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. 2019 Jan 7:8:1.
doi: 10.1186/s40035-018-0141-9. eCollection 2019.

Transcranial direct current stimulation enhances theory of mind in Parkinson's disease patients with mild cognitive impairment: a randomized, double-blind, sham-controlled study

Mauro Adenzato #  1   2 , Rosa Manenti #  3 , Ivan Enrici  4 , Elena Gobbi  3 , Michela Brambilla  3 , Antonella Alberici  5 , Maria Sofia Cotelli  5 , Alessandro Padovani  5 , Barbara Borroni  5 , Maria Cotelli  3
Affiliations

Transcranial direct current stimulation enhances theory of mind in Parkinson's disease patients with mild cognitive impairment: a randomized, double-blind, sham-controlled study

Mauro Adenzato et al. Transl Neurodegener. .

Abstract

Background: Parkinson's Disease (PD) with mild cognitive impairment (MCI) (PD-MCI) represents one of the most dreaded complications for patients with PD and is associated with a higher risk of developing dementia. Although transcranial direct current stimulation (tDCS) has been demonstrated to improve motor and non-motor symptoms in PD, to date, no study has investigated the effects of tDCS on Theory of Mind (ToM), i.e., the ability to understand and predict other people's behaviours, in PD-MCI.

Methods: In this randomized, double-blind, sham-controlled study, we applied active tDCS over the medial frontal cortex (MFC) to modulate ToM performance in twenty patients with PD-MCI. Twenty matched healthy controls (HC) were also enrolled and were asked to perform the ToM task without receiving tDCS.

Results: In the patients with PD-MCI, i) ToM performance was worse than that in the HC, ii) ToM abilities were poorer in those with fronto-executive difficulties, and iii) tDCS over the MFC led to significant shortening of latency for ToM tasks.

Conclusions: We show for the first time that active tDCS over the MFC enhances ToM in patients with PD-MCI, and suggest that non-invasive brain stimulation could be used to ameliorate ToM deficits observed in these patients.

Keywords: Medial frontal cortex (MFC); Mild cognitive impairment (MCI); Parkinson’s disease (PD); Theory of mind (ToM); Transcranial direct current stimulation (tDCS).

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Conflict of interest statement

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee. Informed consent was obtained from all individual participants included in the study. Ethics approval was obtained from the local Ethical Committee (IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy).Not applicableThe authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
a Experimental design. Active or sham tDCS was started 2 min before the beginning of the experimental ToM block and continued throughout the AI task. In the AI task, a short video was played, and the participant was asked to choose the picture representing a logical story ending by pushing one of the two buttons on the button box. One example for each stimulus condition (CInt and PInt) is displayed. b Current flow model for tDCS. The anode was placed over the medial frontal cortex and the cathode was placed between Inion and Oz. The device utilized two 7- × 5-cm sponge pads represented in the transverse view on the Male 1 model in Soterix HD Targets software (Soterix Medical). Arrows represent the direction of current flow
Fig. 2
Fig. 2
Score obtained in the Reading the Mind in the Eyes task in patients with PD-MCI and HC plotted separately. The patients with PD-MCI had significantly worse accuracy than the HC did. Asterisks indicate significant effects (p < 0.05)
Fig. 3
Fig. 3
Reaction times a and accuracy b in the AI task (CInt and PInt conditions) in patients with PD-MCI and HC plotted separately. The patients with PD-MCI had significantly worse accuracy and RTs in the CInt and PInt conditions than the HC did. Asterisks indicate significant effects (p < 0.05)
Fig. 4
Fig. 4
Effects of tDCS on reaction times in the AI task in patients with PD-MCI under the active tDCS and sham tDCS conditions (CInt and PInt conditions plotted separately). The reaction times of patients with PD-MCI in the AI task decreased after active tDCS over the MFC (Fpz site, with the cathode between Oz and Inion) when compared to sham stimulation in both the CInt and Pint conditions. Asterisks indicate significant effects (p < 0.05)
Fig. 5
Fig. 5
Significant correlations between reaction time of the Attribution of Intentions task in sham transcranial direct current stimulation condition and attentional-executive abilities in patients with PD-MCI
See this image and copyright information in PMC

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