title: Divergent functional connectivity during attentional processing in Lewy body dementia and Alzheimer's disease.
abstract: Attention and executive dysfunction are features of Lewy body dementia (LBD) but their neuroanatomical basis is poorly understood. To investigate underlying dysfunctional attention-executive network (EXEC) interactions, we examined functional connectivity (FC) in 30 patients with LBD, 20 patients with Alzheimer's disease (AD), and 21 healthy controls during an event-related functional magnetic resonance imaging (fMRI) experiment. Participants performed a modified Attention Network Test (ANT), where they were instructed to press a button in response to the majority direction of arrows, which were either all pointing in the same direction or with one pointing in the opposite direction. Network activations during both target conditions and a baseline condition (no target) were derived by (ICA) Independent Component Analysis, and interactions between these networks were examined using the beta series correlations approach. Our study revealed that FC of ventral and dorsal attention networks DAN was reduced in LBD during all conditions, although most prominently during incongruent trials. These alterations in connectivity might be driven by a failure of engagement of ventral attention networks, and consequent over-reliance on the DAN. In contrast, when comparing AD patients with the other groups, we found hyperconnectivity between the posterior part of the default mode network (DMN) and the DAN in all conditions, particularly during incongruent trials. This might be attributable to either a compensatory effect to overcome DMN dysfunction, or be arising as a result of a disturbed transition of the DMN from rest to task. Our results demonstrate that dementia syndromes can be characterized both by hyper- and hypoconnectivity of distinct brain networks, depending on the interplay between task demand and available cognitive resources. However these are dependent upon the underlying pathology, which needs to be taken into account when developing specific cognitive therapies for LBD as compared to Alzheimer's.
authors.affiliation: Institute of Neuroscience, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK; Department of Neurology and Neurophysiology, Medical School Hannover, Hannover, Germany; University Hospital Bonn, Clinic for Neurology, Bonn, Germany. Electronic address: xkobeleva@posteo.de.
authors.forename: Xenia
authors.initials: X
authors.lastname: Kobeleva
authors.affiliation: Institute of Neuroscience, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK. Electronic address: michael.firbank@ncl.ac.uk.
authors.forename: Michael
authors.initials: M
authors.lastname: Firbank
authors.affiliation: Institute of Neuroscience, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK.
authors.forename: Luis
authors.initials: L
authors.lastname: Peraza
authors.affiliation: Institute of Neuroscience, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Gallagher
authors.affiliation: Institute of Neuroscience, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Thomas
authors.affiliation: Institute of Neuroscience, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK. Electronic address: david.burn@ncl.ac.uk.
authors.forename: David J
authors.initials: DJ
authors.lastname: Burn
authors.affiliation: Department of Psychiatry, University of Cambridge, Addenbrooke's Hospital, UK. Electronic address: john.obrien@medschl.cam.ac.uk.
authors.forename: John
authors.initials: J
authors.lastname: O'Brien
authors.affiliation: Institute of Neuroscience, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK. Electronic address: john-paul.taylor@ncl.ac.uk.
authors.forename: John-Paul
authors.initials: JP
authors.lastname: Taylor
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000503:physiopathology* / Q000523:psychology; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D020961:Lewy Body Disease / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology; D009434:Neural Pathways / Q000503:physiopathology
keywords: Attention networks; Default mode network; Dementia with Lewy bodies; Executive function; Functional magnetic resonance imaging (fMRI); Hyperconnectivity; Hypoconnectivity; Parkinson's disease dementia