Shared brain areas underlying simulated and perceived self-motion
2018
Mental imagery is an essential ability to infer the future state of one's body. Neuroimaging studies have shown that mental simulations activate sensory or motor structures in the brain that are associated with an overt action or a perception generated by external stimuli.
It is suggested that the mental projection of one’s own body to a different spatial location (egocentric mental rotation) is based on brain areas that are also involved in processing actual self-motion. Evidence for the involvement of vestibular information in simulated changes of self-location stems mainly from behavioural experiments, where healthy participants showed an altered capacity for egocentric mental rotation during vestibular stimulation, and vestibular patients showing a reduced ability to perform egocentric mental rotations. However, those findings are challenged by the conflicting nature of the vestibular stimulation used in different studies, and the cognitive tasks that imply different individual strategies. In the current study we addressed those issues and used fMRI to investigate the brain areas that underlie both, simulated changes of the self in mental space and vestibular processing within the same individuals. Participants performed an egocentric mental rotation task during simultaneous Galvanic Vestibular Stimulation (GVS) or sham stimulation. In line with previous literature, we hypothesized that GVS negatively affects participants’ egocentric mental rotation ability. More importantly, at the neural level we expected an overlap between brain areas activated during vestibular processing and egocentric mental rotation independently within the parieto-insular vestibular cortex (PIVC), which is a core area in vestibular processing.
As predicted, the fMRI data showed an overlap of brain activity within the PIVC for both egocentric mental rotation and vestibular processing. In contrast to our expectations, GVS did not influence the ability to perform egocentric mental rotation.
Our results provide the first neural evidence for shared neural mechanisms underlying perceived and simulated self-motion. They also suggest that the vestibular stimulation was not effective enough to impair egocentric mental rotation. We conclude that mental rotations of one’s body rely on the PIVC, but also suggest that those mental simulations of one’s body might be protected from external interference.
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