Objective: To investigate the neural components of the mirror sensor-motor system recruited by a dance movement in a motor disorder, such as PD is.

Background: The identical sets of neurons can be activated in an individual who is simply witnessing another person performing a movement as the one actually engaged in the action/expression of some emotion/behaviour. The observation of specific and well-decoded movements, such as those of dance, can determine the activation of mirror circuits in expert subjects who have acquired their own motor skills through experience [1].

Methods: Participants included 5 cognitively non-impaired idiopathic PD patients – with motor fluctuations and dyskinesias – and 5 normal controls with high-motor expertise. Subjects underwent a neurological and neuropsychological assessment and questionnaires on behavioral mood changes. Neuroimaging data acquisition was performed on a 3T Philips Ingenia scanner. Subjects had to watch 24 videos of classical dancers performing increasingly complex figures and to estimate their difficulty. We applied a General Linear Model to convolve subjects’ responses with canonical hemodynamic response function in order to investigate their empathy abilities.

Results: During the observation of a dance movement, “mirror” areas are activated at the level of the primary somatosensory cortex (S1) in the normal controls. These areas are implicated in the representation of sensory and proprioceptive features of motion observation. PD subjects does not show activations in S1, while the ventral tegmental area (VTA) is strongly elicited.

Conclusions: Configuration of dance steps is modulated by the experience of fine and specific movements that is characterized by a motor component and the self-perception of the engaged movement. The mirror effect in S1 could be attributed to the activation of cortical areas of self-perception, in the absence of sinesthetic phenomena [2]. VTA, which is part of the subcortical dopaminergic circuit, plays a key role in the “reward” system. It is involved in motivation, gratification and pleasure-related processes [3]. Since motivational processes may be relatively spared in PD, VTA could be a target area for intervention. The study of mirror neurons could shed light on the neurological underpinnings of embodiment, somatosensory empathy and gratification in PD.

References: [1] Calvo-Merino B., Glaser D.E., Grezes J., Passingham R.E., Haggard P. (2005) Action observation and acquired motor skills: an FMRI study with expert dancers. Cereb Cortex, 15, pp. 1243–1249. [2] Arnstein D., Cui F., Keysers C., Maurits N. M. & Gazzola V. (2011) μ-suppression during action observation and execution correlates with BOLD in dorsal premotor, inferior parietal, and SI cortices. Journal of Neuroscience 31(40):14243– 49. [3] Spanagel R., Weiss E. J. (1997) The Dopamine hypotesis of reward: past and current status. Trend Neurosci. 22:521-527.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/what-happens-when-i-watch-a-ballet-preliminary-fmri-findings-on-somatosensory-empathy-in-parkinson-disease/