fMRI congruous word repetition effects reflect memory variability in normal elderly - PubMed (original) (raw)

Comparative Study

fMRI congruous word repetition effects reflect memory variability in normal elderly

John M Olichney et al. Neurobiol Aging. 2010 Nov.

Abstract

Neural circuits mediating repetition effect for semantically congruous words on functional MRI were investigated in seventeen normal elderly (mean age=70). Participants determined if written words were semantically congruent (50% probability) with spoken statements. Subsequent cued-recall revealed robust explicit memory only for congruous items (83% versus 8% for incongruous). Event-related BOLD responses to New>Old congruous words were found in the left>right cingulate and fusiform gyri, left parahippocampal cortex, middle and inferior frontal gyri (IFG). A group with above-median subsequent recall had markedly more widespread BOLD responses than a Low-Recall subgroup, with larger responses in the left medial temporal lobe (LMTL), IFG, and bilateral cingulate gyri. The magnitude of LMTL activation (New-Old) correlated with subsequent cued-recall, while the spatial extent of LMTL activation (New>Old) correlated with recall and recognition. Both magnitude and spatial extent of left fusiform activation correlated with subsequent recall/recognition. A neural circuit of left-hemisphere brain regions, many identified as P600 generators by invasive electrophysiological studies, was activated by New>Old congruous words, likely mediating successful verbal encoding.

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Figures

Fig. 1

Maps of the congruous repetition effect on BOLD response and estimates of the hemodynamic response function (HRF) shown for New and Old congruous words. Clusters of voxels with significant New > Old BOLD (‘hot’ colors) and Old > New BOLD (‘cold’ colors) effects at 3- and 4-TR timepoints are shown (see key for color scheme) superimposed on the group-averaged (n = 17) anatomical image. Slices are labeled with Talairach _x_-coordinates. HRF estimates for selected clusters are shown above; error bars indicate standard error across subjects. *p < 0.05; PHG = parahippocampal gyrus, MTG = middle temporal gyri, STG = superior temporal gyri.

Fig. 2

Maps of the congruous repetition effect on BOLD response for memory-performance subgroups. (A) High Recall (n = 8), and (B) Low Recall (n = 8), superimposed over their respective group-averaged anatomical images. New > Old and Old > New BOLD effects are colored as in Fig. 1 (see key and legend). Slices are labeled with Talairach _x_-coordinates.

Fig. 3

HRF estimates for High- and Low-Recall subgroups selected clusters are shown separately. The chosen clusters showed a significant New > Old BOLD effect over the entire subject group (see Fig. 1). Cluster locations are indicated on representative coronal and sagittal slices (_y_- and _x_-coordinates given) in (A). HRF estimates are shown for (B) High-Recall (n = 8) and (C) Low-Recall (n = 8) subgroups; error bars represent standard error over subjects. *p < 0.05; ROI = region of interest; BA = Brodmann area; PHG = parahippocampal gyrus.

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fMRI congruous word repetition effects reflect memory variability in normal elderly - PubMed (original) (raw)