Hippocampal dentation: Structural variation and its association with episodic memory in healthy adults

Beattie, Julia Fleming; Martin, Roy C.; Kana, Rajesh K.; Deshpande, Hrishikesh; Lee, Seong-Taek; Curé, Joel K.; Hoef, Lawrence Ver

doi:10.1016/j.neuropsychologia.2017.04.036

Cited by 24 publications

(48 citation statements)

References 53 publications

(60 reference statements)

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“…Participants identified themselves as men (n=29), women (n=36), and other (n=1). G*Power 3.1 software was used to calculate a sensitivity power analysis: given our sample of n = 66, we had a power of 0.997 to observe a correlation of r = 0.51 (the strength of the relationship between dentations and episodic memory by Beattie et al, 2017) using a confirmatory one-tailed test. We also had an 80% chance of confirming any medium-sized effect of r = 0.30 or larger.…”

Section: Participantsmentioning

confidence: 99%

“…Direct labeling performance by raters was evaluated using total quantity of dentations, and was found to be very high, ICC = 0.924. Holistic assessment performance by raters was assessed using overall scores for each participant (taken as a sum across hemispheres, following Beattie et al, 2017) and was also very high, ICC = 0.921.…”

Section: Analysis Of Brain Datamentioning

confidence: 99%

“…To date, dentations have been described as falling in both the CA1 and subicular subfields (Beattie et al, 2017;Chang et al, 2018). A novel contribution of our analysis, therefore, was to use our high-resolution hippocampal images to delineate subfields and evaluate their positions relative to these (and other) subfields.…”

Section: Relationship Of Dentations To Ca1mentioning

confidence: 99%

“…Qualitative work of this kind has offered a helpful overall picture of dentations, yet the typical distribution of basic descriptive features in the population, such as their size and positioning, have, remarkably, gone entirely undocumented so far in the hippocampal literature. In fact, to our knowledge, there are only two group studies that have reported any data relevant to hippocampal dentations: one involved trained raters conducting holistic assessments in an n = 22 sample spanning a large age range of 20 to 57 years (Beattie et al, 2017). Another employed a novel PCA-based algorithm for feature extraction to estimate dentations from the mid-20's to 80's (Cai, Yu, & Zhang, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…In light of the known importance of the hippocampus for episodic memory (Moscovitch, Cabeza, Winocur, & Nadel, 2016) including known contributions of the CA1 subfield and subicular region to episodic memory function (Bartsch, Dohring, Rohr, Jansen, & Deuschl, 2011;Farovik, Dupont, & Eichenbaum, 2010), initial exploration of possible functional relevance for episodic memory has focused on that topic. In particular, (Beattie et al, 2017) identified such links between dentations and various measures of episodic memory to assess this putative functional role. As dentations best predicted recognition memory in their study, we incorporated recognition memory measures into our study, as well, complementing these with source memory measures of episodic memory.…”

Section: Introductionmentioning

confidence: 99%

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Structural variation in hippocampal dentations among healthy young adults

Hove¹,

Poppenk

2020

Preprint

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Little is known about hippocampus dentations -or "bumps" on the inferior surface of the hippocampus -and whether they hold functional significance. Empirical work on these features is beginning to emerge, but no study has yet been conducted in which their spatial positions are demarcated, and their putative role in individual differences in memory is based on a single small study. We gathered ultra-high resolution isotropic MTL scans from young-adult sample and performed such measurements. On the long axis, we found smaller and denser dentations moving towards the hippocampus' posterior extent. Although other reports have distinguished the functional characteristics of anterior and posterior hippocampal dentations, we found hardly any were actually localized in the hippocampal head, with half of participants featuring no anterior dentations at all. We also observed more numerous dentations in the left hemisphere than right, and found this asymmetry tracked right-hand dominance. All dentations lay specifically within in the CA1 subfield, which was thicker at dentations -protruding below standard lower boundary of the hippocampus -as well as larger in participants with more dentations, suggesting dentations reflect CA1 growth rather than mere folding. Finally, we observed an association between dentations and visual source memory, but not recognition memory. The current report is the first to characterize the spatial properties of this intriguing neuroanatomical feature, which requires the direct spatial labeling of dentations. Further to better characterizing this intriguing neuroanatomical feature, we provide some confirmatory evidence for a link to episodic memory, although we found evidence for this link to be less overwhelming than initially reported.

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Section: Participantsmentioning

confidence: 99%

Section: Analysis Of Brain Datamentioning

confidence: 99%

Section: Relationship Of Dentations To Ca1mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural variation in hippocampal dentations among healthy young adults

Hove¹,

Poppenk

2020

Preprint

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Development of an objective method to quantify hippocampal dentation

Ramaniharan

Parpura

Zhang

et al. 2023

Human Brain Mapping

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Hippocampal dentation (HD) refers to a series of ridges (dentes) seen on the inferior aspect of the hippocampus. The degree of HD varies dramatically across healthy individuals, and hippocampal pathology may result in loss of HD. Existing studies show associations between HD and memory performance in healthy adults as well as temporal lobe epilepsy (TLE) patients. However, until now studies relied on visual assessment of HD as no objective methods to quantify HD have been described. In this work, we describe a method to objectively quantify HD by transforming the characteristic 3D surface morphology of HD into a simplified 2D plot for which area under the curve (AUC) was calculated. This was applied to T1w scans of 59 TLE subjects, each with one epileptic hippocampus and one normal appearing hippocampus. Results showed that AUC significantly correlated with the number of dentes based on visual inspection ( p < .05) and correctly sorted a set of hippocampi from least to most prominently dentated. Intra‐ and inter‐rater reliability was nearly perfect (ICC ≥ 0.99). AUC values were significantly lower in epileptic hippocampi compared to contralateral hippocampi ( p = .00019), consistent with previously published findings. In the left TLE group, the AUC values from the contralateral hippocampi showed a positive trend ( p = .07) with verbal memory acquisition scores but was not statistically significant. The proposed approach is the first objective, quantitative measurement of dentation described in the literature. The AUC values numerically capture the complex surface contour information of HD and will enable future study of this interesting morphologic feature.

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Uncal apex position varies with normal aging

Poppenk

Initiative²

2020

Hippocampus

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The uncal apex is an anatomical landmark frequently used for segmenting the hippocampus into its anterior and posterior segments, a necessary step for computing many measurements of its long axis. It functions well, as it is both local to the hippocampus and easy to identify. However, in spite of widespread use and definition in the EADC‐ADNI Harmonized Hippocampal Protocol (HarP), how the uncal apex is influenced by gross hippocampal changes during normal aging has not been established, nor has the possible impact on measures of anterior hippocampus (aHPC) and posterior hippocampus (pHPC) volume. Here I drew upon three large data sets to describe and confirm these relationships, investigating them in one large data set and replicating my findings in the two others, evaluating a total of 4,434 hippocampi. I found the uncal apex fell in an increasingly more anterior position with increasing age. This age‐related retraction of the uncus began after age 36, with the sharpest effects arising after age 60. This phenomenon exaggerates age‐related aHPC volume decreases while simultaneously underestimating age‐related pHPC volume decreases, a pattern I confirmed by juxtaposing uncal apex and MNI space‐based landmarking. A hippocampally based reference frame was also rendered unstable by age‐related shifts in the posterior extent of the hippocampus. Both the uncal apex and hippocampal reference frame should therefore be used with caution in aging research, or in research involving other demographic or disease factors known to evoke gross changes in the hippocampus. Instead, MNI coordinate‐based heuristics may be appropriate for segmenting the hippocampus in study designs involving such factors. Apex‐based segmentation is still attractive, however, in study designs where advanced age and atrophy are not used as regressors, including investigations into long‐axis effects in healthy young adults. Progress toward localizing functional divisions within the hippocampus is needed to identify best practices for the field.

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Hippocampal dentation: Structural variation and its association with episodic memory in healthy adults

Cited by 24 publications

References 53 publications

Structural variation in hippocampal dentations among healthy young adults

Structural variation in hippocampal dentations among healthy young adults

Development of an objective method to quantify hippocampal dentation

Uncal apex position varies with normal aging

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