Multiple Time Scales of Temporal Response in Pyramidal and Fast Spiking Cortical Neurons

2006 ◽  
Vol 96 (6) ◽  
pp. 3448-3464 ◽  
Author(s):  
Giancarlo La Camera ◽  
Alexander Rauch ◽  
David Thurbon ◽  
Hans-R. Lüscher ◽  
Walter Senn ◽  
...  
Keyword(s):  
Time Scales ◽  
Cortical Neurons ◽  
Time Course ◽  
Sensory Stimulation ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Wide Range ◽  
Fast Spiking

Neural dynamic processes correlated over several time scales are found in vivo, in stimulus-evoked as well as spontaneous activity, and are thought to affect the way sensory stimulation is processed. Despite their potential computational consequences, a systematic description of the presence of multiple time scales in single cortical neurons is lacking. In this study, we injected fast spiking and pyramidal (PYR) neurons in vitro with long-lasting episodes of step-like and noisy, in-vivo-like current. Several processes shaped the time course of the instantaneous spike frequency, which could be reduced to a small number (1–4) of phenomenological mechanisms, either reducing (adapting) or increasing (facilitating) the neuron's firing rate over time. The different adaptation/facilitation processes cover a wide range of time scales, ranging from initial adaptation (<10 ms, PYR neurons only), to fast adaptation (<300 ms), early facilitation (0.5–1 s, PYR only), and slow (or late) adaptation (order of seconds). These processes are characterized by broad distributions of their magnitudes and time constants across cells, showing that multiple time scales are at play in cortical neurons, even in response to stationary stimuli and in the presence of input fluctuations. These processes might be part of a cascade of processes responsible for the power-law behavior of adaptation observed in several preparations, and may have far-reaching computational consequences that have been recently described.

Possible Effects of Depolarizing GABAA Conductance on the Neuronal Input–Output Relationship: A Modeling Study

2005 ◽  
Vol 93 (6) ◽  
pp. 3504-3523 ◽  
Author(s):  
Kenji Morita ◽  
Kunichika Tsumoto ◽  
Kazuyuki Aihara
Keyword(s):  
Firing Rate ◽  
Cortical Neurons ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Resting Potential ◽  
Input Output ◽  
Wide Range ◽  
The Relationship

Recent in vitro experiments revealed that the GABAA reversal potential is about 10 mV higher than the resting potential in mature mammalian neocortical pyramidal cells; thus GABAergic inputs could have facilitatory, rather than inhibitory, effects on action potential generation under certain conditions. However, how the relationship between excitatory input conductances and the output firing rate is modulated by such depolarizing GABAergic inputs under in vivo circumstances has not yet been understood. We examine herewith the input–output relationship in a simple conductance-based model of cortical neurons with the depolarized GABAA reversal potential, and show that a tonic depolarizing GABAergic conductance up to a certain amount does not change the relationship between a tonic glutamatergic driving conductance and the output firing rate, whereas a higher GABAergic conductance prevents spike generation. When the tonic glutamatergic and GABAergic conductances are replaced by in vivo–like highly fluctuating inputs, on the other hand, the effect of depolarizing GABAergic inputs on the input–output relationship critically depends on the degree of coincidence between glutamatergic input events and GABAergic ones. Although a wide range of depolarizing GABAergic inputs hardly changes the firing rate of a neuron driven by noncoincident glutamatergic inputs, a certain range of these inputs considerably decreases the firing rate if a large number of driving glutamatergic inputs are coincident with them. These results raise the possibility that the depolarized GABAA reversal potential is not a paradoxical mystery, but is instead a sophisticated device for discriminative firing rate modulation.

scholarly journals Meta-control of the exploration-exploitation dilemma emerges from probabilistic inference over a hierarchy of time scales

2019 ◽  
Author(s):  
Dimitrije Marković ◽  
Thomas Goschke ◽  
Stefan J. Kiebel
Keyword(s):  
Cognitive Control ◽  
Time Scales ◽  
Probabilistic Inference ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Dynamic Task ◽  
Wide Range ◽  
Hidden States ◽  
Short Time ◽  
Exploration Exploitation

AbstractCognitive control is typically understood as a set of mechanisms which enable humans to reach goals that require integrating the consequences of actions over longer time scales. Importantly, using routine beheavior or making choices beneficial only at a short time scales would prevent one from attaining these goals. During the past two decades, researchers have proposed various computational cognitive models that successfully account for behaviour related to cognitive control in a wide range of laboratory tasks. As humans operate in a dynamic and uncertain environment, making elaborate plans and integrating experience over multiple time scales is computationally expensive, the specific question of how uncertain consequences at different time scales are integrated into adaptive decisions remains poorly understood. Here, we propose that precisely the problem of integrating experience and forming elaborate plans over multiple time scales is a key component for better understanding how human agents solve cognitive control dilemmas such as the exploration-exploitation dilemma. In support of this conjecture, we present a computational model of probabilistic inference over hidden states and actions, which are represented as a hierarchy of time scales. Simulations of goal-reaching agents instantiating the model in an uncertain and dynamic task environment show how the exploration-exploitation dilemma may be solved by inferring meta-control states which adapt behaviour to changing contexts.

Distinct Time Scales in Cortical Discrimination of Natural Sounds in Songbirds

2006 ◽  
Vol 96 (1) ◽  
pp. 252-258 ◽  
Author(s):  
Rajiv Narayan ◽  
Gilberto Graña ◽  
Kamal Sen
Keyword(s):  
Auditory Cortex ◽  
Time Scales ◽  
Temporal Resolution ◽  
Cortical Neurons ◽  
Temporal Integration ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Neural Responses ◽  
Sensory Stimuli ◽  
Complex Sounds

Understanding how single cortical neurons discriminate between sensory stimuli is fundamental to providing a link between cortical neural responses and perception. The discrimination of sensory stimuli by cortical neurons has been intensively investigated in the visual and somatosensory systems. However, relatively little is known about discrimination of sounds by auditory cortical neurons. Auditory cortex plays a particularly important role in the discrimination of complex sounds, e.g., vocal communication sounds. The rich dynamic structure of such complex sounds on multiple time scales motivates two questions regarding cortical discrimination. How does discrimination depend on the temporal resolution of the cortical response? How does discrimination accuracy evolve over time? Here we investigate these questions in field L, the analogue of primary auditory cortex in zebra finches, analyzing temporal resolution and temporal integration in the discrimination of conspecific songs (songs of the bird's own species) for both anesthetized and awake subjects. We demonstrate the existence of distinct time scales for temporal resolution and temporal integration and explain how they arise from cortical neural responses to complex dynamic sounds.

scholarly journals Fast Rhythmic Bursting Can Be Induced in Layer 2/3 Cortical Neurons by Enhancing Persistent Na+ Conductance or by Blocking BK Channels

2003 ◽  
Vol 89 (2) ◽  
pp. 909-921 ◽  
Author(s):  
Roger D. Traub ◽  
Eberhard H. Buhl ◽  
Tengis Gloveli ◽  
Miles A. Whittington
Keyword(s):  
Cortical Neurons ◽  
Firing Pattern ◽  
Critical Role ◽  
Sensory Stimulation ◽  
Bk Channels ◽  
Bk Channel ◽  
Neocortical Neurons ◽  
Layer 2

Fast rhythmic bursting (or “chattering”) is a firing pattern exhibited by selected neocortical neurons in cats in vivo and in slices of adult ferret and cat brain. Fast rhythmic bursting (FRB) has been recorded in certain superficial and deep principal neurons and in aspiny presumed local circuit neurons; it can be evoked by depolarizing currents or by sensory stimulation and has been proposed to depend on a persistent g Na that causes spike depolarizing afterpotentials. We constructed a multicompartment 11-conductance model of a layer 2/3 pyramidal neuron, containing apical dendritic calcium-mediated electrogenesis; the model can switch between rhythmic spiking (RS) and FRB modes of firing, with various parameter changes. FRB in this model is favored by enhancing persistent g Na and also by measures that reduce [Ca2+]i or that reduce the conductance of g K(C) (a fast voltage- and Ca2+-dependent conductance). Axonal excitability plays a critical role in generating fast bursts in the model. In vitro experiments in rat layer 2/3 neurons confirmed (as shown previously by others) that RS firing could be switched to fast rhythmic bursting, either by buffering [Ca2+]i or by enhancing persistent g Na. In addition, our experiments confirmed the model prediction that reducing g KC (with iberiotoxin) would favor FRB. During the bursts, fast prepotentials (spikelets) could occur that did not originate in apical dendrites and that appear to derive from the axon. We suggest that modulator-induced regulation of [Ca2+] dynamics or of BK channel conductance, for example via protein kinase A, could play a role in determining the firing pattern of neocortical neurons; specifically, such modulation could play a role in regulating whether neurons respond to strong stimulation with fast rhythmic bursts.

scholarly journals Dynamics of Spatial Distortions Reveal Multiple Time Scales of Motion Adaptation

2009 ◽  
Vol 102 (6) ◽  
pp. 3619-3626 ◽  
Author(s):  
Neil W. Roach ◽  
Paul V. McGraw
Keyword(s):  
Time Scales ◽  
Time Course ◽  
Visual Motion ◽  
Prolonged Exposure ◽  
Temporal Dynamics ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Motion Adaptation ◽  
Gradual Process ◽  
Neurophysiological Studies

Prolonged exposure to consistent visual motion can significantly alter the perceived direction and speed of subsequently viewed objects. These perceptual aftereffects have provided invaluable tools with which to study the mechanisms of motion adaptation and draw inferences about the properties of underlying neural populations. Behavioral studies of the time course of motion aftereffects typically reveal a gradual process of adaptation spanning a period of multiple seconds. In contrast, neurophysiological studies have documented multiple motion adaptation effects operating over similar, or substantially faster (i.e., sub-second) time scales. Here we investigated motion adaptation by measuring time-dependent changes in the ability of moving stimuli to distort the perceived position of briefly presented static objects. The temporal dynamics of these motion-induced spatial distortions reveal the operation of two dissociable mechanisms of motion adaptation with differing properties. The first is rapid (subsecond), acts to limit the distortions induced by continuing motion, but is not sufficient to produce an aftereffect once the motion signal disappears. The second gradually accumulates over a period of seconds, does not modulate the size of distortions produced by continuing motion, and produces repulsive aftereffects after motion offset. These results provide new psychophysical evidence for the operation of multiple mechanisms of motion adaptation operating over distinct time scales.

scholarly journals Meta-control of the exploration-exploitation dilemma emerges from probabilistic inference over a hierarchy of time scales

2020 ◽  
Author(s):  
Dimitrije Marković ◽  
Thomas Goschke ◽  
Stefan J. Kiebel
Keyword(s):  
Cognitive Control ◽  
Time Scales ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Single Action ◽  
Wide Range ◽  
Control Concept ◽  
Novel Concept ◽  
Short Time ◽  
Exploration Exploitation

AbstractCognitive control is typically understood as a set of mechanisms that enable humans to reach goals that require integrating the consequences of actions over longer time scales. Importantly, using routine behaviour or making choices beneficial only at short time scales would prevent one from attaining these goals. During the past two decades, researchers have proposed various computational cognitive models that successfully account for behaviour related to cognitive control in a wide range of laboratory tasks. As humans operate in a dynamic and uncertain environment, making elaborate plans and integrating experience over multiple time scales is computationally expensive. Importantly, it remains poorly understood how uncertain consequences at different time scales are integrated into adaptive decisions. Here, we pursue the idea that cognitive control can be cast as active inference over a hierarchy of time scales, where inference, i.e., planning, at higher levels of the hierarchy controls inference at lower levels. We introduce the novel concept of meta-control states, which link higher-level beliefs with lower-level policy inference. Specifically, we conceptualize cognitive control as inference over these meta-control states, where solutions to cognitive control dilemmas emerge through surprisal minimisation at different hierarchy levels. We illustrate this concept using the exploration-exploitation dilemma based on a variant of a restless multi-armed bandit task. We demonstrate that beliefs about contexts and meta-control states at a higher level dynamically modulate the balance of exploration and exploitation at the lower level of a single action. Finally, we discuss the generalisation of this meta-control concept to other control dilemmas.

scholarly journals Rab27a-Dependent Paracrine Communication Controls Dendritic Spine Formation and Sensory Responses in the Barrel Cortex

Cells ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 622
Author(s):  
Longbo Zhang ◽  
Xiaobing Zhang ◽  
Lawrence S. Hsieh ◽  
Tiffany V. Lin ◽  
Angélique Bordey
Keyword(s):  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Barrel Cortex ◽  
Copy Number Variants ◽  
Sensory Stimulation ◽  
Small Gtpase ◽  
Somatosensory Information ◽  
Increased Risk

Rab27a is an evolutionarily conserved small GTPase that regulates vesicle trafficking, and copy number variants of RAB27a are associated with increased risk of autism. However, the function of Rab27a on brain development is unknown. Here, we identified a form of paracrine communication that regulates spine development between distinct populations of developing cortical neurons. In the developing somatosensory cortex of mice, we show that decreasing Rab27a levels in late-born pyramidal neurons destined for layer (L) 2/3 had no cell-autonomous effect on their synaptic integration but increased excitatory synaptic transmission onto L4 neurons that receive somatosensory information. This effect resulted in an increased number of L4 neurons activated by whisker stimulation in juvenile mice. In addition, we found that Rab27a, the level of which decreases as neurons mature, regulates the release of small extracellular vesicles (sEVs) in developing neurons in vitro and decreasing Rab27a levels led to the accumulation of CD63-positive vesicular compartments in L2/3 neurons in vivo. Together, our study reveals that Rab27a-mediated paracrine communication regulates the development of synaptic connectivity, ultimately tuning responses to sensory stimulation, possibly via controlling the release of sEVs.

scholarly journals Mucin CoreO-Glycosylation Is Modulated by Neighboring Residue Glycosylation Status

2002 ◽  
Vol 277 (51) ◽  
pp. 49850-49862 ◽  
Author(s):  
Thomas A. Gerken ◽  
Jiexin Zhang ◽  
Jessica Levine ◽  
Åke Elhammer
Keyword(s):  
Tandem Repeat ◽  
Time Course ◽  
Submaxillary Gland ◽  
Inverse Correlation ◽  
Peptide Sequence ◽  
Glycosylation Pattern ◽  
Glycosylation Sites ◽  
Wide Range

The influence of peptide sequence and environment on the initiation and elongation of mucinO-glycosylation is not well understood. Thein vivoglycosylation pattern of the porcine submaxillary gland mucin (PSM) tandem repeat containing 31O-glycosylation sites (Gerken, T. A., Gilmore, M., and Zhang, J. (2002)J. Biol. Chem.277, 7736–7751) reveals a weak inverse correlation with hydroxyamino acid density (and by inference the density of glycosylation) with the extent of GalNAc glycosylation and core-1 substitution. We now report the time course of thein vitroglycosylation of the apoPSM tandem repeat by recombinant UDP-GalNAc:polypeptide α-GalNAc transferases (ppGalNAc transferase) T1 and T2 that confirm these findings. A wide range of glycosylation rates are found, with several residues showing apparent plateaus in glycosylation. An adjustable kinetic model that reduces the first-order rate constants proportional to neighboring glycosylation status, plus or minus three residues of the site of glycosylation, was found to reasonably reproduce the experimental rate data for both transferases, including apparent plateaus in glycosylation. The unique, transferase-specific, positional weighting constants reveal information on the peptide/glycopeptide recognition site for each transferase. Both transferases displayed high sensitivities to neighboring Ser/Thr glycosylation, whereas ppGalNAc T2 displayed additional high sensitivities to the presence of nonglycosylated Ser/Thr residues. This is the first demonstration of the ability to model mucinO-glycosylation kinetics, confirming that under the appropriate conditions neighboring glycosylation status can be a significant factor modulating the first step of mucinO-glycan biosynthesis.

scholarly journals Implantable microcoils for intracortical magnetic stimulation

2016 ◽  
Vol 2 (12) ◽  
pp. e1600889 ◽  
Author(s):  
Seung Woo Lee ◽  
Florian Fallegger ◽  
Bernard D. F. Casse ◽  
Shelley I. Fried
Keyword(s):  
Cortical Neurons ◽  
Magnetic Stimulation ◽  
Pyramidal Neurons ◽  
Brain Slices ◽  
Behavioral Responses ◽  
Wide Range ◽  
Cortical Pyramidal Neurons ◽  
Over Time

Neural prostheses that stimulate the neocortex have the potential to treat a wide range of neurological disorders. However, the efficacy of electrode-based implants remains limited, with persistent challenges that include an inability to create precise patterns of neural activity as well as difficulties in maintaining response consistency over time. These problems arise from fundamental limitations of electrodes as well as their susceptibility to implantation and have proven difficult to overcome. Magnetic stimulation can address many of these limitations, but coils small enough to be implanted into the cortex were not thought strong enough to activate neurons. We describe a new microcoil design and demonstrate its effectiveness for both activating cortical neurons and driving behavioral responses. The stimulation of cortical pyramidal neurons in brain slices in vitro was reliable and could be confined to spatially narrow regions (<60 μm). The spatially asymmetric fields arising from the coil helped to avoid the simultaneous activation of passing axons. In vivo implantation was safe and resulted in consistent and predictable behavioral responses. The high permeability of magnetic fields to biological substances may yield another important advantage because it suggests that encapsulation and other adverse effects of implantation will not diminish coil performance over time, as happens to electrodes. These findings suggest that a coil-based implant might be a useful alternative to existing electrode-based devices. The enhanced selectivity of microcoil-based magnetic stimulation will be especially useful for visual prostheses as well as for many brain-computer interface applications that require precise activation of the cortex.

Evaluation of 99mTc-Label led Vitamin K4 as an Agent for Testicular Imaging

1991 ◽  
Vol 30 (01) ◽  
pp. 35-39 ◽  
Author(s):  
H. S. Durak ◽  
M. Kitapgi ◽  
B. E. Caner ◽  
R. Senekowitsch ◽  
M. T. Ercan
Keyword(s):  
Soft Tissue ◽  
Room Temperature ◽  
Normal Subjects ◽  
Left Testis ◽  
Wide Range ◽  
Activity Ratios ◽  
The Right ◽  
Radioactivity Levels

Vitamin K4 was labelled with 99mTc with an efficiency higher than 97%. The compound was stable up to 24 h at room temperature, and its biodistribution in NMRI mice indicated its in vivo stability. Blood radioactivity levels were high over a wide range. 10% of the injected activity remained in blood after 24 h. Excretion was mostly via kidneys. Only the liver and kidneys concentrated appreciable amounts of radioactivity. Testis/soft tissue ratios were 1.4 and 1.57 at 6 and 24 h, respectively. Testis/blood ratios were lower than 1. In vitro studies with mouse blood indicated that 33.9 ±9.6% of the radioactivity was associated with RBCs; it was washed out almost completely with saline. Protein binding was 28.7 ±6.3% as determined by TCA precipitation. Blood clearance of 99mTc-l<4 in normal subjects showed a slow decrease of radioactivity, reaching a plateau after 16 h at 20% of the injected activity. In scintigraphic images in men the testes could be well visualized. The right/left testis ratio was 1.08 ±0.13. Testis/soft tissue and testis/blood activity ratios were highest at 3 h. These ratios were higher than those obtained with pertechnetate at 20 min post injection.99mTc-l<4 appears to be a promising radiopharmaceutical for the scintigraphic visualization of testes.

Sign in / Sign up

Export Citation Format

Share Document