BURST GENERATION AND GAMMA BAND OSCILLATIONS

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For many years it has been known that different states of arousal can be classified based upon the predominant frequency of neural oscillations observed in electroencephalograms. The emergence of gamma-band oscillations (30-70Hz) is a hallmark of the transition from sleep states to states of arousal. It is proposed that a subclass of supragranular pyramidal cells, chattering cells, which discharge high frequency action potentials (greater than 250Hz) with interburst intervals in the gamma-band range are important in the generation of neocortical gamma-band oscillations. Preliminary in vitro work has shown that a sub- class of pyramidal neurons can be induced to discharge of action potentials that chattering cells by injection of depolarizing current. The onset of gamma-band oscillations following electrical stimulation of reticular formation activating centers will be assessed in vivo, via intracellular recordings from burst generating neurons and the monitoring of local field potentials in the supragranular layers of cat primary visual cortex. In vitro depolarizing current and the application of cholinergic agonists will be used to study the genesis of burst firing and the biophysical changes that the neuron undergoes when it switches form firing single action potentials to bursts of action potentials. By employing both in vivo and in vitro recording methodologies the role that burst generating neurons have in the development of neuronal synchronization and gamma-band oscillations will assessed.