Alzheimer disease: functional abnormalities in the dorsal visual pathway.
OBJECTIVE
To evaluate whether patients with Alzheimer disease (AD) have altered activation compared with age-matched healthy control (HC) subjects during a task that typically recruits the dorsal visual pathway.


METHODS
The study was performed in accordance with the Declaration of Helsinki, with institutional ethics committee approval, and all subjects provided written informed consent. Two tasks were performed to investigate neural function: face matching and location matching. Twelve patients with mild AD and 14 age-matched HC subjects were included. Brain activation was measured by using functional magnetic resonance imaging. Group statistical analyses were based on a mixed-effects model corrected for multiple comparisons.


RESULTS
Task performance was not statistically different between the two groups, and within groups there were no differences in task performance. In the HC group, the visual perception tasks selectively activated the visual pathways. Conversely in the AD group, there was no selective activation during performance of these same tasks. Along the dorsal visual pathway, the AD group recruited additional regions, primarily in the parietal and frontal lobes, for the location-matching task. There were no differences in activation between groups during the face-matching task.


CONCLUSIONS
The increased activation in the AD group may represent a compensatory mechanism for decreased processing effectiveness in early visual areas of patients with AD. The findings support the idea that the dorsal visual pathway is more susceptible to putative AD-related neuropathologic changes than is the ventral visual pathway.
Bokde
Arun L W
AL
Discipline of Psychiatry, School of Medicine and Trinity College Institute of Neuroscience, Laboratory of Neuroimaging and Biomarker Research, Trinity College Dublin, Adelaide and Meath Hospital incorporating National Children's Hospital, Dublin, Ireland. Arun.Bokde@tcd.ie
Lopez-Bayo
Patricia
P
Born
Christine
C
Ewers
Michael
M
Meindl
Thomas
T
Teipel
Stefen J
SJ
Faltraco
Frank
F
Reiser
Maximilian F
MF
Möller
Hans-Juergen
HJ
Hampel
Harald
H
D000328:Adult; D000368:Aged; D000544:Alzheimer Disease / Q000503:physiopathology*; D001931:Brain Mapping; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D013647:Task Performance and Analysis; D014793:Visual Cortex / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*