scholarly journals Adult-born neurons facilitate olfactory bulb pattern separation during task engagement

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Wankun L Li ◽  
Monica W Chu ◽  
An Wu ◽  
Yusuke Suzuki ◽  
Itaru Imayoshi ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Adult Neurogenesis ◽  
Task Engagement ◽  
Pattern Separation ◽  
Inhibitory Neurons ◽  
Dependent Manner ◽  
Genetic Method ◽  
Two Photon ◽  
Passive Exposure ◽  
Adult Born Neurons

The rodent olfactory bulb incorporates thousands of newly generated inhibitory neurons daily throughout adulthood, but the role of adult neurogenesis in olfactory processing is not fully understood. Here we adopted a genetic method to inducibly suppress adult neurogenesis and investigated its effect on behavior and bulbar activity. Mice without young adult-born neurons (ABNs) showed normal ability in discriminating very different odorants but were impaired in fine discrimination. Furthermore, two-photon calcium imaging of mitral cells (MCs) revealed that the ensemble odor representations of similar odorants were more ambiguous in the ablation animals. This increased ambiguity was primarily due to a decrease in MC suppressive responses. Intriguingly, these deficits in MC encoding were only observed during task engagement but not passive exposure. Our results indicate that young olfactory ABNs are essential for the enhancement of MC pattern separation in a task engagement-dependent manner, potentially functioning as a gateway for top-down modulation.

scholarly journals Author response: Adult-born neurons facilitate olfactory bulb pattern separation during task engagement

2018 ◽  
Author(s):  
Wankun L Li ◽  
Monica W Chu ◽  
An Wu ◽  
Yusuke Suzuki ◽  
Itaru Imayoshi ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Task Engagement ◽  
Pattern Separation ◽  
Author Response ◽  
Adult Born Neurons

scholarly journals Young adult-born neurons improve odor coding by mitral cells

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
H. Shani-Narkiss ◽  
A. Vinograd ◽  
I. D. Landau ◽  
G. Tasaka ◽  
N. Yayon ◽  
...  
Keyword(s):  
Young Adult ◽  
Olfactory Bulb ◽  
Adult Neurogenesis ◽  
Neural Circuits ◽  
Experimental System ◽  
Adult Brain ◽  
Mitral Cells ◽  
Odor Coding ◽  
Adult Born Neurons ◽  
Unique Ability

AbstractNew neurons are continuously generated in the adult brain through a process called adult neurogenesis. This form of plasticity has been correlated with numerous behavioral and cognitive phenomena, but it remains unclear if and how adult-born neurons (abNs) contribute to mature neural circuits. We established a highly specific and efficient experimental system to target abNs for causal manipulations. Using this system with chemogenetics and imaging, we found that abNs effectively sharpen mitral cells (MCs) tuning and improve their power to discriminate among odors. The effects on MCs responses peaked when abNs were young and decreased as they matured. To explain the mechanism of our observations, we simulated the olfactory bulb circuit by modelling the incorporation of abNs into the circuit. We show that higher excitability and broad input connectivity, two well-characterized features of young neurons, underlie their unique ability to boost circuit computation.

scholarly journals The role of microglia and their CX3CR1 signaling in adult neurogenesis in the olfactory bulb

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Ronen Reshef ◽  
Elena Kudryavitskaya ◽  
Haran Shani-Narkiss ◽  
Batya Isaacson ◽  
Neta Rimmerman ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Adult Neurogenesis ◽  
Granule Cells ◽  
Time Lapse ◽  
Spine Density ◽  
Mature Adult ◽  
Two Photon ◽  
Newborn Neurons ◽  
Time Lapse Imaging

Microglia play important roles in perinatal neuro- and synapto-genesis. To test the role of microglia in these processes during adulthood, we examined the effects of microglia depletion, via treatment of mice with the CSF-1 receptor antagonist PLX5622, and abrogated neuronal-microglial communication in CX3C receptor-1 deficient (Cx3cr1−/−) mice. Microglia depletion significantly lowered spine density in young (developing) but not mature adult-born-granule-cells (abGCs) in the olfactory bulb. Two-photon time-lapse imaging indicated that microglia depletion reduced spine formation and elimination. Functionally, odor-evoked responses of mitral cells, which are normally inhibited by abGCs, were increased in microglia-depleted mice. In Cx3cr1−/− mice, abGCs exhibited reduced spine density, dynamics and size, concomitantly with reduced contacts between Cx3cr1-deficient microglia and abGCs' dendritic shafts, along with increased proportion of microglia-contacted spines. Thus, during adult neurogenesis, microglia regulate the elimination (pruning), formation, and maintenance of synapses on newborn neurons, contributing to the functional integrity of the olfactory bulb circuitry.

scholarly journals Enhanced ongoing endogenous activity predicts elimination of adult-born neurons in the mouse olfactory bulb

2020 ◽  
Author(s):  
Xin Su ◽  
Yury Kovalchuk ◽  
Nima Mojtahedi ◽  
Olga Garaschuk
Keyword(s):  
Olfactory Bulb ◽  
Neural Circuitry ◽  
Two Photon ◽  
Dendritic Morphogenesis ◽  
Time Courses ◽  
Adult Born Neurons ◽  
Endogenous Activity ◽  
Dendritic Complexity ◽  
Two Populations

AbstractAdult-born cells, arriving daily into the rodent olfactory bulb, either integrate into the neural circuitry or get eliminated. Whether these two populations differ in their morphological or functional properties remains, however, unclear. Using in vivo two-photon imaging, we monitored longitudinally the dendritic morphogenesis, odor-evoked responsiveness, endogenous Ca2+ signaling and survival/death of adult-born juxtaglomerular neurons (JGNs). We found that JGN maturation is accompanied by a significant reduction in dendritic complexity, with surviving and subsequently eliminated cells showing similar degrees of reduction and dendritic remodeling. Moreover, ∼63% of subsequently eliminated adult-born JGNs acquired odor-responsiveness before death, with amplitudes and time courses of odor-evoked responses similar to those recorded in the surviving cells. We observed, however, a significant long-lasting enhancement of the endogenous Ca2+ signaling in subsequently eliminated JGNs, visible already 6 days before death. These findings identify the ongoing endogenous Ca2+ signaling as a key predictor of the adult-born JGN’s fate.

scholarly journals Seizures start as silent microseizures by neuronal ensembles

2018 ◽  
Author(s):  
Michael Wenzel ◽  
Jordan P. Hamm ◽  
Darcy S. Peterka ◽  
Rafael MD Yuste
Keyword(s):  
Calcium Imaging ◽  
Travelling Wave ◽  
Inhibitory Neurons ◽  
Neural Activation ◽  
Calcium Dynamics ◽  
Neuronal Ensembles ◽  
Two Photon ◽  
Step Model

AbstractUnderstanding seizure formation and spread remains a critical goal of epilepsy research. While many studies have documented seizure spread, it remains mysterious how they start. We used fast in-vivo two-photon calcium imaging to reconstruct, at cellular resolution, the dynamics of focal cortical seizures as they emerge in epileptic foci (intrafocal), and subsequently propagate (extrafocal). We find that seizures start as intrafocal coactivation of small numbers of neurons (ensembles), which are electrographically silent. These silent “microseizures” expand saltatorily until they break into neighboring cortex, where they progress smoothly and first become detectable by LFP. Surprisingly, we find spatially heterogeneous calcium dynamics of local PV interneuron sub-populations, which rules out a simple role of inhibitory neurons during seizures. We propose a two-step model for the circuit mechanisms of focal seizures, where neuronal ensembles first generate a silent microseizure, followed by widespread neural activation in a travelling wave, which is then detected electrophysiologically.

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