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Neurons of the neocortex differ dramatically in the patterns of action potentials they generate in response to current steps. Regular-spiking cells adapt strongly during maintained stimuli, whereas fast-spiking cells can sustain very high firing frequencies with little or no adaptation. Intrinsically bursting cells generate clusters of spikes (bursts),(More)
Extracellular calcium and potassium activities (aCa and aK) as well as neuronal activity were simultaneously recorded with ion-sensitive electrodes in the somatosensory cortex of cats. Baseline aCa was 1.2-1.5 mM/l, baseline aK 2.7-3.2 mM/l. Transient decreases in aCa and simultaneous increases in aK were evoked by repetitive stimulation of the(More)
1. Spike adaptation of neocortical pyramidal neurones was studied with sharp electrode recordings in slices of guinea-pig parietal cortex and whole-cell patch recordings of mouse somatosensory cortex. Repetitive intracellular stimulation with 1 s depolarizing pulses delivered at intervals of < 5 s caused slow, cumulative adaptation of spike firing, which(More)
1. Intracellular recordings were obtained from neurons of the guinea pig sensorimotor cortical slice maintained in vitro. Under control recording conditions input resistances, time constants, and spiking characteristics of slice neurons were well within the ranges reported by other investigators for neocortical neurons in situ. However, resting potentials(More)
In cortical pyramidal neurons, the axon initial segment (AIS) is pivotal in synaptic integration. It has been asserted that this is because there is a high density of Na(+) channels in the AIS. However, we found that action potential-associated Na(+) flux, as measured by high-speed fluorescence Na(+) imaging, was about threefold larger in the rat AIS than(More)
In addition to the well described fast-inactivating component of the Na+ current [transient Na+ current (INaT)], neocortical neurons also exhibit a low-voltage-activated, slowly inactivating "persistent" Na+ current (INaP), which plays a role in determining neuronal excitability and synaptic integration. We investigated the Na+ channels responsible for INaP(More)
1. In whole cell recordings from layer V neurons in slices of mouse somatosensory neocortex, tetrodotoxin (TTX)-sensitive persistent Na+ current (INaP) was studied by blocking K+ currents with intracellular Cs+ and Ca2+ currents with extracellular Cd2+. During slow voltage ramps, INaP began to activate at around -60 mV, and attained a peak at around -25 mV.(More)
The presence of developmental cortical malformations has been associated with the occurrence of epilepsy, and correlative anatomic-clinical electrophysiological studies suggest that microdysgenic lesions may actually initiate epileptiform activity. We have investigated the electrophysiological properties of an animal model of polymicrogyria created by(More)
In neocortical brain slices of the rat that were exposed to 50 microM picrotoxin, low-intensity stimuli evoked all-or-none epileptiform events that propagated across the slice with an average velocity of 0.07 m/s. Simultaneous recordings from pairs of electrodes, in which one was held in a constant position and the other was systematically advanced across(More)
1. The dependence of Ca2+ current inactivation on membrane potential and intracellular Ca2+ concentration ([Ca2+]i) was studied in TEA-loaded, identified Helix neurones which possess a single population of high-voltage-activated Ca2+ channels. During prolonged depolarization, the Ca2+ current declined from its peak with two clearly distinct phases. The time(More)