Intranasal Orexin After Cardiac Arrest Leads to Increased Electroencephalographic Gamma Activity and Enhanced Neurologic Recovery in Rats.

Objectives: Prolonged cardiac arrest is known to cause global ischemic brain injury and functional impairment. Upon resuscitation, electroencephalographic recordings of brain activity begin to resume and can potentially be used to monitor neurologic recovery. We have previously shown that intrathecal orexin shows promise as a restorative drug and arousal agent in rodents.

Band specific changes in thalamocortical synchrony in field potentials after cardiac arrest induced global hypoxia.

Cardiac Arrest (CA) leads to a global hypoxic-ischemic injury in the brain leading to a poor neurological outcome. Understanding the mechanisms of functional disruption in various regions of the brain may be essential for the development of improved diagnostic and therapeutic solutions. Using controlled laboratory experiment with animal models of CA, our primary focus here is on understanding the functional changes in the thalamus and the cortex, associated with the injury and acute recovery upon resuscitation.

Optimal control-based bayesian detection of clinical and behavioral state transitions.

Accurately detecting hidden clinical or behavioral states from sequential measurements is an emerging topic in neuroscience and medicine, which may dramatically impact neural prosthetics, brain-computer interface and drug delivery. For example, early detection of an epileptic seizure from sequential electroencephalographic (EEG) measurements would allow timely administration of anticonvulsant drugs or neurostimulation, thus reducing physical impairment and risks of overtreatment. We develop a Bayesian paradigm for state transition detection that combines optimal control and Markov processes.

A Bayesian framework for analyzing iEEG data from a rat model of epilepsy.

The early detection of epileptic seizures requires computing relevant statistics from multivariate data and defining a robust decision strategy as a function of these statistics that accurately detects the transition from the normal to the peri-ictal (problematic) state. We model the afflicted brain as a hidden Markov model (HMM) with two hidden clinical states (normal and peri-ictal). The output of the HMM is a statistic computed from multivariate neural measurements.

Target-specific catecholamine elevation induced by anticonvulsant thalamic deep brain stimulation.

Purpose: Anterior thalamic nucleus (AN) deep brain stimulation (DBS) is effective in raising EEG and clonic seizure threshold in experimental models. Little is known about the specific properties of DBS that afford its anticonvulsant effect. We sought to test the hypothesis that experimental seizures and the anticonvulsant action of AN DBS alter the underlying regional neurochemistry of AN, specifically with facilitation of the serotonergic system to local electrical stimulation.

Sinusoidal modeling of ictal activity along a thalamus-to-cortex seizure pathway I: new coherence approaches.

Understanding associations in neuronal circuitry is critical for tracing epilepsy pathways. Two new methods of measuring coherence between field potentials and EEG channels are proposed for modeling the level of linear association between channels during epileptic seizures. These methods rely upon modeling the repetitive clonic seizure activity as a sum of sinusoids with varying degrees of phase locking.

Electric field and stimulating influence generated by deep brain stimulation of the subthalamic nucleus.

Objective: The goal of this project was to develop a quantitative understanding of the volume of axonal tissue directly activated by deep brain stimulation (DBS) of the subthalamic nucleus (STN).

Methods: The 3-dimensionally inhomogeneous and anisotropic tissue medium surrounding DBS electrodes complicates our understanding of the electric field and tissue response generated by the stimulation. We developed finite element computer models to address the effects of DBS in a homogeneous isotropic medium, and a medium with tissue conductivity properties derived from human diffusion tensor magnetic resonance data.

Cellular effects of deep brain stimulation: model-based analysis of activation and inhibition.

Deep brain stimulation (DBS) is an effective therapy for medically refractory movement disorders. However, fundamental questions remain about the effects of DBS on neurons surrounding the electrode. Experimental studies have produced apparently contradictory results showing suppression of activity in the stimulated nucleus, but increased inputs to projection nuclei.

Prediction of PTZ-induced seizures using wavelet-based residual entropy of cortical and subcortical field potentials.

Our proposed algorithm for seizure prediction is based on the principle that seizure build-up is always preceded by constantly changing bursting levels. We use a novel measure of residual subband wavelet entropy (RSWE) to directly estimate the entropy of bursts, which is otherwise obscured by the ongoing background activity. Our results are obtained using a slow infusion anesthetized pentylenetetrazol (PTZ) rat model in which we record field potentials (FPs) from frontal cortex and two thalamic areas (anterior and posterior nuclei).

Anterior thalamic mediation of experimental seizures: selective EEG spectral coherence.

Purpose: Physiological evidence has shown that the anterior thalamus (AN) and its associated efferents/afferents constitute an important propagation pathway for pentylenetetrazol (PTZ)-mediated generalized seizures in rodents. Previous work demonstrated metabolic, physical, chemical, and electrical stimulation data supporting a role for AN in the expression of PTZ seizures. We now extend these observations through examination of neuroelectric signal indicators during seizure epochs.

Neurological recovery by EEG bursting after resuscitation from cardiac arrest in rats.

Introduction: The return of neurological function during the early period after resuscitation from cardiac arrest (CA) has not been evaluated systematically. We report the temporal analysis of EEG bursting pattern during the very early periods after resuscitation.

Design/method: A balanced group of good and poor outcome animals was selected from a population of rats subjected to either 5 or 7 min of asphyxial cardiac arrest (ACA) on the basis of a single criteria: 24 h neurobehavioral function based on the neurodeficit score (NDS).