Brain encoding of saltatory velocity-scaled somatosensory array in glabrous hand among neurotypical adults

Neurons in human somatosensory cortex are somatotopically organized, with sensation from the lower limbs mediated by neurons near the midline of the brain, whereas sensations from the upper body, hands and orofacial surfaces are mediated by neurons located more laterally in a sequential map. Neurons in Brodmann\u27s area (BA) 3b are exquisitely sensitive to tactile stimulation of these skin surfaces. Moreover, the location, velocity and direction of tactile stimuli on the skin\u27s surface are discriminable features of somatosensory processing, however their role in fine motor control and passive detection are poorly understood in health, and as a neurotherapeutic agent in sensorimotor rehabilitation. To better understand the representation and processing of dynamic saltatory tactile arrays in the human somatosensory cortex, high resolution functional magnetic resonance (fMRI) is utilized to delineate neural networks involved in processing these complex somatosensory events to the glabrous surface of the hand. The principal goal of this dissertation is to map the relation between a dynamic saltatory pneumatic stimulus array delivered at 3 different velocities on the glabrous hand and the evoked blood-oxygen level-dependent (BOLD) brain response, hypothesized to involve a network consisting of primary and secondary somatosensory cortices (S1 and S2), insular cortex, posterior parietal cortex (PPC), and cerebellar nuclei. A random-balanced block design with fMRI will be used to record the BOLD response in healthy right-handed adults. Development of precise stimulus velocities, rapid rise-fall transitions, salient amplitude, is expected to optimize the BOLD response. Advisor: Steven M. Barlo

BAYESIAN ENSEMBLE LEARNING FOR MEDICAL IMAGE DENOISING

Medical images are often affected by random noise because of both image acquisition from the medical modalities and image transmission from modalities to workspace in the main computer. Medical image denoising removes noise from the CT or MR images and it is an essential step that makes diagnosing more efficient. Many denoising algorithms have been introduced such as Non-local Means, Fields of Experts, and BM3D. In this thesis, we implement the Bayesian ensemble learning for not only natural image denoising but also medical image denoising. The Bayesian ensemble models are Non-local Means and Fields of Experts, the very successful recent algorithms. The Non-local Means presumes that the image contains an extensive amount of self-similarity. The approach of the Fields of Experts model extends traditional Markov Random Field model by learning potential functions over extended pixel neighborhoods. The two models are implemented, and image denoising is performed on both natural images and MR images. For MR images, we used two noise distributions, Gaussian and Rician. The experimental results obtained are used to compare with the single algorithm, and discuss the ensemble learning and their approaches

Brain encoding of saltatory velocity-scaled somatosensory array in glabrous hand among neurotypical adults

Neurons in human somatosensory cortex are somatotopically organized, with sensation from the lower limbs mediated by neurons near the midline of the brain, whereas sensations from the upper body, hands and orofacial surfaces are mediated by neurons located more laterally in a sequential map. Neurons in Brodmann\u27s area (BA) 3b are exquisitely sensitive to tactile stimulation of these skin surfaces. Moreover, the location, velocity and direction of tactile stimuli on the skin\u27s surface are discriminable features of somatosensory processing, however their role in fine motor control and passive detection are poorly understood in health, and as a neurotherapeutic agent in sensorimotor rehabilitation. To better understand the representation and processing of dynamic saltatory tactile arrays in the human somatosensory cortex, high resolution functional magnetic resonance (fMRI) is utilized to delineate neural networks involved in processing these complex somatosensory events to the glabrous surface of the hand. The principal goal of this dissertation is to map the relation between a dynamic saltatory pneumatic stimulus array delivered at 3 different velocities on the glabrous hand and the evoked blood-oxygen level-dependent (BOLD) brain response, hypothesized to involve a network consisting of primary and secondary somatosensory cortices (S1 and S2), insular cortex, posterior parietal cortex (PPC), and cerebellar nuclei. A random-balanced block design with fMRI will be used to record the BOLD response in healthy right-handed adults. Development of precise stimulus velocities, rapid rise-fall transitions, salient amplitude, is expected to optimize the BOLD response. Advisor: Steven M. Barlo

Photoresponsive Systems Based on Self-Assembly

Photoresponsive systems based on self-assembled nanostructures have received considerable attention recently. There is a wide range of applications for these fluids such as in drug delivery, coatings, sensors, or microfluidic valves and dampers. Current photoresponsive systems have typically required the use of specialized molecules with various chemical modifications. However, the requirement of complicated chemical synthesis prevents these systems from being used widely for practical applications. In this study, we focus on creating photoresponsive systems using only commercially available photoresponsive molecules and structure-forming components. In our first study, we describe simple reversible photorheological (PR) fluids, i.e., fluids whose rheological properties can be tuned by light. Our PR fluids are created by combining an azobenzene derivative, 4-azobenzene carboxylic acid (ACA), into micelles of the cationic surfactant erucyl bis(2-hydroxyethyl)methyl ammonium chloride (EHAC). We show that certain aqueous mixtures of EHAC and ACA, which are low-viscosity solutions at the outset, undergo nearly a million-fold increase in viscosity when irradiated with UV light. The same solutions revert to their initial viscosity when subsequently exposed to visible light. The above changes in viscosity are repeatable, and the sample can be reversibly cycled back and forth between low and high viscosity states. In our second study, we report a class of photoresponsive vesicles composed of inexpensive and commercially available cationic and anionic surfactants. The mixture of these amphiphiles forms vesicles due to ionic interactions between the cationic and anionic headgroups. When irradiated by UV light, the cationic surfactant loses its charge and, in turn, the vesicles are converted into micelles due to the loss of ionic interactions. In addition, a mixture of these photoresponsive vesicles and a hydrophobically modified biopolymer gives a photoresponsive vesicle-gel that can undergo a gel-to-sol transition with UV light. In our final study, we demonstrate practical applications of PR fluids as a light-activated fluidic valve in microchannels. Current PR fluid formulations are not suitable for this application. Here, we report a PR fluid composed of alginate, a photoacid generator (PAG) as a photo-trigger, and a chelated complex of divalent strontium (Sr2+) (Sr-EGTA). Upon exposure to UV, free Sr2+ ions are released, which self-assemble with the alginate chains to give a nanostructured gel with a high gel modulus (~ 2000 Pa). We flow our PR fluid in a microchannel and expose a specific point to UV light. At this point, alginate is converted into a gel, which blocks the flow. When the UV light is removed, the gel is gradually dissolved by the flow and the channel reopens. The above concept relies entirely on physical (non-covalent) bonds, i.e., on self-assembly, rather than on covalent crosslinking of dissolved monomers or polymers

Dynamic causal modeling of neural responses to an orofacial pneumotactile velocity array

The effective connectivity of neuronal networks during orofacial pneumotactile stimulation with different velocities is still unknown. The present study aims to characterize the effectivity connectivity elicited by three different saltatory velocities (5, 25, and 65 cm/s) over the lower face using dynamic causal modeling on functional magnetic resonance imaging data of twenty neurotypical adults. Our results revealed the contralateral SI and SII as the most likely sources of the driving inputs within the sensorimotor network for the pneumotactile stimuli, suggesting parallel processing of the orofacial pneumotactile stimuli. The 25 cm/s pneumotactile stimuli modulated forward interhemispheric connection from the contralateral SII to the ipsilateral SII, suggesting a serial interhemispheric connection between the bilateral SII. Moreover, the velocity pneumotactile stimuli influenced the contralateral M1 through contralateral SI and SII, indicating that passive pneumotactile stimulation may positively impact motor function rehabilitation. Furthermore, the medium velocity 25 cm/s pneumotactile stimuli modulated both forward and backward connections between the right cerebellar lobule VI and the contralateral left SI and M1. This result suggests that the right cerebellar lobule VI plays a role in the sensorimotor network through feedforward and feedback neuronal pathways. This study is the first to map similarities and differences of effective connectivity across the three-velocity orofacial pneumotactile stimulation. Our findings shed light on the potential therapeutic use of passive orofacial pneumotactile stimuli using the Galileo system

Brain encoding of saltatory velocity through a pulsed pneumotactile array in the lower face

Processing dynamic tactile inputs is a primary function of the somatosensory system. Spatial velocity encoding mechanisms by the nervous system are important for skilled movement production and may play a role in recovery of sensorimotor function following neurological insult. Little is known about tactile velocity encoding in mechanosensory trigeminal networks required for speech, suck, mastication, and facial gesture. High resolution functional magnetic resonance imaging (fMRI) was used to investigate the neural substrates of velocity encoding in the human orofacial somatosensory system during unilateral saltatory pneumotactile stimulation of perioral and buccal hairy skin in 20 neurotypical adults. A custom multichannel, scalable pneumotactile array consisting of 7 TAC-Cells was used to present 5 stimulus conditions: 5 cm/s, 25 cm/s, 65 cm/s, ALL-ON synchronous activation, and ALL-OFF. The spatiotemporal organization of whole-brain blood oxygen level-dependent (BOLD) response was analyzed with general linear modeling (GLM) and fitted response estimates of percent signal change to compare activations associated with each velocity, and the main effect of velocity alone. Sequential saltatory inputs to the right lower face produced localized BOLD responses in 6 key regions of interest (ROI) including; contralateral precentral and postcentral gyri, and ipsilateral precentral, superior temporal (STG), supramarginal gyri (SMG), and cerebellum. The spatiotemporal organization of the evoked BOLD response was highly dependent on velocity, with the greatest amplitude of BOLD signal change recorded during the 5 cm/s presentation in the contralateral hemisphere. Temporal analysis of BOLD response by velocity indicated rapid adaptation via a scalability of networks processing changing pneumotactile velocity cues

Functional Connectivity Evoked by Orofacial Tactile Perception of Velocity

The cortical representations of orofacial pneumotactile stimulation involve complex neuronal networks, which are still unknown. This study aims to identify the characteristics of functional connectivity (FC) evoked by three different saltatory velocities over the perioral and buccal surface of the lower face using functional magnetic resonance imaging in twenty neurotypical adults. Our results showed a velocity of 25 cm/s evoked stronger connection strength between the right dorsolateral prefrontal cortex and the right thalamus than a velocity of 5 cm/s. The decreased FC between the right secondary somatosensory cortex and right posterior parietal cortex for 5-cm/s velocity versus all three velocities delivered simultaneously (“All ON”) and the increased FC between the right thalamus and bilateral secondary somatosensory cortex for 65 cm/s vs “All ON” indicated that the right secondary somatosensory cortex might play a role in the orofacial tactile perception of velocity. Our results have also shown different patterns of FC for each seed (bilateral primary and secondary somatosensory cortex) at various velocity contrasts (5 vs 25 cm/s, 5 vs 65 cm/s, and 25 vs 65 cm/s). The similarities and differences of FC among three velocities shed light on the neuronal networks encoding the orofacial tactile perception of velocity

G4-Quartet·M+Borate Hydrogels

The ability to modulate the physical properties of a supramolecular hydrogel may be beneficial for biomaterial and biomedical applications. We find that guanosine (G 1), when combined with 0.5 equiv of potassium borate, forms a strong, self-supporting hydrogel with elastic moduli >10 kPa. The countercation in the borate salt (MB(OH)4) significantly alters the physical properties of the hydrogel. The gelator combination of G 1 and KB(OH)4 formed the strongest hydrogel, while the weakest system was obtained with LiB(OH)4, as judged by 1H NMR and rheology. Data from powder XRD, 1H double-quantum solid-state magic-angle spinning (MAS) NMR and small-angle neutron scattering (SANS) were consistent with a structural model that involves formation of borate dimers and G4·K+ quartets by G 1 and KB(OH)4. Stacking of these G4·M+ quartets into G4-nanowires gives a hydrogel. We found that the M+ cation helps stabilize the anionic guanosine-borate (GB) diesters, as well as the G4-quartets. Supplementing the standard gelator mixture of G 1 and 0.5 equiv of KB(OH)4 with additional KCl or KNO3 increased the strength of the hydrogel. We found that thioflavin T fluoresces in the presence of G4·M+ precursor structures. This fluorescence response for thioflavin T was the greatest for the K+ GB system, presumably due to the enhanced interaction of the dye with the more stable G4·K+ quartets. The fluorescence of thioflavin T increased as a function of gelator concentration with an increase that correlated with the system’s gel point, as measured by solution viscosit

Volume of subcortical brain regions in social anxiety disorder:mega-analytic results from 37 samples in the ENIGMA-Anxiety Working Group

There is limited convergence in neuroimaging investigations into volumes of subcortical brain regions in social anxiety disorder (SAD). The inconsistent findings may arise from variations in methodological approaches across studies, including sample selection based on age and clinical characteristics. The ENIGMA-Anxiety Working Group initiated a global mega-analysis to determine whether differences in subcortical volumes can be detected in adults and adolescents with SAD relative to healthy controls. Volumetric data from 37 international samples with 1115 SAD patients and 2775 controls were obtained from ENIGMA-standardized protocols for image segmentation and quality assurance. Linear mixed-effects analyses were adjusted for comparisons across seven subcortical regions in each hemisphere using family-wise error (FWE)-correction. Mixed-effects d effect sizes were calculated. In the full sample, SAD patients showed smaller bilateral putamen volume than controls (left: d = −0.077, pFWE = 0.037; right: d = −0.104, pFWE = 0.001), and a significant interaction between SAD and age was found for the left putamen (r = −0.034, pFWE = 0.045). Smaller bilateral putamen volumes (left: d = −0.141, pFWE &lt; 0.001; right: d = −0.158, pFWE &lt; 0.001) and larger bilateral pallidum volumes (left: d = 0.129, pFWE = 0.006; right: d = 0.099, pFWE = 0.046) were detected in adult SAD patients relative to controls, but no volumetric differences were apparent in adolescent SAD patients relative to controls. Comorbid anxiety disorders and age of SAD onset were additional determinants of SAD-related volumetric differences in subcortical regions. To conclude, subtle volumetric alterations in subcortical regions in SAD were detected. Heterogeneity in age and clinical characteristics may partly explain inconsistencies in previous findings. The association between alterations in subcortical volumes and SAD illness progression deserves further investigation, especially from adolescence into adulthood.</p

Volume of subcortical brain regions in social anxiety disorder:mega-analytic results from 37 samples in the ENIGMA-Anxiety Working Group

There is limited convergence in neuroimaging investigations into volumes of subcortical brain regions in social anxiety disorder (SAD). The inconsistent findings may arise from variations in methodological approaches across studies, including sample selection based on age and clinical characteristics. The ENIGMA-Anxiety Working Group initiated a global mega-analysis to determine whether differences in subcortical volumes can be detected in adults and adolescents with SAD relative to healthy controls. Volumetric data from 37 international samples with 1115 SAD patients and 2775 controls were obtained from ENIGMA-standardized protocols for image segmentation and quality assurance. Linear mixed-effects analyses were adjusted for comparisons across seven subcortical regions in each hemisphere using family-wise error (FWE)-correction. Mixed-effects d effect sizes were calculated. In the full sample, SAD patients showed smaller bilateral putamen volume than controls (left: d = −0.077, pFWE = 0.037; right: d = −0.104, pFWE = 0.001), and a significant interaction between SAD and age was found for the left putamen (r = −0.034, pFWE = 0.045). Smaller bilateral putamen volumes (left: d = −0.141, pFWE &lt; 0.001; right: d = −0.158, pFWE &lt; 0.001) and larger bilateral pallidum volumes (left: d = 0.129, pFWE = 0.006; right: d = 0.099, pFWE = 0.046) were detected in adult SAD patients relative to controls, but no volumetric differences were apparent in adolescent SAD patients relative to controls. Comorbid anxiety disorders and age of SAD onset were additional determinants of SAD-related volumetric differences in subcortical regions. To conclude, subtle volumetric alterations in subcortical regions in SAD were detected. Heterogeneity in age and clinical characteristics may partly explain inconsistencies in previous findings. The association between alterations in subcortical volumes and SAD illness progression deserves further investigation, especially from adolescence into adulthood.</p