Influence of galvanic vestibular stimulation on egocentric and object-based mental transformations

Abstract

The vestibular system analyses angular and linear accelerations of the head that are important information for perceiving the location of one's own body in space. Vestibular stimulation and in particular galvanic vestibular stimulation (GVS) that allow a systematic modiWcation of vestibular signals has so far mainly been used to investigate vestibular inXuence on sensori-motor integration in eye movements and postural control. Comparatively, only a few behavioural and imaging studies have investigated how cognition of space and body may depend on vestibular processing. This study was designed to diVerentiate the inXuence of left versus right anodal GVS compared to sham stimulation on object-based versus egocentric mental transformations. While GVS was applied, subjects made leftright judgments about pictures of a plant or a human body presented at diVerent orientations in the roll plane. All subjects reported illusory sensations of body self-motion and/ or visual Weld motion during GVS. Response times in the mental transformation task were increased during right but not left anodal GVS for the more diYcult stimuli and the larger angles of rotation. Post-hoc analyses suggested that the interfering eVect of right anodal GVS was only present in subjects who reported having imagined turning themselves to solve the mental transformation task (egocentric transformation) as compared to those subjects having imagined turning the picture in space (object-based mental transformation). We suggest that this eVect relies on shared functional and cortical mechanisms in the posterior parietal cortex associated with both right anodal GVS and mental imagery.

Imagined own-body transformations during passive self-motion

“…Only when the imagined and the actual body rotation were in the same direction, imagined body transformation was facilitated, as reflected in faster reaction times. A previous study has used artificial vestibular stimulations and showed a general and non-direction-specific effect of galvanic stimulation on imagined rotation (Lenggenhager et al, 2008). In another study it was found that caloric stimulation that mimics vestibular signals of a rightward head rotation specifically (Falconer & Mast, 2012).…”

“…Kennedy, Lane, Berbaum, & Lilienthal, 1989), the strategy participants used for the mental imagery task (i.e., imagining one's own body rotating vs. imagining the avatar's body rotating; cf. Lenggenhager et al, 2008) and a questionnaire to assess their overall spatial and object imagery abilities (object spatial imagery questionnaire (OSIQ); cf. Blajenkova, Kozhevnikov, & Motes, 2006).…”

“…Participants were passively rotated on a human motion platform in a CW or a CCW direction and performed MBTs that implied either a CW or a CCW rotation direction. Based on previous studies, showing effects of galvanic and caloric vestibular stimulation on the mental rotation of objects and bodily stimuli (Falconer & Mast, 2012;Lenggenhager et al, 2008), in the present study we hypothesized that spatial perspective taking would be facilitated if the implied direction of the mental body rotation was the same as the actual passive own-body rotation. Such a finding would extend previous studies showing facilitatory effects of one's own body posture on spatial perspective taking (Amorim et al, 2006;Kessler & Thomson, 2010) to the domain of vestibular processing.…”

“…It was found that right galvanic vestibular stimulation resulted in slower reaction times during the mental transformation of bodies and objects (Lenggenhager et al, 2008), while caloric vestibular stimulation specifically enhanced the mental transformation of one's own body, but not of body parts or objects (Falconer & Mast, 2012). Thus, the results of these studies are inconclusive and may be related to the different methodologies used to stimulate the vestibular system.…”

“…Two recent studies have addressed the relation between vestibular stimulation and imagined own-body transformation more directly (Falconer & Mast, 2012;Lenggenhager, Lopez, & Blanke, 2008). It was found that right galvanic vestibular stimulation resulted in slower reaction times during the mental transformation of bodies and objects (Lenggenhager et al, 2008), while caloric vestibular stimulation specifically enhanced the mental transformation of one's own body, but not of body parts or objects (Falconer & Mast, 2012).…”