Browsing by Author "Worth, Robert M."

Now showing 1 - 9 of 9
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    Cortex – basal ganglia synchronization in Parkinson’s disease
    (Office of the Vice Chancellor for Research, 2014-04-11) Zauber, S. Elizabeth; Ahn, Sungwoo; Worth, Robert M.; Witt, Thomas C.; Rubchinsky, Leonid L.
    Increased synchrony in the beta band in cortico-basal ganglia circuits is well described in patients with PD. Less is known, however, about how these abnormal firing patterns are correlated across these brain regions. In this study we investigated how this intra-operative data recorded from STN correlates with scalp recorded EEG. Intraoperative single unit recordings and LFPs were obtained from STN and scalp EEG recordings were collected from four electrodes positioned over prefrontal and motor areas. We computed the STN spike-LFP (Local Filed Potential) phase synchrony over short temporal windows as it fluctuates in time. We also computed the EEG phase synchrony index time series for all 6 pairs of EEG electrodes. Next we explored cross-correlation between the two synchrony level time-series of the spike-LFP vs. EEG pairs. EEG synchrony was found to be correlated with spike-LFP synchrony. Correlation between surface EEG and STN was strongest for ipsilateral EEG and STN recordings. Spike-LFP synchronization is believed to characterize the input-output characteristics of STN dynamics and to be strongly relevant to the expression of motor symptoms. Our results indicate that non-invasive and relatively simple EEG recordings retain some information about synchronous dynamics in the subcortical regions, which can be access only in an invasive manner during functional neurosurgical procedures.
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    Critical and Ictal Phases in Simulated EEG Signals on a Small-World Network
    (Frontiers Media, 2021-01-08) Nemzer, Louis R.; Cravens, Gary D.; Worth, Robert M.; Motta, Francis; Placzek, Andon; Castro, Victor; Lou, Jennie Q.; Mathematical Sciences, School of Science
    Healthy brain function is marked by neuronal network dynamics at or near the critical phase, which separates regimes of instability and stasis. A failure to remain at this critical point can lead to neurological disorders such as epilepsy, which is associated with pathological synchronization of neuronal oscillations. Using full Hodgkin-Huxley (HH) simulations on a Small-World Network, we are able to generate synthetic electroencephalogram (EEG) signals with intervals corresponding to seizure (ictal) or non-seizure (interictal) states that can occur based on the hyperexcitability of the artificial neurons and the strength and topology of the synaptic connections between them. These interictal simulations can be further classified into scale-free critical phases and disjoint subcritical exponential phases. By changing the HH parameters, we can model seizures due to a variety of causes, including traumatic brain injury (TBI), congenital channelopathies, and idiopathic etiologies, as well as the effects of anticonvulsant drugs. The results of this work may be used to help identify parameters from actual patient EEG or electrocorticographic (ECoG) data associated with ictogenesis, as well as generating simulated data for training machine-learning seizure prediction algorithms.
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    A Flexible Platform for Biofeedback-driven Control and Personalization of Electrical Nerve Stimulation Therapy
    (IEEE, 2015) Ward, Matthew P.; Qing, Kurt Y.; Otto, Kevin J.; Worth, Robert M.; John, Simon W. M.; Irazoqui, Pedro; Department of Neurological Surgery, IU School of Medicine
    Electrical vagus nerve stimulation is a treatment alternative for many epileptic and depressed patients whose symptoms are not well managed with pharmaceutical therapy. However, the fixed stimulus, open loop dosing mechanism limits its efficacy and precludes major advances in the quality of therapy. A real-time, responsive form of vagus nerve stimulation is needed to control nerve activation according to therapeutic need. This personalized approach to therapy will improve efficacy and reduce the number and severity of side effects. We present autonomous neural control, a responsive, biofeedback-driven approach that uses the degree of measured nerve activation to control stimulus delivery. We demonstrate autonomous neural control in rats, showing that it rapidly learns how to most efficiently activate any desired proportion of vagal A, B, and/or C fibers over time. This system will maximize efficacy by minimizing patient response variability and by minimizing therapeutic failures resulting from longitudinal decreases in nerve activation with increasing durations of treatment. The value of autonomous neural control equally applies to other applications of electrical nerve stimulation.
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    Hospital Length of Stay and Readmission Rate for Neurosurgical Patients
    (Oxford, 2018-02) Ansari, Shaheryar F.; Yan, Hong; Zou, Jian; Worth, Robert M.; Barbaro, Nicholas M.; Neurological Surgery, School of Medicine
    BACKGROUND Hospital readmission rate has become a major indicator of quality of care, with penalties given to hospitals with high rates of readmission. At the same time, insurers are increasing pressure for greater efficiency and reduced costs, including decreasing hospital lengths of stay (LOS). OBJECTIVE To analyze the authors’ service to determine if there is a relationship between LOS and readmission rates. METHODS Records of patients admitted to the authors’ institution from October 2007 through June 2014 were analyzed for several data points, including initial LOS, readmission occurrence, admitting and secondary diagnoses, and discharge disposition. RESULTS Out of 9409 patient encounters, there were 925 readmissions. Average LOS was 6 d. Univariate analysis indicated a higher readmission rate with more diagnoses upon admission (P < .001) and an association between insurance type and readmission (P < .001), as well as decreasing average yearly LOS (P = .0045). Multivariate analysis indicated statistically significant associations between longer LOS (P = .03) and government insurance (P < .01). CONCLUSION A decreasing LOS over time has been associated with an increasing readmission rate at the population level. However, at the individual level, a prolonged LOS was associated with a higher risk of readmission. This was attributed to patient comorbidities. However, this increasing readmission rate may represent many factors including patients’ overall health status. Thus, the rate of readmission may represent a burden of illness rather than a valid metric for quality of care.
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    Interaction of synchronized dynamics in cortical and subcortical circuits in Parkinson’s disease
    (Office of the Vice Chancellor for Research, 2015-04-17) Ahn, Sungwoo; Zauber, S. Elizabeth; Worth, Robert M.; Witt, Thomas; Rubchinsky, Leonid L.
    Parkinson’s disease pathophysiology is marked by increased oscillatory and synchronous activity in the beta frequency band in cortical and basal ganglia circuits. This study explores the functional connections between synchronized dynamics of cortical areas and dynamics of subcortical areas in Parkinson’s disease. We simultaneously recorded neuronal units (spikes) and local field potentials (LFP) from subthalamic nucleus (STN), and electroencephalograms (EEGs) from the scalp in parkinsonian patients and analyzed the correlation between the time-courses of the spike-LFP synchronization and inter-electrode EEG synchronization. We found the (noninvasively obtained) time-course of the synchrony strength between EEG electrodes and the (invasively obtained) time-course of the synchrony between spiking unit and LFP in STN to be weakly, but significantly correlated with each other. This correlation is largest for the bilateral motor EEG synchronization followed by bilateral frontal EEG synchronization. Our observations suggest that there may be multiple functional modes by which the cortical and basal ganglia circuits interact with each other in Parkinson’s disease: not only synchronization may be observed between some areas in cortex and the basal ganglia, but also synchronization within cortex and within basal ganglia may be related, suggesting potentially more global way of functional interaction. More coherent dynamics in one brain region may modulate or activate the dynamics of another brain region in a more powerful way causing correlations between changes in synchrony strength in both regions.
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    Neural synchronization: Average strength vs. temporal patterning
    (Elsevier, 2018-04) Ahn, Sungwoo; Zauber, S. Elizabeth; Worth, Robert M.; Witt, Thomas; Rubchinsky, Leonid L.; Mathematical Sciences, School of Science
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    Synchronized Beta-Band Oscillations in a Model of the Globus Pallidus-Subthalamic Nucleus Network under External Input
    (Frontiers, 2016-12-20) Ahn, Sungwoo; Zauber, S. Elizabeth; Worth, Robert M.; Rubchinsky, Lenold L.; Department of Mathematical Sciences, School of Science
    Hypokinetic symptoms of Parkinson's disease are usually associated with excessively strong oscillations and synchrony in the beta frequency band. The origin of this synchronized oscillatory dynamics is being debated. Cortical circuits may be a critical source of excessive beta in Parkinson's disease. However, subthalamo-pallidal circuits were also suggested to be a substantial component in generation and/or maintenance of Parkinsonian beta activity. Here we study how the subthalamo-pallidal circuits interact with input signals in the beta frequency band, representing cortical input. We use conductance-based models of the subthalamo-pallidal network and two types of input signals: artificially-generated inputs and input signals obtained from recordings in Parkinsonian patients. The resulting model network dynamics is compared with the dynamics of the experimental recordings from patient's basal ganglia. Our results indicate that the subthalamo-pallidal model network exhibits multiple resonances in response to inputs in the beta band. For a relatively broad range of network parameters, there is always a certain input strength, which will induce patterns of synchrony similar to the experimentally observed ones. This ability of the subthalamo-pallidal network to exhibit realistic patterns of synchronous oscillatory activity under broad conditions may indicate that these basal ganglia circuits are directly involved in the expression of Parkinsonian synchronized beta oscillations. Thus, Parkinsonian synchronized beta oscillations may be promoted by the simultaneous action of both cortical (or some other) and subthalamo-pallidal network mechanisms. Hence, these mechanisms are not necessarily mutually exclusive.
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    Temporal patterning of neural synchrony in the basal ganglia in Parkinson’s disease
    (Elsevier, 2015-02) Ratnadurai-Giridharan, Shivakeshavan; Zauber, S. Elizabeth; Worth, Robert M.; Witt, Thomas; Ahn, Sungwoo; Rubchinsky, Leonid L.; Department of Mathematical Sciences, School of Science
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    Thrombus simulating flow void: a pitfall in diagnosing aqueductal patency by high-field MR imaging
    (American Society of Neuroradiology, 1987) Augustyn, Gary T.; D'Amour, Peter G.; Scott, John A.; Worth, Robert M.; Radiology and Imaging Sciences, School of Medicine