We investigate the influence of efficacy of synaptic interaction on firing synchronization in excitatory neuronal networks. We find spike death phenomena: namely, the state of neurons transits from the limit cycle to a fixed point or transient state. The phenomena occur under the perturbation of an excitatory synaptic interaction, which has a high efficacy. We show that the decrease of synaptic...

than expected from the models based on the HH formalism. Moreover, the voltage at which the spike takes off (the threshold) varies remarkably from spike to spike in the same neuron in vivo (Fig. 1, overleaf). Examining several HH-based models, the authors find that none of them can account for both observations — spike sharpness and threshold variability. Indeed, under the HH formalism the spik...

The cerebellum of mormyrid electric fish is unusual for its size and for the regularity of its histology. The circuitry of the mormyrid cerebellum is also different from that of the mammalian cerebellum in that mormyrid Purkinje cell axons terminate locally within the cortex on efferent cells, and the cellular regions of termination for climbing fibers and parallel fibers are well separated. Th...

This study examines the ability of neurons to track temporally varying inputs, namely by investigating how the instantaneous firing rate of a neuron is modulated by a noisy input with a small sinusoidal component with frequency (f). Using numerical simulations of conductance-based neurons and analytical calculations of one-variable nonlinear integrate-and-fire neurons, we characterized the depe...

Most cortical neurons fire regularly when excited by a constant stimulus. In contrast, irregular-spiking (IS) interneurons are remarkable for the intrinsic variability of their spike timing, which can synchronize amongst IS cells via specific gap junctions. Here, we have studied the biophysical mechanisms of this irregular spiking in mice, and how IS cells fire in the context of synchronous net...

Spike-timing variability has a large effect on neural information processing. However, for many systems little is known about the noise sources causing the spike-response variability. Here we investigate potential sources of spike-response variability in auditory receptor neurons of locusts, a classic insect model system. At low-spike frequencies, our data show negative interspike-interval (ISI...

Olfactory perception is influenced by behavioral states, presumably via efferent regulation. Using the whole cell version of patch-clamp recording technique, we discovered that acetylcholine, which is released from efferent fibers in the olfactory mucosa, can directly affect the signal encoding in newt olfactory receptor cells (ORCs). Under current-clamp conditions, application of carbachol, an...

The response of the auditory nerve to electrical stimulation is highly sensitive to small modulations (<0.5%). This report demonstrates that dynamical instability (i.e., a positive Lyapunov exponent) can account for this sensitivity in a modified FitzHugh-Nagumo model of spike generation, so long as the input noise is not too large. This finding suggests both that spike generator instability is...

The spinal cord and spinal motoneurons are densely innervated by terminals of serotonin (5-HT) and norepinephrine (NE) neurons arising mostly from the brain stem, but also from intrinsic spinal neurons. Even after long-term spinal transection (chronic spinal), significant amounts (10%) of 5-HT and NE (monoamines) remain caudal to the injury. To determine the role of such endogenous monoamines, ...

A child with pattern sensitive epilepsy is reported. She had both absences and generalised seizures. The latter occurred spontaneously but the former followed concentration on patterned materials. These self-induced seizures appeared to have an affective component. The EEG showed generalised atypical spike and wave discharges both in the resting state and during intermittent photic and pattern ...