 PERGAMON Neuropsychologia 26 "0888# 764Ð779 9917!2821:88:, ! see front matter Þ 0888 Elsevier Science Ltd[ All rights reserved PII]S9917!2821"87#99028!9 Apraxia and motor!skill acquisition in Alzheimer|s disease are dissociable Daniel H[ Jacobs a\ \ John C[ Adair b \ David J[G[ Williamson c \ Duk L[ Na d \ Michael Gold e \ Anne L[ Foundas f \ Je}rey E[ Shuren g \ Jean E[ Cibula h \ Kenneth M[ Heilman g a Division of Neurolo`y and Memory Disorders Clinic\ Orlando Re`ional Healthcare Systems\ Orlando\ Florida\ USA b Department of Neurolo`y\ The University of New Mexico School of Medicine\ Albuquerque\ New Mexico\ USA c Department of Psycholo`y\ Auburn University\ Auburn\ Geor`ia\ USA d Department of Neurolo`y\ Sun`kyunkwan University\ Samsun` Medical Center\ Seoul\ South Korea e Bristol Myers Squibb Pharmaceutical Research Institute\ USA f Department of Psychiatry and Neurolo`y\ Tulane University School of Medicine and Neurolo`y Service\ Veterans Affairs Medical Center\ New Orleans\ Louisiana\ USA g Department of Neurolo`y\ University of Florida Colle`e of Medicine and Veterans Affairs Medical Center\ Gainesville\ Florida\ USA h University of Kentucky Medical School\ Lexin`ton\ Kentucky\ USA Received 09 September 0885^ accepted 0 September 0887 Abstract Many patients with Alzheimer|s disease "AD# are apraxic and the apraxia has been posited to be related to a loss of movement representations[ Whereas patients with Alzheimer|s disease have been reported to demonstrate normal motor learning on a rotor pursuit skill acquisition task\ it is unknown whether AD subjects who are apraxic demonstrate normal skill!learning[ We tested subjects with probable AD and normal controls on a rotor pursuit task[ We also tested the AD subjects for ideomotor apraxia[ Subjects with AD who were apraxic had normal motor learning[ In addition\ praxis score did not correlate with performance on the skill!acquisition task[ The results suggest that ideomotor praxis and motor learning are at least partly dissociable[ Þ 0888 Elsevier Science Ltd[ All rights reserved[ Keywords] Alzheimer|s disease^ Dementia^ Memory^ Apraxia 0[ Introduction Patients with Alzheimer|s disease "AD# reportedly have normal motor skill!learning on a rotor pursuit ask ð2\ 4Ł[ Whereas some patients with AD are unable to perform learned skilled movements "apraxia#\ others are not imp! aired[ In contrast\ patients with Huntington|s disease "HD# or Parkinson|s disease "PD# do not show normal motor skill!learning on a rotor pursuit task ð3\ 4Ł[ Typi! cally\ patients with HD or PD\ even if demented\ are not apraxic[ Thus de_cits in motor skill!learning and in praxis apparently dissociate in two distinct groups[ However\  Corresponding author[ Orlando Regional Medical Center\ 0393 Kuhl Avenue\ Third Floor Corey Building\ Orlando\ Florida 21795\ USA[ Tel[] ¦0!396!126!5225^ fax] ¦0!396!312!1083^ e!mail] djacobs161 Ýaol[com Supported in part by the Department of Elder A}airs\ State of Florida\ USA[ the above studies ð2\ 4Ł did not examine whether the AD patients with normal motor skill!learning were also apraxic[ Apraxia is de_ned as an inability to perform learned skilled movements exclusive of de_cits due to hemi! paresis\ sensory loss\ movement disorders\ inattention\ or uncooperativeness ð6Ł[ In 0894\ Liepmann proposed that {movement formulae| contain the {timeÐspace form of the movement| or the {spaceÐtime sequences|[ He studied a patient with a callosal lesion and an inability to perform skilled movements with his left hand\ and concluded that the {movement formulae| were represented in the left hemisphere[ Heilman et al[ ð7Ł and Rothi\ Heilman and Watson ð02Ł have provided evidence that these time!space movement engrams are contained in or at least supported by representations in the left parietal lobe[ Although representations of learned skilled move! ments are thought to be stored in the dominant parietal lobe\ more anterior lesions in areas such as the premotor