Self‐motion perception in Parkinson's disease

Abstract

Parkinson's disease (PD), best characterized by its classic motor symptoms, also manifests non-motor symptoms including perceptual impairments. Normal motor and perceptual brain functions interact continuously in an action-perception loop; hence, perceptual and motor dysfunction in PD are likely also intertwined. A vital skill in order to maintain balance, and to move around in the environment is the ability to perceive one's own motion in space (self-motion perception). Self-motion perception is a complex brain process, that requires the integration of information from visual (optic flow), vestibular (gravito-inertial), and somatosensory senses. Yet, not much is known about self-motion perception or multisensory integration in PD.In this review, we highlight the need to better study these important functions in PD.We review perceptual deficits in underlying functions required for adept self-motion perception (visual, vestibular and somatosensory, as well as multisensory integration) and address how these might affect self-motion perception and motor function in PD. We propose that dysfunction of central brain mechanisms, implicated in impaired visual, vestibular and somatosensory function, likely impact self-motion perception in PD. Recent evidence suggests that visual and multisensory integration mechanisms of self-motion perception are indeed impaired in PD. This can affect motor control, gait and balance. Future research is needed to better investigate this important topic. A better understanding of self-motion perception and multisensory integration in PD may aid diagnosis and subtyping and may open new avenues for novel therapies to treat debilitating motor symptoms, including gait and balance impairment, using sensory augmentation devices or sensory retraining.

Visual self-motion cues are impaired yet overweighted during visual–vestibular integration in Parkinson’s disease

“…Furthermore, these unisensory cues need to be integrated to form a unified and reliable percept of self-motion ( Angelaki et al , 2009 ; Butler et al , 2010 ). It is currently not known: (i) whether vestibular/visual perception of self-motion is impaired in Parkinson’s disease or (ii) whether multisensory integration is affected in Parkinson’s disease ( Halperin et al , 2020 ). In this study, we directly tested unisensory vestibular and unisensory visual performance, as well as multisensory integration of visual and vestibular cues for self-motion perception in Parkinson’s disease.…”

The Role of Mental Imagery in Parkinson’s Disease Rehabilitation

“…Sensorimotor deficits in PD [ 11 ] include, among others, impaired proprioception [ 12 , 13 ], disrupted sensitivity to motion [ 14 ], and altered awareness of limb position (i.e., kinesthesia) [ 15 ] and bodily orientation [ 16 ]. Although often unobserved, such deficits precede the onset of the motor [ 17 ] signs in approximately 20% of patients [ 18 ]. Such deficits can directly impact afferent sensory inputs and/or their processing in the central nervous system [ 19 ] as well as affect proper use of internal, proprioceptive stimuli and feedback [ 11 , 14 ].…”

“…Perceptual factors such as attentional focus, proprioception, awareness, and self-motion perception are all inter-related [ 17 , 64 , 65 , 66 ] and impact motor, sensorimotor, and sensory functions and the dynamic interaction between them [ 17 , 64 , 65 , 66 , 67 , 68 ] in PD [ 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ]. One possible path through which these factors could impact motor and non-motor functions in PwP is via the body schema, which is the online mental representation of one’s body segments in space and their spatial relationships to each other [ 77 ].…”

“…The perception–motor pathway is thought to be bidirectional [ 17 , 89 , 91 ] and seems to align with motor learning and control theories in people with and without PD [ 19 , 92 ]. Among PwP, for example, reduced volume and quality of movement (e.g., hypometric movements, diminished movement repertoire, lack of physical activity) could reduce peripheral kinesthetic (and other) afferent stimuli [ 93 ], thus potentially impeding body schema, given the importance of such information flow to body schema formation and maintenance [ 94 ].…”

“…Specifically, non-pharmaceutical and non-invasive therapies that explicitly address body schema deficits and their reframing in PwP are sparse. Therefore, development of therapeutic approaches that can be specifically tailored to PwP and provide a structured framework for patient-based stimuli and training [ 96 ] to include cognitive–perceptual components (e.g., attention, proprioception, awareness, self-motion perception) is essential [ 17 , 97 , 98 , 99 , 100 , 101 ]. One such potential approach is mental imagery, which has the potential to address distortions in body schema.…”