Altered Neural Activity during Semantic Object Memory Retrieval in Amnestic Mild Cognitive Impairment as Measured by Event-Related Potentials

Article type: Research Article

Authors: Chiang, Hsueh-Sheng^{a; b} | Mudar, Raksha A.^{a; b; c} | Pudhiyidath, Athula^a | Spence, Jeffrey S.^a | Womack, Kyle B.^{a; d; e} | Cullum, C. Munro^{d; e} | Tanner, Jeremy A.^f | Eroh, Justin^{a; b} | Kraut, Michael A.^g | Hart Jr., John^{a; b; d; e; *}

Affiliations: [a] Center for BrainHealth, The University of Texas at Dallas, Dallas, TX, USA | [b] School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, USA | [c] Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign, Champaign, IL, USA | [d] Department of Neurology and Neurotherapeutics, The University of Texas Southwestern Medical Center, Dallas, TX, USA | [e] Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA | [f] The Johns Hopkins University School of Medicine, Baltimore, MD, USA | [g] Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA

Correspondence: [*] Correspondence to: John Hart, Jr., MD, Center for BrainHealth, The University of Texas at Dallas, 2200 W. Mockingbird Lane, Dallas, TX 75235, USA. Tel.: +1 972 883 3403; jhart@utdallas.edu

Abstract: Deficits in semantic memory in individuals with amnestic mild cognitive impairment (aMCI) have been previously reported, but the underlying neurobiological mechanisms remain to be clarified. We examined event-related potentials (ERPs) associated with semantic memory retrieval in 16 individuals with aMCI as compared to 17 normal controls using the Semantic Object Retrieval Task (EEG SORT). In this task, subjects judged whether pairs of words (object features) elicited retrieval of an object (retrieval trials) or not (non-retrieval trials). Behavioral findings revealed that aMCI subjects had lower accuracy scores and marginally longer reaction time compared to controls. We used a multivariate analytical technique (STAT-PCA) to investigate similarities and differences in ERPs between aMCI and control groups. STAT-PCA revealed a left fronto-temporal component starting at around 750 ms post-stimulus in both groups. However, unlike controls, aMCI subjects showed an increase in the frontal-parietal scalp potential that distinguished retrieval from non-retrieval trials between 950 and 1050 ms post-stimulus negatively correlated with the performance on the logical memory subtest of the Wechsler Memory Scale-III. Thus, individuals with aMCI were not only impaired in their behavioral performance on SORT relative to controls, but also displayed alteration in the corresponding ERPs. The altered neural activity in aMCI compared to controls suggests a more sustained and effortful search during object memory retrieval, which may be a potential marker indicating disease processes at the pre-dementia stage.

Keywords: Cognition, electroencephalography, event-related potentials, memory, mild cognitive impairment, semantics

DOI: 10.3233/JAD-142781

Journal: Journal of Alzheimer's Disease, vol. 46, no. 3, pp. 703-717, 2015