Related Experiment Video
Updated: Jun 16, 2026
Advanced Diffusion Imaging in The Hippocampus of Rats with Mild Traumatic Brain Injury
Published on: August 14, 2019
Alterations of white matter tracts following neurotoxic hippocampal lesions in macaque monkeys: a diffusion tensor
J L Shamy1, D M Carpenter, S G Fong
1Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, USA.
Abstract:
Diffusion tensor imaging (DTI) is a valuable tool for assessing presumptive white matter alterations in human disease and animal models. The current study used DTI to examine the effects of selective neurotoxic lesions of the hippocampus on major white matter tracts and anatomically related brain regions in macaque monkeys. Two years postlesion, structural MRI, and DTI sequences were acquired for each subject. Volumetric assessment revealed a substantial reduction in the size of the hippocampus in experimental subjects, averaging 72% relative to controls, without apparent damage to adjacent regions. DTI images were processed to yield measures of fractional anisotropy (FA), apparent diffusion coefficient (ADC), parallel diffusivity (lADC), and perpendicular diffusivity (tADC), as well as directional color maps. To evaluate potential changes in major projection systems, a region of interest (ROI) analysis was conducted including the corpus callosum, fornix, temporal stem, cingulum bundle, ventromedial prefrontal white matter, and optic radiations. Lesion-related abnormalities in the integrity of the fiber tracts examined were limited to known hippocampal circuitry, including the fornix and ventromedial prefrontal white matter. These findings are consistent with the notion that hippocampal damage results in altered interactions with multiple memory-related brain regions, including portions of the prefrontal cortex.
Insights
Hippocampal damage in macaque monkeys significantly reduced hippocampal volume and selectively impacted white matter tracts, specifically the fornix and ventromedial prefrontal white matter, two years post-lesion.
Area of Science:
- Neuroscience
- Neuroimaging
Background:
- Diffusion tensor imaging (DTI) is crucial for studying white matter integrity in neurological conditions.
- Understanding the impact of hippocampal damage on brain circuitry is vital for memory research.
Purpose of the Study:
- To investigate the long-term effects of selective hippocampal neurotoxic lesions on white matter tracts in macaque monkeys using DTI.
- To assess alterations in major white matter tracts and related brain regions following hippocampal damage.
Main Methods:
- Structural MRI and DTI were performed on macaque monkeys two years after hippocampal lesions.
- Region of interest (ROI) analysis was used to examine fractional anisotropy (FA) and diffusivity measures in specific white matter tracts.
Main Results:
- Significant hippocampal volume reduction (72%) was observed in lesioned subjects compared to controls.
- DTI revealed abnormalities primarily in the fornix and ventromedial prefrontal white matter, consistent with hippocampal circuitry.
- No apparent damage was noted in regions adjacent to the hippocampus.
Conclusions:
- Selective hippocampal lesions in macaques lead to specific white matter alterations in connected pathways.
- These findings support the hypothesis of disrupted interactions between the hippocampus and prefrontal cortex in memory-related networks.
