Hippocampus Shape Affects How Well Individuals Perform in Memory Tests

Size may not matter as much as we thought.

New work by the Douglas Mental Health University Institute (CIUSSS de l’Ouest-de-l’île-de-MontréalI) computational neuroscientist Mallar Chakravarty, PhD, and in collaboration with researchers at the Centre for Addiction and Mental Health (CAMH) challenges in a thrilling way the long-held belief that a larger hippocampus is directly linked to improved memory function.

The size of the hippocampus, an important structure in the brain’s memory circuit, is typically measured as one method to determine the integrity of the memory circuit. However, the shape of this structure is often neglected. Using a novel algorithmic technique to map the hippocampus, Dr. Chakravarty, Assistant Professor, Department of Psychiatry at McGill University, is shedding new light on its shape. The algorithm developed by the team identifies individuals with differently shaped hippocampi. In fact, the study has found that while stereotypic shapes exist for this structure, individuals with a broader hippocampus tend to perform better on various tests that assess memory. In the study, these shape differences were better predictors of memory function than the bulk volume of the hippocampus.

“This exciting new finding may help us improve our understanding of how to preserve the memory circuit and its function. This work shows the value of multidisciplinary research, as it required the close collaboration of engineers, computer scientists and psychiatrists to complete this work,” says Dr. Chakravarty, senior author on the study. Chakravarty’s student Julie Winterburn notably worked on this project, and was co-first author with Dr. Aristotle Voineskos of CAMH’s Campbell Family Mental Health Research Institute. in Toronto.

This image is Camillo Golgi's drawing of a hippocampus stained using the silver nitrate method.
The study has found that while stereotypic shapes exist for this structure, individuals with a broader hippocampus tend to perform better on various tests that assess memory. The image is for illustrative purposes only. Image credit: Camillo Golgi.

Why it matters

Improving our understanding of the geometry of different structures may have significant implications in understanding neuropsychiatric disorders, such as Alzheimer’s disease, where memory function is significantly compromised. Given the aging demographics of Quebec and Canada, uncovering clues on how to improve memory function, one of the main impairments reported (even in healthy aging), will be critical to relieving the overwhelming burden our health care system currently faces. The results of this recent research are published in Human Brain Mapping, a peer-reviewed scientific journal.

[divider]About this neuroscience and memory research[/divider]

Funding: Dr. Chakravarty’s work is funded by the Canadian Institutes for Health Research, Natural Sciences and Engineering Research Council, Weston Brain Institute, Alzheimer’s Society, and the Michael J. Fox Foundation for Parkinson’s Research.

Source: Florence Meney – Douglas Mental Health Institute
Image Credit: The image is credited to Camillo Golgi and is in the public domain
Original Research: Abstract for “Hippocampal (subfield) volume and shape in relation to cognitive performance across the adult lifespan” by Aristotle N. Voineskos, Julie L. Winterburn, Daniel Felsky, Jon Pipitone, Tarek K. Rajji, Benoit H. Mulsant and M. Mallar Chakravarty in Human Brain Mapping. Published online May 9 2015 doi:10.1002/hbm.22825


Abstract

Hippocampal (subfield) volume and shape in relation to cognitive performance across the adult lifespan

Newer approaches to characterizing hippocampal morphology can provide novel insights regarding cognitive function across the lifespan. We comprehensively assessed the relationships among age, hippocampal morphology, and hippocampal-dependent cognitive function in 137 healthy individuals across the adult lifespan (18–86 years of age). They underwent MRI, cognitive assessments and genotyping for Apolipoprotein E status. We measured hippocampal subfield volumes using a new multiatlas segmentation tool (MAGeT-Brain) and assessed vertex-wise (inward and outward displacements) and global surface-based descriptions of hippocampus morphology. We examined the effects of age on hippocampal morphology, as well as the relationship among age, hippocampal morphology, and episodic and working memory performance. Age and volume were modestly correlated across hippocampal subfields. Significant patterns of inward and outward displacement in hippocampal head and tail were associated with age. The first principal shape component of the left hippocampus, characterized by a lengthening of the antero-posterior axis was prominently associated with working memory performance across the adult lifespan. In contrast, no significant relationships were found among subfield volumes and cognitive performance. Our findings demonstrate that hippocampal shape plays a unique and important role in hippocampal-dependent cognitive aging across the adult lifespan, meriting consideration as a biomarker in strategies targeting the delay of cognitive aging.

“Hippocampal (subfield) volume and shape in relation to cognitive performance across the adult lifespan” by Aristotle N. Voineskos, Julie L. Winterburn, Daniel Felsky, Jon Pipitone, Tarek K. Rajji, Benoit H. Mulsant and M. Mallar Chakravarty in Human Brain Mapping. Published online May 9 2015 doi:10.1002/hbm.22825

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