Introduction to Information Transfer in the Nervous System

2020 ◽  
pp. 25-30
Author(s):  
Thomas Boraud
Keyword(s):  
Nervous System ◽  
Action Potentials ◽  
Information Transfer ◽  
Firing Frequency ◽  
Inhibitory Neurons ◽  
Electric Pulses ◽  
Postsynaptic Receptors ◽  
New Information ◽  
Excitatory Neurotransmitters ◽  
Intrinsic Firing

This chapter discusses the modalities of information transfer in the nervous system. The nervous system is organised around specialised cells called neurons, which work as integration units that transform all received information into new information. The neurons generate unitary electric pulses of invariant form and duration called action potentials or spikes. Neurons have an intrinsic firing frequency that is their frequency of producing spikes when they are not influenced. The chapter then considers the two major families of neurotransmitters. In general, a neuron releases only one type of neurotransmitter belonging to one of these two families. The first family is that of excitatory neurotransmitters; the neurons that release them are naturally called excitatory neurons. When they bind with postsynaptic receptors, they have a facilitating effect on the production of action potentials. Meanwhile, inhibitory neurons release neurotransmitters whose binding with postsynaptic receptors decreases the discharge frequency of the postsynaptic neuron. The chapter also describes a special family of neurotransmitters: the neuro-modulators.

Single-unit analysis of different hippocampal cell types during classical conditioning of rabbit nictitating membrane response

1983 ◽  
Vol 50 (5) ◽  
pp. 1197-1219 ◽  
Author(s):  
T. W. Berger ◽  
P. C. Rinaldi ◽  
D. J. Weisz ◽  
R. F. Thompson
Keyword(s):  
Classical Conditioning ◽  
Pyramidal Cell ◽  
Action Potentials ◽  
Pyramidal Cells ◽  
Cell Types ◽  
Firing Frequency ◽  
Spontaneous Firing ◽  
Nictitating Membrane ◽  
Nictitating Membrane Response ◽  
Firing Characteristics

Extracellular single-unit recordings from neurons in the CA1 and CA3 regions of the dorsal hippocampus were monitored during classical conditioning of the rabbit nictitating membrane response. Neurons were classified as different cell types using response to fornix stimulation (i.e., antidromic or orthodromic activation) and spontaneous firing characteristics as criteria. Results showed that hippocampal pyramidal neurons exhibit learning-related neural plasticity that develops gradually over the course of classical conditioning. The learning-dependent pyramidal cell response is characterized by an increase in frequency of firing within conditioning trials and a within-trial pattern of discharge that correlates strongly with amplitude-time course of the behavioral response. In contrast, pyramidal cell activity recorded from control animals given unpaired presentations of the conditioned and unconditioned stimulus (CS and UCS) does not show enhanced discharge rates with repeated stimulation. Previous studies of hippocampal cellular electrophysiology have described what has been termed a theta-cell (19-21, 45), the activity of which correlates with slow-wave theta rhythm generated in the hippocampus. Neurons classified as theta-cells in the present study exhibit responses during conditioning that are distinctly different than pyramidal cells. theta-Cells respond during paired conditioning trials with a rhythmic bursting; the between-burst interval occurs at or near 8 Hz. In addition, two different types of theta-cells were distinguishable. One type of theta-cell increases firing frequency above pretrial levels while displaying the theta bursting pattern. The other type decreases firing frequency below pretrial rates while showing a theta-locked discharge. In addition to pyramidal and theta-neurons, several other cell types recorded in or near the pyramidal cell layer could be distinguished. One cell type was distinctive in that it could be activated with a short, invariant latency following fornix stimulation, but spontaneous action potentials of such neurons could not be collided with fornix shock-induced action potentials. These neurons exhibit a different profile of spontaneous firing characteristics than those of antidromically identified pyramidal cells. Nevertheless, neurons in this noncollidable category display the same learning-dependent response as pyramidal cells. It is suggested that the noncollidable neurons represent a subpopulation of pyramidal cells that do not project an axon via the fornix but project, instead, to other limbic cortical regions.(ABSTRACT TRUNCATED AT 400 WORDS)

Understanding Neuropathic Pain

CNS Spectrums ◽  
2005 ◽  
Vol 10 (4) ◽  
pp. 298-308 ◽  
Author(s):  
Walter Zieglgänsberger ◽  
Achim Berthele ◽  
Thomas R. Tölle
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Neuropathic Pain ◽  
Neuronal Excitability ◽  
Traumatic Injury ◽  
Nerve Fibers ◽  
Cellular Events ◽  
Excitatory Neurotransmitters ◽  
The Central Nervous System ◽  
Activity Dependent

AbstractNeuropathic pain is defined as a chronic pain condition that occurs or persists after a primary lesion or dysfunction of the peripheral or central nervous system. Traumatic injury of peripheral nerves also increases the excitability of nociceptors in and around nerve trunks and involves components released from nerve terminals (neurogenic inflammation) and immunological and vascular components from cells resident within or recruited into the affected area. Action potentials generated in nociceptors and injured nerve fibers release excitatory neurotransmitters at their synaptic terminals such as L-glutamate and substance P and trigger cellular events in the central nervous system that extend over different time frames. Short-term alterations of neuronal excitability, reflected for example in rapid changes of neuronal discharge activity, are sensitive to conventional analgesics, and do not commonly involve alterations in activity-dependent gene expression. Novel compounds and new regimens for drug treatment to influence activity-dependent long-term changes in pain transducing and suppressive systems (pain matrix) are emerging.

Electrical Properties and Anion Permeability of Doubly Rectifying Junctions in the Leech Central Nervous System

1988 ◽  
Vol 137 (1) ◽  
pp. 1-11
Author(s):  
Susan E. Acklin
Keyword(s):  
Central Nervous System ◽  
T Cells ◽  
Nervous System ◽  
T Cell ◽  
Action Potentials ◽  
Sodium Pump ◽  
Current Flow ◽  
Cell Movement ◽  
Voltage Dependent ◽  
Electrical Connections

A study has been made of the electrical connections between touch sensory (T) neurones in the leech central nervous system (CNS) which display remarkable double rectification: depolarization spreads in both directions although hyperpolarization spreads poorly. Tests were made to determine whether this double rectification was a property of the junctions themselves or whether it resulted from changes in the length constants of processes intervening between the cell body and the junctions. Following trains of action potentials, T cells and their fine processes within the neuropile became hyperpolarized through the activity of an electrogenie sodium pump. When any T cell was hyperpolarized by 25 mV by repetitive stimulation, hyperpolarization failed to spread to the T cells to which it was electrically coupled. Further evidence for double rectification of junctions linking T cells was provided by experiments in which Cl− was injected electrophoretically. Cl− injection into one T cell caused inhibitory potentials recorded in it to become reversed. After a delay, Cl− spread to reverse IPSPs in the coupled T cell. Movement of Cl−, like current flow, was dependent on membrane potential. When the T cell into which Cl− was injected was kept hyperpolarized, Cl− failed to move into the adjacent T cell. Upon release of the hyperpolarization in the injected T cell, Cl− moved and reversed IPSPs in the coupled T cell. Together these results indicate that the gating properties of channels linking T cells are voltage-dependent, such that depolarization of either cell allows channels to open whereas hyperpolarization causes them to close.

Slow Activity in the Nervous System of the Earthworm, Lumbricus Terrestris

1967 ◽  
Vol 46 (3) ◽  
pp. 571-583
Author(s):  
M. B. V. ROBERTS
Keyword(s):  
Nervous System ◽  
Nerve Cord ◽  
Action Potentials ◽  
Longitudinal Muscle ◽  
Lumbricus Terrestris ◽  
Longitudinal Contraction ◽  
Peripheral Stimulation ◽  
Segmental Nerve ◽  
Slow Potentials ◽  
Slow Activity

1. Three thresholds are demonstrated in the first segmental nerve and two (sometimes three) in the second and third segmental nerves together. 2. Slow potentials recorded from the ventral nerve cord consist of several peaks. The first peak is composed of three spikes which make their appearance at different thresholds. Transmission of at least some of the slow potentials is decremental. 3. Transmission speeds in the nerve cord and segmental nerves range from 0.4 to 0.6 m./sec. 4. Action potentials in the longitudinal muscle are recorded in response to slow potentials in the nerve cord. 5. Two slow reflexes, one involving elongation, the other longitudinal contraction, are described. The latter has the lower threshold with peripheral stimulation. 6. Slow activity in the nervous system is discussed in relation to reflex activity of the earthworm and the neurone anatomy of the nerve cord and segmental nerves.

Neural Representation

2020 ◽  
pp. 258-296
Author(s):  
Gualtiero Piccinini
Keyword(s):  
Nervous System ◽  
Action Potentials ◽  
Neural Representation ◽  
Neural Representations

Neural representations are models of the organism and environment built by the nervous system. This chapter provides an account of representational role and content for both indicative and imperative representations. It also argues that, contrary to a mainstream assumption, representations are not merely theoretical posits. Instead, neural representations are observable and are routinely observed and manipulated by experimental neuroscientists in their laboratories. If a type of entity is observable or manipulable, then it exists. Therefore, neural representations are as real as neurons, action potentials, or any other experimentally established entities in our ontology.

Electrophysiological Differences Between Neurogliaform Cells From Monkey and Rat Prefrontal Cortex

2007 ◽  
Vol 97 (2) ◽  
pp. 1030-1039 ◽  
Author(s):  
N. V. Povysheva ◽  
A. V. Zaitsev ◽  
S. Kröner ◽  
O. A. Krimer ◽  
D. C. Rotaru ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Input Resistance ◽  
Firing Frequency ◽  
Morphological Features ◽  
Inhibitory Neurons ◽  
Physiological Properties ◽  
Cortical Circuit ◽  
Current Steps ◽  
Constituent Elements ◽  
Whole Cell Recordings

Current dogma holds that a canonical cortical circuit is formed by cellular elements that are basically identical across species. However, detailed and direct comparisons between species of specific elements of this circuit are limited in number. In this study, we compared the morphological and physiological properties of neurogliaform (NGF) inhibitory neurons in the prefrontal cortex (PFC) of macaque monkeys and rats. In both species, NGF cells were readily identified based on their distinctive morphological features. Indeed, monkey NGF cells had only a few morphological features that differed from rat, including a larger soma, a greater number of dendrites, and a more compact axonal field. In contrast, whole cell recordings of the responses to injected current steps revealed important differences between monkey and rat NGF cells. Monkey NGF cells consistently generated a short-latency first spike riding on an initial depolarizing hump, whereas in rat NGF cells, the first spike appeared after a substantial delay riding on a depolarizing ramp not seen in monkey NGF cells. Thus although rat NGF cells are traditionally classified as late-spiking cells, monkey NGF cells did not meet this physiological criterion. In addition, NGF cells in monkey appeared to be more excitable than those in rat because they displayed a higher input resistance, a lower spike threshold, and a higher firing frequency. Finally, NGF cells in monkey showed a more prominent spike-frequency adaptation as compared with rat. Our findings indicate that the canonical cortical circuit differs in at least some aspects of its constituent elements across species.

Intrinsic Firing Patterns and Whisker-Evoked Synaptic Responses of Neurons in the Rat Barrel Cortex

1999 ◽  
Vol 81 (3) ◽  
pp. 1171-1183 ◽  
Author(s):  
J. Julius Zhu ◽  
Barry W. Connors
Keyword(s):  
Action Potentials ◽  
Barrel Cortex ◽  
Cell Types ◽  
Field Size ◽  
Evoked Responses ◽  
Single Neurons ◽  
Firing Patterns ◽  
Complex Spike ◽  
Intrinsic Firing ◽  
Synaptic Responses

Intrinsic firing patterns and whisker-evoked synaptic responses of neurons in the rat barrel cortex. We have used whole cell recording in the anesthetized rat to study whisker-evoked synaptic and spiking responses of single neurons in the barrel cortex. On the basis of their intrinsic firing patterns, neurons could be classified as either regular-spiking (RS) cells, intrinsically burst-spiking (IB) cells, or fast-spiking (FS) cells. Some recordings responded to current injection with a complex spike pattern characteristic of apical dendrites. All cell types had high rates of spontaneous postsynaptic potentials, both excitatory (EPSPs) and inhibitory (IPSPs). Some spontaneous EPSPs reached threshold, and these typically elicited only single action potentials in RS cells, bursts of action potentials in FS cells and IB cells, and a small, fast spike or a complex spike in dendrites. Deflection of single whiskers evoked a fast initial EPSP, a prolonged IPSP, and delayed EPSPs in all cell types. The intrinsic firing pattern of cells predicted their short-latency whisker-evoked spiking patterns. All cell types responded best to one or, occasionally, two primary whiskers, but typically 6–15 surrounding whiskers also generated significant synaptic responses. The initial EPSP had a relatively fixed amplitude and latency, and its amplitude in response to first-order surrounding whiskers was ∼55% of that induced by the primary whisker. Second- and third-order surrounding whiskers evoked responses of ∼27 and 12%, respectively. The latency of the initial EPSP was shortest for the primary whiskers, longer for surrounding whiskers, and varied with the neurons’ depth below the pia. EPSP latency was shortest in the granular layer, longer in supragranular layers, and longest in infragranular layers. The receptive field size, defined as the total number of fast EPSP-inducing whiskers, was independent of each cell’s intrinsic firing type, its subpial depth, or the whisker stimulus parameters. On average, receptive fields included >10 whiskers. Our results show that single neurons integrate rapid synaptic responses from a large proportion of the mystacial vibrissae, and suggest that the whisker-evoked responses of barrel neurons are a function of both synaptic inputs and intrinsic membrane properties.

Complex Blockade of TTX-Resistant Na+ Currents by Lidocaine and Bupivacaine Reduce Firing Frequency in DRG Neurons

1998 ◽  
Vol 79 (4) ◽  
pp. 1746-1754 ◽  
Author(s):  
Andreas Scholz ◽  
Noboru Kuboyama ◽  
Gunter Hempelmann ◽  
Werner Vogel
Keyword(s):  
Spinal Anesthesia ◽  
Action Potentials ◽  
Sensory Information ◽  
Firing Frequency ◽  
Drg Neurons ◽  
Patch Clamp Technique ◽  
Single Action ◽  
Na Currents ◽  
Frequency Of Action Potentials ◽  
Frequency Of Stimulation

Scholz, Andreas, Noboru Kuboyama, Gunter Hempelmann, and Werner Vogel. Complex blockade of TTX-resistant Na+ currents by lidocaine and bupivacaine reduce firing frequency in DRG neurons. J. Neurophysiol. 79: 1746–1754, 1998. Mechanisms of blockade of tetrodotoxin-resistant (TTXr) Na+ channels by local anesthetics in comparison with the sensitivity of tetrodotoxin-sensitive (TTXs) Na+ channels were studied by means of the patch-clamp technique in neurons of dorsal root ganglions (DRG) of rat. Half-maximum inhibitory concentration (IC50) for the tonic block of TTXr Na+ currents by lidocaine was 210 μmol/l, whereas TTXs Na+ currents showed five times lower IC50 of 42 μmol/l. Bupivacaine blocked TTXr and TTXs Na+ currents more potently with IC50 of 32 and 13 μmol/l, respectively. In the inactivated state, TTXr Na+ channel block by lidocaine showed higher sensitivities (IC50 = 60 μmol/l) than in the resting state underlying tonic blockade. The time constant τ1 of recovery of TTXr Na+ channels from inactivation at −80 mV was slowed from 2 to 5 ms after addition of 10 μmol/l bupivacaine, whereas the τ2 value of ∼500 ms remained unchanged. The use-dependent block of TTXr Na+ channels led to a progressive reduction of current amplitudes with increasing frequency of stimulation, which was ≤53% block at 20 Hz in 10 μmol/l bupivacaine and 81% in 100 μmol lidocaine. The functional importance of the use-dependent block was confirmed in current-clamp experiments where 30 μmol/l of lidocaine or bupivacaine did not suppress the single action potential but clearly reduced the firing frequency of action potentials again with stronger potency of bupivacaine. Because it was found that TTXr Na+ channels predominantly occur in smaller sensory neurons, their blockade might underlie the suppression of the sensation of pain. Different sensitivities and varying proportions of TTXr and TTXs Na+ channels could explain the known differential block in spinal anesthesia. We suggest that the frequency reduction at low local anesthetic concentrations may explain the phenomenon of paresthesia where sensory information are suppressed gradually during spinal anesthesia.

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