Association between precuneus volume and autobiographical memory impairment in posterior cortical atrophy: Beyond the visual syndrome

Abstract

Posterior cortical atrophy is a neurodegenerative syndrome characterised by progressive disruption of visual and perceptual processing, associated with atrophy in the parieto-occipital cortex. Current diagnostic criteria describe relative sparing of episodic memory function, but recent findings suggest that anterograde memory is often impaired. Whether these deficits extend to remote memory has not been addressed. A large body of evidence suggests that the recollection of an autobiographical event from the remote past coincides with the successful retrieval of visual images. We hypothesised that the profound visual processing deficits in posterior cortical atrophy would result in impaired autobiographical memory retrieval. Fourteen posterior cortical atrophy patients, eighteen typical Alzheimer's disease patients and twenty-eight healthy controls completed the Autobiographical Interview. Autobiographical memory in posterior cortical atrophy was characterised by a striking loss of internal, episodic detail relative to controls and to same extent as typical Alzheimer's disease patients, in conjunction with an increase in external details tangential to the memory described. The memory narratives of posterior cortical atrophy patients showed a specific reduction in spatiotemporal and perceptual detail. Voxel-based morphometry analysis revealed atrophy of the parieto-occipital cortices in posterior cortical atrophy but relatively spared hippocampi bilaterally, compared with characteristic atrophy of the medial temporal lobes in typical Alzheimer's disease. Analysis of brain regions showing posterior cortical atrophy-specific atrophy revealed a correlation between perceptual details in autobiographical memory and grey matter density in the right precuneus. This study demonstrates remote memory impairment in posterior cortical atrophy despite relatively preserved medial temporal lobe structures. The results demonstrate, for the first time, profound autobiographical memory impairment in PCA and suggest that this is driven by the well-recognised deficits in higher-order visual processing. The findings are discussed in the context of posterior parietal contributions to imagery and memory, and the clinical implications of autobiographical memory impairment for diagnostic and management protocols in posterior cortical atrophy.

Keywords: Alzheimer's disease; Autobiographical memory; Posterior cortical atrophy; Visual imagery.

Fig. 1

Total scores for internal and external details, summed across all time period, for free and probed retrieval conditions. Error bars represent standard error of mean. (^⁎⁎p < 0.01; ^⁎⁎⁎p < 0.001; ^⁎⁎⁎⁎p < 0.0001). Abbreviations: PCA Posterior cortical atrophy; tAD typical Alzheimer's disease.

Fig. 2

The ratio of internal-to-total details produced by each group. Error bars represent the standard error of the mean. (^⁎⁎p < 0.01; ^⁎⁎⁎⁎p < 0.0001). Abbreviations: PCA Posterior cortical atrophy; tAD typical Alzheimer's disease.

Fig. 3

Profile of probed recall of (A) internal details; (B) external details; and (C) internal-to-total ratio across life epochs. Error bars represent standard error of mean. Abbreviations: PCA Posterior cortical atrophy; tAD typical Alzheimer's disease.

Fig. 4

Segmentation of probed recall of (A) internal details; and (B) external details into contextual categories. Error bars represent standard error of mean. (^⁎⁎p < 0.01; ^⁎⁎⁎p < 0.001; ^⁎⁎⁎⁎p < 0.0001). Abbreviations: PCA Posterior cortical atrophy; tAD typical Alzheimer's disease.

Fig. 5

Voxel based morphometry maps displaying reduced grey matter density in (A) = controls > Posterior cortical atrophy; (B) = controls > typical Alzheimer's disease and (C) = Posterior cortical atrophy < typical Alzheimer's disease. All comparisons were significant at p < 0.05 family-wise error corrected using threshold-free cluster enhancement method. All images in radiological display convention.

Fig. 6

Voxel-based morphometry maps displaying correlation between reduced grey matter density in right precuneus and perceptual details in Posterior cortical atrophy patients. Findings were significant at p < 0.05 family-wise error corrected using threshold-free cluster enhancement method, and the Posterior cortical atrophy < typical Alzhiemer's disease difference from the voxel-based morphometry analysis as a mask. Colour bar indicated t-score. Figure displayed at p < 0.005 uncorrected, for visualisation purposes. All images in radiological display convention.