Fine scale hippocampus morphology variation cross 552 healthy subjects from age 20 to 80

Abstract

The cerebral cortex varies over the course of a person's life span: at birth, the surface is smooth, before becoming more bumpy (deeper sulci and thicker gyri) in middle age, and thinner in senior years. In this work, a similar phenomenon was observed on the hippocampus. It was previously believed the fine-scale morphology of the hippocampus could only be extracted only with high field scanners (7T, 9.4T); however, recent studies show that regular 3T MR scanners can be sufficient for this purpose. This finding opens the door for the study of fine hippocampal morphometry for a large amount of clinical data. In particular, a characteristic bumpy and subtle feature on the inferior aspect of the hippocampus, which we refer to as hippocampal dentation, presents a dramatic degree of variability between individuals from very smooth to highly dentated. In this report, we propose a combined method joining deep learning and sub-pixel level set evolution to efficiently obtain fine-scale hippocampal segmentation on 552 healthy subjects. Through non-linear dentation extraction and fitting, we reveal that the bumpiness of the inferior surface of the human hippocampus has a clear temporal trend. It is bumpiest between 40 and 50 years old. This observation should be aligned with neurodevelopmental and aging stages.

Effects of Diazepam on Hippocampal Blood Flow in People at Clinical High Risk for Psychosis

“…Indeed, prior studies reported peak increases in rCBF in CHR-P individuals within the body/tail of the hippocampus 35 , a finding which was replicated in an independent cohort of CHR-P individuals 36 and in high schizotypy 48 . Additionally, in contrast to the previous study 37 , our study used rCBF which is more tightly coupled to neuronal activity than rCBV 65 , sampled in native vs. common space thereby circumventing normalisation errors 66 , and sampled with individual hippocampal/subfield masks thereby affording higher accuracy given the neuroanatomical diversity among individuals 67 .…”

Effects of diazepam on hippocampal blood flow in people at clinical high risk for psychosis

“…Indeed, prior ASL studies in CHR-P [ 40 , 41 ] and high schizotypy [ 53 ] individuals reported peak increases within the body/tail of the hippocampus. Additionally, our study used rCBF which is more tightly coupled to neuronal activity than rCBV [ 71 ], sampled in native vs. common space thereby circumventing normalization errors [ 72 ], and sampled with individual hippocampal/subfield masks thereby affording higher accuracy given the neuroanatomical diversity among individuals [ 73 ].…”