V6 is active during antero-posterior but not in lateral galvanic vestibular stimulation.

Abstract

Vestibular and visual signals are crucial to navigate. Therefore, it is important to identify the areas devoted to integrate both signals. A recent work has identified 2 cortical areas activated during lateral galvanic vestibular stimulation (GVS): the human medial superior temporal cortex and the cingulate sulcus visual area (CSV) (Smith AT et al, 2012). V6 has been identified to be active during optic flow stimulation but not during lateral GVS (Cardin V & Smith AT, 2011). Here, We investigated the cortical networks processing antero-posterior visuo-vestibular information using fMRI. Particularly whether V6 is involved in antero-posterior vestibular stimulation. GVS evokes antero-posterior or lateral sway according to the stimulation configuration (Séverac-Cauquil A et al, 1998). We randomly applied 1mA, 2-s, GVS in four configurations (front, back, left, right) on 13 subjects while recording their BOLD activity in the scanner. Our results show that BOLD activity for antero-posterior contrasted to lateral stimulation increased significantly in superior dorsal area (SDA) and inferior temporal cortex (ITC). A posteriori region of interest analysis using functional localizers and retinotopic mapping to identify CSV and V6 (Smith AT et al, 2012) showed significantly larger BOLD activation in V6 during antero-posterior compared to lateral stimulation and baseline whereas CSV showed a significant BOLD increase for both axes compared with baseline, but no difference between both conditions. Based on these results, we hypothesize that visual cortical areas V6, SDA and ITC are specific for anterior-posterior direction, while other visual areas, CSV, VIP and MST respond equally to vestibular input in both axes. We concluded that different visual areas are possibly devoted to integrate information coming from different direction of self-motion.

Meeting abstract presented at VSS 2015