scholarly journals Population Coding by Electrosensory Neurons

2008 ◽  
Vol 99 (4) ◽  
pp. 1825-1835 ◽  
Author(s):  
Maurice J. Chacron ◽  
Joseph Bastian
Keyword(s):  
Time Window ◽  
Population Coding ◽  
Weakly Electric Fish ◽  
Critical Feature ◽  
Sensory Stimuli ◽  
Biologically Relevant ◽  
Central Neurons ◽  
Correlated Activity ◽  
The Individual ◽  
Weakly Electric

Sensory stimuli typically activate many receptors at once and therefore should lead to increases in correlated activity among central neurons. Such correlated activity could be a critical feature in the encoding and decoding of information in central circuits. Here we characterize correlated activity in response to two biologically relevant classes of sensory stimuli in the primary electrosensory nuclei, the electrosensory lateral line lobe, of the weakly electric fish Apteronotus leptorhynchus. Our results show that these neurons can display significant correlations in their baseline activities that depend on the amount of receptive field overlap. A detailed analysis of spike trains revealed that correlated activity resulted predominantly from a tendency to fire synchronous or anti-synchronous bursts of spikes. We also explored how different stimulation protocols affected correlated activity: while prey-like stimuli increased correlated activity, conspecific-like stimuli decreased correlated activity. We also computed the correlations between the variabilities of each neuron to repeated presentations of the same stimulus (noise correlations) and found lower amounts of noise correlation for communication stimuli. Therefore the decrease in correlated activity seen with communication stimuli is caused at least in part by reduced noise correlations. This differential modulation in correlated activity occurred because of changes in burst firing at the individual neuron level. Our results show that different categories of behaviorally relevant input will differentially affect correlated activity. In particular, we show that the number of correlated bursts within a given time window could be used by postsynaptic neurons to distinguish between both stimulus categories.

scholarly journals Stimulus background influences phase invariant coding by correlated neural activity

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Michael G Metzen ◽  
Maurice J Chacron
Keyword(s):  
Phase Locking ◽  
Low Frequency ◽  
Weakly Electric Fish ◽  
Neuron Activity ◽  
Invariant Representation ◽  
Communication Signals ◽  
Correlated Activity ◽  
Peripheral Afferents ◽  
And Behavior ◽  
Weakly Electric

Previously we reported that correlations between the activities of peripheral afferents mediate a phase invariant representation of natural communication stimuli that is refined across successive processing stages thereby leading to perception and behavior in the weakly electric fish Apteronotus leptorhynchus (Metzen et al., 2016). Here, we explore how phase invariant coding and perception of natural communication stimuli are affected by changes in the sinusoidal background over which they occur. We found that increasing background frequency led to phase locking, which decreased both detectability and phase invariant coding. Correlated afferent activity was a much better predictor of behavior as assessed from both invariance and detectability than single neuron activity. Thus, our results provide not only further evidence that correlated activity likely determines perception of natural communication signals, but also a novel explanation as to why these preferentially occur on top of low frequency as well as low-intensity sinusoidal backgrounds.

Dendritic Na+ Current Inactivation Can Increase Cell Excitability By Delaying a Somatic Depolarizing Afterpotential

2005 ◽  
Vol 94 (6) ◽  
pp. 3836-3848 ◽  
Author(s):  
Fernando R. Fernandez ◽  
W. Hamish Mehaffey ◽  
Ray W. Turner
Keyword(s):  
Pyramidal Cells ◽  
Firing Frequency ◽  
Weakly Electric Fish ◽  
Dynamical Analysis ◽  
Central Neurons ◽  
Electrophysiological Recordings ◽  
A Cell ◽  
Dendritic Spike ◽  
Weakly Electric ◽  
The Relationship

Many central neurons support active dendritic spike backpropagation mediated by voltage-gated currents. Active spikes in dendrites have been shown capable of providing feedback to the soma to influence somatic excitability and firing dynamics through a depolarizing afterpotential (DAP). In pyramidal cells of the electrosensory lobe of weakly electric fish, Na+ spikes in dendrites undergo a frequency-dependent broadening that enhances the DAP to increase somatic firing frequency. We use a combination of dynamical analysis and electrophysiological recordings to demonstrate that spike broadening in dendrites is primarily caused by a cumulative inactivation of dendritic Na+ current. We further show that a reduction in dendritic Na+ current increases excitability by decreasing the interspike interval and promoting burst firing. This process arises when inactivation of dendritic Na+ current shifts the latency of the dendritic spike to delay the arrival of the DAP sufficiently to increase its impact on somatic membrane potential despite a reduction in dendritic excitability. Furthermore, the relationship between dendritic Na+ current density and somatic excitability is nonmonotonic, as intermediate levels of dendritic Na+ current exert the greatest excitatory influence. These results reveal that temporal shifts in dendritic spike firing provide a novel means for backpropagating spikes to influence the final output of a cell.

scholarly journals Descending pathways mediate adaptive optimized coding of natural stimuli in weakly electric fish

2019 ◽  
Vol 5 (10) ◽  
pp. eaax2211 ◽  
Author(s):  
Chengjie G. Huang ◽  
Michael G. Metzen ◽  
Maurice J. Chacron
Keyword(s):  
Environmental Changes ◽  
Behavioral Responses ◽  
Sensory Systems ◽  
Weakly Electric Fish ◽  
Descending Pathways ◽  
Natural Stimuli ◽  
Central Neurons ◽  
Power Spectral ◽  
Underlying Mechanisms ◽  
Weakly Electric

Biological systems must be flexible to environmental changes to survive. This is exemplified by the fact that sensory systems continuously adapt to changes in the environment to optimize coding and behavioral responses. However, the nature of the underlying mechanisms remains poorly understood in general. Here, we investigated the mechanisms mediating adaptive optimized coding of naturalistic stimuli with varying statistics depending on the animal’s velocity during movement. We found that central neurons adapted their responses to stimuli with different power spectral densities such as to optimally encode them, thereby ensuring that behavioral responses are, in turn, better matched to the new stimulus statistics. Sensory adaptation further required descending inputs from the forebrain as well as the raphe nuclei. Our findings thus reveal a previously unknown functional role for descending pathways in mediating adaptive optimized coding of natural stimuli that is likely generally applicable across sensory systems and species.

scholarly journals Sparse and dense coding of natural stimuli by distinct midbrain neuron subpopulations in weakly electric fish

2011 ◽  
Vol 106 (6) ◽  
pp. 3102-3118 ◽  
Author(s):  
Katrin Vonderschen ◽  
Maurice J. Chacron
Keyword(s):  
Sparse Coding ◽  
Electric Fish ◽  
Neural Representation ◽  
Weakly Electric Fish ◽  
Torus Semicircularis ◽  
Dense Coding ◽  
Natural Stimuli ◽  
Central Neurons ◽  
Weakly Electric ◽  
Peripheral Sensory

While peripheral sensory neurons respond to natural stimuli with a broad range of spatiotemporal frequencies, central neurons instead respond sparsely to specific features in general. The nonlinear transformations leading to this emergent selectivity are not well understood. Here we characterized how the neural representation of stimuli changes across successive brain areas, using the electrosensory system of weakly electric fish as a model system. We found that midbrain torus semicircularis (TS) neurons were on average more selective in their responses than hindbrain electrosensory lateral line lobe (ELL) neurons. Further analysis revealed two categories of TS neurons: dense coding TS neurons that were ELL-like and sparse coding TS neurons that displayed selective responses. These neurons in general responded to preferred stimuli with few spikes and were mostly silent for other stimuli. We further investigated whether information about stimulus attributes was contained in the activities of ELL and TS neurons. To do so, we used a spike train metric to quantify how well stimuli could be discriminated based on spiking responses. We found that sparse coding TS neurons performed poorly even when their activities were combined compared with ELL and dense coding TS neurons. In contrast, combining the activities of as few as 12 dense coding TS neurons could lead to optimal discrimination. On the other hand, sparse coding TS neurons were better detectors of whether their preferred stimulus occurred compared with either dense coding TS or ELL neurons. Our results therefore suggest that the TS implements parallel detection and estimation of sensory input.

scholarly journals Synergistic population coding of natural communication stimuli by hindbrain electrosensory neurons

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ziqi Wang ◽  
Maurice J. Chacron
Keyword(s):  
Electric Fish ◽  
Discrimination Performance ◽  
Population Coding ◽  
Weakly Electric Fish ◽  
Equal Weight ◽  
Electrosensory System ◽  
Synergistic Interactions ◽  
Neural Activities ◽  
Neural Populations ◽  
Weakly Electric

AbstractUnderstanding how neural populations encode natural stimuli with complex spatiotemporal structure to give rise to perception remains a central problem in neuroscience. Here we investigated population coding of natural communication stimuli by hindbrain neurons within the electrosensory system of weakly electric fish Apteronotus leptorhynchus. Overall, we found that simultaneously recorded neural activities were correlated: signal but not noise correlations were variable depending on the stimulus waveform as well as the distance between neurons. Combining the neural activities using an equal-weight sum gave rise to discrimination performance between different stimulus waveforms that was limited by redundancy introduced by noise correlations. However, using an evolutionary algorithm to assign different weights to individual neurons before combining their activities (i.e., a weighted sum) gave rise to increased discrimination performance by revealing synergistic interactions between neural activities. Our results thus demonstrate that correlations between the neural activities of hindbrain electrosensory neurons can enhance information about the structure of natural communication stimuli that allow for reliable discrimination between different waveforms by downstream brain areas.

scholarly journals The weakly electric fish, Apteronotus albifrons, actively avoids experimentally induced hypoxia

2021 ◽  
Author(s):  
Stefan Mucha ◽  
Lauren J. Chapman ◽  
Rüdiger Krahe
Keyword(s):  
Active Avoidance ◽  
Electric Fish ◽  
Electric Organ ◽  
The Other ◽  
Weakly Electric Fish ◽  
Dissolved Oxygen Concentration ◽  
Shuttle Box ◽  
Freshwater Habitats ◽  
Electric Organ Discharges ◽  
Weakly Electric

AbstractAnthropogenic environmental degradation has led to an increase in the frequency and prevalence of aquatic hypoxia (low dissolved oxygen concentration, DO), which may affect habitat quality for water-breathing fishes. The weakly electric black ghost knifefish, Apteronotus albifrons, is typically found in well-oxygenated freshwater habitats in South America. Using a shuttle-box design, we exposed juvenile A. albifrons to a stepwise decline in DO from normoxia (> 95% air saturation) to extreme hypoxia (10% air saturation) in one compartment and chronic normoxia in the other. On average, A. albifrons actively avoided the hypoxic compartment below 22% air saturation. Hypoxia avoidance was correlated with upregulated swimming activity. Following avoidance, fish regularly ventured back briefly into deep hypoxia. Hypoxia did not affect the frequency of their electric organ discharges. Our results show that A. albifrons is able to sense hypoxia at non-lethal levels and uses active avoidance to mitigate its adverse effects.

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