Lower delayed but comparable working memory performance in patients with Parkinson disease

Intruduction The present study examined nature of memory deficits and its associations with MRI structural metrics in patients with Parkinson disease (PD). Methods Nineteen PD and 23 matched controls underwent two memory experiments. In experiment 1 (delayed memory task), subjects were asked to remember an array of colored rectangles with varying memory set sizes [Low-Load (2 items), Low-Load with distractors, & High-Load (5 items)]. After a 7s delay period, they reported whether the orientation of any relevant figures had changed (test period). In experiment 2 (working memory task), memory arrays were presented in varying set sizes (2 to 6 items) but with no distractors and they were followed by a 2s delay period and subsequent test period. Brain MRI data were acquired to assess morphological differences (volumes and cortical thickness) in brain areas related to attentional filtering (middle frontal gyrus and basal ganglia) and memory storage and consolidation (intraparietal sulcus and medial temporal corticies). Results Compared to controls, PD patients had lower memory capacity scores in all memory conditions for the experiment 1 (p <0.021) whereas there were no memory score group differences in any memory set sizes for the experiment 2 (p>0.06). In addition, there were no group differences in structural metrics for any ROI and no asccociations of strucrutal metrics with delayed memory scores (p>0.056). Discussion The present findings suggest that both lower attentional filtering and memory storage may contribute to lower delayed memory scores in PD. Memory storage capacity for visuospatial working memory in PD, however, appeared to be comparable to that of controls at least in the absence of apparent distractors. In addition, lower delayed memory in PD may partly be associated with early brain structural or functional changes that may occur before morphological changes. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by the Dong-A University research fund. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All participants gave their informed consent according to procedures approved by the ethics board at the University of Missouri-Columbia (protocol code: 1170557 on 2010.09.01) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors