Faculty Opinions recommendation of Increasing Ca2+ transients by broadening postsynaptic action potentials enhances timing-dependent synaptic depression.

2005 ◽  
Author(s):  
Dan Johnston
Keyword(s):  
Action Potentials ◽  
Synaptic Depression ◽  
Postsynaptic Action

scholarly journals Increasing Ca2+ transients by broadening postsynaptic action potentials enhances timing-dependent synaptic depression

2005 ◽  
Vol 102 (52) ◽  
pp. 19121-19125 ◽  
Author(s):  
Y.-D. Zhou ◽  
C. D. Acker ◽  
T. I. Netoff ◽  
K. Sen ◽  
J. A. White
Keyword(s):  
Action Potentials ◽  
Synaptic Depression ◽  
Postsynaptic Action

Neuronal Activity Regulates Diffusion Across the Neck of Dendritic Spines

Science ◽  
2005 ◽  
Vol 310 (5749) ◽  
pp. 866-869 ◽  
Author(s):  
Brenda L. Bloodgood ◽  
Bernardo L. Sabatini
Keyword(s):  
Neuronal Activity ◽  
Dendritic Spines ◽  
Action Potentials ◽  
Synaptic Activation ◽  
Postsynaptic Potentials ◽  
Electrical Isolation ◽  
Spine Head ◽  
Postsynaptic Action ◽  
Excitatory Neurons

In mammalian excitatory neurons, dendritic spines are separated from dendrites by thin necks. Diffusion across the neck limits the chemical and electrical isolation of each spine. We found that spine/dendrite diffusional coupling is heterogeneous and uncovered a class of diffusionally isolated spines. The barrier to diffusion posed by the neck and the number of diffusionally isolated spines is bidirectionally regulated by neuronal activity. Furthermore, coincident synaptic activation and postsynaptic action potentials rapidly restrict diffusion across the neck. The regulation of diffusional coupling provides a possible mechanism for determining the amplitude of postsynaptic potentials and the accumulation of plasticity-inducing molecules within the spine head.

Posttetanic potentiation of group Ia EPSPs: possible mechanisms for differential distribution among medial gastrocnemius motoneurons

1983 ◽  
Vol 50 (2) ◽  
pp. 379-398 ◽  
Author(s):  
A. Lev-Tov ◽  
M. J. Pinter ◽  
R. E. Burke
Keyword(s):  
Negative Correlation ◽  
Action Potentials ◽  
Input Resistance ◽  
Mean Amplitude ◽  
Synaptic Depression ◽  
Medial Gastrocnemius ◽  
Posttetanic Potentiation ◽  
Differential Distribution ◽  
Strong Negative Correlation ◽  
Statistical Probability

We have reinvestigated the phenomenon of posttetanic potentiation (PTP) of group Ia monosynaptic excitatory postsynaptic potentials (EPSPs) in medial gastrocnemius (MG) alpha-motoneurons of pentobarbital-anesthetized cats. The results generally confirm earlier reports by Luscher and colleagues (43, 44) of a negative correlation between the maximum percentage potentiation of Ia EPSP amplitude (Pmax) and 1) the mean amplitude of the pretetanic control EPSP in the same cell and 2) the input resistance of the postsynaptic motoneuron. These negative correlations, which we will refer to as "differential distribution of PTP" within the MG motor pool, were less strong in the present work than reported by Luscher et al. (43, 44). We also found a relatively strong negative correlation between posttetanic EPSP depression, assessed by the amplitude of the first posttetanic EPSP, and the level of Pmax subsequently attained. We found no evidence that posttetanic depression is caused by failure of presynaptic action potentials. We investigated a second type of depression, referred to as "specific" synaptic depression, in which the second EPSP of paired responses (interval 250 ms) is, on average, smaller in peak amplitude than the first EPSP. This phenomenon appears to reflect decreases in the probability of transmitter release from previously activated synapses. Specific synaptic depression was consistently increased when paired responses were conditioned by a high-frequency tetanus. This is most easily explained by postulating that PTP results, at least in part, from an increase in the statistical probability of transmitter liberation from group Ia synapses that are activated (i.e., presumably invaded by action potentials) both before and after afferent tetanization. On the basis of the present results and other available evidence, we conclude that the differential distribution of PTP can be explained by two main factors: 1) the nonlinear relation between conductance and voltage changes inherent in all chemical synapses and 2) systematic variations in the properties of group Ia synapses that innervated different motoneurons, which remain to be clarified.

Analysis of synaptic depression contributing to habituation of gill-withdrawal reflex in Aplysia californica

1982 ◽  
Vol 48 (2) ◽  
pp. 431-438 ◽  
Author(s):  
J. H. Byrne
Keyword(s):  
Sensory Neuron ◽  
Motor Neurons ◽  
Action Potentials ◽  
Time Course ◽  
Complex Function ◽  
Synaptic Depression ◽  
Short Term ◽  
Withdrawal Reflex ◽  
Single Complex ◽  
Gradual Decay

1. Repeated stimulation of the siphon skin results in short-term habituation of the reflex contractions of the gill (38). The habituation, in turn, is correlated with a depression of the excitatory postsynaptic potentials (EPSPs) in motor neurons from mechanoreceptor sensory neurons (SN) (7, 16). The present study was undertaken to examine the parametric features of the synaptic depression and gain insights into the mechanisms underlying the reduced transmitter release. 2. Single sensory neuron action potentials were repeatedly elicited with depolarizing current pulses while the amplitude of the resultant EPSPs in the motor neuron was monitored. Synaptic depression varies as a complex function of interstimulus interval (ISI). At an ISI of 1 s, depression is rapid and reaches a plateau at 36% of control. In contrast, the depression at an ISI of 100 s is less pronounced, showing a gradual decay to 65% of control with the 10th EPSP. Surprisingly, there are no significant differences in time course or magnitude of depression across a broad range of intermediate ISIs (3, 10, and 30 s), although depression at these ISIs is intermediate between the 1 and 100 s ISIs. 3. There is also a complex relationship between spike interval and the depression of the second of two EPSPs. Thus, depression of the second of two EPSPs or depression of a train of EPSPs is not a monotonic function of spike interval. Indeed, the data suggest that there may be a slight underlying facilitatory process with short spike intervals. 4. The results also indicate that the recovery of synaptic depression following a train of 10 stimuli is not constant. Shorter spike intervals produce more rapid recovery. 5. These data are inconsistent with a classical depletion model (33) for synaptic depression and indicate that either a single complex function of time and ISI or multiple functions underlie synaptic depression and its recovery at the sensory neuron synapse.

Local and Global Gating of Synaptic Plasticity

2000 ◽  
Vol 12 (3) ◽  
pp. 519-529 ◽  
Author(s):  
Manuel A. Sánchez-Montañés ◽  
Paul F. M. J. Verschure ◽  
Peter König
Keyword(s):  
Basal Forebrain ◽  
Cortical Neurons ◽  
Action Potentials ◽  
Learning Rule ◽  
Global Scale ◽  
Local Learning ◽  
Relative Timing ◽  
Fast Learning ◽  
Learning Rates ◽  
Postsynaptic Action

Mechanisms influencing learning in neural networks are usually investigated on either a local or a global scale. The former relates to synaptic processes, the latter to unspecific modulatory systems. Here we study the interaction of a local learning rule that evaluates coincidences of pre- and postsynaptic action potentials and a global modulatory mechanism, such as the action of the basal forebrain onto cortical neurons. The simulations demonstrate that the interaction of these mechanisms leads to a learning rule supporting fast learning rates, stability, and flexibility. Furthermore, the simulations generate two experimentally testable predictions on the dependence of backpropagating action potential on basal forebrain activity and the relative timing of the activity of inhibitory and excitatory neurons in the neocortex.

Functional Connectivity in Layer IV Local Excitatory Circuits of Rat Somatosensory Cortex

2004 ◽  
Vol 92 (4) ◽  
pp. 2137-2150 ◽  
Author(s):  
Anna I. Cowan ◽  
Christian Stricker
Keyword(s):  
Functional Connectivity ◽  
Somatosensory Cortex ◽  
Action Potentials ◽  
Barrel Cortex ◽  
Synaptic Depression ◽  
Synaptic Efficacy ◽  
Intrinsic Properties ◽  
Presynaptic Neuron ◽  
Synaptic Dynamics ◽  
Rat Somatosensory Cortex

There are two types of excitatory neurons within layer IV of rat somatosensory cortex: star pyramidal (SP) and spiny stellate cells (SS). We examined the intrinsic properties and connectivity between these neurons to determine differences in function. Eighty-four whole cell recordings of pairs of neurons were examined in slices of rat barrel cortex at 36 ± 1°C. Only minimal differences in intrinsic properties were found; however, differences in synaptic strength could clearly be shown. Connections between homonymous pairs (SS–SS or SP–SP) had a higher efficacy than heteronymous connections. This difference was mainly a result of quantal content. In 42 pairs, synaptic dynamics were examined. Sequences of action potentials (3–20 Hz) in the presynaptic neuron consistently caused synaptic depression ( Ē2/ Ē1 = 0.53 ± 0.18). The dominant component of depression was release-independent; this depression occurred even when preceding action potentials had failed to cause a response. The release-dependence of depression was target specific; in addition, release-independence was greater for postsynaptic SPs. In a subset of connections formed only between SP and any other cell type (43%), synaptic efficacy was dependent on the presynaptic membrane potential ( Vm); at −55 mV, the connections were almost silent, whereas at −85 mV, transmission was very reliable. We suggest that, within layer IV, there is stronger efficacy between homonymous than between heteronymous excitatory connections. Under dynamic conditions, the functional connectivity is shaped by synaptic efficacy at individual connections, by Vm, and by the specificity in the types of synaptic depression.

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