en Cognitive Neuroscience Cognitive Neuroscience Original Original <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:Tahoma;"><span style="line-height:2;"><span sans-serif=""><b><span lang="EN-GB"><span style="color:black">Background: </span></span></b><span style="background:white"><span style="color:black">Apathy as a neuropsychiatric disorder </span></span><span style="color:black">has been<span style="background:white"> reported in Parkinson&#39;s disease (PD) after subthalamic deep brain stimulation (STN-DBS). </span>Theunderlying mechanism by which this occurs is not known;hence, we investigated the structural and functional changes of serotonergic system in PD patients underwent STN-DBS with pure apathy.</span></span><br> <span sans-serif=""><b><span lang="EN-GB"><span style="color:black">Methods: </span></span></b><span style="background:white"><span style="color:black">Twenty-three PD patients underwent STN-DBS and 10 healthy controls (HC) were recruited. PD patients divided into pure apathy (PDA) (n = 10) and without apathy (PDNA) (n = 13) groups. We evaluated the effects of bilateral STN-DBS on the serotonergic brain regions by structural (Diffusion tensor imaging) and functional (resting‐state functional MRI) neuroimaging techniques. Clinicaland neuropsychiatry assessment was performed before and after DBS. </span></span><span style="color:black">Apathy was evaluated with the Apathy Evaluation Scale (AES).<span style="background:white"></span></span></span><br> <span sans-serif=""><b><span lang="EN-GB"><span style="color:black">Results: </span></span></b><span style="background:white"><span style="color:black">The results showed that STN-DBS significantly induces pure apathy in PDA patients, and there was significant correlation between apathy severity and serotonergic alterations. Apathetic group had reduced </span></span><span style="color:black">fractional anisotropy (FA)<span style="background:white"> value in the dorsal raphe nucleus (DRN), left caudate nuclei, dorsolateral prefrontal cortex (DLPFC) and left nucleus accumbens (NAc). The apathy severity was associated with decreased functional connectivity (FC) in DRN, left caudate nucleus, medial orbitofrontal cortex and right amygdala in apathetic patients. </span></span></span><br> <span sans-serif=""><b><span lang="EN-GB"><span style="color:black">Conclusions: </span></span></b><span style="color:black">Our results demonstrated that pure apathy after STN-DBS is not necessarily association to dopamine withdrawal and stimulation had an inhibitory effect on the serotonergicsystem especiallyin the DRN. Our results enhance the knowledge for better defining the pathophysiology of induced apathy in PD patient and its therapeutic protocol in future.</span></span></span></span></span></div> Parkinson’s disease, Apathy, Subthalamic deep brain stimulation, Serotonergic system, Magnetic resonance imaging. 0 0 http://bcn.iums.ac.ir/browse.php?a_code=A-10-8695-1&slc_lang=en&sid=1 Abolfazl Mohammadi MOHAMMADI_AM@YAHOO.COM 13700319475328460059459 13700319475328460059459 No Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran, Iran Mohammad Taghi Joghataei mt.joghataei@yahoo.com 13700319475328460059460 13700319475328460059460 No Department of Neurology, Rasoul Akram Hospital, Iran University of Medical Science, Tehran, Iran. Seyed Amir Hassan Habibi habibi.sah@iums.ac.ir 13700319475328460059461 13700319475328460059461 No Department of Neurology, Rasoul Akram Hospital, Iran University of Medical Science, Tehran, Iran Mansour Parvaresh m_parvaresh@yahoo.com 13700319475328460059462 13700319475328460059462 Yes Department of Neurosurgery, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.