Welcome to the lab for Clinical
& Integrative Neuroscience
Electrophysiological imaging and functional connectivity in Parkinson’s disease
Various perspectives on Parkinson's Disease (PD) analyze its pathological centers, dopaminergic loss, and metabolic changes. In this project, we focus more on the systematic understanding of how neuronal communications are altered in PD compared to healthy controls. The electroencephalogram (EEG) data collected were analyzed for both functional connectivity and phase-amplitude correlation in rolandic regions. The results were also correlated to the severity of disease in various categories. This project will not only improve understanding of PD pathologies in a systematic way, but its procedural basis can be applied to other neurodegenerative disorders affected by an aging-related decrease in communication efficiency.
Burst stimulation effect measured using FDG-PET
Burst stimulation of the brain is a neuromodulation technique that aims to increase regional spontaneous activity of excitatory neurons by using short-period focused electrical stimulation. If it can be used clinically to alleviate chronic pain, burst stimlation could become one of the most accessible neuromodulation tools available. To test its efficacy, we have taken subjective measurements of pain at patients' baselines, after tonic (regular stimulation over threshold), and after burst applications. Additionally, we have taken static FDG PET scans for each session--a widely used molecular imaging technique for measuring metabolic changes. The analysis of these FDG PET images will demonstrate the metabolic effects caused by spontaneous activity changes after electrical stimulation.
Resting state functional connectivity analysis in chronic tinnitus patients
Chronic tinnitus is a disorder that cannot be simply characterized as a result of sensory loss. Our previous studies on cortical thickness and white matter fiber changes showed that aging and hearing loss are main factors in structural degenerations in chronic tinnitus patients. In this project, we utilize graph theory measures on wavelet-transformed timeseries of resting fMRI signals, hoping to systematically understand how top-down compensatory or noise-cancellation mechanisms are functionally organized in the connectome. In addition, network measures are correlated to tinnitus-related measures such as distress or perceived loudness level in order to analyze the differences between individual systems.
Robustness and dynamicity of functional networks in phantom percept
The brain is modeled as a non-linear machine that is capable of change and adaptation. These properties of the brain can be exploited when trying to modify a pathological network. Although several neuromodulatory studies targeting auditory and non-auditory areas are under investigation, none of them present a cure for tinnitus. This has lead us to hypothesize that networks of brain regions could be effective targets for neuromodulation rather than single, specific brain areas. This study aims to investigate the resilience of both a tinnitus and a control network while targeting the nodes of distinct subnetworks in order to better understand the network topology of a phantom percept.
Assessing the “state” of the brain in tinnitus
Due to the non-linearity of the brain, a small perturbation can quickly accelerate the brain's plasticity. With the passage of time, the brain adapts to a new “state” and stabilizes itself in said state, unable (or unwilling) to reverse itself. Chronic neuropathology is hypothesized by some to be new “stable states” of the brain from which the brain is simply unable to revert to normal. This project aims to investigate the changes in the non-linear dynamics of the brain in tinnitus patients by investigating the “state” of the brain in comparison to that of controls.
Tinnitus as a result of a prediction error
The brain is constantly exposed to environmental stimuli, so it is also constantly learning. Over years of exposure to sensory stimuli, the brain learns to predict upcoming sensory input and the correct response to that sensory input. In the event of a sensory deafferentation, the brain is presented with a salience or “surprise” and hence experiences a discrepancy between the bottom-up information and top-down prediction. As a compensatory mechanism for this “prediction error” the brain is hypothesized to “fill in” the missing sensory information with a phantom. Contemporarily, tinnitus is thought to be the result of sensoneural hearing loss. This project aims at presenting tinnitus as the result of a cognitive prediction error by investigating the auditory evoked potentials in a cohort of young tinnitus patients who have near-normal hearing in comparison to an age and gender matched control group.
Identifying patterns of functional connectivity in the chronic tinnitus brain using graph theory
Tinnitus--once thought to be a phenomenon originating in the peripheral auditory system--has since been identified as a neurological disorder. Though intuition would suggest that auditory brain areas would still be responsible for phantom percepts, recent research has shown that auditory cortex dysfunction is necessary but not sufficient to explain the generation of tinnitus on its own. The present study seeks to identify the specific brain networks contributing to the generation of tinnitus percepts and how these networks are functionally connected. This will be accomplished by analyzing functional brain imaging data from a large sample of human subjects suffering from chronic tinnitus using techniques within network science and graph theory. Future studies in this area will focus on applying neuromodulation techniques to the identified areas and networks to determine whether they significantly reduce the magnitude of the tinnitus percept and tinnitus-associated distress.
Salivary stress related responses in tinnitus.
In this study we examined if differences in reaction to stressful situations could be detected in secretions of the autonomic, sympathetic, and immune systems as measured by salivary cortisol, salivary alpha-amylase, and salivary neopterin. The results of this study point toward impaired stress mechanisms in subjects with tinnitus: salivary alpha amylase underwent smaller stress induced changes in both the endocrine system (as measured by salivary cortisol) and the immune system (as measured by salivary neopterin) compared to controls.
The neural correlates of vertigo proneness in humans.
Vestibular signals are of significant importance for many functions, including spatial perception, navigation, cognition, and bodily self-awareness. The vestibular network governs functions that might be impaired in patients affected with chronic vertigo. In this study, we addressed the underlying mechanisms of chronic symptoms of vertigo in the human brain. Using resting state source localized electroencephalography in a non-vertiginous state, we examined both the electrophysiological changes in activity and functional connectivity changes in patients with chronic symptoms of vertigo. The results of this study suggested that chronic vertigo is associated with distinct brain regions that are only marginally functionally connected.
Can Transcranial electrical stimulation suppress tinnitus loudness and related distress?
Noninvasive neuromodulation techniques such as transcranial direct current stimulation (tDCS), and transcranial Random Noise Stimulation (tRNS) have been used with tinnitus and shown to produce significant neuromodulatory changes in spontaneous firing in localized cortical areas. These changes are reflected as an alteration in tinnitus perception, reduction of tinnitus distress, and reduced tinnitus intensity. In this study, we wanted to investigate the effectiveness of combining these two noninvasive neuromodulation tES techniques in order to examine whether the combination of both could be used as an enhanced treatment tool to suppress tinnitus loudness and related distress.
Specific brain activity and chronicity of symptoms in tinnitus.
Brain changes over a period of illness are a topic that has been increasingly recognized in recent years and has warranted considerable research attention, predominately in relation to conditions such as pain, posttraumatic stress disorders, and mental illness. Using resting state source localized electroencephalography of different subgroups of patients with tinnitus, this study examines the electrophysiological changes in activity and functional connectivity in patients with tinnitus related to chronification of symptoms in order to examine whether different temporal aspects of tinnitus symptoms exhibit distinct brain activity or functional/morphological alterations.
The investigation of the underlying molecular aspects contributing to variations in tinnitus intensity and tinnitus-related distress is rather new; however, research has shown that psychological and behavioral factors can heighten the intensity of tinnitus. Tinnitus distress symptoms are characterized by a brain network of increased activity that involve regions that exhibit variations of molecular activity, eliciting concern that the examination of the underlying molecular mechanisms might become necessary for the successful monitoring of tinnitus distress. In this study, we consider the association between pathophysiological alterations of genetic markers in relation to tinnitus distress. This study will facilitate a close examination of the molecular and neural brain dynamics related to tinnitus distress in chronic tinnitus patients, which we hope will offer new insights regarding the underlying mechanisms of tinnitus and contribute to the development of individualized treatment options.
Lab for Clinical & Integrative Neuroscience, School of Behavioral and Brain Sciences, University of Texas at Dallas © 2016