A5074956203- Advanced MRI Techniques and Applications
- Functional Brain Connectivity Studies
- Optical Imaging and Spectroscopy Techniques
- Neural dynamics and brain function
- Advanced Neuroimaging Techniques and Applications
- Visual perception and processing mechanisms
- Atomic and Subatomic Physics Research
- Retinal Development and Disorders
- Anesthesia and Neurotoxicity Research
- Ophthalmology and Eye Disorders
- Diet and metabolism studies
Baylor College of Medicine
2017-2022
The University of Texas at Austin
2012
The blood oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI) signal depends on an interplay of cerebral flow (CBF), oxygen metabolism, and volume. Despite wide usage BOLD fMRI, it is not clear how these physiological components create the signal. Here, baseline CBF its dynamics evoked by a brief stimulus (2 s) in human visual cortex were measured at 3T. We found stereotypical response: immediate increase, rising to peak few second after stimulus, followed significant...
Abstract The hemodynamic response function (HRF) measured with functional magnetic resonance imaging is generated by vascular and metabolic responses evoked brief (<4 s) stimuli. It known that the human HRF varies across cortex, between subjects, stimulus paradigms, even different measurements in same cortical location. However, our results demonstrate strong HRFs are remarkably repeatable sessions separated time intervals up to 3 months. In this study, a multisensory was used activate...
We investigate dynamics of the negative hemodynamic response function (nHRF), blood-oxygen-level-dependent (BOLD) (NBR) evoked by a brief stimulus, in human early visual cortex. Here, we show that nHRFs are not inverted versions corresponding pHRFs. The nHRF has complex varied significantly with eccentricity. results also shift-invariant temporal linearity does hold for NBR.
Abstract Dorsal human midbrain contains two nuclei with clear laminar organization, the superior and inferior colliculi. These extend in depth between superficial dorsal surface of a deep nucleus, periaqueductal gray matter (PAG). The PAG, turn, surrounds cerebral aqueduct (CA). This study examined use metrics to characterize thickness relationships within using CA as references. first utilized nearest‐neighbor Euclidean distance from one reference surface, while second used level‐set...
We proposed a 7T laminar concurrent ASL, VASO and BOLD fMRI sequence to obtain quantitative CBF, CBV, T2-BOLD CMRO2 measurements with high resolution specificity detect layer-dependent vascular metabolic activities. Ipsilateral visual stimuli (eccentricity of 4°–6°) induced ring-shaped CBF signal increase on cortical surface corresponding the pattern stimulus while decreased BOLD/CBF signals can be seen in adjacent fovea regions. In negative response (NBR) regions, moderate decrease CBV...
Motivation: To better understand the complex interplay between neurovascular responses and metabolism. Goal(s): The goal was to develop a multi-contrast laminar fMRI tool concurrently measure CBF, CBV, BOLD, CMRO2 signals. Approach: We employed novel pulse sequence simultaneously acquire ASL VASO T2-BOLD signals at high spatial resolution of 7T. also incorporated calibrated approach (Davis model) calculate CMRO2, using parameters estimated from breath-hold induced hypercapnia. Results: found...
Neural activity triggers a vascular response in the brain that leads to transient changes oxygen transport, and this mechanism is basis for popular powerful functional imaging methods. However, there limited understanding of delivery cerebral cortex both steady state during perturbations. In study, computational model transport was developed used fit polarographic measurements stimulation cortex. The hemodynamic function (HRF) modeled with convection-diffusion four-compartment system...
Summary The superior colliculus (SC) is a layered midbrain structure involved in directing eye movements and coordinating visual attention. Electrical stimulation neuronal recordings the intermediate layers of monkey SC have shown retinotopic organization for mediation saccadic eye-movements. However, human topography saccades unknown. Here, novel experimental paradigm highresolution (1.2-mm) functional magnetic resonance imaging methods were used to measure activity evoked by within SC....