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Examining the Characteristics of Episodic Memory using Event-related Potentials in Patients with Alzheimer's Disease
Published on: August 30, 2011
fMRI activation changes during successful episodic memory encoding and recognition in amnestic mild cognitive
Mehul A Trivedi1, Christopher M Murphy, Celine Goetz
1Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612, USA.
Background/Aims:
Previous functional MRI studies in individuals with amnestic mild cognitive impairment (AMCI), a putative, prodromal form of Alzheimer's disease, reveal substantial regional changes in brain activation during episodic memory function.
Methods:
Functional MRI was applied to examine changes in brain activation during different stages of episodic memory function using a subsequent memory task in individuals with AMCI relative to older normal controls.
Results:
We found that the AMCI group displayed greater activation in the right hippocampus but less activation in the frontal cortex relative to the older normal control group during intentional encoding of items that were subsequently recognized. We observed nearly the opposite pattern of results for successful recognition. The AMCI group displayed less activation in the medial temporal cortex but greater activation in the frontal cortex. In addition, the AMCI group showed reduced activation in the medial temporal and frontal cortices during incidental encoding of novel information during recognition.
Conclusion:
The results of the present study suggest that brain activation differences in individuals with AMCI are modulated by the stage of episodic memory examined (i.e. intentional vs. incidental encoding vs. recognition). These observations may help to clarify some of the conflicting findings regarding brain activation changes in AMCI.
Insights
Brain activation patterns in amnestic mild cognitive impairment (AMCI) differ based on memory task stage. Findings highlight distinct hippocampal and frontal cortex activity during encoding and recognition in AMCI patients.
Area of Science:
- Neuroimaging
- Cognitive Neuroscience
- Alzheimer's Disease Research
Background:
- Amnestic mild cognitive impairment (AMCI) is a precursor to Alzheimer's disease.
- Previous functional MRI studies show altered brain activation in AMCI during memory tasks.
Purpose of the Study:
- To investigate brain activation differences in AMCI during various episodic memory stages.
- To compare AMCI patients with healthy older adults using functional MRI.
Main Methods:
- Functional MRI (fMRI) was used to assess brain activation.
- A subsequent memory task was employed to examine encoding and recognition phases.
- Participants included individuals with AMCI and age-matched normal controls.
Main Results:
- AMCI group showed increased right hippocampus activation but decreased frontal cortex activation during intentional encoding for recognized items.
- For successful recognition, the AMCI group exhibited decreased medial temporal cortex activation and increased frontal cortex activation.
- Reduced activation in medial temporal and frontal cortices was observed in the AMCI group during incidental encoding.
Conclusions:
- Brain activation in AMCI is stage-dependent, varying between intentional encoding, incidental encoding, and recognition.
- These findings may help reconcile conflicting results from prior AMCI brain activation studies.
