New Test Can Detect Who is Most at Risk for Alzheimer’s Disease

Researchers at Center for BrainHealth at UT Dallas have developed a test that may help detect who is at risk for Alzheimer’s disease.

In a study published in the Journal of Alzheimer’s Disease, scientists found that individuals with amnestic mild cognitive impairment (aMCI) have twice the risk of others in their age group of progressing to Alzheimer’s after identifying a specific variation in their brain waves.

The test uses electroencephalogram (EEG) technology, a more affordable and non-invasive alternative compared to other methods, to measure neural responses, while participants access their semantic memory — long-term memory that represents general knowledge and concepts. The findings reveal a pattern of delayed neural activity that is directly related to the severity of cognitive impairment during a word task and may indicate an early progression to Alzheimer’s.

“This is a promising start at looking at a group of MCI patients. The long-term goal is whether this can be applied to individual patients one day,” said study principal investigator Dr. John Hart Jr., Medical Science Director at the Center for BrainHealth and Distinguished Chair in Neuroscience and the Jane and Bud Smith Distinguished Chair.

Impaired episodic memory, the ability to retain new memories such as recent conversations, events or upcoming appointments, is a hallmark symptom of Alzheimer’s. While mild cognitive impairment (MCI) is the state between healthy aging and Alzheimer’s, aMCI is a specific type characterized by deficits in episodic memory.

In the study, individuals with aMCI were less accurate and slower on the semantic memory task than other participants. EEG results showed delayed brain activity during the task. In the episodic memory evaluation, researchers found that the worse the performance, the greater the delayed brain activity.

For the study, 16 individuals with aMCI and 17 age-matched healthy controls were monitored by EEG and presented with pairs of words that either described features of an object or were randomly paired. For example, “humps” and “desert” would evoke the memory of the word “camel,” but “humps” and “monitor” would be considered a random pair. Participants were then asked to indicate whether the pair conjured any particular object memory.

Illustration of a brain from a person with Alzheimer's.
Impaired episodic memory, the ability to retain new memories such as recent conversations, events or upcoming appointments, is a hallmark symptom of Alzheimer’s. While mild cognitive impairment (MCI) is the state between healthy aging and Alzheimer’s, aMCI is a specific type characterized by deficits in episodic memory. Image is for illustrative purposes only.

“The majority of EEG research in aMCI has focused on looking at the mind ‘at rest,’ but we are looking at the brain while it is engaged in the object memory retrieval process. We think this might be more sensitive and more specific in pointing out certain cognitive deficits, in this case semantic memory, than other non-EEG methods available, because EEG reflects direct neural activity,” said study lead author Dr. Hsueh-Sheng Chiang, a postdoctoral fellow at UT Southwestern Medical Center who was a research doctoral student at the Center for BrainHealth at the time of the study.

“This protocol could potentially provide complementary information for diagnosis of pre-dementia stages including MCI and identify neural changes that can occur in cases of Alzheimer’s disease,” he said.

Chiang and Hart will continue to develop this prospective diagnostic tool.

[divider]About this visual neuroscience research[/divider]

Dr. Raksha Anand Mudar from the University of Illinois at Urbana-Champaign was a principal investigator, and researchers from UT Southwestern Medical Center and Johns Hopkins University School of Medicine also co-authored the article.

Funding: The study was funded by the National Institute of Health, the RGK Foundation, Alzheimer’s Association New Investigator Grant, the Berman Research Initiative at the Center for BrainHealth, and the Linda and Joel Robuck Friends of BrainHealth New Scientist Award.

Source: Emily Bywaters – UT Dallas
Image Source: The image is in the public domain
Original Research: Abstract for “Altered Neural Activity during Semantic Object Memory Retrieval in Amnestic Mild Cognitive Impairment as Measured by Event-Related Potentials” by Chiang, Hsueh-Sheng; Mudar, Raksha A.; Pudhiyidath, Athula; Spence, Jeffrey S.; Womack, Kyle B.; Cullum, C. Munro; Tanner, Jeremy A.; Eroh, Justin; Kraut, Michael A.; and Hart Jr., John in Journal of Alzheimer’s Disease. Published online August 2015 doi:10.3233/JAD-142781


Abstract

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

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.

“Altered Neural Activity during Semantic Object Memory Retrieval in Amnestic Mild Cognitive Impairment as Measured by Event-Related Potentials” by Chiang, Hsueh-Sheng; Mudar, Raksha A.; Pudhiyidath, Athula; Spence, Jeffrey S.; Womack, Kyle B.; Cullum, C. Munro; Tanner, Jeremy A.; Eroh, Justin; Kraut, Michael A.; and Hart Jr., John in Journal of Alzheimer’s Disease. Published online August 2015 doi:10.3233/JAD-142781

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