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The antennal lobe (AL) of the Noctuid moth Agrotis ipsilon has emerged as an excellent model for studying olfactory processing and its plasticity in the central nervous system. Odor-evoked responses of AL neurons and input-to-output... more
The antennal lobe (AL) of the Noctuid moth Agrotis ipsilon has emerged as an excellent model for studying olfactory processing and its plasticity in the central nervous system. Odor-evoked responses of AL neurons and input-to-output transformations involved in pheromone processing are well characterized in this species. However, the intrinsic electrical properties responsible of the firing of AL neurons are poorly known. To this end, patch-clamp recordings in current- and voltage-clamp mode from neurons located in the two main clusters of cell bodies in the ALs were combined with intracellular staining on A. ipsilon males. Staining indicated that the lateral cluster (LC) is composed of 85% of local neurons (LNs) and 15% of projection neurons (PNs). The medial cluster (MC) contains only PNs. Action potentials were readily recorded from the soma in LNs and PNs located in the LC but not from PNs in the MC where recordings showed small or no action potentials. In the LC, the spontaneous...
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Response properties of the receptor potential at steady state were analyzed in a biophysical model of an olfactory sensory neuron embedded in a multicell environment. The neuron structure was described as a set of several identical... more
Response properties of the receptor potential at steady state were analyzed in a biophysical model of an olfactory sensory neuron embedded in a multicell environment. The neuron structure was described as a set of several identical dendrites (or cilia) bearing the transduction mechanisms, joined to a nonsensory part--dendritic knob, soma, and axon. The different ionic compositions of the media surrounding the neuron sensory and nonsensory parts and the extraneuronal voltage sources, which both result from the presence of auxiliary cells, were also taken into account. Analytical solutions were found to describe how the receptor potential at the nonsensory part responds to a uniform change in the odorant-dependent conductance resulting from odorant stimulation of the sensory dendrites. We investigated the influence of various geometrical and electrical parameters on the receptor-potential response in the classical model neuron within a homogeneous environment and in the model neuron s...
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Olfactory stimuli are complex chemical signals whose composition varies quantitatively and qualitatively in space and time. Olfactory receptor neurones (ORNs) can monitor these variations and convey raw data to the brain from which... more
Olfactory stimuli are complex chemical signals whose composition varies quantitatively and qualitatively in space and time. Olfactory receptor neurones (ORNs) can monitor these variations and convey raw data to the brain from which biologically ...
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We analyze the first phase of information transduction in the model of the olfactory receptor neuron of the male moth Antheraea polyphemus. We predict such stimulus characteristics that enable the system to perform optimally, i.e., to... more
We analyze the first phase of information transduction in the model of the olfactory receptor neuron of the male moth Antheraea polyphemus. We predict such stimulus characteristics that enable the system to perform optimally, i.e., to transfer as much information as possible. Few a priori constraints on the nature of stimulus and stimulus-to-signal transduction are assumed. The results are given in terms of stimulus distributions and intermittency factors which makes direct comparison with experimental data possible. Optimal stimulus is approximatelly described by exponential or log-normal probability density function which is in agreement with experiment and the predicted intermittency factors fall within the lowest range of observed values. The results are discussed with respect to electroantennogram measurements and behavioral observations.
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Research Interests: Animal Behavior, Biological Sciences, Female, Animals, Smell, and 7 moreMale, Plants, The, Neurons, Odors, Interneurons, and Experimental Biology
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The perireceptor and receptor events in a model of the single olfactory receptor neuron of the male moth Antheraea polyphemus are studied. This first stage of signal transduction imposes limiting conditions on the amount of information... more
The perireceptor and receptor events in a model of the single olfactory receptor neuron of the male moth Antheraea polyphemus are studied. This first stage of signal transduction imposes limiting conditions on the amount of information the olfactory neuron can process. ...
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Abstract A basic deterministic and stochastic model of the olfactory sensory neuron under steady-state conditions is proposed. It is composed of three modules that describe the main steps of the neuron response to a stimulation, ie... more
Abstract A basic deterministic and stochastic model of the olfactory sensory neuron under steady-state conditions is proposed. It is composed of three modules that describe the main steps of the neuron response to a stimulation, ie interaction of odorant molecules with ...
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... Printed in the UK Coding of odour quality: roles of convergence and inhibition Jean-Pierre Rosparst and Jean-Claude Fort$ t hboratoire de Biom6Uie. ... JP Rospars and JC FOG Odorant property Figure 2. Response frequencies of... more
... Printed in the UK Coding of odour quality: roles of convergence and inhibition Jean-Pierre Rosparst and Jean-Claude Fort$ t hboratoire de Biom6Uie. ... JP Rospars and JC FOG Odorant property Figure 2. Response frequencies of neumreceptor types to odorant properties. ...
Orientation towards food and mate, especially in insects, is an olfactory-controlled behavior which relies on the detection of small amounts of odorant molecules delivered in turbulent atmospheric conditions, so that randomness in... more
Orientation towards food and mate, especially in insects, is an olfactory-controlled behavior which relies on the detection of small amounts of odorant molecules delivered in turbulent atmospheric conditions, so that randomness in magnitude and time is a major feature of the natural stimulus. The effect of random delivery on the initial step of olfactory transduction, the formation of the receptor-ligand complex, is analyzed in the case of the moth pheromonal system. Two types of randomness are compared, Gaussian (regular) and exponential (irregular). The influence of noise is quantified either with the maxima of the receptor-ligand complex, or with the times at which the concentration of complex crosses a given threshold level. It is shown that the stochastic features of the stimulus helps its detection and that the exponential distribution appears not only as a better description of the natural stimulus, but also as the most efficient from a biological point of view.
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A method is presented for solving the cable equation for a spiking neuron below firing threshold or a nonspiking neuron of arbitrary geometry under constant stimulation. The neuron structure is considered as a tree composed of a set of... more
A method is presented for solving the cable equation for a spiking neuron below firing threshold or a nonspiking neuron of arbitrary geometry under constant stimulation. The neuron structure is considered as a tree composed of a set of cylinder cables of three types (terminal, intermediate and branching) characterized by their lengths, diameters and linear membrane properties. The stimulation can result from either a uniform conductance-change over a whole cable segment or a point injection of a current. Other special segments are considered (synapses, voltage clamp, lumped soma). Equations are given for replacing any segment with its Thévenin equivalent, i.e. resistance and electromotive force. The step by step use of these elementary equations allows one to find the Thévenin equivalent of the whole neuron and to determine the steady-state membrane potential at any point.
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A biochemical model of the receptor, G-protein and effector (RGE) interactions during transduction in the cilia of vertebrate olfactory receptor neurons (ORNs) was developed and calibrated to experimental recordings of cAMP levels and the... more
A biochemical model of the receptor, G-protein and effector (RGE) interactions during transduction in the cilia of vertebrate olfactory receptor neurons (ORNs) was developed and calibrated to experimental recordings of cAMP levels and the receptor current (RC). The model describes the steps from odorant binding to activation of the effector enzyme which catalyzes the conversion of ATP to cAMP, and shows how odorant stimulation is amplified and delayed by the RGE transduction cascade. A time-dependent sensitivity analysis was performed on the model. The model output-the cAMP production rate-is particularly sensitive to a few, dominant parameters. During odorant stimulation it depends mainly on the initial density of G-proteins and the catalytic constant for cAMP production.
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Insect receptor neurons are surrounded with auxiliary cells and encased in a hair. Their electrical activity is usually recorded with an electrode located at the tip of the hair. Analytical expressions giving the membrane potential along... more
Insect receptor neurons are surrounded with auxiliary cells and encased in a hair. Their electrical activity is usually recorded with an electrode located at the tip of the hair. Analytical expressions giving the membrane potential along the sensory dendrite and the tip-recorded potential are derived for a neuron in steady-state conditions. They formally close the gap between theoretical models and experimental measurements, when transduction mechanisms and active membrane properties are not taken into account. It is shown that the tip-recorded potential reflects correctly the relative variations of the dendritic membrane potential as a function of stimulus intensity over a large range of parameters. The geometric and electrical characteristics of the sensillum that need be known to compute the dendritic membrane potential from the tip-recorded potential are given.
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Spontaneous firing of olfactory receptor neurons (ORNs) was recently shown to be required for the survival of ORNs and the maintenance of their appropriate synaptic connections with mitral cells in the olfactory bulb. ORN spontaneous... more
Spontaneous firing of olfactory receptor neurons (ORNs) was recently shown to be required for the survival of ORNs and the maintenance of their appropriate synaptic connections with mitral cells in the olfactory bulb. ORN spontaneous activity has never been described or characterized quantitatively in mammals. To do so we have made extracellular single unit recordings from ORNs of freely breathing (FB) and tracheotomized (TT) rats. We show that the firing behavior of TT neurons was relatively simple: they tended to fire spikes at the same average frequency according to purely random (Poisson) or simple (Gamma or Weibull) statistical laws. A minority of them were bursting with relatively infrequent and short bursts. The activity of FB neurons was less simple: their firing rates were more diverse, some of them showed trends or were driven by breathing. Although more of them were regular, only a minority could be described by simple laws; the majority displayed random bursts with more spikes than the bursts of TT neurons. In both categories bursts and isolated spikes (outside bursts) occurred completely at random. The spontaneous activity of ORNs in rats resembles that of frogs, but is higher, which may be due to a difference in body temperature. These results suggest that, in addition to the intrinsic thermal noise, spontaneous activity is provoked in part by mechanical, thermal, or chemical (odorant molecules) effects of air movements due to respiration, this extrinsic part being naturally larger in FB neurons. It is suggested that spontaneous activity may be modulated by respiration. Because natural sampling of odors is synchronized with breathing, such modulation may prepare and keep olfactory bulb circuits tuned to process odor stimuli.
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The glomerular organization of the hemideutocerebrum is analyzed quantitatively, using only spatial position, in four individuals (eight hDTCs) after a visual identification of glomeruli on graphic reconstructions. In order to assess... more
The glomerular organization of the hemideutocerebrum is analyzed quantitatively, using only spatial position, in four individuals (eight hDTCs) after a visual identification of glomeruli on graphic reconstructions. In order to assess directly the invariance of the neuropil in an insect brain the following is done: (1) The position of each glomerulus is compared to the position A&#39; it should occupy if the hDTCs were identical. It is shown that in 80 and 71% of the cases, respectively, intra- and interindividual comparisons in the studied glomerulus is the nearest to A&#39;. (2) The actual position is equally compared to the theoretical location A&quot; each glomerulus should occupy if its absolute position could be changed but not its relative position with respect to its neighbors. The calculation of A&quot; is based on process (3). In 86 and 80% of the cases, respectively, it is found that the actual position is that which is nearest to A&quot;. (3) An automated identification process, based on absolute and relative locations, but completely independent of visual identification, is described. It allows the identification of 77 and 74% of glomeruli, respectively. These matchings are in 96 and 90% of the cases identical to the visual matchings. The location predictability of most glomeruli is discussed to show the existence, nature, and limits of the hemideutocerebral invariance.
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The role of Ca(2+) in insect olfactory transduction was studied in the moth Spodoptera littoralis. Single sensillum recordings were made to investigate in vivo the role of sensillar Ca(2+) on the electrophysiological properties of sex... more
The role of Ca(2+) in insect olfactory transduction was studied in the moth Spodoptera littoralis. Single sensillum recordings were made to investigate in vivo the role of sensillar Ca(2+) on the electrophysiological properties of sex pheromone responsive olfactory receptor neurons (ORNs). Lowering the sensillar Ca(2+) concentration to 2 x 10(-8) M increased ORN spontaneous firing activity and induced long bursts of action potentials (APs) superimposed on spontaneous negative deflections of the transepithelial potential. We inferred that Ca(2+) stabilizes the membrane potential of ORNs, keeping the spontaneous firing activity at a low and regular level. Neither the amplitude and kinetics of the rising phase of sensillar potentials (SPs) recorded in response to pheromone stimuli nor the AP generation during stimulation depended on the extracellular Ca(2+) concentration. Thus, extracellular Ca(2+) is not absolutely necessary for ORN response. Partial inhibition of responses with a calmodulin antagonist, W-7, also indicates that intracellular Ca(2+) contributes to the ORN response and suggests that Ca(2+) release from internal stores is involved. In 2 x 10(-8) M Ca(2+), the repolarization of the SP was delayed when compared with higher Ca(2+) concentrations. Therefore, in contrast to depolarization, ORN repolarization depends on extracellular Ca(2+). Ca(2+)-gated K(+) channels identified from cultured ORNs with whole-cell recordings are good candidates to mediate ORN repolarization.
Research Interests: Kinetics, Calcium, Pheromones, Chemical, Patch-clamp and imaging techniques, and 13 moreBiological Sciences, Evoked Potentials, Animals, Male, Calcium Signaling, Whole cell recording, Calmodulin, Sex Pheromone, Chemical Senses, Action potential, Membrane Potential, Patch Clamp, and Spodoptera littoralis
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Research Interests: Cognitive Science, Information Theory, Signal Transduction, Brain, Humans, and 14 moreStatistical Inference, Computer Simulation, Sensation, Animals, Information Transfer, Sensory Neuron, Fisher information, Artifacts, Transfer Function, Input Output, Point of View, Action Potentials, Neurosciences, and Generic model
The spontaneous activity of first-order neurons (neuroreceptors of the mucosa) and second-order neurons (mitral cells of the bulb) was recorded extracellularly in the frog olfactory system. To assess the influence of peripheral inputs... more
The spontaneous activity of first-order neurons (neuroreceptors of the mucosa) and second-order neurons (mitral cells of the bulb) was recorded extracellularly in the frog olfactory system. To assess the influence of peripheral inputs upon mitral cells, the bulb was either normally connected or partially deafferented. Our first set of findings concern the firing behavior. We found that most neurons generated interspike intervals (ISIs) that were stationary in mean and variance, and were not serially correlated at first and second order. Individual spikes in mitral cells and bursts of spikes in neuroreceptors were found to be generated by a Poisson process. Stochastic modeling suggests that the Poissonian behavior depends on the mean value of the membrane potential at the axon hillock. In these models, the mean potential in mitral cells would be far below the firing threshold and in neuroreceptors it would fluctuate at random between two states, one close to resting potential (between bursts) and the other close to the firing threshold with occasional crossings (within bursts). Secondly, partially deafferented mitral cells had significantly higher activity and lower variance than mitral cells receiving normal afferent input. This effect gives evidence that peripheral inputs influence mitral cells at rest not only through direct excitation but also through indirect inhibition exerted by local neurons. Thus, the unstimulated state of the olfactory bulb would not be qualitatively different from its stimulated state in the sense that both states involve the same types of synaptic interactions. Consequently, understanding the synaptic relationships that take place in the bulb network can benefit from studies of its spontaneous activity.
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Research Interests: Cognitive Science, Signal Transduction, Stochastic processes, Brain, Animals, and 13 moreSmell, Male, Reaction Time, First-Order Logic, First Order Logic, Sex Pheromone, Moths, Statistical Model, Action potential, Stochastic Model, Temporal Coding, Multivariate Normal Distribution, and Neurosciences
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A male moth locates a conspecific female by detecting her sexual-pheromone blend. This detection is carried out in the antennal lobe, the first stage of olfactory information processing, where local inhibitory neurons and projection... more
A male moth locates a conspecific female by detecting her sexual-pheromone blend. This detection is carried out in the antennal lobe, the first stage of olfactory information processing, where local inhibitory neurons and projection (relay) neurons interact. Antennal-lobe neurons exhibit low-frequency (&lt; 10 Hz) background activity and bursting (&gt; 100 Hz) activity in response to pheromone stimulation. We describe this behavior by a realistic biophysical neuron model. The bursting behavior of the model is the result of both intrinsic cellular properties and network interaction. A slowly activating and inactivating calcium channel provides a depolarizing current for bursting and disinhibition is shown to be a feasible network mechanism for triggering this calcium channel. Small neural networks utilizing disinhibition are presented with local neurons intercalated between receptor and projection neurons. The firing behaviors of projection neurons in response to stimulation by the pheromone blend or its components are in accordance with experimental results. This network architecture offers an alternative view of olfactory processing from the classical architecture derived from vertebrate studies.
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The first step of olfactory transduction consists of the interaction of odorant molecules with receptor proteins. This interaction can be described either as a single-step reaction (binding only) or as a double-step one (binding and... more
The first step of olfactory transduction consists of the interaction of odorant molecules with receptor proteins. This interaction can be described either as a single-step reaction (binding only) or as a double-step one (binding and activation). The number of bound or activated receptors is analyzed as a function of the external concentration of odorant molecules in two models of the neuron environment. In one model the odorant molecules can freely access and leave the vicinity of receptors, whereas in the other a real perireceptor space, partly isolated from the external environment is considered. The steady state and time variable responses to the stimulus are investigated.
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The temporal patterns of action potentials fired by a two-point stochastic neuron model were investigated. In this model the membrane potential of the dendritic compartment follows the Orstein-Uhlenbeck process and is not affected by the... more
The temporal patterns of action potentials fired by a two-point stochastic neuron model were investigated. In this model the membrane potential of the dendritic compartment follows the Orstein-Uhlenbeck process and is not affected by the spiking activity. The axonal compartment, corresponding to the spike initiation site, is described by a simplified RC circuit. Estimators of the mean and variance of