Characterization of synaptic conductances and integrative properties during electrically induced EEG-activated states in neocortical neurons in vivo.
The activation of the electroencephalogram (EEG) is paralleled with an increase in the firing rate of cortical neurons, but little is known concerning the conductance state of their membrane and its impact on their integrative properties. Here, we combined in vivo intracellular recordings with computational models to investigate EEG-activated states induced by stimulation of the brain stem ascending arousal system. Electrical stimulation of the pedonculopontine tegmental (PPT) nucleus produced long-lasting (approximately 20 s) periods of desynchronized EEG activity similar to the EEG of awake animals. Intracellularly, PPT stimulation locked the membrane into a depolarized state, similar to the up-states seen during deep anesthesia. During these EEG-activated states, however, the input resistance was higher than that during up-states. Conductance measurements were performed using different methods, which all indicate that EEG-activated states were associated with a synaptic activity dominated by inhibitory conductances. These results were confirmed by computational models of reconstructed pyramidal neurons constrained by the corresponding intracellular recordings. These models indicate that, during EEG-activated states, neocortical neurons are in a high-conductance state consistent with a stochastic integrative mode. The amplitude and timing of somatic excitatory postsynaptic potentials were nearly independent of the position of the synapses in dendrites, suggesting that EEG-activated states are compatible with coding paradigms involving the precise timing of synaptic events.
Rudolph
Michael
M
Unité de Neuroscience Intégratives et Computationnelles, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
Pelletier
Joe Guillaume
JG
Paré
Denis
D
Destexhe
Alain
A
D000818:Animals; D002415:Cats; D004307:Dose-Response Relationship, Radiation; D004553:Electric Conductivity; D004558:Electric Stimulation; D004569:Electroencephalography / Q000528:radiation effects*; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D008959:Models, Neurological; D019579:Neocortex / Q000166:cytology*; D009433:Neural Inhibition / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000528:radiation effects*; D016011:Normal Distribution; D011188:Potassium / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods; D009435:Synaptic Transmission / Q000528:radiation effects*; D013997:Time Factors; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D005680:gamma-Aminobutyric Acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D011188:Potassium