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P2–384: Serial MRI measurement of temporal lobe and global atrophy progression in semantic dementia
Author(s) -
Rohrer Jonathan D.,
Omar Rohani,
Anderson Valerie M.,
Price Shona L.,
Warren Jason D.,
Fox Nick C.
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.2006.05.1224
Subject(s) - atrophy , temporal lobe , dementia , semantic dementia , medicine , cardiology , frontotemporal lobar degeneration , lobe , magnetic resonance imaging , psychology , nuclear medicine , frontotemporal dementia , pathology , radiology , disease , psychiatry , epilepsy
novel information are impaired early in Alzheimer’s disease (AD), but less is known about the neural responses to highly familiarized information. While fMRI studies have reported decreased medial temporal lobe activation in AD for novel versus repeated contrasts compared to older controls, it remains unclear whether AD patients demonstrate an intact habituation to repeated stimuli. Our initial fMRI investigation of 10 older controls (OC) and 10 AD patients revealed evidence of increased hippocampal responses to repeated stimuli in AD. Objective(s): To investigate the relationship between level of cognitive impairment and neural responses to repeated stimuli in a larger cohort of individuals across the continuum from normal aging to mild cognitive impairment (MCI) and AD. Methods: Twenty-nine OC (CDR 0.0), 38 subjects with MCI (defined here as CDR 0.5) and 15 mild AD patients (CDR 1.0) were scanned on a face-name associative encoding paradigm. The fMRI session consisted of six runs with alternating blocks of Novel and Repeated face-name pairs and visual Fixation. For the Repeated blocks, one male and one female pair was presented 42 times over the experiment. We compared responses to Repeated versus Fixation (RvF). Data were analyzed using FSL/FEAT5.43. Results: AD patients demonstrated increased right (30,-24,-14; z 2.56, p 0.005) and left (-34,22,-16; z 3.10, p 0.001) hippocampal responses in the RvF contrast compared to OC, as well as increased right (30,-16,-18; z 3.25, p 0.001) and left (-32,-22,-16; z 3.20, p 0.001) hippocampal activation when compared to MCI. No significant MTL differences were found between the OC and MCI groups. Within MCI subjects, however, we found a correlation between severity of impairment (assessed by CDR Sum-of-Boxes) and degree of RvF activation, such that greater impairment was associated with greater left hippocampal (-34,-20,-20; z 2.80, p 0.003) activation to Repeated stimuli. Conclusions: These findings suggest that hippocampal responses to repeated stimuli are distinctly altered in AD and also in more impaired MCI subjects. Failure of habituation to repeated stimulus exposure may prove to be a sensitive marker of hippocampal dysfunction due to AD pathology. Research supported by NINDS K23-NS02189; NIA PO1AG04953; NIA P50-AG00513421; Academy of Finland.