Background and Purpose: There is increasing evidence for subtle motor dysfunction early in Alzheimer disease (AD), including common motor behaviors that were once considered unaffected early in the disease process. Our objective was to assess whether functional neural networks underlying motor behavior are altered by AD.
Methods: We investigated AD-related differences in regional brain activation during motor performance. Nine older adults with early-stage AD and 10 without dementia underwent functional magnetic resonance imaging while performing a visually directed simple motor task (hand squeeze).
Results: Despite some similarity in brain activation during motor performance, we found that individuals without dementia exhibited greater activation in accessory motor regions, supplementary motor area, and cerebellum compared with those with AD. We also assessed disease-related differences in regions where activity was functionally integrated with primary motor cortex. Using a psychophysiological interaction analysis, we found that those with AD displayed increased coactivation with primary motor cortex of bilateral motor and visual regions.
Discussion and Conclusions: These AD-related differences in regional coactivation during motor execution may represent inefficiency in the motor network as a consequence of the disease process. Alternatively, they may represent compensatory activation. These findings provide further evidence that in early stages of AD, neuromotor function is altered even during simple motor behaviors. The results may have implications for performance of more complex tasks and may be associated with the well-characterized decline in dual-task performance in those with AD.
Department of Neurology, University of Kansas Medical Center, Kansas City (E.D.V., R.A.H., J.M.B.); Dartmouth-Hitchcock Medical Center, Manchester, New Hampshire (G.P.T.); and American Academy of Family Physicians, Leawood, Kansas (N.L.).
Correspondence: Eric D. Vidoni, PT, PhD, Department of Neurology, KU Alzheimer's Disease Center, University of Kansas Medical Center, MS 1063, 3901 Rainbow Blvd, Kansas City, KS 66160 (firstname.lastname@example.org).
This study was supported by grants from the DANA Foundation, and the National Institute of Aging from the National Institute on Neurological Disorders and Stroke to J.M.B. (AG026374, AG029615, and K23NS058252). N.L. was supported by a training grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (T32HD057850). E.D.V. was supported in part by a fellowship from the Foundation for Physical Therapy, the Heartland Institute for Clinical & Translational Research, University of Kansas Medical Center CTSA (KL2 RR033177 and UL1 RR033179). J.M.B. and E.D.V. were supported by the University of Kansas Alzheimer's Disease Center (P30AG035982). The Hoglund Brain Imaging Center provided imaging and clinical support (C76HF00201).
The authors declare no conflict of interest.