Although radial oblique dendrites are a major synaptic input site in CA1 pyramidal neurons, little is known about their integrative properties. We have used multisite two-photon glutamate uncaging to ...deliver different spatiotemporal input patterns to single branches while simultaneously recording the uncaging-evoked excitatory postsynaptic potentials and local Ca
2+ signals. Asynchronous input patterns sum linearly in spite of the spatial clustering and produce Ca
2+ signals that are mediated by NMDA receptors (NMDARs). Appropriately timed and sized input patterns (∼20 inputs within ∼6 ms) produce a supralinear summation due to the initiation of a dendritic spike. The Ca
2+ signals associated with synchronous input were larger and mediated by influx through both NMDARs and voltage-gated Ca
2+ channels (VGCCs). The oblique spike is a fast Na
+ spike whose duration is shaped by the coincident activation of NMDAR, VGCCs, and transient K
+ currents. Our results suggest that individual branches can function as single integrative compartments.
Depending on the behavioral state, hippocampal CA1 pyramidal neurons receive very distinct patterns of synaptic input and likewise produce very different output patterns. We have used simultaneous ...dendritic and somatic recordings and multisite glutamate uncaging to investigate the relationship between synaptic input pattern, the form of dendritic integration, and action potential output in CA1 neurons. We found that when synaptic input arrives asynchronously or highly distributed in space, the dendritic arbor performs a linear integration that allows the action potential rate and timing to vary as a function of the quantity of the input. In contrast, when synaptic input arrives synchronously and spatially clustered, the dendritic compartment receiving the clustered input produces a highly nonlinear integration that leads to an action potential output that is extraordinarily precise and invariant. We also present evidence that both of these forms of information processing may be independently engaged during the two distinct behavioral states of the hippocampus such that individual CA1 pyramidal neurons could perform two different state-dependent computations: input strength encoding during theta states and feature detection during sharp waves.
A fundamental function of nerve cells is the transformation of incoming synaptic information into specific patterns of action potential output. An important component of this transformation is ...synaptic integration--the combination of voltage deflections produced by a myriad of synaptic inputs into a singular change in membrane potential. There are three basic elements involved in integration: the amplitude of the unitary postsynaptic potential; the manner in which non-simultaneous unitary events add in time (temporal summation), and the addition of unitary events occurring simultaneously in separate regions of the dendritic arbor (spatial summation). This review discusses how passive and active dendritic properties, and the functional characteristics of the synapse, shape these three elements of synaptic integration.
Step hyperpolarizations evoked slowly activating, noninactivating, and slowly deactivating inward currents from membrane patches recorded in the cell-attached patch configuration from the soma and ...apical dendrites of hippocampal CA1 pyramidal neurons. The density of these hyperpolarization-activated currents (Ih) increased over sixfold from soma to distal dendrites. Activation curves demonstrate that a significant fraction of Ih channels is active near rest and that the range is hyperpolarized relatively more in the distal dendrites. Ih activation and deactivation kinetics are voltage-and temperature-dependent, with time constants of activation and deactivation decreasing with hyperpolarization and depolarization, respectively. Ih demonstrated a mixed Na+-K+ conductance and was sensitive to low concentrations of external CsCl. Dual whole-cell recordings revealed regional differences in input resistance (Rin) and membrane polarization rates (taumem) across the somatodendritic axis that are attributable to the spatial gradient of Ih channels. As a result of these membrane effects the propagation of subthreshold voltage transients is directionally specific. The elevated dendritic Ih density decreases EPSP amplitude and duration and reduces the time window over which temporal summation takes place. The backpropagation of action potentials into the dendritic arborization was impacted only slightly by dendritic Ih, with the most consistent effect being a decrease in dendritic action potential duration and an increase in afterhyperpolarization. Overall, Ih acts to dampen dendritic excitability, but its largest impact is on the subthreshold range of membrane potentials where the integration of inhibitory and excitatory synaptic inputs takes place.
From Power to Action Galinsky, Adam D; Gruenfeld, Deborah H; Magee, Joe C
Journal of personality and social psychology,
09/2003, Letnik:
85, Številka:
3
Journal Article
Recenzirano
Three experiments investigated the hypothesis that power increases an action orientation in the power holder, even in contexts where power is not directly experienced. In Experiment 1, participants ...who possessed structural power in a group task were more likely to take a card in a simulated game of blackjack than those who lacked power. In Experiment 2, participants primed with high power were more likely to act against an annoying stimulus (a fan) in the environment, suggesting that the experience of power leads to the performance of goal-directed behavior. In Experiment 3, priming high power led to action in a social dilemma regardless of whether that action had prosocial or antisocial consequences. The effects of priming power are discussed in relation to the broader literature on conceptual and mind-set priming.
Under certain conditions, regenerative voltage spikes can be initiated locally in the dendrites of CA1 pyramidal neurons. These are interesting events that could potentially provide neurons with ...additional computational abilities. Using whole-cell dendritic recordings from the distal apical trunk and proximal tuft regions and realistic computer modeling, we have determined that highly synchronized and moderately clustered inputs are required for dendritic spike initiation: approximately 50 synaptic inputs spread over 100 mum of the apical trunk/tuft need to be activated within 3 msec. Dendritic spikes are characterized by a more depolarized voltage threshold than at the soma -48 +/- 1 mV (n = 30) vs -56 +/- 1 mV (n = 7), respectively and are mainly generated and shaped by dendritic Na+ and K+ currents. The relative contribution of AMPA and NMDA currents is also important in determining the actual spatiotemporal requirements for dendritic spike initiation. Once initiated, dendritic spikes can easily reach the soma, but their propagation is only moderately strong, so that it can be modulated by physiologically relevant factors such as changes in the V(m) and the ionic composition of the extracellular solution. With effective spike propagation, an extremely short-latency neuronal output is produced for greatly reduced input levels. Therefore, dendritic spikes function as efficient detectors of specific input patterns, ensuring that the neuronal response to high levels of input synchrony is a precisely timed action potential output.
Plasticity of dendritic function Magee, Jeffrey C; Johnston, Daniel
Current opinion in neurobiology,
06/2005, Letnik:
15, Številka:
3
Journal Article
Recenzirano
The various properties of neuronal dendrites — their morphology, active membrane and synaptic properties — all play important roles in determining the functional capabilities of central nervous ...system neurons. Because of their fundamental involvement in both synaptic integration and synaptic plasticity, the active dendritic properties are important for both neuronal information processing and storage. The active properties of dendrites are determined by the densities of voltage-gated ion channels located within the dendrites in addition to the biophysical characteristics of those channels. The real power of this system resides in the level of plasticity that is provided by the many forms of channel modulation known to exist in neurons. Indeed, voltage gated ion channel modulation shapes the active properties of neuronal dendrites to specific conditions, thus tailoring the functional role of the single neuron within its circuit.
Though robust clinical data are available within transplantation, these data are not used for broad‐based, multicentered quality improvement initiates. This article describes a targeted quality ...improvement initiative within the Studies of Pediatric Liver Transplantation (SPLIT) Registry. Using standard statistical techniques and clinical expertise to adjust for data and statistical reliability, we identified the pediatric liver transplant centers in North America with the lowest hepatic artery thrombosis rate and biliary complication rates. A survey was completed to establish current practices within the entire SPLIT group. Surgeons from the highest performing centers presented a detailed, technically oriented overview of their current practices. The presentations and discussion that followed were recorded and form the basis of the best practices described herein. We frame this work as a unique six‐step approach roadmap that may serve as an efficient and cost effective model for novel broad‐based quality improvement initiatives within transplantation.
This viewpoint describes a multi‐institutional quality collaborative approach within the Studies in Pediatric Liver Transplantation group and may represent a useful framework for physician‐driven, broad‐based quality improvement within transplantation. See editorial by Emond on page 2267.
Most neurons receive thousands of synaptic inputs onto widely spread dendrites. Because of dendritic filtering, distant synapses should have less efficacy than proximal ones. To investigate this, we ...characterized the amplitude and kinetics of excitatory synaptic input across the apical dendrites of CA1 pyramidal neurons using dual whole-cell recordings. We found that dendritic EPSP amplitude increases with distance from the soma, counterbalancing the filtering effects of the dendrites and reducing the location dependence of somatic EPSP amplitude. Dendritic current injections and a multi-compartmental computer model demonstrated that dendritic membrane properties have only a minor role in elevating the local EPSP. Instead a progressive increase in synaptic conductance seems to be primarily responsible for normalizing the amplitudes of individual inputs.
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