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Showing papers on "Summation published in 1980"


Journal ArticleDOI
TL;DR: Percutaneous recordings from single nociceptive Aδ- and C-fibres from the superficial radial nerves of conscious human subjects indicated that under the conditions of the authors' experiments summation of input from nocICEptors is needed in order to induce pain sensations.

62 citations


Journal ArticleDOI
TL;DR: Intracellular injections of horseradish peroxidase suggest that these recordings were obtained primarily, but not exclusively, from magnocellular neuroendocrine cells, consistent with previous anatomical studies on the location of magno cell elements in p.v.n.
Abstract: 1. The electrical activity of thirty-five neurones in the lateral area of the paraventricular nucleus (p.v.n.) was recorded intracellularly in vitro from slices of rat hypothalamus. 2. Spontaneously occurring action potentials were observed in twenty-four of the neurones. The temporal pattern of action potentials was generally slow and irregular; occasionally some cells fired bursts of action potentials. 3. Depolarizations with a fast rising phase and slow decay occurred spontaneously in most cells. These depolarizations exhibited a wide range of amplitudes in each cell (up to 33 mV), showed temporal summation, and could serve as pre-potentials for spontaneously occurring action potentials. Presumably, these depolarizations were excitatory post-synaptic potentials (e.p.s.p.s.). 4. Depolarizing current injection could evoke action potentials. Extracellular stimuli dorsolateral to the fornix column occasionally elicited action potentials which had a short and invariant latency and which could respond to stimulation rates of 100 Hz. In some cases, extracellular stimuli in the same area evoked depolarizations which had long and variable latency and were similar to those occurring spontaneously. These two types of responses probably represent antidromic and orthodromic activation respectively. 5. Intracellular injections of horseradish peroxidase suggest that these recordings were obtained primarily, but not exclusively, from magnocellular neuroendocrine cells. This is consistent with previous anatomical studies on the location of magnocellular elements in p.v.n.

62 citations


Journal ArticleDOI
TL;DR: Sinusoidal temporal modulation of the contrast of sinusoidal gratings has been used to provide one description of the temporal properties of neurones in area 17 of the cat's visual cortex.
Abstract: Sinusoidal temporal modulation of the contrast of sinusoidal gratings has been used to provide one description of the temporal properties of neurones in area 17 of the cat's visual cortex. Concurrently, the waveforms of the neurones' responses to 2 s flashes of identical gratings were examined. In most neurones, the response to the long flash was much more transient than would be expected from the shape of the temporal-frequency tuning curve. Temporal summation in cortical neurones is non-linear.

55 citations


Journal ArticleDOI
09 May 1980-Science
TL;DR: Analysis of membrane conductance fluctuations induced by iontophoresis of glycine and gamma-aminobutyric acid indicates that the relaxation kinetics of activated inhibitory channels are rate-limiting during decay of the inhibitory postsynaptic current.
Abstract: In the goldfish Mauthner cell, inhibitory postsynaptic currents evoked by intracellular stimulation of presynaptic neurons decay exponentially, with a mean time constant of 6.65 milliseconds. Analysis of membrane conductance fluctuations induced by iontophoresis of glycine and gamma-aminobutyric acid indicates a mean inhibitory channel lifetime of 7.15 milliseconds. The results thus suggest that the relaxation kinetics of activated inhibitory channels are rate-limiting during decay of the inhibitory postsynaptic current.

45 citations



Journal ArticleDOI
TL;DR: Bath application of L-glutamate at concentrations higher than 1 × 10 4M suppressed excitatory postsynaptic potentials and evoked both a depolarisation and a reduction in the input resistance of the muscle fibre, compatible with the hypothesis that L- glutamate is an exciteatory transmitter at the neuromuscular junction.

25 citations


Journal ArticleDOI
TL;DR: It is clear that the spatial summation process involved in texture discrimination has a time course consistent with counting models for decision making and the receptive field structures of salient texture features, in particular-orientation, seem to involve simple excitatory center and inhibitory surround mechanisms.
Abstract: In this paper we consider some spatial and temporal properties of visual textures which either inhibit or enhance their discrimination. From exposure time and texture mixing studies two findings emerge. First, it is clear that the spatial summation process involved in texture discrimination has a time course consistent with counting models for decision making. Secondly, the receptive field structures of salient texture features, in particular-orientation, seem to involve simple excitatory center and inhibitory surround mechanisms.

17 citations


Journal ArticleDOI
TL;DR: It is suggested that the inhibitory action is transmitted to the DSCT-cell through a number of synapses distributed over the dendrites, which causes a constant reduction in firing frequency independent of the excitatory drive of the cell.
Abstract: Dorsal spinocerebellar tract (DSCT) neurones adequately activated by primary afferents from the muscle spindles in one muscle in the hindleg of the cat, is regularly inhibited by primary afferents from other muscles. The inhibitory input causes a constant reduction in firing frequency independent of the excitatory drive of the cell. In a simple model the effects of presynaptic inhibition and of postsynaptic inhibition with different time course of the inhibitory action, have been explored. Within the scope of this model, only postsynaptic inhibition with a very long time-constant could explain the experimental results. It is suggested that the inhibitory action is transmitted to the DSCT-cell through a number of synapses distributed over the dendrites.

7 citations



Journal ArticleDOI
TL;DR: Temporal processing in the B or the D sub-system described by Jung was compared by analysing output variables in response to a range of electrophysiological and perceptual responses run in parallel: the temporal summation law is found to be obeyed in both B and D subsystems.

1 citations



Book ChapterDOI
01 Jan 1980
TL;DR: This chapter describes the neuronal integration mechanism in the body; the basic mechanisms used in integrating synaptic potentials are generally the same in all neurons, but the details depend on the exact neuronal type.
Abstract: This chapter describes the neuronal integration mechanism in the body The basic mechanisms used in integrating synaptic potentials are generally the same in all neurons, but the details depend on the exact neuronal type Projection neurons, such as motor neurons, are polarized; they receive inputs on their dendrites and soma and transmit action potentials via axons Integration in dendrites is either passive (electrotonic) or active—involving patches of membrane capable of firing action potentials Local circuit neurons, which are nonpolarized and do not have axons, have another means of integration These cells receive inputs on dendrites and the soma, but the fibers and synapses that bring in these inputs to the target cell are also the ones that take the latter's output away Therefore, as the presynaptic elements of these two-way junctions are located very close to the outgoing postsynaptic activity, the graded electrotonic and summation decay of the postsynaptic potentials is sufficient to modulate the output of these axonless cells

ReportDOI
27 Oct 1980
TL;DR: In this article, spatial summation functions were determined for three deuteranopes and three age-matched normal trichromats under stimulus conditions which favored stimulation of the long-wavelength receptor system.
Abstract: : Spatial summation functions were determined for three deuteranopes and three age-matched normal trichromats under stimulus conditions which favored stimulation of the long-wavelength receptor system. No differences were found in the data of two groups suggesting that some modification of existing threshold models is necessary.