title: Shared neural correlates of limb apraxia in early stages of Alzheimer's dementia and behavioural variant frontotemporal dementia.
abstract: Limb apraxia denotes a cognitive impairment of gesture production. Lesion studies in patients with stroke point towards distinct neural processing streams for limb imitation and object-pantomime within left parietal and temporal cortex, respectively. Despite its frequent occurrence as an early symptom in both, Alzheimer's dementia (AD) and behavioural variant frontotemporal dementia (bvFTD), neural correlates of limb apraxia within these patient groups remain unexplored. Using voxel-based morphometry and multiple regression models, associations between limb apraxia and gray matter (GM) volume were investigated in 36 dementia patients (18 AD, 18 bvFTD) in early disease stages. Both dementia subtypes showed a comparable degree of limb apraxia. Although the patient groups showed distinct atrophy patterns with significantly more severe frontal GM loss in bvFTD, we found similar neural correlates of limb apraxia within posterior brain regions for both dementia subtypes: limb-imitation was associated with bilateral atrophy of superior, inferior and medial parietal cortex. Object-pantomime showed associations with GM volume in right middle temporal and angular gyrus. Our results argue for shared neural correlates of limb apraxia in AD and bvFTD and validate the syndrome as an important neuropsychological feature across different etiologies. Moreover, our results are compatible with neural models derived from patients with stroke, suggesting partly distinct neural representations of imitation and pantomime. Compared to patients with stroke however, AD and bvFTD showed more bilateral or even right lateralized neural representations of limb apraxia, proposing a greater influence of visuospatial impairments and spatial body representation deficits on praxis performance.
authors.affiliation: Department of Neurology, University Hospital Münster, Germany. Electronic address: a.johnen@uni-muenster.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Johnen
authors.affiliation: Department of Neurology, University Hospital Münster, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Brandstetter
authors.affiliation: Division of Forensic Psychiatry, Department of Psychiatry, Psychotherapy and Preventive Medicine, LWL-University Hospital Bochum, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kärgel
authors.affiliation: Department of Neurology, University Hospital Münster, Germany.
authors.forename: Heinz
authors.initials: H
authors.lastname: Wiendl
authors.affiliation: Department of Neurology, University Hospital Münster, Germany.
authors.forename: Hubertus
authors.initials: H
authors.lastname: Lohmann
authors.affiliation: Department of Neurology, University Hospital Münster, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Duning
mesh_terms: D000328:Adult; D000368:Aged; D000544:Alzheimer Disease / Q000150:complications* / Q000175:diagnosis / Q000473:pathology; D001259:Ataxia / Q000209:etiology*; D001284:Atrophy; D001519:Behavior; D001931:Brain Mapping; D042241:Early Diagnosis; D005260:Female; D057180:Frontotemporal Dementia / Q000150:complications* / Q000175:diagnosis / Q000473:pathology / Q000523:psychology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D020521:Stroke / Q000150:complications
keywords: Alzheimer's dementia (AD); Behavioural variant frontotemporal dementia (bvFTD); Limb apraxia; Voxel-based morphometry (VBM)