scholarly journals Low–threshold calcium spike bursts in the human thalamus

Brain ◽  
1996 ◽  
Vol 119 (2) ◽  
pp. 363-375 ◽  
Author(s):  
D. Jeanmonod ◽  
M. Magnin ◽  
A. Morel
Keyword(s):  
Human Thalamus ◽  
Low Threshold ◽  
Spike Bursts

scholarly journals Are sleep spindles poised on supercritical Hopf bifurcations?

2019 ◽  
Author(s):  
M. Ospeck
Keyword(s):  
Resting State ◽  
Underlying Mechanism ◽  
Frequency Selectivity ◽  
Long Term Memory ◽  
Sleep Spindles ◽  
Calcium Conductance ◽  
Sinusoidal Input ◽  
Low Threshold ◽  
Spike Bursts ◽  
Relay Neurons

ABSTRACTSleep spindles are recognized as an important intermediate state of long term memory formation. During non REM sleep, large numbers of thalamic relay neurons synchronize their spike bursts for one half to two seconds, entraining many millions of neurons, and constituting a sleep spindle. Here we study spindle amplification, entrainment, synchronization and decay. Relay neurons have both a high resting state near −60 millivolts (mV) and low resting state near −75 mV. Due to the neuron’s sodium conductance, low-threshold calcium conductance, and calcium-dependent H conductance, it exhibits a number of bifurcations, like its supercritical Hopf at −61 mV. Here low-threshold calcium conductance destabilizes membrane potential to birth a small limit-cycle in the 7-16 Hz range. Supercritical Hopfbifurcations are the underlying mechanism for amplification and frequency selectivity in hearing: hair cells are forced by sinusoidal input currents driving their mainly capacitive loads, with the forcing currents locking at 90 degree phase leads with respect to their oscillating membrane potentials. Here we model a small part of a spindle, with 6 cross-coupled relay neurons all poised on Hopfbifurcations. One neuron is forced by a weak noisy train of periodic current impulses that typically lock at a 90 degree phase lead with respect to its voltage oscillation. It then drives its neighbors, causing them to drive each other at much smaller phase angles, usually less than ±10 degrees. The system of Hopf oscillators exhibit small signal amplification and frequency selectivity, high degrees of synchronization and noise rejection, and switch-ability. These argue in favor of spindling relay neurons poising on, or very near to, supercritical Hopfbifurcations. Also, during the phase-locking of their spike bursts, calcium conductance oscillations increase internal calcium, which turns on slow H current. This depolarizes the relay cells, pushing them below their Hopfbifurcations and terminating the spindle.

Bursting and tonic discharges in two classes of reticular thalamic neurons

1992 ◽  
Vol 68 (3) ◽  
pp. 973-977 ◽  
Author(s):  
D. Contreras ◽  
R. Curro Dossi ◽  
M. Steriade
Keyword(s):  
Internal Capsule ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Tonic Firing ◽  
Common View ◽  
Current Pulses ◽  
Low Threshold ◽  
I Cells ◽  
Spike Bursts

1. Two types of cat reticular (RE) thalamic cells were disclosed by means of intracellular recordings under urethan anesthesia. The RE neurons were identified by their typical depolarizing spindle oscillations in response to synchronous stimulation of the internal capsule. 2. In type I neurons (n = 41), depolarizing current pulses induced tonic firing at the resting or slightly depolarized membrane potential (Vm) and triggered high-frequency spike bursts at a Vm more negative than -75 mV. As well, these cells discharged rebound bursts at the break of a hyperpolarizing current pulse. Internal capsule stimulation elicited spindle sequences made off by depolarizing waves giving rise to spike bursts. 3. Type II cells (n = 9) did not discharge spike bursts to large depolarizing current pulses even when the Vm reached -100 mV, nor did they fire rebound bursts after long-lasting hyperpolarizing current pulses or spike bursts riding on the rhythmic depolarizing components of spindle sequences. 4. Compared with type I cells, type II cells showed less frequency accommodation during tonic firing. The latter neuronal class discharged at high frequencies (40 Hz) with slight DC depolarization, approximately 8-10 Hz at the resting Vm, and no underlying synaptic or subthreshold oscillatory events could be detected when the firing was blocked by DC hyperpolarization. 5. The presence of two cell classes in the RE nucleus challenges the common view that this nucleus consists of a single neuronal class. We suggest that a different set of conductances is present in type II RE neurons, thus preventing the low-threshold Ca2+ current from dominating the behavior of these cells.

Diverse Synaptic Connections Between Peptidergic Radula Mechanoafferent Neurons and Neurons in the Feeding System ofAplysia

2000 ◽  
Vol 83 (3) ◽  
pp. 1605-1620 ◽  
Author(s):  
Steven C. Rosen ◽  
Mark W. Miller ◽  
Colin G. Evans ◽  
Elizabeth C. Cropper ◽  
Irving Kupfermann
Keyword(s):  
Motor Neurons ◽  
Synaptic Connections ◽  
Buccal Ganglion ◽  
Motor Programs ◽  
Rhythmic Motor ◽  
Identified Neuron ◽  
Low Threshold ◽  
Sensory Responses ◽  
Fast Chemical ◽  
Spike Bursts

The buccal ganglion of Aplysia contains a heterogeneous population of peptidergic, radula mechanoafferent (RM) neurons. To investigate their function, two of the larger RM cells (B21, B22) were identified by morphological and electrophysiological criteria. Both are low-threshold, rapidly adapting, mechanoafferent neurons that responded to touch of the radula, the structure that grasps food during ingestive and egestive feeding movements. Sensory responses of the cells consisted of spike bursts at frequencies of 8–35 Hz. Each cell was found to make chemical, electrical, or combined synapses with other sensory neurons, motor neurons and interneurons involved in radula closure and/or protraction-retraction movements of the odontophore. Motor neurons receiving input included the following: B8a/b, B15, and B16, which innervate muscles contributing to radula closing; and B82, a newly identified neuron that innervates the anterodorsal region of the I1/I3 muscles of the buccal mass. B21 and B22 can affect buccal motor programs by way of their connections to interneurons such as B19 and B64. Fast, chemical, excitatory postsynaptic potentials (EPSPs) produced by RM neurons, such as B21, exhibited strong, frequency-dependent facilitation, a form of homosynaptic plasticity. Firing B21 also produced a slow EPSP in B15 that increased the excitability of the cell. Thus a sensory neuron mediating a behavioral response may have modulatory effects. The data suggest multiple functions for RM neurons including 1) triggering of phase transitions in rhythmic motor programs, 2) adjusting the force of radula closure, 3) switching from biting to swallowing or swallowing to rejection, and 4) enhancing food-induced arousal.

Abolition of spindle oscillations in thalamic neurons disconnected from nucleus reticularis thalami

1985 ◽  
Vol 54 (6) ◽  
pp. 1473-1497 ◽  
Author(s):  
M. Steriade ◽  
M. Deschenes ◽  
L. Domich ◽  
C. Mulle
Keyword(s):  
High Frequency ◽  
Temporal Integration ◽  
Burst Activity ◽  
Thalamic Nuclei ◽  
Intrinsic Structure ◽  
Thalamic Neurons ◽  
Thalamic Input ◽  
Thalamic Relay ◽  
Low Threshold ◽  
Spike Bursts

The effects of depriving thalamic relay and intralaminar nuclei from their reticularis thalami (RE) inputs were investigated in acute and chronic experiments on cat. In acutely prepared animals, two (frontal and parasagittal) thalamic transections were made; extracellular and intracellular recordings were performed in RE-disconnected thalamic nuclei. In chronic experiments, the RE nuclear complex was lesioned by means of kainic acid injections; the activity of RE-deprived thalamocortical neurons was extracellularly studied during wakefulness and synchronized sleep. Two features distinguish RE-deprived nuclei from normal thalamic nuclei: absence of spindle-wave rhythmicity and all-burst activity of neurons. The abolition of spindle-related rhythms (sequences of 7- to 14-Hz waves recurring periodically with a rhythm of 0.1-0.2 Hz) in RE-disconnected thalamic nuclei and ipsilateral neocortical areas contrasted with normal spindling rhythmicity in contralateral EEG leads. Spontaneously occurring, rhythmic, long-lasting inhibitory postsynaptic potentials (IPSPs), as observed in intact preparations, were no longer observed in RE-disconnected thalamic neurons. The remaining inhibitory events consisted of short-duration IPSPs. The possibility that RE nucleus is a pacemaker for spindling rhythms, imposing them through inhibitory projections to target thalamic areas, is supported by our concurrent experiments that indicate RE neurons preserve their rhythmicity after disconnection from their major (cortical and thalamic) input sources. RE-deprived thalamocortical neurons exclusively exhibit high-frequency spike bursts whose intrinsic structure is identical to that of intact thalamic relay cells. Instead of the spindle-related sequences of bursts seen in normal animals, the bursts of RE-disconnected thalamocortical neurons are single events, with a dramatic rhythmicity at 1-2 Hz. The presumed mechanism of this rhythmicity is the periodic activation of a low-threshold somatic conductance whose deinactivation is brought about by temporal integration of short-lasting IPSPs. It is known that high-frequency spike bursts of thalamic relay neurons result from hyperpolarization of cell membrane. We blocked the underlying inhibitory events by bicuculline and reversibly changed the all-burst activity of RE-disconnected neurons into a tonic mode. Since the only activity of RE-deprived thalamocortical neurons consists of burst discharges, we hypothesize that local-circuit GABAergic neurons are released from inhibition after RE disconnection or lesion.

Low threshold open science

2014 ◽  
Author(s):  
Chris H. J. Hartgerink
Keyword(s):  
Open Science ◽  
Low Threshold

Iberis amara L. desensitizes low-threshold mechano-sensitive afferents of the colon

Planta Medica ◽  
2011 ◽  
Vol 77 (12) ◽  
Author(s):  
S Mittler ◽  
MH Müller ◽  
MS Kasparek ◽  
O Kelber ◽  
D Weiser ◽  
...  
Keyword(s):  
Iberis Amara ◽  
Low Threshold

Sans Souci and the Pedagogical Experience

2011 ◽  
Vol 4 (1) ◽  
pp. 93-109 ◽  
Author(s):  
Anne Reinertsen
Keyword(s):  
Critical Thinking ◽  
Student Teachers ◽  
Modern Society ◽  
Modern School ◽  
Low Threshold ◽  
Scientific Competence

This is about the pedagogical experience ahead of or beyond any pedagogical activity or action. It is therefore about perfectibility and/or dealing with something both theoretically and existentially. It is about inclusion and dialogue, but in an indirect manner, and school as a low threshold institution: heterogeneity, pluralism and multiculturalism as the primary characteristics of a modern school in a modern society. This makes school an institution important to life and knowledge. The need for a pedagogy created through a strong scientific orientation through practice or as I prefer; realism, urgent: Pedagogy framed by a good, relevant and strong understanding of context. This makes demands on teachers' competence. It demands more than possessing pedagogical scientific competence. A certain extent of double(d) competence and more is demanded both about what happens in science and about what happens in society and openness always through language and critical thinking or philosophy. This is about becoming teacher in/and for the fractured future and about what we might “give” (student) teachers in addition.

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