scholarly journals Serotonin inhibits low‐threshold spike interneurons in the striatum

2012 ◽  
Vol 590 (10) ◽  
pp. 2241-2252 ◽  
Author(s):  
Sarah Cains ◽  
Craig P. Blomeley ◽  
Enrico Bracci
Keyword(s):  
Low Threshold Spike ◽  
Low Threshold

Receiver operating characteristic (ROC) analysis of neurons in the cat's lateral geniculate nucleus during tonic and burst response mode

1995 ◽  
Vol 12 (4) ◽  
pp. 723-741 ◽  
Author(s):  
W. Guido ◽  
S.-M. Lu ◽  
J.W. Vaughan ◽  
Dwayne W. Godwin ◽  
S. Murray Sherman
Keyword(s):  
Visual Stimulus ◽  
Action Potentials ◽  
Operating Characteristic ◽  
Visual Stimuli ◽  
Roc Curves ◽  
Response Mode ◽  
Burst Mode ◽  
Low Threshold Spike ◽  
Low Threshold ◽  
Roc Area

AbstractRelay cells of the lateral geniculate nucleus respond to visual stimuli in one of two modes: burst and tonic. The burst mode depends on the activation of a voltage-dependent, Ca2+ conductance underlying the low threshold spike. This conductance is inactivated at depolarized membrane potentials, but when activated from hyperpolarized levels, it leads to a large, triangular, nearly all-or-none depolarization. Typically, riding its crest is a high-frequency barrage of action potentials. Low threshold spikes thus provide a nonlinear amplification allowing hyperpolarized relay neurons to respond to depolarizing inputs, including retinal EPSPs. In contrast, the tonic mode is characterized by a steady stream of unitary action potentials that more linearly reflects the visual stimulus. In this study, we tested possible differences in detection between response modes of 103 geniculate neurons by constructing receiver operating characteristic (ROC) curves for responses to visual stimuli (drifting sine-wave gratings and flashing spots). Detectability was determined from the ROC curves by computing the area under each curve, known as the ROC area. Most cells switched between modes during recording, evidently due to small shifts in membrane potential that affected the activation state of the low threshold spike. We found that the more often a cell responded in burst mode, the larger its ROC area. This was true for responses to optimal and nonoptimal visual stimuli, the latter including nonoptimal spatial frequencies and low stimulus contrasts. The larger ROC areas associated with burst mode were due to a reduced spontaneous activity and roughly equivalent level of visually evoked response when compared to tonic mode. We performed a within-cell analysis on a subset of 22 cells that switched modes during recording. Every cell, whether tested with a low contrast or high contrast visual stimulus exhibited a larger ROC area during its burst response mode than during its tonic mode. We conclude that burst responses better support signal detection than do tonic responses. Thus, burst responses, while less linear and perhaps less useful in providing a detailed analysis of visual stimuli, improve target detection. The tonic mode, with its more linear response, seems better suited for signal analysis rather than signal detection.

scholarly journals Autonomous firing of low-threshold spike interneurons in the striatum

2010 ◽  
Vol 11 (S1) ◽  
Author(s):  
Joseph A Beatty ◽  
Charles J Wilson
Keyword(s):  
Low Threshold Spike ◽  
Low Threshold

Increased Synchrony with Increase of a Low-Threshold Calcium Conductance in a Model Thalamic Network: A Phase-Shift Mechanism

2000 ◽  
Vol 12 (7) ◽  
pp. 1553-1571 ◽  
Author(s):  
Elizabeth Thomas ◽  
Thierry Grisar
Keyword(s):  
Phase Shift ◽  
Computer Model ◽  
Calcium Current ◽  
Epileptic Activity ◽  
Absence Epilepsy ◽  
Similar Increase ◽  
Calcium Conductance ◽  
Synchronous Firing ◽  
Low Threshold Spike ◽  
Low Threshold

A computer model of a thalamic network was used in order to examine the effects of an isolated augmentation in a low-threshold calcium current. Such an isolated augmentation has been observed in the reticular thalamic (RE) nucleus of the genetic absence epilepsy rat from the Strasbourg (GAERS) model of absence epilepsy. An augmentation of the low-threshold calcium conductance in the RE neurons (gTs) of the model thalamic network was found to lead to an increase in the synchronized firing of the network. This supports the hypothesis that the isolated increase in gTs may be responsible for epileptic activity in the GAERS rat. The increase of gTs in the RE neurons led to a slight increase in the period of the isolated RE neuron firing. In contrast, the low-threshold spike of the RE neuron remained relatively unchanged by the increase of gTs. This suggests that the enhanced synchrony in the network was primarily due to a phase shift in the firing of the RE neurons with respect to the thalamocortical neurons. The ability of this phase-shift mechanism to lead to changes in synchrony was further examined using the model thalamic network. A similar increase in the period of RE neuron oscillations was obtained through an increase in the conductance of the calcium-mediated potassium channel. This change was once again found to increase synchronous firing in the network.

scholarly journals Complex autonomous firing patterns of striatal low-threshold spike interneurons

2012 ◽  
Vol 108 (3) ◽  
pp. 771-781 ◽  
Author(s):  
Joseph A. Beatty ◽  
Matthew A. Sullivan ◽  
Hitoshi Morikawa ◽  
Charles J. Wilson
Keyword(s):  
Nitric Oxide ◽  
Brain Slices ◽  
Calcium Currents ◽  
Firing Patterns ◽  
Cholinergic Interneurons ◽  
Subthreshold Oscillations ◽  
Low Threshold Spike ◽  
Low Threshold ◽  
Oscillatory Mechanisms ◽  
Intrinsic Firing

During sensorimotor learning, tonically active neurons (TANs) in the striatum acquire bursts and pauses in their firing based on the salience of the stimulus. Striatal cholinergic interneurons display tonic intrinsic firing, even in the absence of synaptic input, that resembles TAN activity seen in vivo. However, whether there are other striatal neurons among the group identified as TANs is unknown. We used transgenic mice expressing green fluorescent protein under control of neuronal nitric oxide synthase or neuropeptide-Y promoters to aid in identifying low-threshold spike (LTS) interneurons in brain slices. We found that these neurons exhibit autonomous firing consisting of spontaneous transitions between regular, irregular, and burst firing, similar to cholinergic interneurons. As in cholinergic interneurons, these firing patterns arise from interactions between multiple intrinsic oscillatory mechanisms, but the mechanisms responsible differ. Both neurons maintain tonic firing because of persistent sodium currents, but the mechanisms of the subthreshold oscillations responsible for irregular firing are different. In LTS interneurons they rely on depolarization-activated noninactivating calcium currents, whereas those in cholinergic interneurons arise from a hyperpolarization-activated potassium conductance. Sustained membrane hyperpolarizations induce a bursting pattern in LTS interneurons, probably by recruiting a low-threshold, inactivating calcium conductance and by moving the membrane potential out of the activation range of the oscillatory mechanisms responsible for single spiking, in contrast to the bursting driven by noninactivating currents in cholinergic interneurons. The complex intrinsic firing patterns of LTS interneurons may subserve differential release of classic and peptide neurotransmitters as well as nitric oxide.

scholarly journals Dynamics of Low-Threshold Spike Activation in Relay Neurons of the Cat Lateral Geniculate Nucleus

2001 ◽  
Vol 21 (3) ◽  
pp. 1022-1032 ◽  
Author(s):  
Carolina Gutierrez ◽  
Charles L. Cox ◽  
John Rinzel ◽  
S. Murray Sherman
Keyword(s):  
Lateral Geniculate Nucleus ◽  
Lateral Geniculate ◽  
Low Threshold Spike ◽  
Low Threshold ◽  
Relay Neurons

Low-threshold calcium current and resonance in thalamic neurons: a model of frequency preference

1994 ◽  
Vol 71 (2) ◽  
pp. 583-594 ◽  
Author(s):  
B. Hutcheon ◽  
R. M. Miura ◽  
Y. Yarom ◽  
E. Puil
Keyword(s):  
Steady State ◽  
Low Frequency ◽  
High Threshold ◽  
Voltage Response ◽  
Inactivation Curve ◽  
Low Threshold Spike ◽  
Voltage Dependent ◽  
K Current ◽  
Low Threshold ◽  
Oscillatory Current

1. We constructed a mathematical model of the subthreshold electrical behavior of neurons in the nucleus mediodorsalis thalami (MDT) to elucidate the basis of a Ni(2+)-sensitive low-frequency (2-4 Hz) resonance found previously in these neurons. 2. A model that included the low- and high-threshold Ca2+ currents (IT and IL), a Ca(2+)-activated K+ current (IC), a rapidly inactivating K+ current (IA), a voltage-dependent K+ current which we call IKx, and a voltage-independent leak current (Il), successfully simulated the low-threshold spike observed in MDT neurons. This model (the MDT model) and a minimal version of the model containing only IT and I1 (the minimal MDT model) were used in the analysis. 3. An impedance function was derived for a linearized version of the MDT model. This showed that the model predicts a low-frequency (2-4 Hz) resonance in the voltage response to "small" oscillatory current inputs (producing voltage changes of < 10 mV) when the membrane potential is between -60 and -85 mV. 4. Further examination of the impedances for the MDT and minimal MDT models shows that IT underlies the frequency- and voltage-dependent resonance. The slow inactivation of IT results in an attenuation of voltage responses to low frequencies, resulting in a band-pass behavior. The fast activation of IT amplifies the resonance and modulates the peak frequency but does not, in itself, cause resonance. 5. When voltage responses are small (< 10 mV), the strength and voltage-dependence of resonance of the minimal MDT model are determined by the steady-state window conductance, gw, due to IT. This steady-state conductance arises where the steady-state activation, m(infinity2)(V), and inactivation, h(infinity) (V), curves overlap. Parallel shifts in the inactivation curve can eliminate or enhance resonance with little effect on the IT-dependent low-threshold spike evoked after hyperpolarizing current pulses. When the peak magnitude of gw was large, the minimal MDT model showed spontaneous oscillations at 3 Hz with amplitudes > 30 mV. 6. Large oscillatory current inputs evoked significantly nonlinear voltage responses in the minimal MDT model, but the 2- to 4-Hz frequency selectivity (predicted from the linearized impedance) remained. 7. We conclude that the properties of the low-threshold Ca2+ current, IT, are sufficient to explain the Ni(2+)-sensitive 2- to 4-Hz resonance seen in MDT neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

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