Year: 2009
Type: article
Abstract: Cognitive deficits in Alzheimer's disease result from years and possibly decades of pathological (e.g. amyloid) and physiological alterations (e.g. hypometabolism) in the brain. Our aim is to extend the understanding these physiological changes to those that are altered during memory processes, specifically encoding and recognition. Our investigation focused on the dynamic aspects of encoding by using a repetition-suppression paradigm with demonstrated differences between healthy adults and those with mild cognitive impairment. Thirty-two participants underwent an fMRI experiment consisting of two components. In the first component, participants where shown 40 line drawings three times each in a pseudo-random order and asked to make a judgment as to whether the drawing was a man-made object or a natural object. In the second component, participants viewed the same 40 drawings intermixed with 40 novel drawings and asked to make a judgment as to whether the drawing was old or new. Estimates for the BOLD response to each repetition, old items, and new items were computed for each participant. The estimates were entered into repeated measures ANOVAs to probe for the effects of family history (FH) and apolipoprotein E (APOE). The average encoding response in the FH+ group was decreased compared to the FH- group in regions including the right hippocampus, anterior cingulate cortex, and bilateral lateral occipital cortices. Additionally, the slope was significantly decreased in a region on the border of the posterior and middle cingulate cortices. In contrast, the average encoding response in the APOE+ group was larger than the APOE- group in regions including bilateral hippocampus and cingulate cortex. The slope across repetitions was greater in several regions including the anterior cingulate cortex. Although, the recognition component revealed far fewer group differences; the results were consistent with the literature. These findings demonstrate early and extensive neurophysiological changes with risk during both encoding and recognition. Interestingly, the effect of risk had a more significant modulatory effect during encoding than recognition. Thus, future research should focus on understanding the dynamics of encoding and how these dynamics are altered by disease processes.
Source: Alzheimer s & Dementia
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2103314758