scholarly journals Magnetic Resonance Elastography of Human Hippocampal Subfields: CA3-Dentate Gyrus Viscoelasticity Predicts Relational Memory Accuracy

2020 ◽  
Vol 32 (9) ◽  
pp. 1704-1713
Author(s):  
Ana M. Daugherty ◽  
Hillary D. Schwarb ◽  
Matthew D. J. McGarry ◽  
Curtis L. Johnson ◽  
Neal J. Cohen
Keyword(s):  
Magnetic Resonance ◽  
Dentate Gyrus ◽  
Damping Ratio ◽  
Memory Function ◽  
Magnetic Resonance Elastography ◽  
Elastic Behavior ◽  
Relational Memory ◽  
Hippocampal Subfields ◽  
Memory Accuracy

The hippocampus is necessary for binding and reconstituting information in relational memory. These essential memory functions are supported by the distinct cytoarchitecture of the hippocampal subfields. Magnetic resonance elastography is an emerging tool that provides sensitive estimates of microstructure vis-à-vis tissue mechanical properties. Here, we report the first in vivo study of human hippocampal subfield viscoelastic stiffness and damping ratio. Stiffness describes resistance of a viscoelastic tissue to a stress and is thought to reflect the relative composition of tissue at the microscale; damping ratio describes relative viscous-to-elastic behavior and is thought to generally reflect microstructural organization. Measures from the subiculum (combined with presubiculum and parasubiculum), cornu ammonis (CA) 1–2, and CA3-dentate gyrus (CA3-DG) were collected in a sample of healthy, cognitively normal men ( n = 20, age = 18–33 years). In line with known cytoarchitecture, the subiculum demonstrated the lowest damping ratio, followed by CA3-DG and then combined CA1–CA2. Moreover, damping ratio of the CA3-DG—potentially reflective of number of cells and their connections—predicted relational memory accuracy and alone replicated most of the variance in performance that was explained by the whole hippocampus. Stiffness did not differentiate the hippocampal subfields and was unrelated to task performance in this sample. Viscoelasticity measured with magnetic resonance elastography appears to be sensitive to microstructural properties relevant to specific memory function, even in healthy younger adults, and is a promising tool for future studies of hippocampal structure in aging and related diseases.

scholarly journals In-vivo waveguide cardiac magnetic resonance elastography

2015 ◽  
Vol 17 (S1) ◽  
Author(s):  
Ria Mazumder ◽  
Bradley D Clymer ◽  
Richard D White ◽  
Anthony Romano ◽  
Arunark Kolipaka
Keyword(s):  
Cardiac Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Elastography

Magnetic Resonance Elastography for the Measurement of Annulus Fibrosus Material Properties

2011 ◽  
Author(s):  
Daniel H. Cortes ◽  
Lachlan J. Smith ◽  
Sung M. Moon ◽  
Jeremy F. Magland ◽  
Alexander C. Wright ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnetic Resonance ◽  
Shear Modulus ◽  
Disc Degeneration ◽  
Annulus Fibrosus ◽  
Pulse Sequence ◽  
Imaging Techniques ◽  
Mechanical Vibration ◽  
Magnetic Resonance Elastography

Intervertebral disc degeneration is characterized by a progressive cascade of structural, biochemical and biomechanical changes affecting the annulus fibrosus (AF), nucleus pulposus (NP) and end plates (EP). These changes are considered to contribute to the onset of back pain. It has been shown that mechanical properties of the AF and NP change significantly with degeneration [1,2]. Therefore, mechanical properties have the potential to serve as a biomarker for diagnosis of disc degeneration. Currently, disc degeneration is diagnosed based on the detection of structural and compositional changes using MRI, X-ray, discography and other imaging techniques. These methods, however, do not measure directly the mechanical properties of the extracellular matrix of the disc. Magnetic Resonance Elastography (MRE) is a technique that has been used to measure in vivo mechanical properties of soft tissue by applying a mechanical vibration and measuring displacements with a motion-sensitized MRI pulse sequence [3]. The mechanical properties (e.g., the shear modulus) are calculated from the displacement field using an inverse method. Since the applied displacements are in the order of few microns, fibers may not be stretched enough to remove crimping. Therefore, it is unknown if the anisotropy of the AF due to the contribution of the fibers is detectable using MRE. The objective of this study is twofold: to measure shear properties of AF in different orientations to determine the degree of AF anisotropy observable by MRE, and to identify the contribution of different AF constituents to the measured shear modulus by applying different biochemical treatments.

scholarly journals In vivo characterization of 3D skull and brain motion during dynamic head vibration using magnetic resonance elastography

2018 ◽  
Vol 80 (6) ◽  
pp. 2573-2585 ◽  
Author(s):  
Ziying Yin ◽  
Yi Sui ◽  
Joshua D. Trzasko ◽  
Phillip J. Rossman ◽  
Armando Manduca ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Elastography ◽  
Brain Motion ◽  
Dynamic Head ◽  
In Vivo Characterization

scholarly journals Reduced GluN1 in mouse dentate gyrus is associated with CA3 hyperactivity and psychosis-like behaviors

2018 ◽  
Vol 25 (11) ◽  
pp. 2832-2843 ◽  
Author(s):  
Amir Segev ◽  
Masaya Yanagi ◽  
Daniel Scott ◽  
Sarah A. Southcott ◽  
Jacob M. Lister ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Basolateral Amygdala ◽  
Pyramidal Neurons ◽  
Mossy Fibers ◽  
Model Systems ◽  
Memory Processing ◽  
Hippocampal Subfields ◽  
Whole Cell Patch Clamp ◽  
Hippocampal Activity

Abstract Recent findings from in vivo-imaging and human post-mortem tissue studies in schizophrenic psychosis (SzP), have demonstrated functional and molecular changes in hippocampal subfields that can be associated with hippocampal hyperexcitability. In this study, we used a subfield-specific GluN1 knockout mouse with a disease-like molecular perturbation expressed only in hippocampal dentate gyrus (DG) and assessed its association with hippocampal physiology and psychosis-like behaviors. First, we used whole-cell patch-clamp recordings to measure the physiological changes in hippocampal subfields and cFos immunohistochemistry to examine cellular excitability. DG-GluN1 KO mice show CA3 cellular hyperactivity, detected using two approaches: (1) increased excitatory glutamate transmission at mossy fibers (MF)-CA3 synapses, and (2) an increased number of cFos-activated pyramidal neurons in CA3, an outcome that appears to project downstream to CA1 and basolateral amygdala (BLA). Furthermore, we examined psychosis-like behaviors and pathological memory processing; these show an increase in fear conditioning (FC), a reduction in prepulse inhibition (PPI) in the KO animal, along with a deterioration in memory accuracy with Morris Water Maze (MWM) and reduced social memory (SM). Moreover, with DREADD vectors, we demonstrate a remarkably similar behavioral profile when we induce CA3 hyperactivity. These hippocampal subfield changes could provide the basis for the observed increase in human hippocampal activity in SzP, based on the shared DG-specific GluN1 reduction. With further characterization, these animal model systems may serve as targets to test psychosis mechanisms related to hippocampus and assess potential hippocampus-directed treatments.

Determination of In-Vivo Elastic Properties of Soft Tissue Using Magnetic Resonance Elastography

2003 ◽  
Author(s):  
Francis E. Kennedy ◽  
Marvin M. Doyley ◽  
Elijah E. W. Van Houten ◽  
John B. Weaver ◽  
Keith D. Paulsen
Keyword(s):  
Magnetic Resonance ◽  
Soft Tissue ◽  
Elastic Properties ◽  
Magnetic Resonance Elastography ◽  
Tissue Properties ◽  
In Vivo Measurement ◽  
Ultrasonic Methods ◽  
Accurate Quantification

In-vivo measurement of the elastic properties of soft tissue have been made using a variety of direct techniques, such as indentation probes and rotary shear actuators, but they are unable to access much of the soft tissue of interest. Indirect ultrasonic methods for imaging elastic properties of soft tissue were first introduced about 15 years ago, see Ophir (1991). Although the results of ultrasonic elastography studies have been quite promising, they may not be suited for applications requiring accurate quantification of soft tissue properties. An alternative to ultrasound, magnetic resonance imaging, has the advantage of enabling precise measurement of all three components of tissue displacement. The reconstruction of elastic properties from the imaged displacement field is called magnetic resonance elastography (MRE), and is the subject of this paper.

scholarly journals P.063 Stereotactic targeting of hippocampal substructures using ultra-high field magnetic resonance imaging: Feasibility study in patients with epilepsy

2018 ◽  
Vol 45 (s2) ◽  
pp. S32-S33
Author(s):  
JC Lau ◽  
J DeKraker ◽  
KW MacDougall ◽  
H Joswig ◽  
AG Parrent ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Dentate Gyrus ◽  
High Field ◽  
Longitudinal Axis ◽  
The Body ◽  
7 Tesla ◽  
Resonance Imaging ◽  
Ultra High Field

Background: The hippocampus can be divided longitudinally into the head, body, and tail; and unfolded medial-to-laterally into the subiculum, cornu ammonis (CA) sectors, and the dentate gyrus. Ultra-high field (≥ 7 Tesla; 7T) magnetic resonance imaging (MRI) enables submillimetric visualization of these hippocampal substructures which could be valuable for surgical targeting. Here, we assess the feasibility of using 7T MRI in conjunction with a novel computational unfolding method for image-based stereotactic targeting of hippocampal substructures. Methods: 53 patients with drug-resistant epilepsy were identified undergoing first-time implantation of the hippocampus. An image processing pipeline was created for computationally transforming post-operative electrode contact locations into our hippocampal coordinate system. Results: Of 178 implanted hippocampal electrodes (88 left; 49.4%), 25 (14.0%) were predominantly in the subiculum, 85 (47.8%) were in CA1, 23 (12.9%) were in CA2, 18 (10.1%) were in CA3/CA4, and 27 (15.2%) were in dentate gyrus. Along the longitudinal axis, hippocampal electrodes were most commonly implanted in the body (92; 51.7%) followed by the head (86; 48.3%). Conclusions: 7T MRI enables high-resolution anatomical imaging on the submillimeter scale in in vivo subjects. Here, we demonstrate the utility of 7T imaging for identifying the relative location of SEEG electrode implantations within hippocampal substructures for the invasive investigation of epilepsy.

In Vivo Determination of Hepatic Stiffness Using Steady-State Free Precession Magnetic Resonance Elastography

2006 ◽  
Vol 41 (12) ◽  
pp. 841-848 ◽  
Author(s):  
Dieter Klatt ◽  
Patrick Asbach ◽  
Jens Rump ◽  
Sebastian Papazoglou ◽  
Rajan Somasundaram ◽  
...  
Keyword(s):  
Steady State ◽  
Magnetic Resonance ◽  
Steady State Free Precession ◽  
Magnetic Resonance Elastography ◽  
Free Precession

In vivo multifrequency magnetic resonance elastography of the human intervertebral disk

2014 ◽  
Vol 74 (5) ◽  
pp. 1380-1387 ◽  
Author(s):  
Kaspar-Josche Streitberger ◽  
Gerd Diederichs ◽  
Jing Guo ◽  
Andreas Fehlner ◽  
Bernd Hamm ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Intervertebral Disk ◽  
Magnetic Resonance Elastography

scholarly journals Brain Stiffness Relates to Dynamic Balance Reactions in Children With Cerebral Palsy

2020 ◽  
Vol 35 (7) ◽  
pp. 463-471 ◽  
Author(s):  
Grace McIlvain ◽  
James B. Tracy ◽  
Charlotte A. Chaze ◽  
Drew A. Petersen ◽  
Gabrielle M. Villermaux ◽  
...  
Keyword(s):  
Cerebral Palsy ◽  
Magnetic Resonance ◽  
Dynamic Balance ◽  
Superior Temporal Gyrus ◽  
Brain Regions ◽  
Magnetic Resonance Elastography ◽  
Neural Basis ◽  
Balance Impairment ◽  
Children With Cerebral Palsy

Cerebral palsy is a neurodevelopmental movement disorder that affects coordination and balance. Therapeutic treatments for balance deficiencies in this population primarily focus on the musculoskeletal system, whereas the neural basis of balance impairment is often overlooked. Magnetic resonance elastography (MRE) is an emerging technique that has the ability to sensitively assess microstructural brain health through in vivo measurements of neural tissue stiffness. Using magnetic resonance elastography, we have previously measured significantly softer grey matter in children with cerebral palsy as compared with typically developing children. To further allow magnetic resonance elastography to be a clinically useful tool in rehabilitation, we aim to understand how brain stiffness in children with cerebral palsy is related to dynamic balance reaction performance as measured through anterior and posterior single-stepping thresholds, defined as the standing perturbation magnitudes that elicit anterior or posterior recovery steps. We found that global brain stiffness is significantly correlated with posterior stepping thresholds ( P = .024) such that higher brain stiffness was related to better balance recovery. We further identified specific regions of the brain where stiffness was correlated with stepping thresholds, including the precentral and postcentral gyri, the precuneus and cuneus, and the superior temporal gyrus. Identifying brain regions affected in cerebral palsy and related to balance impairment can help inform rehabilitation strategies targeting neuroplasticity to improve motor function.

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