Tractography reveals patterns of hippocampal innervation in the human temporal lobe Lauren Gricec, Chandler Fountainb, and Michel Modoa-c McGowan Institute for Regenerative Medicine, bDepartment of Radiology, cDepartment of Bioengineering, dUniversity of Pittsburgh Medical Center, University of Pittsburgh, Pittsburgh, PA, USA Regenerative Imaging Laboratory, McGowan Institute for Regenerative Medicine, University of Pittsburgh, PA, USA a
Lauren Grice
Lauren Grice is a senior Bioengineering major with minors in Electrical Engineering and Neuroscience. She is motivated by understanding the merger between healthcare and technology. After graduation, plans to attend graduate school to study the development of brain computer interfaces for the treatment of neurological disease.
Abstract
Until recently, medical imaging technology has not been sophisticated enough to develop maps of neuronal connections within the human brain. Such information would be immensely useful as it could help to identify the causes and prognoses of neurological diseases. Diffusion tensor imaging (DTI) is a form of magnetic resonance imaging that can detect the water diffusion vectors in an image. Using tractography, said vectors can be computationally “traced” to create visual representations of neuronal connections. Although DTI has previously been used to identify white matter tracks in the human brain, little research has shown neuronal connectivity within and between grey matter regions. This study applies DTI and tractography to develop a map of hippocampal connections within a healthy human temporal lobe. The results show that the healthy, human hippocampus innervates with two main grey matter structures: the amygdala and the inferior temporal gyrus. This is a significant finding because in the case of disease, changes in the interconnectivity of the hippocampus with the amygdala and inferior temporal gyrus could be an indication of disease onset or prognosis.
1. Introduction Dr. Michel Modo holds a PhD in Neuroscience from King’s College London. He joined the Department of Radiology at the University of Pittsburgh in 2011 and his laboratory’s main focus is to develop novel imaging tools to visualize brain repair using stem cells and biomaterials. Dr. Michel Modo
Significance Statement
The temporal lobe is an important brain structure affected by Alzheimer’s disease and epilepsy. This study seeks to establish maps of neuronal connections between grey matter regions in the temporal lobe. Importantly, it is shown that diffusion tensor imaging can effectively characterize grey matter connections in the brain.
Category: Experimental research
Keywords: temporal lobe, diffusion tensor imaging, tractography
34 Undergraduate Research at the Swanson School of Engineering
Historically, research on neurological disease has focused on modeling whole brain structures to identify abnormalities. However, because of technological limitations, little research has been performed to establish a map of white matter connections between grey matter structures in the human brain. When considering connectivity within the brain, the temporal lobe (TL) region is of particular interest as it contains important grey matter structures like the hippocampus and amygdala which play significant roles in memory and processing of emotions. Additionally, the TL is targeted by debilitating conditions like epilepsy and Alzheimer’s disease. In an effort to better understand the function of the TL, this project addresses the need for visual maps of microstructural anatomy in a healthy, human TL to develop accurate representations of hippocampal connections and their patterns of cortical innervation. In this study, mesoscale, T2-weighted, diffusion tensor imaging (DTI) was used to quantify changes in neuronal connectivity. DTI is a specialized form of magnetic resonance imaging (MRI) that is sensitive to the magnitude and orientation of water movement [1]. Software can be used to detect the water diffusion vectors in an image to calculate both the mean diffusivity (MD) and fractional anisotropy (FA), or the directional dependence of diffusion in tissue [2]. Furthermore, using computational methods, the vectors in each voxel, or unit, of a DT image can be weighted by FA and “traced” to create streamlines, or three-dimensional representations of neuronal bundles. In healthy brain tissue, the flow of water molecules in white and grey matter demonstrates low diffusion and tends to be directionally-dependent, or anisotropic. Because of this diffusion behavior, constructed streamlines in DTIs of healthy brains should demonstrate high microstructural organization. However, in conditions like epilepsy and Alzheimer’s disease, brain cells die and
