Contribution of the motor system to the perception of reachable space: an fMRI study

Abstract

The present functional magnetic resonance imaging (fMRI) study investigates the neural correlates of reachability judgements. In a block design experiment, 14 healthy participants judged whether a visual target presented at different distances in a virtual environment display was reachable or not with the right hand. In two control tasks, they judged the colour or the relative position of the visual target according to flankers. Contrasting the activations registered in the reachability judgement task and in the control tasks, we found activations in the frontal structures, and in the bilateral inferior and superior parietal lobe, including the precuneus, and the bilateral cerebellum. This fronto-parietal network including the cerebellum overlaps with the brain network usually activated during actual motor production and motor imagery. In a following event-related design experiment, we contrasted brain activations when targets were rated as 'reachable' with those when they were rated as 'unreachable'. We found activations in the left premotor cortex, the bilateral frontal structures, and the left middle temporal gyrus. At a lower threshold, we also found activations in the left motor cortex, and in the bilateral cerebellum. Given that reaction time increased with target distance in reachable space, we performed a subsequent parametric analysis that revealed a related increase of activity in the fronto-parietal network including the cerebellum. Unreachable targets did not show similar activation, and particularly in regions associated to motor production and motor imagery. Taken together, these results suggest that dynamical motor representations used to determine what is reachable are also part of the perceptual process leading to the distinct representation of peripersonal and extrapersonal spaces.

Evidence for the embodiment of space perception: concurrent hand but not arm action moderates reachability and egocentric distance perception

“…These observations suggest that egocentric perspective might recruit motor representations to a greater extent than the allocentric perspective. Consistent with these arguments, it has also been shown that the perception of reachable versus unreachable objects activates fronto-parietal networks (i.e., the precuneus and the parieto-occipital junction, the anterior parts of the cingulate gyrus and superior and medial frontal gyri, bilaterally) and the cerebellum, suggesting a contribution of dynamic motor representations facilitating the perceptive discrimination of peri- and extrapersonal spaces ( Gallivan et al, 2009 ; Bartolo et al, 2014 ).…”

Sensori-motor adaptation to novel limb dynamics influences the representation of peripersonal space

“…Several studies have reported the same results (Valdès-Conroy et al 2012;Bartolo et al, 2014;Grade et al, 2015;Wamain et al, 2016), which could be due to participants experiencing difficulty responding around the more uncertain reachable space boundary.…”

“…Behavioural as well as neuroimaging studies of the human neurotypical brain have provided evidence suggesting the specific processing of information in peripersonal and extrapersonal spaces. Object perception, in particular, seems to be associated with an activation of the motor system only when the object appears within the peripersonal space (Mark et al, 1997;Costantini et al, 2010;Iachini et al, 2014;Coello et al, 2008;Gallivan et al, 2009Gallivan et al, , 2011Bartolo et al, 2014). Thus, visual presentation of objects in peripersonal space has been found to activate not only occipital but also parietal, ventral and premotor cortices (Chao & Martin, 2000;Chao et al 2002;Creem-Regehr & Lee, 2005;Kan et al 2006;Martin, 2007), and sensori-motor cortices (Cardellicchio et al, 2011;Grafton et al, 1997;Matelli et al, 1985;Gallivan et al, 2011;Wamain et al, 2016).…”

Large-scale dissociations between views of objects, scenes, and reachable-scale environments in visual cortex

“…High-resolution anatomical images were collected with a T1-weighted magnetization-prepared rapid gradient multi-echo sequence (multi-echo MPRAGE [1], 176 sagittal slices, TR=2530 ms, TEs=1.69, 3.55, 5.41, and 7.27 ms, TI=1100 ms, flip angle=7°, 1 mm3 voxels, FOV=256 mm, GRAPPA acceleration=2). For functional runs, blood oxygenation level-dependent (BOLD) data were collected via a T2*-weighted echo-planar imaging (EPI) pulse sequence that employed multiband RF pulses and Simultaneous Multi-Slice (SMS) acquisition [2][3][4][5]. For the task runs, the EPI parameters were: 69 interleaved axial-oblique slices (25 degrees toward coronal from ACPC alignment), TR=1500 ms, TE=30 ms, flip angle=75°, 2.0 mm isotropic voxels, FOV=208 mm, in-plane acceleration factor (GRAPPA)=2, SMS factor=3).…”