Diffusion tensor imaging reveals microstructural alterations in corpus callosum and associated transcallosal fiber tracts in adult macaques with neonatal hippocampal lesions

• Type of Material: Article
• Authors: Yuguang Meng, Emory University; Xiaodong Zhang, Emory University; Xiaoping Hu, Emory University; Jocelyne Bachevalier, Emory University
• Language: English
• Date: 2018-11-01
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2018 Wiley Periodicals, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1002/hipo.23006
• Title of Journal or Parent Work: Hippocampus
• Volume: 28
• Issue: 11
• Start Page: 838
• End Page: 845
• Grant/Funding Information: This project was funded by NIH/NIMH grant MH0588446 (JB), the National Center for Research Resources P51RR000165 and is currently supported by the Office of Research Infrastructure Programs / OD P51OD011132.
• Keywords: AMYGDALA; WHITE-MATTER; hippocampus; INFANT RHESUS MACAQUES; Neurosciences; Life Sciences & Biomedicine; MONKEY RETROSPLENIAL CORTEX; non-human primate; Science & Technology; FRONTAL-CORTEX; WORKING-MEMORY; corpus callosum; tract-based spatial statistics; CONNECTIONS; diffusion tensor imaging; TBSS; Neurosciences & Neurology; SPATIAL LOCATION; RECOGNITION; PATHOLOGY
• Research Categories: Health Sciences, Pathology

Abstract

To investigate the effects of neonatal hippocampal lesions on the microstructural integrity of the corpus callosum (CC) in adulthood, macaque monkeys (n = 5) with neonatal bilateral neurotoxic hippocampal lesion (Neo-Hibo) and sham-operated controls (Neo-C, n = 5) were scanned using magnetic resonance diffusion tensor imaging (DTI) technique at 8–10 years old. CC was segmented into seven regionsgrouped into anterior CC (rostrum, genu, rostral body and anterior midbody) and posterior CC (posterior midbody, isthmus and splenium) for data analysis. Associated transcallosal fiber tracts were delineated using probabilistic tractography and evaluated with tract-based spatial statistics (TBSS). Neo-Hibo lesions resulted in significant increased diffusivity indices (mean, axial and radial diffusivity) in CC posterior segments. Also, significant decreased fractional anisotropy (FA) and increased diffusivity indices were seen in the associated transcallosal fiber tracts proximal to motor, posterior parietal and retrosplenial cortices. In Neo-Hibo animals, increased mean diffusivity (MD) in posterior midbody negatively correlated with reduction of CC surface areaand the magnitude of their memory impairments was significantly correlated with FA in transcallosal fiber tracts across splenium. Although no microstructural changes were observed in CC anterior segments, changes in FA values and diffusivity indices were observed in the white matter fibers of the ventromedial prefrontal cortex. Thus, Neo-H lesions resulted in enduring degradation in transcallosal fibers proximal to parietal and retrosplenial cortices, and hemispheric connections through posterior CC. The findings may provide complementary information for understanding the neural substrate of behavioral and cognitive deficits observed in patients with early insult to the hippocampus.