Abstract
Objectives The ability to stop a pending action is fundamental for survival because it allows to adapt to unpredictable changes in the external environment. Despite the importance of this executive function both neural substrates and their roles are still debated. It has been suggested that inhibitory control relies upon a right-lateralized network comprising the right subthalamic nucleus (STN; e.g. 1). The aim of the present work was to assess its role. Methods We administered a countermanding reaching task to twenty Parkinson’s patients receiving deep-brain stimulation (DBS) of the STN either of the left (n = 10) or of the right hemisphere (n = 10), and to 20 age-matched subjects. We compared the performance of Parkinson’s patients in two experimental conditions: DBS-ON, DBS-OFF. Results As expected, we found that PD patients are significantly more impaired in proactive and reactive inhibition than healthy subjects. However, reactive inhibitory control is not improved when either the right or the left DBS is active, i.e. the reaction time to the stop signal (SSRT) is not significantly different in the DBS-ON versus DBS-OFF condition, irrespectively of the DBS placement. Differently, when either the right or the left DBS is turned on there is a partial recovery of proactive motor strategies. Conclusions Our results confirm that (i) reactive inhibitory control is affected by Parkinson’s disease; (ii) only bilateral stimulation of STN restores the inhibitory control to a near-normal level (2); (iii) unilateral STN stimulation allows a partial recovery of proactive inhibition with respect to bilateral stimulation (3). All in all, these findings do not the hypothesis according to which the right STN plays a key role in inhibitory control. Instead, our data suggests that this executive function relies on the cooperation between the two STN ( Aron, 2007 , Mirabella, 2012 , Mirabella, 2013 ).
Published Version
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