In vivo Exploration of the Connectivity between the Subthalamic Nucleus and the Globus Pallidus in the Human Brain Using Multi-Fiber Tractography

Abstract Short association fibers (U-fibers) connect proximal cortical areas and constitute the majority of white matter connections in the human brain. U-fibers play an important role in brain development, function, and pathology but are underrepresented in current descriptions of the human brain connectome, primarily due to methodological challenges in diffusion magnetic resonance imaging (dMRI) of these fibers. High spatial resolution and dedicated fiber and tractography models are required to reliably map the U-fibers. Moreover, limited quantitative knowledge of their geometry and distribution makes validation of U-fiber tractography challenging. Submillimeter resolution diffusion MRI—facilitated by a cutting-edge MRI scanner with 300 mT/m maximum gradient amplitude—was used to map U-fiber connectivity between primary and secondary visual cortical areas (V1 and V2, respectively) in vivo. V1 and V2 retinotopic maps were obtained using functional MRI at 7T. The mapped V1–V2 connectivity was retinotopically organized, demonstrating higher connectivity for retinotopically corresponding areas in V1 and V2 as expected. The results were highly reproducible, as demonstrated by repeated measurements in the same participants and by an independent replication group study. This study demonstrates a robust U-fiber connectivity mapping in vivo and is an important step toward construction of a more complete human brain connectome.

Download Full-text

Euclidean distance as a measure to distinguish ventral and dorsal white matter connectivity in the human brain

10.1101/053959 ◽

2016 ◽

Author(s):

Philipp Kellmeyer ◽

Magnus-Sebastian Vry

Keyword(s):

White Matter ◽

Human Brain ◽

Cognitive Processing ◽

Euclidean Distance ◽

Large Scale ◽

Diffusion Tensor ◽

Large Body ◽

Coordinate Space ◽

Fiber Tractography

AbstractFiber tractography based on diffusion tensor imaging (DTI) has become an important research tool for investigating the anatomical connectivity between brain regions in vivo. Combining DTI with functional magnetic resonance imaging (fMRI) allows for the mapping of structural and functional architecture of large-scale networks for cognitive processing. This line of research has shown that ventral and dorsal fiber pathways subserve different aspects of bottom-up- and top-down processing in the human brain.Here, we investigate the feasibility and applicability of Euclidean distance as a simple geometric measure to differentiate ventral and dorsal long-range white matter fiber pathways tween parietal and inferior frontal cortical regions, employing a body of studies that used probabilistic tractography.We show that ventral pathways between parietal and inferior frontal cortex have on average a significantly longer Euclidean distance in 3D-coordinate space than dorsal pathways. We argue that Euclidean distance could provide a simple measure and potentially a boundary value to assess patterns of connectivity in fMRI studies. This would allow for a much broader assessment of general patterns of ventral and dorsal large-scale fiber connectivity for different cognitive operations in the large body of existing fMRI studies lacking additional DTI data.

Download Full-text

Sparse but Selective and Potent Synaptic Transmission From the Globus Pallidus to the Subthalamic Nucleus

Journal of Neurophysiology ◽

10.1152/jn.00305.2009 ◽

2009 ◽

Vol 102 (1) ◽

pp. 532-545 ◽

Cited By ~ 51

Author(s):

Jérôme Baufreton ◽

Erin Kirkham ◽

Jeremy F. Atherton ◽

Ariane Menard ◽

Peter J. Magill ◽

...

Keyword(s):

Globus Pallidus ◽

Subthalamic Nucleus ◽

Brain Slices ◽

Synaptic Connections ◽

Electron Microscopic ◽

Autonomous Activity ◽

The Impact ◽

Stimulation Technique ◽

Minimal Stimulation

The reciprocally connected GABAergic globus pallidus (GP)-glutamatergic subthalamic nucleus (STN) network is critical for voluntary movement and an important site of dysfunction in movement disorders such as Parkinson's disease. Although the GP is a key determinant of STN activity, correlated GP-STN activity is rare under normal conditions. Here we define fundamental features of the GP-STN connection that contribute to poorly correlated GP-STN activity. Juxtacellular labeling of single GP neurons in vivo and stereological estimation of the total number of GABAergic GP-STN synapses suggest that the GP-STN connection is surprisingly sparse: single GP neurons maximally contact only 2% of STN neurons and single STN neurons maximally receive input from 2% of GP neurons. However, GP-STN connectivity may be considerably more selective than even these estimates imply. Light and electron microscopic analyses revealed that single GP axons give rise to sparsely distributed terminal clusters, many of which correspond to multiple synapses with individual STN neurons. Application of the minimal stimulation technique in brain slices confirmed that STN neurons receive multisynaptic unitary inputs and that these inputs largely arise from different sets of GABAergic axons. Finally, the dynamic-clamp technique was applied to quantify the impact of GP-STN inputs on STN activity. Small fractions of GP-STN input were sufficiently powerful to inhibit and synchronize the autonomous activity of STN neurons. Together these data are consistent with the conclusion that the rarity of correlated GP-STN activity in vivo is due to the sparsity and selectivity, rather than the potency, of GP-STN synaptic connections.

Download Full-text

In vivo 3D Reconstruction of the Human Pallidothalamic and Nigrothalamic Pathways With Super-Resolution 7T MR Track Density Imaging and Fiber Tractography

Frontiers in Neuroanatomy ◽

10.3389/fnana.2021.739576 ◽

2021 ◽

Vol 15 ◽

Author(s):

Dae-Hyuk Kwon ◽

Sun Ha Paek ◽

Young-Bo Kim ◽

Haigun Lee ◽

Zang-Hee Cho

Keyword(s):

Basal Ganglia ◽

3D Reconstruction ◽

Human Brain ◽

Super Resolution ◽

Track Density ◽

7 Tesla ◽

Fiber Tractography ◽

Resolution Limit ◽

Magnetic Resonance Imaging Mri

The output network of the basal ganglia plays an important role in motor, associative, and limbic processing and is generally characterized by the pallidothalamic and nigrothalamic pathways. However, these connections in the human brain remain difficult to elucidate because of the resolution limit of current neuroimaging techniques. The present study aimed to investigate the mesoscopic nature of these connections between the thalamus, substantia nigra pars reticulata, and globus pallidus internal segment using 7 Tesla (7T) magnetic resonance imaging (MRI). In this study, track-density imaging (TDI) of the whole human brain was employed to overcome the limitations of observing the pallidothalamic and nigrothalamic tracts. Owing to the super-resolution of the TD images, the substructures of the SN, as well as the associated tracts, were identified. This study demonstrates that 7T MRI and MR tractography can be used to visualize anatomical details, as well as 3D reconstruction, of the output projections of the basal ganglia.

Download Full-text

In Vivo 1H MR Spectroscopic Imaging of Human Brain

Journal of the Korean Radiological Society ◽

10.3348/jkrs.1994.31.2.185 ◽

1994 ◽

Vol 31 (2) ◽

pp. 185

Author(s):

Yong Whee Bahk ◽

Kyung Sub Shinn ◽

Tae Suk Suh ◽

Bo Young Choe ◽

Kyo Ho Choi

Keyword(s):

Human Brain ◽

Spectroscopic Imaging ◽

Mr Spectroscopic Imaging

Download Full-text

In vivo magnetic resonance imaging and 31P spectroscopy of large human brain tumours at 1.5 tesla

Acta Radiologica ◽

10.3109/02841858809171216 ◽

1988 ◽

Vol 29 (1) ◽

pp. 77-82 ◽

Cited By ~ 3

Author(s):

C. Thomsen ◽

K. E. Jensen ◽

E. Achten ◽

O. Henriksen

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

Human Brain ◽

Brain Tumours ◽

Resonance Imaging ◽

Human Brain Tumours

Download Full-text

Tractography Alterations in the Arcuate and Uncinate Fasciculi in Post-Stroke Aphasia

Brain Sciences ◽

10.3390/brainsci11010053 ◽

2021 ◽

Vol 11 (1) ◽

pp. 53

Author(s):

Sara Kierońska ◽

Milena Świtońska ◽

Grzegorz Meder ◽

Magdalena Piotrowska ◽

Paweł Sokal

Keyword(s):

White Matter ◽

Brain Connectivity ◽

Three Dimensional ◽

Cerebral White Matter ◽

Neural Pathways ◽

Uncinate Fasciculus ◽

Arcuate Fasciculus ◽

Fiber Tractography ◽

Post Stroke

Fiber tractography based on diffuse tensor imaging (DTI) can reveal three-dimensional white matter connectivity of the human brain. Tractography is a non-invasive method of visualizing cerebral white matter structures in vivo, including neural pathways surrounding the ischemic area. DTI may be useful for elucidating alterations in brain connectivity resulting from neuroplasticity after stroke. We present a case of a male patient who developed significant mixed aphasia following ischemic stroke. The patient had been treated by mechanical thrombectomy followed by an early rehabilitation, in conjunction with transcranial direct current stimulation (tDCS). DTI was used to examine the arcuate fasciculus and uncinate fasciculus upon admission and again at three months post-stroke. Results showed an improvement in the patient’s symptoms of aphasia, which was associated with changes in the volume and numbers of tracts in the uncinate fasciculus and the arcuate fasciculus.

Download Full-text

In vivo proton magnetic resonance spectroscopy studies of human brain

Magnetic Resonance Imaging ◽

10.1016/0730-725x(91)90415-i ◽

1991 ◽

Vol 9 (3) ◽

pp. 303-308 ◽

Cited By ~ 64

Author(s):

P.A. Narayana ◽

D. Johnston ◽

D.P. Flamig

Keyword(s):

Magnetic Resonance ◽

Magnetic Resonance Spectroscopy ◽

Human Brain ◽

Proton Magnetic Resonance ◽

Proton Magnetic Resonance Spectroscopy ◽

Resonance Spectroscopy ◽

Spectroscopy Studies

Download Full-text

Meyer’s Loop Anatomy Demonstrated Using Diffusion Tensor MR Imaging and Fiber Tractography at 3T

Acta Medica Marisiensis ◽

10.2478/amma-2014-0045 ◽

2014 ◽

Vol 60 (5) ◽

pp. 215-222 ◽

Cited By ~ 1

Author(s):

Cristina Goga ◽

Zeynep Firat ◽

Klara Brinzaniuc ◽

Is Florian

Keyword(s):

Diffusion Tensor Imaging ◽

Diffusion Tensor ◽

Region Of Interest ◽

Fiber Tractography ◽

Brain Images ◽

3 Dimensional ◽

Software Release ◽

Magnetic Resonance Imaging Mri ◽

Meyer’S Loop

Abstract Objective: The ultimate anatomy of the Meyer’s loop continues to elude us. Diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) may be able to demonstrate, in vivo, the anatomy of the complex network of white matter fibers surrounding the Meyer’s loop and the optic radiations. This study aims at exploring the anatomy of the Meyer’s loop by using DTI and fiber tractography. Methods: Ten healthy subjects underwent magnetic resonance imaging (MRI) with DTI at 3 T. Using a region-of-interest (ROI) based diffusion tensor imaging and fiber tracking software (Release 2.6, Achieva, Philips), sequential ROI were placed to reconstruct visual fibers and neighboring projection fibers involved in the formation of Meyer’s loop. The 3-dimensional (3D) reconstructed fibers were visualized by superimposition on 3-planar MRI brain images to enhance their precise anatomical localization and relationship with other anatomical structures. Results: Several projection fiber including the optic radiation, occipitopontine/parietopontine fibers and posterior thalamic peduncle participated in the formation of Meyer’s loop. Two patterns of angulation of the Meyer’s loop were found. Conclusions: DTI with DTT provides a complimentary, in vivo, method to study the details of the anatomy of the Meyer’s loop.

Download Full-text