Differential parietal activations for spatial remapping and saccadic control in a visual memory task

Abstract

Remapping is a process that updates visual information in internal spatial representations across eye movements, allowing for stable perception of the environment. Previous work has demonstrated visual remapping activity in parietal cortex during saccades, but it remains unclear whether remapping is triggered by overt saccades only (or by attentional shifts also), and whether it engages parietal areas only (or other cortical areas). Here, we used fMRI to investigate spatial remapping during two visuospatial memory tasks requiring either overt (accompanied by a saccade) or covert (with central fixation) attention shifts to peripheral distracters. Participants had to remember the position and color of a lateralized dot during a saccade or attention shift, requiring them to update the dot position in memory, and then indicate if a second dot matched the first. Differential activation patterns were observed within parietal cortex as a function of the different visual, motor, and interhemispheric remapping demands in the saccade task, presumably mediating the maintenance of spatial position in perceptual and motor maps. Remapping engaged parietal areas adjacent to, but not overlapping with, those activated by saccade execution, while it did not engage the frontal eye fields, pointing to distinct neural substrates for ocular motor and spatial updating processes. No differential activation related to remapping was found during the covert attention shift task, suggesting that this condition did not necessitate the same remapping as the saccade condition. Overall these results further elucidate the mechanisms of spatial remapping in human parietal cortex and their relationship with attention processing and ocular motor behavior, with implications for understanding visuospatial attention deficits in hemispatial neglect.

The Visuospatial and Sensorimotor Functions of Posterior Parietal Cortex in Drawing Tasks: A Review

“…The neurons that encode saccades and coupling previous and current stimuli are located in the lateral IPS (LIP) of primates (Duhamel et al, 1992 ; Heiser and Colby, 2006 ; Subramanian and Colby, 2014 ; Mirpour and Bisley, 2016 ). The homologous region, SMG in humans, is specifically sensitive to detect intrasaccade orientation changes in goal-driven movements and is activated in tasks that depend on spatial remapping (Parks and Corballis, 2010 ; Pierce et al, 2019 ; Baltaretu et al, 2020 ). Spatial remapping impairments explain the failure of patients with CA to copy accurately, leading to disorganized, inaccurate images (Pierce and Saj, 2019 ; Pierce et al, 2019 ).…”

“…The homologous region, SMG in humans, is specifically sensitive to detect intrasaccade orientation changes in goal-driven movements and is activated in tasks that depend on spatial remapping (Parks and Corballis, 2010 ; Pierce et al, 2019 ; Baltaretu et al, 2020 ). Spatial remapping impairments explain the failure of patients with CA to copy accurately, leading to disorganized, inaccurate images (Pierce and Saj, 2019 ; Pierce et al, 2019 ). Right AG atrophy is associated with spatial remapping dysfunction (Serra et al, 2014 ).…”

An integrative model of visual control of action

“…Neurophysiological evidence suggests a separation between motor control and spatial updating processes (Pierce, Saj, & Vuilleumier, 2019). Posterior parietal areas might hold a sensory representation of visual space primarily based on bottom-up inputs (visual -Goodale & Milner, 1992;Ungerleider & Mishkin, 1982;vestibular and kinesthetic -Lackner & DiZio, 2005), thus related to spatial updating processes, while more anterior parietal areas might integrate these representations with top-down factors related to attention and motor demands of the task, which would be more influenced by high-order cognitive processes.…”