Background: Cognitive deficits in Parkinson's disease (PD) are heterogeneous and can be classified into cognitive domains. Quantitative EEG is related to and predictive of cognitive status in PD. In this cross-sectional study, the relationship of cognitive domains and EEG slowing in PD patients without dementia is investigated. Methods: A total of 48 patients with idiopathic PD were neuropsychologically tested. Cognitive domain scores were calculated combining Z-scores of test variables. Slowing of EEG was measured with median EEG frequency. Linear regression was used for correlational analyses and to control for confounding factors. Results: EEG median frequency was significantly correlated to cognitive performance in most domains (episodic long-term memory, rho = 0.54; overall cognitive score, rho = 0.47; fluency, rho = 0.39; attention, rho = 0.37; executive function, rho = 0.34), but not to visuospatial functions and working memory. Conclusion: Global EEG slowing is a marker for overall cognitive impairment in PD and correlates with impairment in the domains attention, executive function, verbal fluency, and episodic long-term memory, but not with working memory and visuospatial functions. These disparate effects warrant further investigations.

Caviness JN, Driver-Dunckley E, Connor DJ, Sabbagh MN, Hentz JG, Noble B, et al: Defining mild cognitive impairment in Parkinson's disease. Mov Disord 2007;22:1272-1277.
Kehagia AA, Barker RA, Robbins TW: Neuropsychological and clinical heterogeneity of cognitive impairment and dementia in patients with Parkinson's disease. Lancet Neurol 2010;9:1200-1213.
Litvan I, Aarsland D, Adler CH, Goldman JG, Kulisevsky J, Mollenhauer B, et al: MDS task force on mild cognitive impairment in Parkinson's disease: critical review of PD-MCI. Mov Disord 2011;26:1814-1824.
Litvan I, Goldman JG, Tröster AI, Schmand BA, Weintraub D, Petersen RC, et al: Diagnostic criteria for mild cognitive impairment in Parkinson's disease: Movement Disorder Society Task Force guidelines. Mov Disord 2012;27:349-356.
Cholerton BA, Zabetian CP, Wan JY, Montine TJ, Quinn JF, Mata IF, et al: Evaluation of mild cognitive impairment subtypes in Parkinson's disease. Mov Disord 2014;29:756-764.
Soikkeli R, Partanen J, Soininen H, Pääkkönen A, Riekkinen P: Slowing of EEG in Parkinson's disease. Electroencephalogr Clin Neurophysiol 1991;79:159-165.
Sinanović O, Kapidzić A, Kovacević L, Hudić J, Smajlović D: EEG frequency and cognitive dysfunction in patients with Parkinson's disease. Med Arh 2005;59:286-287.
Caviness JN, Hentz JG, Evidente VG, Driver-Dunckley E, Samanta J, Mahant P, et al: Both early and late cognitive dysfunction affects the electroencephalogram in Parkinson's disease. Parkinsonism Relat Disord 2007;13:348-354.
Kamei S, Morita A, Serizawa K, Mizutani T, Hirayanagi K: Quantitative EEG analysis of executive dysfunction in Parkinson disease. J Clin Neurophysiol 2010;27:193-197.
Morita A, Kamei S, Mizutani T: Relationship between slowing of the EEG and cognitive impairment in Parkinson disease. J Clin Neurophysiol 2011;28:384-387.
Olde Dubbelink KTE, Stoffers D, Deijen JB, Twisk JWR, Stam CJ, Berendse HW: Cognitive decline in Parkinson's disease is associated with slowing of resting-state brain activity: a longitudinal study. Neurobiol Aging 2013;34:408-418.
Klassen BT, Hentz JG, Shill HA, Driver-Dunckley E, Evidente VGH, Sabbagh MN, et al: Quantitative EEG as a predictive biomarker for Parkinson disease dementia. Neurology 2011;77:118-124.
Olde Dubbelink KTE, Hillebrand A, Twisk JWR, Deijen JB, Stoffers D, Schmand BA, et al: Predicting dementia in Parkinson disease by combining neurophysiologic and cognitive markers. Neurology 2014;82:263-270.
Gibb WR, Lees AJ: The relevance of the Lewy body to the pathogenesis of idiopathic Parkinson's disease. J Neurol Neurosurg Psychiatry 1988;51:745-752.
Strauss E, Sherman EMS, Spreen O: A Compendium of Neuropsychological Tests : Administration, Norms, and Commentary, ed 3. Oxford , Oxford University Press, 2006.
Zimmermann P, Fimm B: Testbatterie zur Aufmerksamkeitsprüfung. Herzogenrath, Psytest Psychologische Testsysteme, 2007.
Berres M, Zehnder A, Bläsi S, Monsch AU: Evaluation of diagnostic scores with adjustment for covariates. Stat Med 2008;27:1777-1790.
Hatz F, Hardmeier M, Bousleiman H, Rüegg S, Schindler C, Fuhr P: Reliability of fully automated versus visually controlled pre- and post-processing of resting-state EEG. Clin Neurophysiol 2014, Epub ahead of print.
Welch P: The use of fast Fourier transform for the estimation of power spectra: a method based on time averaging over short, modified periodograms. IEEE Trans Audio Electroacoustics 1967;15:70-73.
R Core Team: R: A Language and Environment for Statistical Computing. Vienna, R Foundation for Statistical Computing, 2012.
StataCorp: Stata Statistical Software: Release 12. College Station, StataCorp LP, 2011. (accessed November 12, 2014).
Grömping U: Relative importance for linear regression in R: the package relaimpo. J Stat Softw 2006;17:1-27.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.