Brain mechanisms of successful compensation during learning in Alzheimer disease.
OBJECTIVE
To determine whether patients with Alzheimer disease (AD) compensate for neuropathologic changes when performing a mnemonic task by recruiting 1) the same brain regions as age-matched, healthy controls, but to a greater extent; 2) additional brain regions not activated by controls; or 3) both.


METHODS
Twelve patients with mild probable AD and 12 healthy age- and education-matched controls participated in an fMRI study of successful encoding and retrieval of visuospatial paired associates. To ensure successful performance in both groups, participants were given multiple attempts to learn associations between two and three object locations.


RESULTS
The pattern of brain activity in patients with AD performing an easy version of the task was indistinguishable from that of controls performing a harder version of the task. Increased activation in left medial and right lateral prefrontal cortices was found in patients with AD compared to controls during encoding of two object locations, but not when this level of encoding in patients was compared with encoding of three object locations in controls.


CONCLUSIONS
There was no evidence of neural plasticity in the form of recruitment of novel brain regions in patients with Alzheimer disease. Data supported greater recruitment of the same brain regions as age-matched controls as a means of compensating for neuropathology and associated cognitive impairment in Alzheimer disease.
Gould
R L
RL
MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, Section of Old Age Psychiatry, London, UK. r.gould@iop.kcl.ac.uk
Arroyo
B
B
Brown
R G
RG
Owen
A M
AM
Bullmore
E T
ET
Howard
R J
RJ
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D001931:Brain Mapping; D016022:Case-Control Studies; D035881:Compensation and Redress; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007858:Learning / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010100:Oxygen / Q000097:blood; D011597:Psychomotor Performance / Q000502:physiology; D013028:Space Perception / Q000502:physiology
D010100:Oxygen