Nitish Thakor | PubMed Health

PubMed2004

EEG signal modeling using adaptive Markov process amplitude.

In this paper, an adaptive Markov process amplitude algorithm is used to model and simulate electroencephalogram (EEG) signals. EEG signal modeling is used as a tool to identify pathophysiological EEG changes potentially useful in clinical diagnosis. The least mean square algorithm is adopted to continuously estimate the parameters of a first-order Markov process model. EEG signals recorded from rodent brains during injury and recovery following global cerebral ischemia are utilized as input signals to the model. The EEG was recorded in a controlled experimental brain injury model of hypoxic-ischemic cardiac arrest. The signals from the injured brain during various phases of injury and recovery were modeled. Results show that the adaptive model is accurate in simulating EEG signal variations following brain injury. The dynamics of the model coefficients successfully capture the presence of spiking and bursting in EEG.

Algorithms↗

PubMed2002

Early restitution of electrocorticogram predicts subsequent behavioral recovery from cardiac arrest.

Previous studies have shown that parameters of EEG restitution reflect the severity of global hypoxic-ischemic brain injury. Here, the hypothesis is tested that patterns of EEG restitution during the first 4 hours predict later behavioral recovery. Time course and correlations between behavior, electrocorticogram (EcoG), and neuronal injury were investigated in a rodent model of asphyctic cardiac arrest. Forty Wistar rats were subjected to 5 minutes of asphyxia and cardiopulmonary resuscitation. Behavior was assessed by repeated scoring of neurodeficits and open field activity until euthanasia at 48 hours. Electrocorticographic bursting occurred at 13.2 +/- 4 minutes after resuscitation. Bursts increased in frequency and duration until the EcoG reverted to a continuous signal. The resuscitation-continuous EcoG interval correlated with the first appearance of spontaneous movements (r = 0.80, P < 0.05). Larger intervals were associated with hyperactivity in the open field at 24 hours (r = 0.61, P < 0.05), indicating a more severe behavioral deficit. Larger intervals were also associated with worse 48-hour neurodeficit scores (P < 0.05). Neuronal damage in the hippocampus correlated with the degree of open field hyperactivity at 14 hours (P < 0.05). These findings demonstrate a close temporal and prognostic relationship between electrical and behavioral recovery after hypoxic-ischemic brain injury.

Animals↗