[Mechanisms of generation of fast (20 80 Hz) oscillations in thalamocortical circuits].
OBJECTIVE
This review focuses on the mechanisms of generation of fast (20 80 Hz) oscillations in thalamocortical networks and their possible functional role.


METHODS
Fast oscillations appear in the electroencephalogram in a transitory fashion, during behavioral tasks that require increased alertness or during responses to optimal sensory stimulation in animals and humans. Fast oscillations also appear spontaneously during activated states (awake state and paradoxical sleep) and during the depolarizing phases of the slow oscillation that characterize slow wave sleep and anesthesia. Fast oscillations are generated in thalamic and cortical circuits as the result of the activity of pacemaker cells, or as the result of the synaptic interactions among excitatory and inhibitory cells. The synchronization of fast oscillations has been proposed as a possible solution to the binding problem. The formation of neuronal ensembles containing specific sets of cells oscillating together would be the code representing sensory input and coordination between sensory and motor activity. However, oscillating neurons coexist with equal numbers of non oscillating neurons.


CONCLUSIONS
Understanding the rules of coexistence of these two regimes of network activity is key to understanding information processing in the brain. As a first step, and in order to understand the possible role of fast oscillations, it is necessary to understand the mechanisms by which they are generated.
Contreras
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Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6074, USA. diegoc@mail.med.upenn.edu
D004569:Electroencephalography; D006801:Humans; D007395:Interneurons / Q000502:physiology; D009415:Nerve Net / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology; D013788:Thalamus / Q000502:physiology*