scholarly journals Downstream Effect of Ramping Neuronal Activity through Synapses with Short-Term Plasticity

2016 ◽  
Vol 28 (4) ◽  
pp. 652-666 ◽  
Author(s):  
Wei Wei ◽  
Xiao-Jing Wang
Keyword(s):  
Neuronal Activity ◽  
Time Constant ◽  
Task Difficulty ◽  
Perceptual Decision Making ◽  
Short Term ◽  
Short Term Plasticity ◽  
A Value ◽  
Analytical Result ◽  
Decision Circuit ◽  
The Impact

Ramping neuronal activity refers to spiking activity with a rate that increases quasi-linearly over time. It has been observed in multiple cortical areas and is correlated with evidence accumulation processes or timing. In this work, we investigated the downstream effect of ramping neuronal activity through synapses that display short-term facilitation (STF) or depression (STD). We obtained an analytical result for a synapse driven by deterministic linear ramping input that exhibits pure STF or STD and numerically investigated the general case when a synapse displays both STF and STD. We show that the analytical deterministic solution gives an accurate description of the averaging synaptic activation of many inputs converging onto a postsynaptic neuron, even when fluctuations in the ramping input are strong. Activation of a synapse with STF shows an initial cubical increase with time, followed by a linear ramping similar to a synapse without STF. Activation of a synapse with STD grows in time to a maximum before falling and reaching a plateau, and this steady state is independent of the slope of the ramping input. For a synapse displaying both STF and STD, an increase in the depression time constant from a value much smaller than the facilitation time constant [Formula: see text] to a value much larger than [Formula: see text] leads to a transition from facilitation dominance to depression dominance. Therefore, our work provides insights into the impact of ramping neuronal activity on downstream neurons through synapses that display short-term plasticity. In a perceptual decision-making process, ramping activity has been observed in the parietal and prefrontal cortices, with a slope that decreases with task difficulty. Our work predicts that neurons downstream from such a decision circuit could instead display a firing plateau independent of the task difficulty, provided that the synaptic connection is endowed with short-term depression.

scholarly journals Synapsin Controls Both Reserve and Releasable Synaptic Vesicle Pools during Neuronal Activity and Short-Term Plasticity inAplysia

2001 ◽  
Vol 21 (12) ◽  
pp. 4195-4206 ◽  
Author(s):  
Yann Humeau ◽  
Frédéric Doussau ◽  
Francesco Vitiello ◽  
Paul Greengard ◽  
Fabio Benfenati ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Neuronal Activity ◽  
Short Term ◽  
Short Term Plasticity ◽  
Vesicle Pools

scholarly journals Circuit mechanisms for the maintenance and manipulation of information in working memory

2018 ◽  
Author(s):  
Nicolas Y. Masse ◽  
Guangyu R. Yang ◽  
H. Francis Song ◽  
Xiao-Jing Wang ◽  
David J. Freedman
Keyword(s):  
Working Memory ◽  
Neuronal Activity ◽  
Short Term Memory ◽  
Current Debate ◽  
Memory Representation ◽  
Short Term ◽  
Short Term Plasticity ◽  
Hidden States ◽  
Dependent Tasks ◽  
External Stimuli

SummaryRecently it has been proposed that information in short-term memory may not always be stored in persistent neuronal activity, but can be maintained in “activity-silent” hidden states such as synaptic efficacies endowed with short-term plasticity (STP). However, working memory involves manipulation as well as maintenance of information in the absence of external stimuli. In this work, we investigated working memory representation using recurrent neural network (RNN) models trained to perform several working memory dependent tasks. We found that STP can support the short-term maintenance of information provided that the memory delay period is sufficiently short. However, in tasks that require actively manipulating information, persistent neuronal activity naturally emerges from learning, and the amount of persistent neuronal activity scales with the degree of manipulation required. These results shed insight into the current debate on working memory encoding, and suggest that persistent neural activity can vary markedly between tasks used in different experiments.

scholarly journals Coincident glutamatergic depolarizations enhance GABAA receptor-dependent Cl- influx in mature and suppress Cl- efflux in immature neurons

2020 ◽  
Author(s):  
Aniello Lombardi ◽  
Peter Jedlicka ◽  
Heiko J. Luhmann ◽  
Werner Kilb
Keyword(s):  
Gaba Receptors ◽  
Temporal Correlation ◽  
Gabaergic Inhibition ◽  
Relevant Factor ◽  
Decay Kinetics ◽  
Short Term ◽  
Substantial Impact ◽  
Short Term Plasticity ◽  
The Impact ◽  
The Brain

AbstractThe impact of GABAergic transmission on neuronal excitability depends on the Cl−-gradient across membranes. However, the Cl−-fluxes through GABAA receptors alter the intracellular Cl− concentration ([Cl−]i) and in turn attenuate GABAergic responses, a process termed ionic plasticity. Recently it has been shown that coincident glutamatergic inputs significantly affect ionic plasticity. Yet how the [Cl−]i changes depend on the properties of glutamatergic inputs and their spatiotemporal relation to GABAergic stimuli is unknown. To investigate this issue, we used compartmental biophysical models of Cl− dynamics simulating either a simple ball-and-stick topology or a reconstructed immature CA3 neuron. These computational experiments demonstrated that glutamatergic co-stimulation enhances GABA receptor-mediated Cl− influx at low and attenuates or reverses the Cl− efflux at high initial [Cl−]i. The size of glutamatergic influence on GABAergic Cl−-fluxes depends on the conductance, decay kinetics, and localization of glutamatergic inputs. Surprisingly, the glutamatergic shift in GABAergic Cl−-fluxes is invariant to latencies between GABAergic and glutamatergic inputs over a substantial interval. In agreement with experimental data, simulations in a reconstructed CA3 pyramidal neuron with physiological patterns of correlated activity revealed that coincident glutamatergic synaptic inputs contribute significantly to the activity-dependent [Cl−]i changes. Whereas the influence of spatial correlation between distributed glutamatergic and GABAergic inputs was negligible, their temporal correlation played a significant role. In summary, our results demonstrate that glutamatergic co-stimulation had a substantial impact on ionic plasticity of GABAergic responses, enhancing the destabilization of GABAergic inhibition in the mature nervous systems, but suppressing GABAergic [Cl−]i changes in the immature brain. Therefore, glutamatergic shift in GABAergic Cl−-fluxes should be considered as a relevant factor of short term plasticity.Author SummaryInformation processing in the brain requires that excitation and inhibition are balanced. The main inhibitory neurotransmitter in the brain is gamma-amino-butyric acid (GABA). GABA actions depend on the Cl−-gradient, but activation of ionotropic GABA receptors causes Cl−-fluxes and thus reduces GABAergic inhibition. Here, we investigated how a coincident membrane depolarization by excitatory, glutamatergic synapses influences GABA-induced Cl−-fluxes using a biophysical compartmental model of Cl− dynamics, simulating either simple or realistic neuron topologies. We demonstrate that glutamatergic co-stimulation directly affects GABA-induced Cl−-fluxes, with the size of glutamatergic effects depending on the conductance, the decay kinetics, and localization of glutamatergic inputs. We also show that the glutamatergic shift in GABAergic Cl−-fluxes is surprisingly stable over a substantial range of latencies between glutamatergic and GABAergic inputs. We conclude from these results that glutamatergic co-stimulation alters GABAergic Cl−-fluxes and in turn affects the strength of GABAergic inhibition. These coincidence-dependent ionic changes should be considered as a relevant factor of short term plasticity in the CNS.

A Newspaper’s Effect on the Strength of Automatic Associations in Memory

2012 ◽  
Vol 24 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Florian Arendt
Keyword(s):  
Treatment Group ◽  
Term Effect ◽  
Control Group ◽  
Implicit Measure ◽  
Short Term ◽  
Short Term Treatment ◽  
Short Term Effect ◽  
Automatic Associations ◽  
Foreign Nationality ◽  
The Impact

A test was done to see if reading a newspaper which consistently overrepresents foreigners as criminals strengthens the automatic association between foreign country and criminal in memory (i.e., implicit cultivation). Further, an investigation was done to find out if reading articles from the same newspaper produces a short-term effect on the same measure and if (1) emotionalization of the newspaper texts, (2) emotional reactions of the reader (indicated by arousal), and (3) attributed text credibility moderate the short-term treatment effect. Eighty-five participants were assigned to one of three experimental conditions. Participants in the control group received short factual crime texts, where the nationality of the offender was not mentioned. Participants in the factual treatment group received the same texts, but the foreign nationality was mentioned. Participants in the emotionalized treatment group received emotionalized articles (i.e., texts which are high in vividness and frequency) covering the same crimes, with the foreign nationality mentioned. Supporting empirical evidence for implicit cultivation and a short-term effect was found. However, only emotionalized articles produced a short-term effect on the strength of the automatic association, indicating that newspaper texts must have a minimum of stimulus intensity to overcome an effect threshold. There were no moderating effects of arousal or credibility pertaining to the impact on the implicit measure. However, credibility moderated the short-term effect on a first-order judgment (i.e., estimated frequency of foreigners of all criminals). This indicates that a newspaper’s effect on the strength of automatic associations is relatively independent from processes of propositional reasoning.

The Effect of Task Difficulty and Hybrid Lists on Short-Term False Memories

2013 ◽  
Author(s):  
Rachael A. Wynne ◽  
Georgina A. Tolan ◽  
Gerald Tehan
Keyword(s):  
Task Difficulty ◽  
False Memories ◽  
Short Term
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