Subthalamic Nucleus Deep Brain Stimulation Improves Somatosensory Function in Parkinson’s Disease Joshua E. Aman, PhD, 1,3 * Aviva Abosch, MD, PhD, 2,3 Maggie Bebler, APRN, 2 Chia-Hao Lu, PhD, 1,3 and J€ urgen Konczak, PhD 1,3 1 Human Sensorimotor Control Laboratory, University of Minnesota, Minneapolis, Minnesota, USA 2 Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota, USA 3 Center for Clinical Movement Science, University of Minnesota, Minneapolis, Minnesota, USA ABSTRACT: An established treatment for the motor symptoms of Parkinson’s disease (PD) is deep brain stimulation (DBS) of the subthalamic nucleus (STN). Mounting evidence suggests that PD is also associated with somatosensory deficits, yet the effect of STN-DBS on somatosensory processing is largely unknown. This study investigated whether STN-DBS affects somatosen- sory processing, specifically the processing of tactile and proprioceptive cues, by systematically examining the accuracy of haptic perception of object size. (Haptic perception refers to one’s ability to extract object fea- tures such as shape and size by active touch.) Without vision, 13 PD patients with implanted STN-DBS and 13 healthy controls haptically explored the heights of 2 suc- cessively presented 3-dimensional (3D) blocks using a precision grip. Participants verbally indicated which block was taller and then used their nonprobing hand to motorically match the perceived size of the comparison block. Patients were tested during ON and OFF stimula- tion, following a 12-hour medication washout period. First, when compared to controls, the PD group’s haptic discrimination threshold during OFF stimulation was ele- vated by 192% and mean hand aperture error was increased by 105%. Second, DBS lowered the haptic discrimination threshold by 26% and aperture error decreased by 20%. Third, during DBS ON, probing with the motorically more affected hand decreased haptic precision compared to probing with the less affected hand. This study offers the first evidence that STN-DBS improves haptic precision, further indicating that somato- sensory function is improved by STN-DBS. We conclude that DBS-related improvements are not explained by improvements in motor function alone, but rather by enhanced somatosensory processing. V C 2013 Interna- tional Parkinson and Movement Disorder Society Key Words: basal ganglia; deep brain stimulation; haptic perception; human; sensorimotor; somatosen- sory; DBS; STN Parkinson’s disease (PD) is a neurodegenerative dis- ease affecting the dopamine producing neurons of the substantia nigra pars compacta that results in a pro- gressive decline of motor function. Increasing evidence documents that PD not only induces motor deficits, but also may lead to impaired kinesthetic, tactile, and haptic function. 1–7 Haptic perception is defined as an individual’s sensibility to its adjacent surroundings by use of their body and refers to one’s ability to extract object features such as shape and texture by actively touching the object. 8 Haptic perception relies on the integration of proprioceptive, tactile, and pressure cues combined with efferent motor commands. 2 Hence, examining haptic function provides a window for investigating somatosensory processing. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become an increasingly common neurosurgical intervention for PD patients and is known to alleviate certain cardinal motor symptoms associated with PD such as bradykinesia and ------------------------------------------------------------ *Correspondence to: Dr. Joshua E. Aman, PhD, University of Minne- sota, Human Sensorimotor Control Laboratory School of Kinesiology, Cooke Hall, 1900 University Ave. SE Minneapolis, MN 55455, USA; aman0038@umn.edu Relevant conflicts of interest/financial disclosures: Dr. Aviva Abosch has performed Ad-hoc consulting with Medtronic, Inc. (Minneapolis, MN) and is PI of an investigator-initiated research grant funded by Medtronic. All PD subjects in this study have implanted electrodes developed by Medtronic. All surgeries occurred prior to this study and no funding or devices were provided by Medtronic for this study. Full financial disclosures and author roles may be found in the online version of this article. Received: 7 March 2013; Revised: 30 August 2013; Accepted: 6 October 2013 Published online 00 Month 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/mds.25731 RESEARCH ARTICLE Movement Disorders, Vol. 00, No. 00, 2013 1