Hemispheric asymmetry in Alzheimer's disease is apparent in motor functioning

We examined the prevalence and correlates of anomalous motor speed asymmetry in 104 right-handed patients with a diagnosis of probable Alzheimer's disease (AD). On the Halstead-Reitan Finger Tapping Test, over 60% of the AD patients exhibited notable departures from expected finger tapping asymmetry; 26% displayed an exaggerated right hand tapping advantage (ASYM RIGHT patients) and 37% showed a reversal of expected asymmetry (left hand speed equal to or greater than right hand speed, ASYM LEFT patients). ASYM-RIGHT patients had significantly more years of education than the ASYM-LEFT patients, suggesting that these patients had higher premorbid verbal abilities and possibly had a left hemisphere that was relatively resilient to the effects of AD. Motor speed asymmetry was correlated significantly with cognitive asymmetries (e.g., Verbal IQ vs. Performance IQ, naming vs. figure copying). Finally, ASYM-RIGHT patients exhibited a lower incidence of hallucinations and apathy than ASYM-LEFT patients or patients with normal motor asymmetry.