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Broster LS, Jenkins SL, Holmes SD, Edwards MG, Jicha GA, Jiang Y. Electrophysiological repetition effects in persons with mild cognitive impairment depend upon working memory demand. Neuropsychologia 2018; 117:13-25. [PMID: 29746820 PMCID: PMC6086740 DOI: 10.1016/j.neuropsychologia.2018.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 04/30/2018] [Accepted: 05/01/2018] [Indexed: 02/04/2023]
Abstract
Forms of implicit memory, including repetition effects, are preserved relative to explicit memory in clinical Alzheimer's disease. Consequently, cognitive interventions for persons with Alzheimer's disease have been developed that leverage this fact. However, despite the clinical robustness of behavioral repetition effects, altered neural mechanisms of repetition effects are studied as biomarkers of both clinical Alzheimer's disease and pre-morbid Alzheimer's changes in the brain. We hypothesized that the clinical preservation of behavioral repetition effects results in part from concurrent operation of discrete memory systems. We developed two experiments that included probes of emotional repetition effects differing in that one included an embedded working memory task. We found that neural repetition effects manifested in patients with amnestic mild cognitive impairment, the earliest form of clinical Alzheimer's disease, during emotional working memory tasks, but they did not manifest during the task that lacked the embedded working memory manipulation. Specifically, the working memory task evoked neural repetition effects in the P600 time-window, but the same neural mechanism was only minimally implicated in the task without a working memory component. We also found that group differences in behavioral repetition effects were smaller in the experiment with a working memory task. We suggest that cross-domain cognitive challenge can expose "defunct" neural capabilities of individuals with amnestic mild cognitive impairment.
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Affiliation(s)
- Lucas S Broster
- Department of Behavioral Science, University of Kentucky, USA; Department of Psychiatry, University of California, San Francisco, USA
| | - Shonna L Jenkins
- Department of Behavioral Science, University of Kentucky, USA; Movement Disorders Program, Medical University of South Carolina, USA
| | - Sarah D Holmes
- Department of Behavioral Science, University of Kentucky, USA; Department of Gerontology, University of Maryland, USA
| | | | - Gregory A Jicha
- Department of Neurology, University of Kentucky, USA; Sanders-Brown Center on Aging, University of Kentucky, USA
| | - Yang Jiang
- Department of Behavioral Science, University of Kentucky, USA; Sanders-Brown Center on Aging, University of Kentucky, USA
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Broster LS, Li J, Wagner B, Smith CD, Jicha GA, Schmitt FA, Munro N, Haney RH, Jiang Y. Spared behavioral repetition effects in Alzheimer's disease linked to an altered neural mechanism at posterior cortex. J Clin Exp Neuropsychol 2018; 40:761-776. [PMID: 29463181 DOI: 10.1080/13803395.2018.1430230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
OBJECTIVE Individuals with dementia of the Alzheimer type (AD) classically show disproportionate impairment in measures of working memory, but repetition learning effects are relatively preserved. As AD affects brain regions implicated in both working memory and repetition effects, the neural basis of this discrepancy is poorly understood. We hypothesized that the posterior repetition effect could account for this discrepancy due to the milder effects of AD at visual cortex. METHOD Participants with early AD, amnestic mild cognitive impairment (MCI), and healthy controls performed a working memory task with superimposed repetition effects while electroencephalography was collected to identify possible neural mechanisms of preserved repetition effects. RESULTS Participants with AD showed preserved behavioral repetition effects and a change in the posterior repetition effect. CONCLUSION Visual cortex may play a role in maintained repetition effects in persons with early AD.
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Affiliation(s)
- Lucas S Broster
- a Department of Behavioral Science , University of Kentucky College of Medicine , Lexington , KY , USA.,b Department of Psychiatry , University of California , San Francisco , CA , USA
| | - Juan Li
- a Department of Behavioral Science , University of Kentucky College of Medicine , Lexington , KY , USA.,c Key Laboratory of Mental Health , Institute of Psychology, Chinese Academy of Sciences , Beijing , China
| | - Benjamin Wagner
- a Department of Behavioral Science , University of Kentucky College of Medicine , Lexington , KY , USA
| | - Charles D Smith
- d Department of Neurology , University of Kentucky College of Medicine , Lexington , KY , USA.,e Sanders-Brown Center on Aging , University of Kentucky College of Medicine , Lexington , KY , USA.,f Magnetic Resonance Imaging and Spectroscopy Center, University of Kentucky College of Medicine , Lexington , KY , USA
| | - Gregory A Jicha
- d Department of Neurology , University of Kentucky College of Medicine , Lexington , KY , USA.,e Sanders-Brown Center on Aging , University of Kentucky College of Medicine , Lexington , KY , USA
| | - Frederick A Schmitt
- b Department of Psychiatry , University of California , San Francisco , CA , USA.,d Department of Neurology , University of Kentucky College of Medicine , Lexington , KY , USA.,e Sanders-Brown Center on Aging , University of Kentucky College of Medicine , Lexington , KY , USA
| | - Nancy Munro
- g Oak Ridge National Laboratory , Oak Ridge , TN , USA
| | - Ryan H Haney
- a Department of Behavioral Science , University of Kentucky College of Medicine , Lexington , KY , USA
| | - Yang Jiang
- a Department of Behavioral Science , University of Kentucky College of Medicine , Lexington , KY , USA.,e Sanders-Brown Center on Aging , University of Kentucky College of Medicine , Lexington , KY , USA.,f Magnetic Resonance Imaging and Spectroscopy Center, University of Kentucky College of Medicine , Lexington , KY , USA
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Ober BA, Shenaut GK. Repetition priming of words and nonwords in Alzheimer's disease and normal aging. Neuropsychology 2014; 28:973-83. [PMID: 25000325 PMCID: PMC4227941 DOI: 10.1037/neu0000112] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
OBJECTIVE This study examines the magnitude and direction of nonword and word lexical decision repetition priming effects in Alzheimer's disease (AD) and normal aging, focusing specifically on the negative priming effect sometimes observed with repeated nonwords. METHOD Probable AD patients (30), elderly normal controls (34), and young normal controls (49) participated in a repetition priming experiment using low-frequency words and word-like nonwords with a letter-level orthographic orienting task at study followed by a lexical decision test phase. RESULTS Although participants' reaction times (RTs) were longer in AD compared with elderly normal, and elderly normal compared with young normal, the repetition priming effect and the degree to which the repetition priming effect was reversed for nonwords compared to words was unaffected by AD or normal aging. CONCLUSION AD patients, like young and elderly normal participants, are able to modify (in the case of words) and create (in the case of nonwords) long-term memory traces for lexical stimuli, based on a single orthographic processing trial. The nonword repetition results are discussed from the perspective of new vocabulary learning commencing with a provisional lexical memory trace created after orthographic encoding of a novel word-like letter string.
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Affiliation(s)
- Beth A Ober
- Human Development Unit, Department of Human Ecology, University of California-Davis
| | - Gregory K Shenaut
- Human Development Unit, Department of Human Ecology, University of California-Davis
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Abstract
The oral word reading speed of patients with Alzheimer's disease (AD) and healthy young and older control participants was evaluated across a broad range of stimulus contrast levels in two experiments. The impact of stimulus repetition on reading speed also was examined. It was found that the older adult participants, and particularly the AD patients, were more sensitive to contrast reductions. Each subject group was able to read repeated words more rapidly than novel words but this repetition effect emerged only at lower stimulus contrast levels. It was concluded that AD patients have feature extraction speeds comparable to non-demented older adults but only when the stimuli are presented at a relatively high contrast. These findings suggest that the automatic encoding processes involved in word recognition remain intact in mildly demented AD patients given stimuli of sufficient strength.
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Affiliation(s)
- Grover C Gilmore
- Case Western Reserve University, Cleveland, Ohio 44121-7123, USA.
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