28 research outputs found
The Problem of Helping Behavior in the Context of Professional Training of College Students
На современном этапе развития нашего общества все актуальнее становится помогающая деятельность, которая является основной и важной частью социального развития в таких сферах, как здравоохранение, охрана окружающей среды, общественная безопасность и многое другое. В статье рассматриваются психологические особенности студентов медицинского колледжа, занимающихся и не занимающихся волонтерской деятельностью.At the present stage of development of our society, helping behavior becomes relevant. This is especially true in such areas as healthcare, environmental protection, and public safety. The article discusses the psychological characteristics of medical college students engaged and not engaged in volunteer activities
Cerebrospinal fluid sodium rhythms
Background: Cerebrospinal fluid (CSF) sodium levels have been reported to rise during episodic migraine. Since
migraine frequently starts in early morning or late afternoon, we hypothesized that natural sodium chronobiology
may predispose susceptible persons when extracellular CSF sodium increases. Since no mammalian brain sodium
rhythms are known, we designed a study of healthy humans to test if cation rhythms exist in CSF.
Methods: Lumbar CSF was collected every ten minutes at 0.1 mL/min for 24 h from six healthy participants. CSF
sodium and potassium concentrations were measured by ion chromatography, total protein by fluorescent
spectrometry, and osmolarity by freezing point depression. We analyzed cation and protein distributions over the
24 h period and spectral and permutation tests to identify significant rhythms. We applied the False Discovery Rate
method to adjust significance levels for multiple tests and Spearman correlations to compare sodium fluctuations
with potassium, protein, and osmolarity.
Results: The distribution of sodium varied much more than potassium, and there were statistically significant
rhythms at 12 and 1.65 h periods. Curve fitting to the average time course of the mean sodium of all six subjects
revealed the lowest sodium levels at 03.20 h and highest at 08.00 h, a second nadir at 09.50 h and a second peak
at 18.10 h. Sodium levels were not correlated with potassium or protein concentration, or with osmolarity.
Conclusion: These CSF rhythms are the first reports of sodium chronobiology in the human nervous system. The
results are consistent with our hypothesis that rising levels of extracellular sodium may contribute to the timing of
migraine onset. The physiological importance of sodium in the nervous system suggests that these rhythms may
have additional repercussions on ultradian functions
Stochastically Gating Ion Channels Enable Patterned Spike Firing through Activity-Dependent Modulation of Spike Probability
The transformation of synaptic input into patterns of spike output is a
fundamental operation that is determined by the particular complement of ion
channels that a neuron expresses. Although it is well established that
individual ion channel proteins make stochastic transitions between conducting
and non-conducting states, most models of synaptic integration are
deterministic, and relatively little is known about the functional consequences
of interactions between stochastically gating ion channels. Here, we show that a
model of stellate neurons from layer II of the medial entorhinal cortex
implemented with either stochastic or deterministically gating ion channels can
reproduce the resting membrane properties of stellate neurons, but only the
stochastic version of the model can fully account for perithreshold membrane
potential fluctuations and clustered patterns of spike output that are recorded
from stellate neurons during depolarized states. We demonstrate that the
stochastic model implements an example of a general mechanism for patterning of
neuronal output through activity-dependent changes in the probability of spike
firing. Unlike deterministic mechanisms that generate spike patterns through
slow changes in the state of model parameters, this general stochastic mechanism
does not require retention of information beyond the duration of a single spike
and its associated afterhyperpolarization. Instead, clustered patterns of spikes
emerge in the stochastic model of stellate neurons as a result of a transient
increase in firing probability driven by activation of HCN channels during
recovery from the spike afterhyperpolarization. Using this model, we infer
conditions in which stochastic ion channel gating may influence firing patterns
in vivo and predict consequences of modifications of HCN
channel function for in vivo firing patterns
Section: Cell physiology Dynamics of rat entorhinal cortex layer II/III cells: characteristics of membrane potential resonance at rest predict oscillation properties near threshold
Abstract Neurons generate intrinsic subthreshold membrane potential oscillations (MPOs) under various physiological and behavioural conditions. These oscillations influence neural responses and coding properties on many levels. On the single-cell level, MPOs modulate the temporal precision of action potentials; they also have a pronounced impact on large-scale cortical activity. Recent studies have described a close association between the MPOs of a given neuron and its electrical resonance properties. Using intracellular sharp micro-electrode recordings we examine both dynamical characteristics in layers II and III of the entorhinal cortex (EC). Our data from EC-layer-II stellate cells show strong membrane potential resonances and oscillations, both in the range of 5-15 Hz. At the resonance maximum, the membrane impedance can be more than twice as large as the input resistance. In EC-layer-III cells, MPOs could not be elicited, and frequency-resolved impedances decay monotonically with increasing frequency or has only a small peak followed by a subsequent decay. To quantify and compare the resonance and oscillation properties, we use a simple mathematical model that includes stochastic components to capture channel noise. Based on this model we demonstrate that electrical resonance is closely related though not equivalent to the occurrence of sag-potentials and MPOs. MPO frequencies can be predicted from the membrane impedance curve for stellate cells. The model also explains the broad-band nature of the observed MPOs. This underscores the importance of intrinsic noise sources for subthreshold phenomena and rules out a deterministic description of MPOs. In addition, our results show that the two identified cell classes in the superficial EC layers, which are known to target different areas in the hippocampus, also have different preferred frequency ranges and dynamic characteristics. Intrinsic cell properties may thus play a major role for the frequency-dependent information flow in the hippocampal formation.
Subthreshold Membrane-Potential Resonances Shape Spike-Train Patterns in the Entorhinal Cortex
Many neurons exhibit subthreshold membrane-potential resonances, such that the largest voltage responses occur at preferred stimulation frequencies. Because subthreshold resonances are known to influence the rhythmic activity at the network level, it is vital to understand how they affect spike generation on the single-cell level. We therefore investigated both resonant and nonresonant neurons of rat entorhinal cortex. A minimal resonate-and-fire type model based on measured physiological parameters captures fundamental properties of neuronal firing statistics surprisingly well and helps to shed light on the mechanisms that shape spike patterns: 1) subthreshold resonance together with a spike-induced reset of subthreshold oscillations leads to spike clustering and 2) spike-induced dynamics influence the fine structure of interspike interval (ISI) distributions and are responsible for ISI correlations appearing at higher firing rates (≥3 Hz). Both mechanisms are likely to account for the specific discharge characteristics of various cell types