous studies have identified a network of parietal and frontal areas that is crucial for the visual control of prehension movements. Electrical microstimulation of 3D shape-selective clusters in AIP during functional magnetic resonance imaging activates areas F5a and 45B, suggesting that these frontal areas may represent important downstream areas for object processing during grasping, but the role of area F5a and 45B in grasping is unknown. To assess their causal role in the frontal grasping network, we reversibly inactivated 45B, F5a, and F5p during visually guided grasping in macaque monkeys. First, we recorded single neuron activity in 45B, F5a, and F5p to identify sites with object responses during grasping. Then, we injected muscimol or saline to measure the grasping deficit induced by the temporary disruption of each of these three nodes in the grasping network. The inactivation of all three areas resulted in a significant increase in the grasping time in both animals, with the strongest effect observed in area F5p. These results not only confirm a clear involvement of F5p, but also indicate causal contributions of area F5a and 45B in visually guided object grasping.
Highlights
To grasp an object, the brain needs to have a fine representation of its shape in order to adjust the hand efficiently before contact
We investigated the causal role of area 45B, F5a and F5p in the grasping network during a visually-guided grasping (VGG) task
Guided by a previous monkey fMRI study (Joly et al, 2009), Theys et al (2012a-b) reported robust selectivity for the 3D structure of surfaces defined by binocular disparity in F5a, similar to its input area AIP (Srivastava et al, 2009; Premereur et al, 2015)
Summary
The brain needs to have a fine representation of its shape in order to adjust the hand efficiently before contact. Area 45B, a neighboring area located in the anterior bank of the arcuate sulcus, is connected to the posterior subsector of AIP, as demonstrated with electrical microstimulation during fMRI (Premereur et al, 2015; Caprara et al, 2018), which suggests a role in the visuomotor grasping network. Gerbella et al (2010) initially hypothesized an involvement in the oculomotor system similar to the Frontal Eye Fields (FEF), the ability of 45B neurons to encode images of objects has been extensively documented (Caprara et al, 2018) It remains unclear whether neurons in 45B are part of a more extended grasping network, together with the different subsectors of F5. We hypothesized thatif area 45B and F5a are involved in object grasping, we would observe a behavioral deficit as previously described after F5p inactivation
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