Neural mechanisms for updating grasp plans: An fMRI study

Abstract

Reach and grasp plans must adapt to both externally and internally imposed changes. For example, a number of studies have considered mechanisms for updating reach direction plans in light of object location changes (Pelisson et al., 1986) or internally generated changes in eye orientation (Medendorp et al., 2003). In comparison, less is known about how grasp plans are updated in light of external and internal changes (Le et al., 2014). Here, we used an fMRI-adaptation inspired protocol to investigate cortical mechanisms for updating grasp plans during changes in object orientation and/or gaze location. In each trial of our paradigm, participants (n=5, four of which met our criteria) were instructed to always fixate on the LED that was on. An oriented object (0° or 135°) was illuminated twice. Across the two illuminations, the object was presented at the same orientation (Repeat condition) or different orientations (Novel condition). After the second illumination of the object, participants were required to grasp the object. We analyzed the second illumination period to identify areas that change the grasp plan based on: 1) feature parameters (Novel Orientation > Repeat Orientation) and 2) spatial parameters (Novel Visual Field (VF) > Repeat VF). Preliminary results suggest that the Novel > Repeat condition recruits cuneus, precuneus, right posterior lingual gyrus, bilateral superior temporal sulcus, left inferior parietal superior frontal gyrus. In contrast, the Novel VF > Repeat VF condition implicates bilateral anterior lingual gyrus, right inferior occipital gyrus, bilateral superior occipital gyrus, left primary motor cortex and right superior frontal gyrus (including frontal eye fields). Overall, the brain regions involved in processing spatial properties tap into the occipital (visual)- frontal (motor) network, whereas feature properties activate areas along the occipito-temporal and occipito-frontal pathways. Our future analysis will focus on the intersection of these mechanisms for the updating of object orientation across eye movements.

Meeting abstract presented at VSS 2017