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Subregions in the medial temporal lobe (MTL) are affected early by Alzheimer’s disease (AD) pathology and subject to grey matter atrophy. Measuring the earliest AD-related atrophy in the hippocampus is challenging as region-of-interest (ROI) analyses of hippocampal subregional volumes collapse across voxels within anatomical subregions. PET imaging studies, however, report accumulation of tau pathology between anatomical subregions in the earliest disease stages (Berron et al., 2021) fitting reports from the neuropathological literature (Lace et al., 2019; Ravikumar et al., 2021). Thus, sensitive in vivo methods of point-wise structural measures are needed in order to detect the earliest hippocampal thinning in AD along the anterior-posterior as well as the medial-lateral hippocampal axis.MethodHere we analyzed data from 76 amyloid-beta negative (Ab-) cognitively normal (CN), 46 Ab+ CN individuals and 25 Ab+ patients with mild cognitive impairment (MCI) from the BioFINDER-2 study, who underwent 7 Tesla T2-weighted structural magnetic resonance imaging, tau positron emission tomography imaging (using 18F-RO-948) and cognitive assessments. First, we segmented hippocampal subfields and extrahippocampal subregions. Second, we calculated point-wise hippocampal thickness estimates (Diers et al.) of hippocampal subfields subiculum, cornu ammonis (CA)1, CA2 and CA3 on the level of the hippocampal body. Thirdly, we extracted local tau-PET SUVR from Area 35 (A35), entorhinal cortex and amygdala. Finally, we assessed relationships between hippocampal local thickness and tau accumulation as well as cognitive performance.ResultOur analyses revealed earliest hippocampal thinning associated with tau accumulation in an area spanning the boundary of subiculum and CA1 at the level of the anterior hippocampal body. Ab+ MCI patients showed more posterior thinning in comparison to Ab- CU participants. Median thickness in an ROI comprising vertices with A35 tau-related thinning (A35-TauThinning-ROI) was significantly lower in MCI Ab+ and tended to be lower in CU Ab+ compared to CU Ab-. Higher median thickness in the hippocampal A35-TauThinning-ROI, but not whole CA1 nor subiculum thickness, was associated with better 10-Word-Delayed-Recall and higher PACC scores.ConclusionOur results suggest that tau-related thinning of hippocampal subregions can be observed already in early disease stages. Tau-related point-wise thickness measures were more sensitive compared to volumetric measures of anatomical subregions.

Introduction:The Stop the Bleed campaign in the United States aims to teach bleeding control techniques, such as tourniquets, to the public. Educational consortium guidelines advocate using brief web- or video-based material. Another option is posters or flyers distributed at, for example, workplaces or public spaces.Aim:The aim of the current study was to evaluate the relative efficacy between a flyer and a video to teach tourniquet application skills to members of the public in Sweden.Methods:A total of 38 participants (27 male, 11 female) from the general public completed the study. Their ages ranged from 19 to 73 (M=32, SD=14). None had prior experience with tourniquet applications. One group (n=18) received tourniquet instructions on a flyer and one (n=20) received a 5-minute video instruction. Both groups completed pre- and post-questionnaires and a practical tourniquet application test.Results:Independent samples t-tests showed that the video-based instructions resulted in fewer application errors (M=1.40 out of 10, SD=1.19) compared to the flyer group (M=3.61, SD=2.40), t(36)=3.651, p=0.001, and higher post-task satisfaction (M=3.89 out of 5, SD=0.74 compared to M=3.39, SD=1.15). However, the flyer-group was faster (M=86.22 seconds, SD=27.28) compared to the video group (M=112.25, SD=42.22), t(36)=2.229, p=0.032.Discussion:Video instructions appear superior to flyers in terms of teaching correct tourniquet application to the general public. The longer total application time includes steps taken after bleeding control has been achieved (e.g. securing tourniquet straps and time notation), which may have contributed to the application time difference. The results support the educational guidelines that suggest video-based instructions for teaching basic tourniquet skills to laypeople are more effective.