Psychomotor slowing in mild cognitive impairment, Alzheimer's disease and lewy body dementia: mechanisms and diagnostic value.
BACKGROUND
Although psychomotor slowing is frequent in Alzheimer's disease (AD) and Lewy body dementia (LBD), its mechanism and diagnostic value have not been examined.


OBJECTIVE
To (i) assess psychomotor speed in patients with mild cognitive impairment (MCI), AD and LBD, (ii) determine the underlying mechanisms, and (iii) examine whether psychomotor slowing constitutes a useful diagnostic marker.


METHODS
Psychomotor speed was assessed in MCI (n = 11) and mild dementia due to AD (n = 23) or LBD (n = 18) and controls (n = 52) with visual inspection time (VIT), digital tapping, simple reaction time (SRT) and choice reaction time (CRT) tests.


RESULTS
MCI did not differ from controls. Both dementia groups showed different patterns. In AD, VIT (p = 0.0001), tapping (p = 0.021), SRT (p = 0.0001) and decision time (p = 0.0001) were impaired as compared to controls. In LBD, VIT (p = 0.0001) was very impaired and correlated with visual hallucinations (p = 0.001); SRT lengthening (p = 0.0001) was related to attentional disorders (p = 0.0001).


CONCLUSIONS
Psychomotor slowing of AD is due to slower perceptuomotor and decision processes. In LBD, psychomotor slowing is due to visual and attention disorders, and subtle visual disorders contribute to hallucinations. VIT and CRT are useful diagnostic markers.
Bailon
Olivier
O
Department of Neurology and the Laboratoire de Neurosciences Fonctionnelles et Pathologies (UMR CNRS 8160), University Hospital of Lille, Lille, and University Hospital of Amiens, Amiens, France.
Roussel
Martine
M
Boucart
Muriel
M
Krystkowiak
Pierre
P
Godefroy
Olivier
O
D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000523:psychology*; D001288:Attention / Q000502:physiology; D002544:Cerebral Infarction / Q000473:pathology; D003072:Cognition Disorders / Q000175:diagnosis / Q000523:psychology*; D003657:Decision Making; D005260:Female; D006801:Humans; D020961:Lewy Body Disease / Q000175:diagnosis / Q000523:psychology*; D016015:Logistic Models; D008297:Male; D009048:Motor Skills / Q000502:physiology; D009483:Neuropsychological Tests; D010465:Perception / Q000502:physiology; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time