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IC–P–061: Functional stress test for incipient dementia: A connectivity fMRI analysis of the effect of task load memory gradient in early Alzheimer's disease
Author(s) -
Valenzuela Michael,
Breakspear Michael
Publication year - 2006
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2006.05.2266
Subject(s) - psychology , dementia , functional magnetic resonance imaging , cognitive psychology , cognition , episodic memory , neuroscience , disease , medicine , pathology
Background: There is evidence that compensatory, atypical memoryrelated networks are implicated in early dementia as a response to deactivation of normative memory-dependent functional networks secondary to incipient disease. There is as yet, however, no data to determine whether recruitment of such networks is prognostic of subsequent clinical progression. Objective(s): To present preliminary data from a new functional memory paradigm which systematically increases task load whilst keeping visuospatial and perceptual input constant. Recent innovations in connectivity theory will be employed for their analysis. The long term objective is to determine whether an individual’s capacity for compensatory atypical memory network activation is related to incidence of clinical dementia. Methods: This study forms one arm of the LAPSES study, a populationbased longitudinal investigation of psychiatric, cognitive, neurological and neuroimaging characteristics of individuals with early memory complaints. Our paradigm is a 3T fMRI delayed match-to-sample task focused on episodic and spatial memory retrieval, in which the number of active visuospatial elements which define ‘easy,’ ‘moderate’ and ‘hard’ task difficulty conditions is matched across subjects in pretesting by application of 90%, 70% and 50% performance criteria, respectively. Whilst the active visuospatial elements vary across task difficulty, the overall number of elements is held constant by employing ‘filler’ stimuli, thus matching the perceptual load within subjects across the experiment. Connectivity tools employed to characterize functionally active memory-dependent networks will include Principal Component Analysis and wavelet analysis. Results: Preliminary functional connectivity data from 10 individuals with early memory complaints will be presented, with a focus on differential network activation when undergoing tasks of contrasting difficulty level. Conclusions: The significance of differential network activation with respect to task gradient will be discussed in relation to clinical neuroscience and prognosis of dementia.