Neurophysiological and other features of working memory in older adults at risk for dementia.

Theta-gamma coupling (TGC) is a neurophysiological process that supports working memory. Working memory is associated with other clinical and biological features. The extent to which TGC is associated with these other features and whether it contributes to working memory beyond these features is unknown. Two-hundred-and-three older participants at risk for Alzheimer's dementia-98 with mild cognitive impairment (MCI), 39 with major depressive disorder (MDD) in remission, and 66 with MCI and MDD (MCI + MDD)-completed a clinical assessment, N-back-EEG, and brain MRI. Among them, 190 completed genetic testing, and 121 completed [ ¹¹ C] Pittsburgh Compound B ([11C] PIB) PET imaging. Hierarchical linear regressions were used to assess whether TGC is associated with demographic and clinical variables; Alzheimer's disease-related features ( APOE ε4 carrier status and β-amyloid load); and structural features related to working memory. Then, linear regressions were used to assess whether TGC is associated with 2-back performance after accounting for these features. Other than age, TGC was not associated with any non-neurophysiological features. In contrast, TGC (β = 0.27; p  = 0.006), age (β = - 0.29; p  = 0.012), and parietal cortical thickness (β = 0.24; p  = 0.020) were associated with 2-back performance. We also examined two other EEG features that are linked to working memory-theta event-related synchronization and alpha event-related desynchronization-and found them not to be associated with any feature or performance after accounting for TGC. Our findings suggest that TGC is a process that is independent of other clinical, genetic, neurochemical, and structural variables, and supports working memory in older adults at risk for dementia.
Supplementary Information: The online version contains supplementary material available at 10.1007/s11571-023-09938-y.
Competing Interests: Conflict of interestRP, HB, AG, NH, MM, NRR, WW and RZ report no biomedical financial interests or potential conflicts of interest. DMB receives research support from the CIHR, NIH, Brain Canada and the Temerty Family Foundation through the CAMH Foundation and the Campbell Research Institute. He received research support and in-kind equipment support for an investigator-initiated study from Brainsway Ltd, and he was the principal site investigator for three sponsor-initiated studies for Brainsway Ltd. He receives in-kind equipment support from Magventure for investigator-initiated research. He received medication supplies for an investigator-initiated trial from Indivior. He has participated in a scientific advisory board meeting for Janssen and Welcony Inc. CEF receives grant funding from Brain Canada, Patient Centred Outcomes Research Institute (PCORI), St. Michaels Hospital Foundation, Hoffman LaRoche and Vielight Inc. AJF has received grant support from the U.S. National Institutes of Health, the Patient Centered Outcomes Research Institute, the Canadian Institutes of Health Research, Brain Canada, the Ontario Brain Institute, the Alzheimer's Association, AGE-WELL, and the Canadian Foundation for Healthcare Improvement. AGG has obtained academic grants during the last 5 years from Canadian Institute of Health Research, Centre for Aging and Brain Health Innovation, Brain Canada Foundation, Brain & Behavior Research Foundation, Ontario Ministry of Economic Development and Innovation, Ontario Mental Health Foundation, Ontario Ministry of Health and Long Term Care Alternate Funding Plan, American Foundation for Suicide Prevention, Catalyst Fund: Miner's Lamp Innovation Fund in Prevention and Early Detection of Severe Mental Illness, Northern Ontario Academic Medicine Association, Society for Nuclear Medicine and Molecular Imaging, Researcher-Clinician Partnership Program (RCP2), Spark, W. Garfield Weston Foundation, Labatt Family Network for Research on the Biology of Depression, and PSI Foundation. JLK is a member of the Scientific Advisory Board (unpaid) of Myriad Genetics, and is author on patents relating to pharmacogenetics of psychiatric disorders. SK has received grant support from Brain Canada, NIH, Brain and Behavior Foundation (NARSAD), BrightFocus Foundation, Weston Brain Institute, Canadian Centre for Aging and Brain Health Innovation, CAMH foundation and University of Toronto, and in Kind equipment support from Soterix Medical Inc. KLL has grant support from the U.S. National Institutes of Health, the Canadian Institutes of Health Research, the Weston Brain Institute, the Alzheimer's Drug Discovery Foundation, and the Alzheimer's Association, has received consultation fees from Acadia, BioXcel Therapeutics, Cerevel Therapeutics, ICG Pharma, Kondor Pharma, Otsuka, and holds stock options in Highmark Interactive. LM reports no biomedical financial interests or potential conflicts of interest. BHM holds and receives support from the Labatt Family Chair in Biology of Depression in Late-Life Adults at the University of Toronto. He currently receives research support from Brain Canada, the Canadian Institutes of Health Research, the CAMH Foundation, the Patient-Centered Outcomes Research Institute (PCORI), the US National Institute of Health (NIH), Capital Solution Design LLC (software used in a study founded by CAMH Foundation), and HAPPYneuron (software used in a study founded by Brain Canada). Within the past 5 years, he has also received research support from Eli Lilly (medications for a NIH-funded clinical trial) and Pfizer (medications for a NIH-funded clinical trial). BGP is holder of United States Provisional Patent No. 16/490,680, Canadian Provisional Patent No. 3,054,093 and of United States Provisional Patent No.17/396,030 for a cell-based assay and kits for assessing serum anticholinergic activity. AV receives funding from the National Institute of Mental Health, Canadian Institutes of Health Research, Canada Foundation for Innovation, CAMH Foundation, and the University of Toronto. TKR has received research support from Brain Canada, Brain and Behavior Research Foundation, BrightFocus Foundation, Canada Foundation for Innovation, Canada Research Chair, Canadian Institutes of Health Research, Centre for Aging and Brain Health Innovation, National Institutes of Health, Ontario Ministry of Health and Long-Term Care, Ontario Ministry of Research and Innovation, and the Weston Brain Institute. TKR also received in-kind equipment support for an investigator-initiated study from Magstim, and in-kind research accounts from Scientific Brain Training Pro. TKR participated in 2021 in an advisory board for Biogen Canada Inc. TKR is also holder of the United States Provisional Patent No. 17/396,030 that describes cell-based assays and kits for assessing serum cholinergic receptor activity.
(© The Author(s), under exclusive licence to Springer Nature B.V. 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)