scholarly journals Modulation of Neural Microcircuits That Control Complex Dynamics in Olfactory Networks

2021 ◽  
Vol 15 ◽  
Author(s):  
Zhenbo Huang ◽  
Roberta Tatti ◽  
Ashley M. Loeven ◽  
Daniel R. Landi Conde ◽  
Debra Ann Fadool
Keyword(s):  
Complex Dynamics ◽  
Cell Activity ◽  
Spike Frequency ◽  
Neuronal Firing ◽  
Granule Cell Layer ◽  
Research Report ◽  
Original Research ◽  
Sensory Inputs ◽  
Local Interneurons ◽  
Control Complex

Neuromodulation influences neuronal processing, conferring neuronal circuits the flexibility to integrate sensory inputs with behavioral states and the ability to adapt to a continuously changing environment. In this original research report, we broadly discuss the basis of neuromodulation that is known to regulate intrinsic firing activity, synaptic communication, and voltage-dependent channels in the olfactory bulb. Because the olfactory system is positioned to integrate sensory inputs with information regarding the internal chemical and behavioral state of an animal, how olfactory information is modulated provides flexibility in coding and behavioral output. Herein we discuss how neuronal microcircuits control complex dynamics of the olfactory networks by homing in on a special class of local interneurons as an example. While receptors for neuromodulation and metabolic peptides are widely expressed in the olfactory circuitry, centrifugal serotonergic and cholinergic inputs modulate glomerular activity and are involved in odor investigation and odor-dependent learning. Little is known about how metabolic peptides and neuromodulators control specific neuronal subpopulations. There is a microcircuit between mitral cells and interneurons that is comprised of deep-short-axon cells in the granule cell layer. These local interneurons express pre-pro-glucagon (PPG) and regulate mitral cell activity, but it is unknown what initiates this type of regulation. Our study investigates the means by which PPG neurons could be recruited by classical neuromodulators and hormonal peptides. We found that two gut hormones, leptin and cholecystokinin, differentially modulate PPG neurons. Cholecystokinin reduces or increases spike frequency, suggesting a heterogeneous signaling pathway in different PPG neurons, while leptin does not affect PPG neuronal firing. Acetylcholine modulates PPG neurons by increasing the spike frequency and eliciting bursts of action potentials, while serotonin does not affect PPG neuron excitability. The mechanisms behind this diverse modulation are not known, however, these results clearly indicate a complex interplay of metabolic signaling molecules and neuromodulators that may fine-tune neuronal microcircuits.

scholarly journals Self-splitting Abelian groups

2001 ◽  
Vol 64 (1) ◽  
pp. 71-79 ◽  
Author(s):  
P. Schultz
Keyword(s):  
Abelian Group ◽  
Direct Product ◽  
Free Module ◽  
Research Report ◽  
Original Form ◽  
Original Research ◽  
Direct Sum ◽  
The University ◽  
Torsion Free ◽  
Made In

G is reduced torsion-free A belian group such that for every direct sum ⊕G of copies of G, Ext(⊕G, ⊕G) = 0 if and only if G is a free module over a rank 1 ring. For every direct product ΠG of copies of G, Ext(ΠG,ΠG) = 0 if and only if G is cotorsion.This paper began as a Research Report of the Department of Mathematics of the University of Western Australia in 1988, and circulated among members of the Abelian group community. However, it was never submitted for publication. The results have been cited, widely, and since copies of the original research report are no longer available, the paper is presented here in its original form in Sections 1 to 5. In Section 6, I survey the progress that has been made in the topic since 1988.

scholarly journals Efficient neural decoding of self-location with a deep recurrent network

2018 ◽  
Author(s):  
Ardi Tampuu ◽  
Tambet Matiisen ◽  
H. Freyja Ólafsdóttir ◽  
Caswell Barry ◽  
Raul Vicente
Keyword(s):  
Hippocampal Neurons ◽  
Cell Activity ◽  
Recurrent Network ◽  
Brain Network ◽  
Place Cells ◽  
Neuronal Firing ◽  
Temporal Context ◽  
Central Component ◽  
Neural Decoding ◽  
Freely Moving

AbstractPlace cells in the mammalian hippocampus signal self-location with sparse spatially stable firing fields. Based on observation of place cell activity it is possible to accurately decode an animal’s location. The precision of this decoding sets a lower bound for the amount of information that the hippocampal population conveys about the location of the animal. In this work we use a novel recurrent neural network (RNN) decoder to infer the location of freely moving rats from single unit hippocampal recordings. RNNs are biologically plausible models of neural circuits that learn to incorporate relevant temporal context without the need to make complicated assumptions about the use of prior information to predict the current state. When decoding animal position from spike counts in 1D and 2D-environments, we show that the RNN consistently outperforms a standard Bayesian model with flat priors. In addition, we also conducted a set of sensitivity analysis on the RNN decoder to determine which neurons and sections of firing fields were the most influential. We found that the application of RNNs to neural data allowed flexible integration of temporal context, yielding improved accuracy relative to a commonly used Bayesian approach and opens new avenues for exploration of the neural code.Author summaryBeing able to accurately self-localize is critical for most motile organisms. In mammals, place cells in the hippocampus appear to be a central component of the brain network responsible for this ability. In this work we recorded the activity of a population of hippocampal neurons from freely moving rodents and carried out neural decoding to determine the animals’ locations. We found that a machine learning approach using recurrent neural networks (RNNs) allowed us to predict the rodents’ true positions more accurately than a standard Bayesian method with flat priors. The RNNs are able to take into account past neural activity without making assumptions about the statistics of neuronal firing. Further, by analyzing the representations learned by the network we were able to determine which neurons, and which aspects of their activity, contributed most strongly to the accurate decoding.

Upper body accelerations during level walking in transtibial amputees

2018 ◽  
Vol 43 (2) ◽  
pp. 204-212 ◽  
Author(s):  
Francesco Paradisi ◽  
Eugenio Di Stanislao ◽  
Aurora Summa ◽  
Stefano Brunelli ◽  
M Traballesi ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Body Movement ◽  
Transverse Plane ◽  
Upper Body ◽  
Research Report ◽  
Original Research ◽  
Clinical Approach ◽  
Mean Square ◽  
Level Walking ◽  
Transtibial Amputees

Background: The observation of upper body movement is gaining interest in the gait analysis community. Recent studies involved the use of body-worn motion sensors, allowing translation of laboratory measurements to real-life settings in the context of patient monitoring and fall prevention. Objectives: It was shown that amputee persons demonstrate altered acceleration patterns due to the presence of prosthetic components, while no information is available on how accelerations propagate upwards to the head during level walking. This descriptive study aims to fill this gap. Study design: Original research report. Methods: Twenty definitive prosthesis users with transtibial amputation and 20 age-matched able-bodied individuals participated in the study. Three magneto-inertial measurement units were placed at head, sternum and pelvis level to assess acceleration root mean square. Three repetitions of the 10-m walking test were performed at a self-selected speed. Results: Acceleration root mean square was significantly larger at pelvis and head level in individuals with amputation than in able-bodied participants, mainly in the transverse plane ( p < 0.05). Differences were also observed in how accelerations propagate upwards, highlighting that a different motor strategy is adopted in amputee persons gait to compensate for increased instability. Conclusion: The obtained parameters allow an objective mobility assessment of amputee persons that can integrate with the traditional clinical approach. Clinical relevance Transtibial amputees exhibit asymmetries due to the sound limb’s support prevalence during gait: this is evidenced by amplified accelerations on the transverse plane and by related differences in upper body movement control. Assessing these accelerations and their attenuations upwards may be helpful to understand amputee’s motor strategies and to improve prosthetic training.

Calcium Coding and Adaptive Temporal Computation in Cortical Pyramidal Neurons

1998 ◽  
Vol 79 (3) ◽  
pp. 1549-1566 ◽  
Author(s):  
Xiao-Jing Wang
Keyword(s):  
Current Pulse ◽  
Pyramidal Neurons ◽  
Model Neuron ◽  
Pyramidal Cells ◽  
Spike Frequency ◽  
Neuronal Firing ◽  
Spike Frequency Adaptation ◽  
Synaptic Inputs ◽  
Cortical Pyramidal Neurons ◽  
Intracellular Ca

Wang, Xiao-Jing. Calcium coding and adaptive temporal computation in cortical pyramidal neurons. J. Neurophysiol. 79: 1549–1566, 1998. In this work, we present a quantitative theory of temporal spike-frequency adaptation in cortical pyramidal cells. Our model pyramidal neuron has two-compartments (a “soma” and a “dendrite”) with a voltage-gated Ca2+ conductance ( g Ca) and a Ca2+-dependent K+ conductance ( g AHP) located at the dendrite or at both compartments. Its frequency-current relations are comparable with data from cortical pyramidal cells, and the properties of spike-evoked intracellular [Ca2+] transients are matched with recent dendritic [Ca2+] imaging measurements. Spike-frequency adaptation in response to a current pulse is characterized by an adaptation time constant τadap and percentage adaptation of spike frequency F adap [% (peak − steady state)/peak]. We show how τadap and F adap can be derived in terms of the biophysical parameters of the neural membrane and [Ca2+] dynamics. Two simple, experimentally testable, relations between τadap and F adap are predicted. The dependence of τadap and F adap on current pulse intensity, electrotonic coupling between the two compartments, g AHP as well the [Ca2+] decay time constant τCa, is assessed quantitatively. In addition, we demonstrate that the intracellular [Ca2+] signal can encode the instantaneous neuronal firing rate and that the conductance-based model can be reduced to a simple calcium-model of neuronal activity that faithfully predicts the neuronal firing output even when the input varies relatively rapidly in time (tens to hundreds of milliseconds). Extensive simulations have been carried out for the model neuron with random excitatory synaptic inputs mimicked by a Poisson process. Our findings include 1) the instantaneous firing frequency (averaged over trials) shows strong adaptation similar to the case with current pulses; 2) when the g AHP is blocked, the dendritic g Ca could produce a hysteresis phenomenon where the neuron is driven to switch randomly between a quiescent state and a repetitive firing state. The firing pattern is very irregular with a large coefficient of variation of the interspike intervals (ISI CV > 1). The ISI distribution shows a long tail but is not bimodal. 3) By contrast, in an intrinsically bursting regime (with different parameter values), the model neuron displays a random temporal mixture of single action potentials and brief bursts of spikes. Its ISI distribution is often bimodal and its power spectrum has a peak. 4) The spike-adapting current I AHP, as delayed inhibition through intracellular Ca2+ accumulation, generates a “forward masking” effect, where a masking input dramatically reduces or completely suppresses the neuronal response to a subsequent test input. When two inputs are presented repetitively in time, this mechanism greatly enhances the ratio of the responses to the stronger and weaker inputs, fulfilling a cellular form of lateral inhibition in time. 5) The [Ca2+]-dependent I AHP provides a mechanism by which the neuron unceasingly adapts to the stochastic synaptic inputs, even in the stationary state following the input onset. This creates strong negative correlations between output ISIs in a frequency-dependent manner, while the Poisson input is totally uncorrelated in time. Possible functional implications of these results are discussed.

Descending control of nonspiking local interneurons in the terminal abdominal ganglion of the crayfish

1994 ◽  
Vol 72 (1) ◽  
pp. 235-247 ◽  
Author(s):  
H. Namba ◽  
T. Nagayama ◽  
M. Hisada
Keyword(s):  
Electrical Stimulation ◽  
Motor Neuron ◽  
Motor Neurons ◽  
Sensory Stimulation ◽  
Full Extension ◽  
Sensory Inputs ◽  
Reflex Pathways ◽  
Local Interneurons ◽  
Parallel Connections ◽  
Stimulation Of

1. Electrical stimulation of afferents innervating an exopodite causes a closing pattern of activity in the uropod motor neurons. In this reflex two distinct types of nonspiking local interneurons, posterolateral (PL) and anterolateral (AL) types, classified by their gross morphology and somata location, receive sensory inputs and control the motor output to the uropod. 2. In the sensory-motor pathway, the PL and AL nonspiking local interneurons formed opposing and parallel connections with uropod motor neurons. For example, the PL interneurons that excited the closer, reductor motor neuron by injecting depolarizing current received depolarizing postsynaptic potentials (PSPs), whereas the AL interneurons of the same output received hyperpolarizing PSPs. The PL interneurons that inhibited the reductor motor neuron received hyperpolarizing PSPs, whereas the AL interneurons of the similar output received depolarizing PSPs. 3. During fictive abdominal extension, induced by electrical stimulation of extension-evoking command fibers in the second-third abdominal connective, the uropod motor neurons show an opening pattern of activity that is opposite to the pattern elicited by sensory stimulation. Furthermore, sensory stimulation during ongoing fictive abdominal extension has little effect on the uropod motor neurons. 4. Except for the nonspiking local interneurons, the majority of other local circuit neurons, i.e., spiking local interneurons and ascending interneurons, are not driven by the descending inputs during abdominal extension. 5. A comparison of the responses of the nonspiking local interneurons to both sensory and descending inputs reveals that the majority of nonspiking local interneurons receive both inputs, but the sign of response to each is frequently opposite. This study suggests that the degree of excitability of two distinct types of PL and AL nonspiking local interneurons induced by sensory inputs changes depending on whether the crayfish is in a resting posture or is active with full extension of the abdomen. Ongoing abdominal extension in swimming or defensive crayfish would shift the gain of reflex pathways through the PL and AL interneurons, and motor response resulting from sensory inputs would be modulated.

Modelling Dynamical Arterial Adaptations to Altered Chemo-Mechanical Environments

2008 ◽  
Author(s):  
Luca Cardamone ◽  
Arturo Valentin ◽  
Jay D. Humphrey
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Smooth Muscle ◽  
Vascular Tone ◽  
Complex Dynamics ◽  
Cell Activity ◽  
Mechanical Stimuli ◽  
Mechanical Environment ◽  
Sense And Respond

Vascular smooth muscle cells (SMC), endothelial cells (EC), and fibroblasts exist in a dynamic mechanical environment and can sense and respond to mechanical stimuli in vivo (McKnight and Frangos [1]). It is becoming more and more clear that complex dynamics not only influences vascular tone but also SMC proliferation (see Dancu et al. [2]) and extracellular matrix turnover (Cummins et al. [3]) by stimulating cell activity.

Capsaicin Infused Into the PAG Affects Rat Tail Flick Responses to Noxious Heat and Alters Neuronal Firing in the RVM

2003 ◽  
Vol 90 (4) ◽  
pp. 2702-2710 ◽  
Author(s):  
Steve McGaraughty ◽  
Katharine L. Chu ◽  
Robert S. Bitner ◽  
Brenda Martino ◽  
Rachid El Kouhen ◽  
...  
Keyword(s):  
Spontaneous Activity ◽  
Neuronal Activity ◽  
Cell Activity ◽  
Brain Regions ◽  
Neuronal Firing ◽  
Tail Flick ◽  
Noxious Stimulation ◽  
Noxious Heat ◽  
Tail Flick Latency ◽  
Ventromedial Medulla

It is well established that the vanilloid receptor, VR1, is an important peripheral mediator of nociception. VR1 receptors are also located in several brain regions, yet it is uncertain whether these supraspinal VR1 receptors have any influence on the nociceptive system. To investigate a possible nociceptive role for supraspinal VR1 receptors, capsaicin (10 nmol in 0.4 μl) was microinjected into either the dorsal (dPAG) or ventral (vPAG) regions of the periaqueductal gray. Capsaicin-related effects on tail flick latency (immersion in 52°C water) and on neuronal activity (on-, off-, and neutral cells) in the rostral ventromedial medulla (RVM) were measured in lightly anesthetized rats. Administration of capsaicin into the dPAG but not the vPAG caused an initial hyperalgesic response followed later by analgesia (125 ± 20.96 min postinjection). The tail flick–related burst in on-cell activity was triggered earlier in the hyperalgesic phase and was delayed or absent during the analgesic phase. Spontaneous activity of on-cells increased at the onset of the hyperalgesic phase and decreased before and during the analgesic phase. The tail flick–related pause in off-cell activity as well as spontaneous firing for these cells was unchanged in the hyperalgesic phase. During the analgesic phase, off-cells no longer paused during noxious stimulation and had increased levels of spontaneous activity. Neutral cell firing was unaffected in either phase. Pretreatment with the VR1 receptor antagonist, capsazepine (10 nmol in 0.4 μl), into the dPAG blocked the capsaicin-induced hyperalgesia as well as the corresponding changes in on- and off-cell activity. VR1 receptor immunostaining was observed in the dPAG of untreated rats. Microinjection of capsaicin likely sensitized and then desensitized dPAG neurons affecting nocifensive reflexes and RVM neuronal activity. These results suggest that supraspinal VR1 receptors in the dPAG contribute to descending modulation of nociception.

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