Working memory training increases neural efficiency in Parkinson's disease: a randomized controlled trial

Kathrin Giehl; Anja Ophey; Jochen Hammes; Sarah Rehberg; Thorsten Lichtenstein; Paul Reker; Carsten Eggers; Elke Kalbe; Thilo van Eimeren

doi:10.1093/braincomms/fcaa115

Working memory training increases neural efficiency in Parkinson's disease: a randomized controlled trial

Brain Commun. 2020 Aug 27;2(2):fcaa115. doi: 10.1093/braincomms/fcaa115. eCollection 2020.

Authors

Kathrin Giehl^{1

2}, Anja Ophey³, Jochen Hammes¹, Sarah Rehberg³, Thorsten Lichtenstein⁴, Paul Reker⁵, Carsten Eggers⁶, Elke Kalbe³, Thilo van Eimeren^{1

5

7}

Affiliations

¹ Faculty of Medicine and University Hospital of Cologne, Department of Nuclear Medicine, University of Cologne, Cologne, Germany.
² Research Centre Jülich, Institute of Neuroscience and Medicine (INM-2), Jülich, Germany.
³ Faculty of Medicine and University Hospital of Cologne, Department of Medical Psychology, Neuropsychology and Gender Studies and Center for Neuropsychological Diagnostics and Intervention (CeNDI), University of Cologne, Cologne, Germany.
⁴ Faculty of Medicine and University Hospital of Cologne, Department for Radiology, University of Cologne, Cologne, Germany.
⁵ Faculty of Medicine and University Hospital of Cologne, Department of Neurology, University of Cologne, Cologne, Germany.
⁶ Faculty of Medicine and University Hospital of Marburg, Department of Neurology and Center for Mind, Brain and Behavior, University of Marburg, Marburg, Germany.
⁷ German Center for Neurodegenerative Diseases (DZNE), Bonn-Cologne, Germany.

Abstract

Impairment of working memory and executive functions is already frequently observed in early stages of Parkinson's disease. Improvements in working memory performance in this cohort could potentially be achieved via working memory training. However, the specific neural mechanisms underlying different working memory processes such as maintenance as opposed to manipulation are largely under-investigated in Parkinson's disease. Moreover, the plasticity of these correlates as a function of working memory training is currently unknown in this population. Thus, the working memory subprocesses of maintenance and manipulation were assessed in 41 cognitively healthy patients with Parkinson's disease using a newly developed working memory paradigm and functional MRI. Nineteen patients were randomized to a 5-week home-based digital working memory training intervention while the remaining patients entered a control, wait list condition. Working memory task-related activation patterns and context-dependent functional connectivity, as well as the change of these neural correlates as a function of training, were assessed. While both working memory processes activated an extended frontoparietal-cerebellar network, only the manipulation of items within working memory also recruited the anterior striatum. The intervention effect on the neural correlates was small, but decreased activation in areas relevant for working memory could be observed, with activation changes correlating with behavioural change. Moreover, training seemed to result in decreased functional connectivity when pure maintenance was required, and in a reorganization of functional connectivity when items had to be manipulated. In accordance with the neural efficacy hypothesis, training resulted in overall reduced activation and reorganized functional connectivity, with a differential effect on the different working memory processes under investigation. Now, larger trials including follow-up examinations are needed to further explore the long-term effects of such interventions on a neural level and to estimate the clinical relevance to potentially delay cognitive decline in cognitively healthy patients with Parkinson's disease.

Keywords: blood oxygen level dependent signal; functional connectivity; functional magnetic resonance imaging; home-based working memory training; idiopathic Parkinson’s disease.