An anatomic review of thalamolimbic fiber tractography: ultra-high resolution direct visualization of thalamolimbic fibers anterior thalamic radiation, superolateral and inferomedial medial forebrain bundles, and newly identified septum pellucidum tract

Abstract

Background: Images obtained through ultra-high-field 7.0-tesla magnetic resonance imaging with track-density imaging provide clear, high-resolution tractograms that have been hitherto unavailable, especially in deep brain areas such as the limbic and thalamic regions. This study is a largely pictorial description of the deep fiber tracts in the brain using track-density images obtained with 7.0-T diffusion-weighted imaging.

Methods: To identify the fiber tracts, we selected 3 sets of tractograms and performed interaxis correlation between them. These tractograms offered an opportunity to extract new information in areas that have previously been difficult to examine using either in vivo or in vitro human brain tractography.

Results: With this new technique, we identified 4 fiber tracts that have not previously been directly visualized in vivo: septum pellucidum tract, anterior thalamic radiation, superolateral medial forebrain bundle, and inferomedial forebrain bundle.

Conclusions: We present the high-resolution images as a tool for researchers and clinicians working with neurodegenerative and psychiatric diseases, such as Parkinson disease, Alzheimer disease, and depression, in which the accurate positioning of deep brain stimulation is essential for precise targeting of nuclei and fiber tracts.

Keywords: Affective disorders; Alzheimer disease; Anterior thalamic radiation; Deep brain stimulation; Depressive disorder; Diffusion tensor imaging; Inferomedial medial forebrain bundle; Limbic system; Magnetic resonance Imaging; Parkinson disease; Septum pellucidum tract; Superolateral medial forebrain bundle; Track density imaging; Tractography; Ultra high field MRI.