Abstract
Vision is important for estimating self-motion, which is thought to involve optic-flow processing. Here, we investigated the fMRI response profiles in visual area V6, the precuneus motion area (PcM), and the cingulate sulcus visual area (CSv)—three medial brain regions recently shown to be sensitive to optic-flow. We used wide-view stereoscopic stimulation to induce robust self-motion processing. Stimuli included static, randomly moving, and coherently moving dots (simulating forward self-motion). We varied the stimulus size and the presence of stereoscopic information. A combination of univariate and multi-voxel pattern analyses (MVPA) revealed that fMRI responses in the three regions differed from each other. The univariate analysis identified optic-flow selectivity and an effect of stimulus size in V6, PcM, and CSv, among which only CSv showed a significantly lower response to random motion stimuli compared with static conditions. Furthermore, MVPA revealed an optic-flow specific multi-voxel pattern in the PcM and CSv, where the discrimination of coherent motion from both random motion and static conditions showed above-chance prediction accuracy, but that of random motion from static conditions did not. Additionally, while area V6 successfully classified different stimulus sizes regardless of motion pattern, this classification was only partial in PcM and was absent in CSv. This may reflect the known retinotopic representation in V6 and the absence of such clear visuospatial representation in CSv. We also found significant correlations between the strength of subjective self-motion and univariate activation in all examined regions except for primary visual cortex (V1). This neuro-perceptual correlation was significantly higher for V6, PcM, and CSv when compared with V1, and higher for CSv when compared with the visual motion area hMT+. Our convergent results suggest the significant involvement of CSv in self-motion processing, which may give rise to its percept.
Highlights
Sensing how our bodies move in relation to our surrounding environment is vital for spatial orientation and navigation (Gibson, 1986)
These studies have described optic-flow sensitivity in multiple cortical regions, including the human medial superior temporal area in the visual motion complex hMT+ (Peuskens et al, 2001; Smith et al, 2006), the cortical vestibular area in the parieto-insular vestibular cortex (PIVC; Cardin and Smith, 2010), and the ventral intraparietal area (VIP; Peuskens et al, 2001; Wall and Smith, 2008; Cardin and Smith, 2010), which correspond to results from several monkey studies (e.g., MST: Saito et al, 1986; Tanaka et al, 1986, 1989; Tanaka and Saito, 1989; Duffy and Wurtz, 1991a,b, 1995; Graziano et al, 1994; Lagae et al, 1994; Page and Duffy, 2003; PIVC: Akbarian et al, 1988; VIP: Schaafsma and Duysens, 1996; Schaafsma et al, 1997; Bremmer et al, 2002)
Using statistical parametric mapping (SPM) analysis, we identified 22 clusters of activation that met the criteria for cluster-level false discovery rate (FDR) control (Table 1)
Summary
Sensing how our bodies move in relation to our surrounding environment is vital for spatial orientation and navigation (Gibson, 1986). Human neuroimaging investigations of visual self-motion have largely focused on neural responses to optic-flow (de Jong et al, 1994; Brandt et al, 1998; Previc et al, 2000; Rutschmann et al, 2000; Peuskens et al, 2001; Wiest et al, 2001; Kleinschmidt et al, 2002; Deutschländer et al, 2004; Kovács et al, 2008; Wall and Smith, 2008; Cardin and Smith, 2010, 2011; Pitzalis et al, 2010, 2013; Becker-Bense et al, 2012; Cardin et al, 2012; Arnoldussen et al, 2013). The CSv has been reported to have vestibular sensitivity, along with the hMST and PIVC (Smith et al, 2012) These studies suggest differential roles for the medial optic-flow regions in visual self-motion processing. Electrophysiological evidence is minimal, and the way in which these regions differ in representing and processing visual self-motion signals (i.e., optic-flow) remains elusive
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