Related Experiment Video
Updated: Jun 13, 2026
Examining the Characteristics of Episodic Memory using Event-related Potentials in Patients with Alzheimer's Disease
Published on: August 30, 2011
fMRI responses to words repeated in a congruous semantic context are abnormal in mild Alzheimer's disease
John M Olichney1, Jason R Taylor, Shiaohui Chan
1Department of Neurology, University of California, Davis, Davis, CA 95618-5412, USA. jmolichney@ucdavis.edu
Background:
We adapted an event-related brain potential word repetition paradigm, sensitive to early Alzheimer's disease (AD), for functional MRI (fMRI). We hypothesized that AD would be associated with reduced differential response to New/Old congruous words.
Methods:
Fifteen mild AD patients (mean age=72.9) and 15 normal elderly underwent 1.5T fMRI during a semantic category decision task.
Results:
We found robust between-groups differences in BOLD response to congruous words. In controls, the New>Old contrast demonstrated larger responses in much of the left-hemisphere (including putative P600 generators: parahippocampal, cingulate, fusiform, perirhinal, middle temporal (MTG) and inferior frontal gyri (IFG)); the Old>New contrast showed modest activation, mainly in right parietal and prefrontal cortex. By contrast, there were relatively few regions of significant New>Old responses in AD patients, mainly in the right-hemisphere, and their Old>New contrast did not demonstrate a right-hemisphere predominance. Across subjects, the spatial extent of New>Old responses in left medial temporal lobe (MTL) correlated with subsequent recall and recognition (r's>or=0.60). In controls, the magnitude of New-Old response in left MTL, fusiform, IFG, MTG, superior temporal and cingulate gyrus correlated with subsequent cued recall and/or recognition (0.51
Conclusions:
A distributed network of mostly left-hemisphere structures, which are putative P600 generators, appears important for successful verbal encoding (with New>Old responses to congruous words in normal elderly). This network appears dysfunctional in mild AD patients, as reflected in decreased word repetition effects particularly in left association cortex, paralimbic and MTL structures.
Insights
Early Alzheimer's disease (AD) impairs brain networks involved in word repetition, showing reduced responses in mild AD patients compared to controls. This suggests functional MRI can detect early AD-related changes in verbal encoding.
Area of Science:
- Neuroimaging
- Cognitive Neuroscience
- Neurology
Background:
- An event-related brain potential word repetition paradigm, sensitive to early Alzheimer's disease (AD), was adapted for functional MRI (fMRI).
- Early AD is hypothesized to be associated with reduced differential brain response to new versus old congruous words.
Purpose of the Study:
- To investigate functional MRI (fMRI) differences in brain activity between mild Alzheimer's disease (AD) patients and normal elderly individuals using a word repetition paradigm.
- To identify brain regions and networks associated with verbal encoding and their dysfunction in early AD.
Main Methods:
- Fifteen mild AD patients and 15 normal elderly controls underwent 1.5T fMRI during a semantic category decision task.
- Analysis focused on Blood-Oxygen-Level-Dependent (BOLD) responses to congruous words, comparing new versus old stimuli (New>Old contrast) and old versus new stimuli (Old>New contrast).
Main Results:
- Robust group differences in BOLD response to congruous words were observed.
- In controls, New>Old responses were prominent in the left hemisphere, including areas associated with P600 generation (parahippocampal, cingulate, fusiform, perirhinal, middle temporal, and inferior frontal gyri).
- Mild AD patients showed significantly fewer New>Old responses, primarily in the right hemisphere, indicating dysfunction in the left-hemisphere network crucial for verbal encoding.
Conclusions:
- A distributed left-hemisphere network, including P600 generators, is vital for successful verbal encoding in normal elderly individuals.
- This network appears dysfunctional in mild AD patients, evidenced by decreased word repetition effects, particularly in left association cortex, paralimbic, and medial temporal lobe structures.
- fMRI adaptation of the word repetition paradigm effectively detects early AD-related neural deficits in verbal memory processes.
More Related Videos
06:48Lexical Decision Task for Studying Written Word Recognition in Adults with and without Dementia or Mild Cognitive Impairment
Published on: June 25, 2019
12:50Lesion Explorer: A Video-guided, Standardized Protocol for Accurate and Reliable MRI-derived Volumetrics in Alzheimer's Disease and Normal Elderly
Published on: April 14, 2014
Related Concept Videos
01:23Alzheimer Disease ll: Pathophysiology
01:26Alzheimer's Disease: Overview
The clinical diagnosis of AD hinges on the presence of memory and other cognitive impairments. Biomarkers, such as changes in Aβ and tau...
01:29Alzheimer Disease l: Introduction
01:22Alzheimer's Disease: Treatment
01:22Dementia l: Introduction