Multiple candidates for the ventral intraparietal area (VIP) in humans

The macaque ventral intraparietal area (VIP) in the fundus of the intraparietal sulcus (IPS) is functionally characterized by its response to multimodal (visual, tactile, auditory) stimuli moving within peripersonal space – especially around the face. In humans, possible VIP homologues have been identified in the IPS using different criteria, such as by presenting visuotactile stimuli on/around the face or by showing coherently moving visual stimuli. It is unclear whether these methods converge into a common definition of VIP, with a recent review (Foster et al. 2022) suggesting the existence of up to there different VIP candidates in the human IPS. Here we tackled this issue by analyzing an fMRI dataset acquired on 15 human volunteers (10 females, 35– 48 years) under two conditions: while observing optic flow patterns (coherently moving visual dots) and random motion patterns in alternating blocks, and – in separate scans – while being tactilely stimulated on several locations on the face through air puffs. Images were preprocessed with fMRIprep and analyzed through a standard whole-brain random-effects approach, using a surface-based general linear model in fsLR32 space. In both hemispheres we observed a parietal region in the dorsal bank of the IPS (LH: -30 -45 60; RH: 34 -48 59) which was activated by contralateral air puffs. This VIP candidate was close to, but not overlapping with a more posterior IPS region activated by optic flow vs. random motion patterns (LH: -24 -64 49; RH: 22 -64 55). Both regions were more strongly activated in the left hemisphere. These results show that several functional properties which have been associated with monkey VIP may be instead localized in distinct, though neighboring, IPS regions in humans, giving direct support to Foster’s (2022) hypothesis of a VIP expansion into different regions in humans.