Abstract
While the parietal cortex plays an integral role in visual attention and short-term memory, the mechanisms underlying these cognitive functions are elusive. Retinotopic mapping studies have demonstrated a mapping structure of parietal cortex using attended stimuli that traverse the visual field by moving through continguous spatial locations. While phase-encoded mapping methods depend upon this stimulus pattern, newer methods such as population receptive field mapping (pRF) allow for presentation of stimuli in randomized locations. In contrast to parietal cortex, occipital cortical maps have been found using non-contiguous mapping stimuli have been used to demonstrate maps in occipital cortex questioning whether contiguous stimuli offer attentional cues that facilitate retinotopic mapping in the parietal cortex. In order to test this assumption, contiguous and non-contiguous stimuli were used to assess pRFs in the parietal cortex. Participants maintained fixation while a checkerboard bar traversed the visual field and monitored for a dimming of the mapping stimulus. To determine whether discontiguous stimuli elicit retinotopic structure, the preferred location and visual field extent were compared across the two stimulus conditions. Then each condition was split into two sets of runs and the test-retest reliability of each measure was compared. The results suggest only a modest relationship between contiguous and discontiguous stimulus presentations. Furthermore, test-rest reliability was higher for the contiguous stimulus presentation condition. Together these results suggest that contiguous stimuli are most effective for demonstrating map structure in parietal cortex. However, pRF size was larger in the contiguous stimulus presentation condition, supporting claims that visual field maps are susceptible to stimulus motion direction for continuous stimuli. These results demonstrate a benefit for contiguous stimuli for retinotopic mapping in parietal cortex and suggest that retinotopic mapping can yield insights into the cognitive mechanisms underlying acitivity in parietal cortex.