Grey and white matter correlates of recent and remote autobiographical memory retrieval:Insights from the dementias

The capacity to remember self-referential past events relies on the integrity of a distributed neural network. Controversy exists, however, regarding the involvement of specific brain structures for the retrieval of recently experienced versus more distant events. Here, we explored how characteristic patterns of atrophy in neurodegenerative disorders differentially disrupt remote versus recent autobiographical memory. Eleven behavioural-variant frontotemporal dementia, 10 semantic dementia, 15 Alzheimer's disease patients and 14 healthy older Controls completed the Autobiographical Interview. All patient groups displayed significant remote memory impairments relative to Controls. Similarly, recent period retrieval was significantly compromised in behavioural-variant frontotemporal dementia and Alzheimer's disease, yet semantic dementia patients scored in line with Controls. Voxel-based morphometry and diffusion tensor imaging analyses, for all participants combined, were conducted to investigate grey and white matter correlates of remote and recent autobiographical memory retrieval. Neural correlates common to both recent and remote time periods were identified, including the hippocampus, medial prefrontal, and frontopolar cortices, and the forceps minor and left hippocampal portion of the cingulum bundle. Regions exclusively implicated in each time period were also identified. The integrity of the anterior temporal cortices was related to the retrieval of remote memories, whereas the posterior cingulate cortex emerged as a structure significantly associated with recent autobiographical memory retrieval. This study represents the first investigation of the grey and white matter correlates of remote and recent autobiographical memory retrieval in neurodegenerative disorders. Our findings demonstrate the importance of core brain structures, including the medial prefrontal cortex and hippocampus, irrespective of time period, and point towards the contribution of discrete regions in mediating successful retrieval of distant versus recently experienced events

Migration of Self-Introduced Acupuncture Needle into the Brainstem

Acupuncture-related injuries to the central nervous system are a rare but well-documented occurrence. This report describes the case of a self-introduced acupuncture needle migrating into the brainstem following an initial failed attempt at surgical extraction. The patient displayed no neurological deficits, and the needle was eventually successfully removed under direct vision intraoperatively. We discuss the role of various imaging modalities in pre- and post-operative assessment of penetrating foreign bodies in the brainstem. We also discuss the options available for the management of such foreign bodies, including possible approaches for operative intervention, and the risks involved with both surgical and conservative management

Relationship between fractional anisotropy (FA) values in white matter tracts of interest and recent memory.

<p>All participants included in the analyses (n = 49). Age is included as a covariate in the analyses. Plotted data depict a positive association between fractional anisotropy values and memory performance, with the magnitude of this relationship calculated using Pearson's R correlations (r).</p

Total internal (episodic) details retrieved across remote and recent periods on the Autobiographical Interview.

<p>Error bars represent the standard error of the mean. * <i>p</i><.05; ** <i>p</i> = .001; n/s = non-significant. Group differences refer to contrasts between patient groups and Controls. No significant differences were evident between the patient groups for remote or recent retrieval.</p

Tract-based spatial statistics results showing regions of white matter integrity decrease in each of the patient groups compared with Controls^a

a<p>Diffusion tensor imaging data not available for 1 bvFTD patient. Age is included as a covariate in all contrasts. All clusters reported using threshold-free cluster enhancement method and corrected for Family-Wise Error (FWE) at <i>p</i><.05. BvFTD = behavioural-variant frontotemporal dementia; SD = semantic dementia; AD = Alzheimer's disease; L = Left; B = Bilateral; MNI = Montreal Neurological Institute.</p><p>Tract-based spatial statistics results showing regions of white matter integrity decrease in each of the patient groups compared with Controls^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113081#nt109" target="_blank">a</a>}</p

Voxel-based morphometry results showing regions of grey matter intensity that covary with remote and recent autobiographical memory (ABM) retrieval in all participants combined (n = 50).

<p>All clusters reported using voxel-wise contrasts and uncorrected at <i>p</i><.001. Age is included as a covariate in all contrasts. All clusters reported at <i>t</i>>3.80 with a cluster threshold of 300 contiguous voxels. L = Left; R = Right; B = Bilateral; MNI = Montreal Neurological Institute.</p><p>Voxel-based morphometry results showing regions of grey matter intensity that covary with remote and recent autobiographical memory (ABM) retrieval in all participants combined (n = 50).</p

Overlap and exclusive masking results showing brain regions in which grey matter intensity correlates significantly with autobiographical memory retrieval.

<p>(A) Overlap in regions irrespective of time period; (B) Regions exclusively implicated in remote memory; (C) Regions exclusively implicated in recent memory. Coloured voxels show regions that were significant in the voxel-based morphometry covariate analyses with <i>p</i><.001 uncorrected with a cluster threshold of 300 contiguous voxels. All clusters reported <i>t</i>>3.80 and depict a positive association between grey matter integrity and memory performance. Clusters are overlaid on the Montreal Neurological Institute standard brain. Age is included as a covariate in the analyses.</p

Demographic and clinical characteristics of study cohort.

<p>Maximum score for each test in brackets where applicable.</p><p>*<i>p</i><.05;</p><p>**<i>p</i><.005;</p><p>***<i>p</i><.0001;</p><p>n/s = not significant; n/a = not applicable; bvFTD = behavioural-variant frontotemporal dementia; SD = semantic dementia; AD = Alzheimer's disease; FRS = Frontotemporal Dementia Functional Rating Scale; ACE-R = Addenbrooke's Cognitive Examination Revised; RAVLT = Rey Auditory Verbal Learning Test; RCF = Rey Complex Figure. FRS data not available for 1 AD patient; Trails data available for 9 AD, 10 bvFTD patients, and 13 Controls; Naming data available for 13 Controls; Comprehension data available for 9 bvFTD patients and 13 Controls; RAVLT not administered in SD patients due to the high verbal loading of the task; RCF recall data available for 10 bvFTD and 9 SD patients; Letter fluency data available for 14 AD patients.</p><p>Demographic and clinical characteristics of study cohort.</p

Regions of significant grey matter intensity decrease in patient groups versus Controls.

<p>(A) BvFTD (MNI coordinates: <i>x</i> = −14, <i>y</i> = 10, <i>z</i> = −22), (B) SD (<i>x</i> = −42, <i>y</i> = −8, <i>z</i> = −38), and (C) AD (<i>x</i> = 14, <i>y</i> = −20, <i>z</i> = −24). Coloured voxels show regions that were significant in the voxel-based morphometry analyses at <i>p</i><.001 corrected for Family-Wise Error using the threshold free cluster enhancement method (tfce). Clusters are overlaid on the Montreal Neurological Institute standard brain. Age is included as a covariate in the analyses.</p

Voxel-based morphometry results showing regions of significant grey matter intensity decrease for contrasts across patient samples (bvFTD, SD, AD) in comparison with Controls.

<p>All clusters reported using threshold free cluster enhancement technique (tfce) and corrected for Family-Wise Error (FWE) at <i>p</i><.001. For brevity only those clusters above 1,000 contiguous voxels are reported here. BvFTD = behavioural-variant frontotemporal dementia; SD = semantic dementia; AD = Alzheimer's disease; L = Left; R = Right; B = Bilateral; MNI = Montreal Neurological Institute.</p><p>Voxel-based morphometry results showing regions of significant grey matter intensity decrease for contrasts across patient samples (bvFTD, SD, AD) in comparison with Controls.</p