scholarly journals Circuit and cellular mechanisms facilitate the transformation from dense to sparse coding in the insect olfactory system

2017 ◽  
Author(s):  
Rinaldo Betkiewicz ◽  
Benjamin Lindner ◽  
Martin P. Nawrot
Keyword(s):  
Lateral Inhibition ◽  
Olfactory System ◽  
Mushroom Body ◽  
Stimulus Onset ◽  
Cellular Level ◽  
Neural Mechanisms ◽  
Testable Hypothesis ◽  
Cellular Mechanisms ◽  
Spatio Temporal ◽  
Spiking Model

AbstractTransformations between sensory representations are shaped by neural mechanisms at the cellular and the circuit level. In the insect olfactory system encoding of odor information undergoes a transition from a dense spatio-temporal population code in the antennal lobe to a sparse code in the mushroom body. However, the exact mechanisms shaping odor representations and their role in sensory processing are incompletely identified. Here, we investigate the transformation from dense to sparse odor representations in a spiking model of the insect olfactory system, focusing on two ubiquitous neural mechanisms: spike-frequency adaptation at the cellular level and lateral inhibition at the circuit level. We find that cellular adaptation is essential for sparse representations in time (temporal sparseness), while lateral inhibition regulates sparseness in the neuronal space (population sparseness). The interplay of both mechanisms shapes dynamical odor representations, which are optimized for discrimination of odors during stimulus onset and offset. In addition, we find that odor identity is stored on a prolonged time scale in the adaptation levels but not in the spiking activity of the principal cells of the mushroom body, providing a testable hypothesis for the location of the so-called odor trace.

Information Processing in the Mammalian Olfactory System

2005 ◽  
Vol 85 (1) ◽  
pp. 281-317 ◽  
Author(s):  
Pierre-Marie Lledo ◽  
Gilles Gheusi ◽  
Jean-Didier Vincent
Keyword(s):  
Olfactory System ◽  
Cellular Level ◽  
Adult Brain ◽  
Organizational Strategies ◽  
Cellular Mechanisms ◽  
Brain Functions ◽  
Olfactory Systems ◽  
And Behavior ◽  
High Degree ◽  
The Brain

Recently, modern neuroscience has made considerable progress in understanding how the brain perceives, discriminates, and recognizes odorant molecules. This growing knowledge took over when the sense of smell was no longer considered only as a matter for poetry or the perfume industry. Over the last decades, chemical senses captured the attention of scientists who started to investigate the different stages of olfactory pathways. Distinct fields such as genetic, biochemistry, cellular biology, neurophysiology, and behavior have contributed to provide a picture of how odor information is processed in the olfactory system as it moves from the periphery to higher areas of the brain. So far, the combination of these approaches has been most effective at the cellular level, but there are already signs, and even greater hope, that the same is gradually happening at the systems level. This review summarizes the current ideas concerning the cellular mechanisms and organizational strategies used by the olfactory system to process olfactory information. We present findings that exemplified the high degree of olfactory plasticity, with special emphasis on the first central relay of the olfactory system. Recent observations supporting the necessity of such plasticity for adult brain functions are also discussed. Due to space constraints, this review focuses mainly on the olfactory systems of vertebrates, and primarily those of mammals.

scholarly journals Human spatial representation: what we cannot learn from the studies of rodent navigation

2018 ◽  
Vol 120 (5) ◽  
pp. 2453-2465 ◽  
Author(s):  
Mintao Zhao
Keyword(s):  
Spatial Representation ◽  
Spatial Information ◽  
Storage System ◽  
Neural Mechanisms ◽  
Cellular Mechanisms ◽  
Human Navigation ◽  
Behavioral Studies ◽  
Closing The Loop ◽  
Species Similarity ◽  
Shed Light

Studies of human and rodent navigation often reveal a remarkable cross-species similarity between the cognitive and neural mechanisms of navigation. Such cross-species resemblance often overshadows some critical differences between how humans and nonhuman animals navigate. In this review, I propose that a navigation system requires both a storage system (i.e., representing spatial information) and a positioning system (i.e., sensing spatial information) to operate. I then argue that the way humans represent spatial information is different from that inferred from the cellular activity observed during rodent navigation. Such difference spans the whole hierarchy of spatial representation, from representing the structure of an environment to the representation of subregions of an environment, routes and paths, and the distance and direction relative to a goal location. These cross-species inconsistencies suggest that what we learn from rodent navigation does not always transfer to human navigation. Finally, I argue for closing the loop for the dominant, unidirectional animal-to-human approach in navigation research so that insights from behavioral studies of human navigation may also flow back to shed light on the cellular mechanisms of navigation for both humans and other mammals (i.e., a human-to-animal approach).

5-HT Prolongs Ventral Root Bursting Via Presynaptic Inhibition of Synaptic Activity During Fictive Locomotion in Lamprey

2005 ◽  
Vol 93 (2) ◽  
pp. 980-988 ◽  
Author(s):  
Eric J. Schwartz ◽  
Tatyana Gerachshenko ◽  
Simon Alford
Keyword(s):  
Synaptic Transmission ◽  
Presynaptic Inhibition ◽  
Cellular Level ◽  
Ventral Horn ◽  
Pattern Generation ◽  
Ventral Root ◽  
Synaptic Activity ◽  
Fictive Locomotion ◽  
Cellular Mechanisms ◽  
Bath Application

Locomotor pattern generation is maintained by integration of the intrinsic properties of spinal central pattern generator (CPG) neurons in conjunction with synaptic activity of the neural network. In the lamprey, the spinal locomotor CPG is modulated by 5-HT. On a cellular level, 5-HT presynaptically inhibits synaptic transmission and postsynaptically inhibits a Ca2+-activated K+ current responsible for the slow afterhyperpolarization (sAHP) that follows action potentials in ventral horn neurons. To understand the contribution of these cellular mechanisms to the modulation of the spinal CPG, we have tested the effect of selective 5-HT analogues against fictive locomotion initiated by bath application of N-methyl-d-aspartate (NMDA). We found that the 5-HT1D agonist, L694-247, dramatically prolongs the frequency of ventral root bursting. Furthermore, we show that L694-247 presynaptically inhibits synaptic transmission without altering postsynaptic Ca2+ -activated K+ currents. We also confirm that 5-HT inhibits synaptic transmission at concentrations that modulate locomotion. To examine the mechanism by which selective presynaptic inhibition modulates the frequency of fictive locomotion, we performed voltage- and current-clamp recordings of CPG neurons during locomotion. Our results show that 5-HT decreases glutamatergic synaptic drive within the locomotor CPG during fictive locomotion. Thus we conclude that presynaptic inhibition of neurotransmitter release contributes to 5-HT–mediated modulation of locomotor activity.

scholarly journals Neural mechanisms underlying regulation of empathy and altruism by beliefs of others' pain

2021 ◽  
Author(s):  
Tao Yu ◽  
Shihui Han
Keyword(s):  
Real Life ◽  
Stimulus Onset ◽  
Neural Mechanisms ◽  
Altruistic Behavior ◽  
Emotional States ◽  
Neural Responses ◽  
Temporoparietal Junction ◽  
Subjective Estimation ◽  
Show Evidence

Perceived cues signaling others' pain induce empathy that in turn motivates altruistic behavior toward those who appear suffering. This perception-emotion-behavior reactivity is the core of human altruism but does not always occur in real life situations. Here, by integrating behavioral and multimodal neuroimaging measures, we investigate neural mechanisms underlying the functional role of beliefs of others' pain in modulating empathy and altruism. We show evidence that decreasing (or enhancing) beliefs of others' pain reduces (or increases) subjective estimation of others' painful emotional states and monetary donations to those who show pain expressions. Moreover, decreasing beliefs of others' pain attenuates neural responses to perceived cues signaling others' pain within 200 ms after stimulus onset and modulate neural responses to others' pain in the frontal cortices and temporoparietal junction. Our findings highlight beliefs of others' pain as a fundamental cognitive basis of human empathy and altruism and unravel the intermediate neural architecture.

scholarly journals Dependence of the stimulus-driven microsaccade rate signature on visual stimulus polarity

2020 ◽  
Author(s):  
Tatiana Malevich ◽  
Antimo Buonocore ◽  
Ziad M. Hafed
Keyword(s):  
Stimulus Onset ◽  
Neural Mechanisms ◽  
Oculomotor Control ◽  
Background Luminance ◽  
Subsequent Increase ◽  
Rapid Reduction ◽  
Sensory Stimuli ◽  
Gaze Fixation ◽  
Early Access ◽  
Steady Rate

AbstractMicrosaccades have a steady rate of occurrence during maintained gaze fixation, which gets transiently modulated by abrupt sensory stimuli. Such modulation, characterized by a rapid reduction in microsaccade frequency followed by a stronger rebound phase of high microsaccade rate, is often described as the microsaccadic rate signature, owing to its stereotyped nature. Here we investigated the impacts of stimulus polarity (luminance increments or luminance decrements relative to background luminance) and size on the microsaccadic rate signature. We presented brief visual flashes consisting of large or small white or black stimuli over an otherwise gray image background. Both large and small stimuli caused robust early microsaccadic inhibition, but only small ones caused a subsequent increase in microsaccade frequency above baseline microsaccade rate. Critically, small black stimuli were always associated with stronger modulations in microsaccade rate after stimulus onset than small white stimuli, particularly in the post-inhibition rebound phase of the microsaccadic rate signature. Because small stimuli were also associated with expected direction oscillations to and away from their locations of appearance, these stronger rate modulations in the rebound phase meant higher likelihoods of microsaccades opposite the black flash locations relative to the white flash locations. Our results demonstrate that the microsaccadic rate signature is sensitive to stimulus polarity, and they point to dissociable neural mechanisms underlying early microsaccadic inhibition after stimulus onset and later microsaccadic rate rebound at longer times thereafter. These results also demonstrate early access of oculomotor control circuitry to sensory representations, particularly for momentarily inhibiting saccade generation.New and noteworthyMicrosaccades are small saccades that occur during gaze fixation. Microsaccade rate is transiently reduced after sudden stimulus onsets, and then strongly rebounds before returning to baseline. We explored the influence of stimulus polarity (black versus white) on this “rate signature”. We found that small black stimuli cause stronger microsaccadic modulations than white ones, but primarily in the rebound phase. This suggests dissociated neural mechanisms for microsaccadic inhibition and subsequent rebound in the microsaccadic rate signature.

scholarly journals p190RhoGAPs, the ARHGAP35- and ARHGAP5-Encoded Proteins, in Health and Disease

Cells ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 351 ◽  
Author(s):  
Héraud ◽  
Pinault ◽  
Lagrée ◽  
Moreau
Keyword(s):  
Rho Gtpases ◽  
Large Family ◽  
Negative Regulator ◽  
Nucleotide Exchange ◽  
Cellular Mechanisms ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Physiological Processes ◽  
Ras Superfamily ◽  
Spatio Temporal

Small guanosine triphosphatases (GTPases) gathered in the Rat sarcoma (Ras) superfamily represent a large family of proteins involved in several key cellular mechanisms. Within the Ras superfamily, the Ras homolog (Rho) family is specialized in the regulation of actin cytoskeleton-based mechanisms. These proteins switch between an active and an inactive state, resulting in subsequent inhibiting or activating downstream signals, leading finally to regulation of actin-based processes. The On/Off status of Rho GTPases implicates two subsets of regulators: GEFs (guanine nucleotide exchange factors), which favor the active GTP (guanosine triphosphate) status of the GTPase and GAPs (GTPase activating proteins), which inhibit the GTPase by enhancing the GTP hydrolysis. In humans, the 20 identified Rho GTPases are regulated by over 70 GAP proteins suggesting a complex, but well-defined, spatio-temporal implication of these GAPs. Among the quite large number of RhoGAPs, we focus on p190RhoGAP, which is known as the main negative regulator of RhoA, but not exclusively. Two isoforms, p190A and p190B, are encoded by ARHGAP35 and ARHGAP5 genes, respectively. We describe here the function of each of these isoforms in physiological processes and sum up findings on their role in pathological conditions such as neurological disorders and cancers.

Comparison of Early Cortical Networks in Efficient and Inefficient Visual Search: An Event-Related Potential Study

2003 ◽  
Vol 15 (7) ◽  
pp. 1039-1051 ◽  
Author(s):  
Ute Leonards ◽  
Julie Palix ◽  
Christoph Michel ◽  
Vicente Ibanez
Keyword(s):  
Event Related Potentials ◽  
Temporal Correlation ◽  
Temporal Analysis ◽  
Search Display ◽  
Stimulus Onset ◽  
Event Related Potential ◽  
Time Range ◽  
Cortical Networks ◽  
Related Potentials ◽  
Spatio Temporal

Functional magnetic resonance imaging studies have indicated that efficient feature search (FS) and inefficient conjunction search (CS) activate partially distinct frontoparietal cortical networks. However, it remains a matter of debate whether the differences in these networks reflect differences in the early processing during FS and CS. In addition, the relationship between the differences in the networks and spatial shifts of attention also remains unknown. We examined these issues by applying a spatio-temporal analysis method to high-resolution visual event-related potentials (ERPs) and investigated how spatio-temporal activation patterns differ for FS and CS tasks. Within the first 450 msec after stimulus onset, scalp potential distributions (ERP maps) revealed 7 different electric field configurations for each search task. Configuration changes occurred simultaneously in the two tasks, suggesting that contributing processes were not significantly delayed in one task compared to the other. Despite this high spatial and temporal correlation, two ERP maps (120–190 and 250–300 msec) differed between the FS and CS. Lateralized distributions were observed only in the ERP map at 250–300 msec for the FS. This distribution corresponds to that previously described as the N2pc component (a negativity in the time range of the N2 complex over posterior electrodes of the hemisphere contralateral to the target hemifield), which has been associated with the focusing of attention onto potential target items in the search display. Thus, our results indicate that the cortical networks involved in feature and conjunction searching partially differ as early as 120 msec after stimulus onset and that the differences between the networks employed during the early stages of FS and CS are not necessarily caused by spatial attention shifts.

scholarly journals Feature integration within discrete time windows

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Leila Drissi-Daoudi ◽  
Adrien Doerig ◽  
Michael H. Herzog
Keyword(s):  
Computational Model ◽  
Discrete Time ◽  
Time Windows ◽  
Temporal Integration ◽  
Sensory Information ◽  
Stimulus Onset ◽  
Feature Integration ◽  
Spatio Temporal ◽  
The Individual ◽  
Over Time

Abstract Sensory information must be integrated over time to perceive, for example, motion and melodies. Here, to study temporal integration, we used the sequential metacontrast paradigm in which two expanding streams of lines are presented. When a line in one stream is offset observers perceive all other lines to be offset too, even though they are straight. When more lines are offset the offsets integrate mandatorily, i.e., observers cannot report the individual offsets. We show that mandatory integration lasts for up to 450 ms, depending on the observer. Importantly, integration occurs only when offsets are presented within a discrete window of time. Even stimuli that are in close spatio-temporal proximity do not integrate if they are in different windows. A window of integration starts with stimulus onset and integration in the next window has similar characteristics. We present a two-stage computational model based on discrete time windows that captures these effects.

scholarly journals Growth dynamics of the Arabidopsis fruit is mediated by cell expansion

2019 ◽  
Vol 116 (50) ◽  
pp. 25333-25342 ◽  
Author(s):  
Juan-José Ripoll ◽  
Mingyuan Zhu ◽  
Stephanie Brocke ◽  
Cindy T. Hon ◽  
Martin F. Yanofsky ◽  
...  
Keyword(s):  
Computational Modeling ◽  
Cell Expansion ◽  
Growth Dynamics ◽  
Spatial Separation ◽  
Cellular Level ◽  
Fruit Growth ◽  
Signaling Cascades ◽  
Comprehensive Understanding ◽  
Cellular Mechanisms ◽  
Plant Reproductive Success

Fruit have evolved a sophisticated tissue and cellular architecture to secure plant reproductive success. Postfertilization growth is perhaps the most dramatic event during fruit morphogenesis. Several studies have proposed that fertilized ovules and developing seeds initiate signaling cascades to coordinate and promote the growth of the accompanying fruit tissues. This dynamic process allows the fruit to conspicuously increase its size and acquire its final shape and means for seed dispersal. All these features are key for plant survival and crop yield. Despite its importance, we lack a high-resolution spatiotemporal map of how postfertilization fruit growth proceeds at the cellular level. In this study, we have combined live imaging, mutant backgrounds in which fertilization can be controlled, and computational modeling to monitor and predict postfertilization fruit growth in Arabidopsis. We have uncovered that, unlike leaves, sepals, or roots, fruit do not exhibit a spatial separation of cell division and expansion domains; instead, there is a separation into temporal stages with fertilization as the trigger for transitioning to cell expansion, which drives postfertilization fruit growth. We quantified the coordination between fertilization and fruit growth by imaging no transmitting tract (ntt) mutants, in which fertilization fails in the bottom half of the fruit. By combining our experimental data with computational modeling, we delineated the mobility properties of the seed-derived signaling cascades promoting growth in the fruit. Our study provides the basis for generating a comprehensive understanding of the molecular and cellular mechanisms governing fruit growth and shape.

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