Memory impairments associated with hippocampal versus parahippocampal ! gyrus atrophy ] an MR volumetry study in Alzheimer | s disease

Delayed memory impairments and medial temporal! lobe atrophy are considered to be cardinal features of Alzheimer|s disease "AD#[ The goal of the present magnetic resonance "MR# volumetry study was to investigate the relationship between both features[ We determined MR! derived estimates of hippocampal and parahippocampal volume in a sample of 16 AD patients and in a group of 15 healthy control subjects "NCs# of comparable age and education[ We examined the performance of the two groups on immediate and delayed recall trials of an auditoryÐverbal list! learning task "CVLT#\ a visual non! verbal memory task "Visual Reproduction of the WMS! R#\ and a screening procedure that provides an estimate of overall cognitive functioning "DRS#[ Volumes of the hippocampus and the parahippocampal gyrus were signi_cantly smaller in AD patients than in NCs[ AD patients were impaired in their overall level of cognitive functioning and showed memory de_cits under immediate and delayed recall conditions[ The association between medial temporal! lobe atrophy and cognitive impairments in AD was found to be highly speci_c] Hippo! campal volume correlated positively with delayed but not immediate recall of the verbalÐauditory list learning task[ In contrast\ parahippocampal gyrus volume\ speci_cally in the right hemisphere\ was positively related to delayed but not immediate recall of the non! verbal visual memory task[ In NCs\ there was a trend towards a negative association between hippocampal volumes and delayed verbal recall[ Our results suggest that hippocampal and parahippocampal gyrus atrophy in AD are related to distinct aspects of the patients| memory impairments[ Our _ndings have implications for current discussions regarding contributions of the hippocampus and the parahippocampal gyrus to memory in the intact human brain[ Þ 0887 Elsevier Science Ltd[ All rights reserved[ Key Words] anterograde amnesia^ hippocampus^ medial temporal lobes^ human^ episodic memory^ magnetic resonance[ Impairments in episodic memory\ i[e[ memory for events distinct in time and space\ and medial temporal! lobe atrophy are considered to be core features of Alzheimer|s disease "AD# and play a crucial role in its diagnosis ð09\ 17\ 65\ 72Ł[ A large body of neuropsychological and neurological research has focused on either one or the other but few studies have investigated both abnor! malities together in the same participants[ Recently\ how! %% Author to whom all correspondence should be addressed] Stefan Ko hler\ PhD\ who is now at the Montreal Neurological Institute Cognitive Neuroscience Unit\ McGill University\ 2790 University Street\ Montreal\ Quebec\ Canada H2A 1B3[ Fax] ¦¦ "403# 287! 7439[ 890 ever\ research has started to address the relationship between memory impairments and medial temporal! lobe atrophy in AD ð02\ 05\ 51\ 73Ł[ In the present study\ we aim to show how an investigation of this relationship may help not only to determine the neural basis of speci_c cognitive impairments in AD but also to contribute to understanding of the organization of memory in the