Brain Correlates of Performance in a Free/Cued Recall Task With Semantic Encoding in Alzheimer Disease

Abstract

Summary:The goal of this study was to explore in patients with Alzheimer's disease (AD) the brain correlates of free and cued recall performance using an adaptation of the procedure developed by Grober and Buschke (1987). This procedure, which ensures semantic processing and coordinates encoding and retrieval, has been shown to be very sensitive to an early diagnosis of AD. Statistical parametric mapping (SPM 99) was used to establish clinicometabolic correlations between performance at free and cued verbal recall and resting brain metabolism in 31 patients with AD. Results showed that patient's score on free recall correlated with metabolic activity in right frontal regions (BA 10 and BA 45), suggesting that performance reflected a strategic retrieval attempt. Poor retrieval performance was tentatively attributed to a loss of functional correlation between frontal and medial temporal regions in patients with AD compared with elderly controls. Performance on cued recall was correlated to residual metabolic activity in bilateral parahippocampal regions (BA 36), suggesting that performance reflected retrieval of semantic associations, without recollection in AD. In conclusion, this study demonstrates that the diagnostic sensitivity for Alzheimer's disease of the cued recall performance in the Grober and Buschke procedure (1987) depends on the activity of parahippocampal regions, one of the earliest targets of the disease. Moreover, the results suggest that the poor performance of patients with AD during free and cued recall is related to a decreased connectivity between parahippocampal regions and frontal areas.

Neuroanatomical Comparison of the “Word” and “Picture” Versions of the Free and Cued Selective Reminding Test in Alzheimer’s Disease

“…A similar result has been reported by Lekeu et al in AD patients [17] and has been recently reported by Philippi et al in patients with mild cognitive impairment using the Word version of the FCSRT [20]. It has been suggested that this association is related to the implication of search activity and strategic retrieval of the information during free recall [20].…”

“…This interference task was followed by a free recall trial for all 16 items, and a cued recall trial for those items not retrieved at free recall, and for which the same semantic cues as those used during encoding were verbally given. The first and second recall trials were followed by 20 seconds of counting backwards [17]. Overall, both versions of the FCSRT yield several memory measurements, namely the immediate recall (IR) (for the study phase), free recall (FR), cued recall, total recall (TR) scores (maximum score = 48) and sensitivity to cueing index (for the memory phase).…”

“…The latter explanation could suggest involvement of different cognitive processes and therefore different neural networks supporting performance on each version of the test. PET studies have reported an association between free recall of the Word version of the FCSRT and right frontal perfusion, with cued recall associated instead with parahippocampal metabolism [17]. Furthermore, structural neuroimaging studies with the FCSRT Word version have exhibited an association between free recall and hippocampal volume measured with MRI-based volumetry in AD and MCI patients [18][19][20].…”

Two aspects of impaired consciousness in Alzheimer's disease

“…Consistent with the second interpretation, a number of neuropathological, neuropsychological, and neuroimaging studies have suggested that AD can be characterized as a disconnection syndrome (Azari et al, 1992;Leuchter et al, 1992;Morris, 1994;Collette et al, 2002;Lekeu et al, 2003a). Thus, loss of synaptic contacts in associative cortices and limbic structures would interrupt long connecting pathways in AD (Hyman et al, 1984;Pearson et al, 1985).…”

Diffusion Tensor Tractography Reveals Abnormal Topological Organization in Structural Cortical Networks in Alzheimer's Disease

“…Notably, decreased efficiency in the frontal regions was mainly located in the right hemisphere. Previous studies have shown that the decreased activity of right prefrontal regions are associated with the worse memory performance in AD patients (Grady et al, 2001;Lekeu et al, 2003), implying that the structural decline in the right hemisphere likely links with the memory loss. Together, our results suggest that the WM degenerated alterations in these frontal regions might influence information transmission and functional integration for AD patients.…”