Andrew Alexander, PhD – Slide of the Week

Andrew Alexander, PhD - Slide of the Week

Title: Functional and Structural Connectivity of the Hippocampus

Legend: Functional and structural hippocampal networks in pediatric cohort. A,B: Network of brain regions with significant functional connectivity to the hippocampus. C: Left hippocampal structural connectome. Abbreviations: parahippocampal gyrus (PG), thalamus (Thal), medial occipito-temporal and lingual sulcus (collateral sulcus, CS), amygdala (Amyg), temporal pole (TP), calcarine sulcus (CalcS), anterior transverse collateral sulcus (ATCS), lingual gyrus (LG).

Citation: Guerrero-Gonzalez, J. M., Kirk, G. R., Birn, R., Bigler, E. D., Bowen, K., Broman, A. T., Rosario, B. L., Butt, W., Beers, S. R., Bell, M. J., Alexander, A. L., Ferrazzano, P. A., & ADAPT MRI Biomarkers Investigators (2024). Multi-modal MRI of hippocampal morphometry and connectivity after pediatric severe TBI. Brain imaging and behavior, 18(1), 159–170.

Abstract: This investigation explores memory performance using the California Verbal Learning Test in relation to morphometric and connectivity measures of the memory network in severe traumatic brain injury. Twenty-two adolescents with severe traumatic brain injury were recruited for multimodal MRI scanning 1-2 years post-injury at 13 participating sites. Analyses included hippocampal volume derived from anatomical T1-weighted imaging, fornix white matter microstructure from diffusion tensor imaging, and hippocampal resting-state functional magnetic resonance imaging connectivity as well as diffusion-based structural connectivity. A typically developing control cohort of forty-nine age-matched children also underwent scanning and neurocognitive assessment. Results showed hippocampus volume was decreased in traumatic brain injury with respect to controls. Further, hippocampal volume loss was associated with worse performance on memory and learning in traumatic brain injury subjects. Similarly, hippocampal fornix fractional anisotropy was reduced in traumatic brain injury with respect to controls, while decreased fractional anisotropy in the hippocampal fornix also was associated with worse performance on memory and learning in traumatic brain injury subjects. Additionally, reduced structural connectivity of left hippocampus to thalamus and calcarine sulcus was associated with memory and learning in traumatic brain injury subjects. Functional connectivity in the left hippocampal network was also associated with memory and learning in traumatic brain injury subjects. These regional findings from a multi-modal neuroimaging approach should not only be useful for gaining valuable insight into traumatic brain injury induced memory and learning disfunction, but may also be informative for monitoring injury progression, recovery, and for developing rehabilitation as well as therapy strategies.

Andrew Alexander, PhD
Andrew Alexander, PhD

Investigator: Andrew Alexander, PhD

About the Lab: Alexander’s research focuses on the use of magnetic resonance imaging (MRI) for mapping and measuring the functional and structural organization of the human brain. These techniques are used to investigate the brain in both typically developing individuals and subjects with developmental disorders including autism. Functional MRI (fMRI) is used to assess brain regions associated with cognition and affect and their dysfunctions in these populations. Diffusion tensor MRI (DT-MRI) is used to study the patterns of structural connectivity between brain activity regions. Anatomic imaging methods are used to assess longitudinal structural changes in brain regions. These measurements are ultimately compared with measures of affect, behavior and cognition in specific population groups. Visit the Quantitative Brain Imaging Technology Lab for more information.

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