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Summation

About: Summation is a research topic. Over the lifetime, 954 publications have been published within this topic receiving 45593 citations. The topic is also known as: summation & sum of a sequence.


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Journal ArticleDOI
TL;DR: Intracellular recordings from rat somatic sensory vibrissa/barrel cortex demonstrate that whisker displacements evoke short latency excitatory postsynaptic potentials followed by longer lasting inhibitory potentials.

106 citations

Journal ArticleDOI
01 Jan 1983-Pain
TL;DR: The findings suggest that the non‐pain sensations evoked in tooth pulp are mediated by a distinct population of afferents that are not involved in the coding of pain.
Abstract: This study investigated the quality and magnitude of sensations evoked by electrical tooth pulp stimulation. Detection threshold (the minimum current intensity that evoked a sensation) and pain threshold were determined for tooth pulp stimuli varying in frequency from 5 to 500 Hz. The effect of frequency and intensity of tooth pulp stimulation on the magnitude of sensations was assessed using visual analog scales and verbal descriptor scales. Detection thresholds were stable over experimental sessions and independent of the frequency of the stimulating current. Pain threshold varied as a function of frequency with a minimum value at 100 Hz. Stimuli that evoked non-pain sensations at low frequencies evoked pain sensations when frequency was increased from 5 to 100 Hz. Subjects were able to scale non-pain sensations over a range of stimulus intensities and frequencies. The lowest currents evoked sensations that were nonpainful and were of constant magnitude despite changes in the frequency of stimulation. Higher stimulus currents evoked sensations that were non-painful at low stimulus frequencies and painful at high stimulus frequencies. Sensation magnitude at each stimulus intensity increased as a function of frequency. Temporal summation occurred in proportion to stimulus intensity. These findings suggest that the non-pain sensations evoked in tooth pulp are mediated by a distinct population of afferents that are not involved in the coding of pain. High frequency stimulation that increased the discharge rate of the lowest thershold pulpal afferents resulted in no summation of non-pain sensation and never produced pain. However, high frequency stimulation evocked greater magnitude sensations at higher stimulas currents, indicating that central summation mechanisms were critical for higher threshold afferents signaling more intense non-pain and pain sensations.

103 citations

Journal ArticleDOI
TL;DR: Geniculate spike trains could be predicted from retinal spike trains on the basis of postsynaptic summation, explaining the response differences between a geniculate neuron and its main retinal driver, and thereby determines the flow of visual information to cortex.
Abstract: At many synapses in the central nervous system, spikes within high-frequency trains have a better chance of driving the postsynaptic neuron than spikes occurring in isolation. We asked what mechanism accounts for this selectivity at the retinogeniculate synapse. The amplitude of synaptic potentials was remarkably constant, ruling out a major role for presynaptic mechanisms such as synaptic facilitation. Instead, geniculate spike trains could be predicted from retinal spike trains on the basis of postsynaptic summation. This simple form of integration explains the response differences between a geniculate neuron and its main retinal driver, and thereby determines the flow of visual information to cortex.

103 citations

Journal ArticleDOI
01 Sep 1962-Nature
TL;DR: In this article, successive spike potentials of a cat motoneurone resulted in a considerable summation of after-hyperpolarization and there was a corresponding increase in the membrane conductance.
Abstract: WHEN recorded intracellularly, the soma-dendritic spike potential of cat spinal motoneurones (SD spike1) is followed by a brief phase of depolarization which reverses to a prolonged hyperpolarization (duration, 60–250 msec.)1,2. Investigation of after-hyperpolarization has yielded three experimental results which conjointly led to the hypothesis that it is due to a prolonged increase in permeability to potassium ions3: there is an increased membrane conductance; when the membrane potential is changed by applying current intracellularly, the size of the after-hyperpolarization is increased by depolarization and decreased by hyperpolarization, being reduced to zero at about 20-mV. hyperpolarization; this equilibrium potential is shifted in the depolarizing direction by an electrophoretic injection of sodium ions into the motoneurone, which would of course result in a decrease of intracellular potassium ion concentration. In the present investigation on after-hyperpolarization, successive spike potentials of a cat motoneurone resulted in a considerable summation of after-hyperpolarizations and there was a corresponding increase in the membrane conductance.

103 citations

Journal ArticleDOI
TL;DR: It is shown that the total number of Ih channels, not their distribution, governs the degree of temporal summation of EPSPs, and suggested that neurons are provided with two independent degrees of freedom for different functions: the total amount and the dendritic spatial distribution.
Abstract: The hyperpolarization-activated cation current I h exhibits a steep gradient of channel density in dendrites of pyramidal neurons, which is associated with location independence of temporal summation of EPSPs at the soma. In striking contrast, here we show by using dendritic patch-clamp recordings that in cerebellar Purkinje cells, the principal neurons of the cerebellar cortex, I h exhibits a uniform dendritic density, while location independence of EPSP summation is observed. Using compartmental modeling in realistic and simplified dendritic geometries, we demonstrate that the dendritic distribution of I h only weakly affects the degree of temporal summation at the soma, while having an impact at the dendritic input location. We further analyze the effect of I h on temporal summation using cable theory and derive bounds for temporal summation for any spatial distribution of I h. We show that the total number of I h channels, not their distribution, governs the degree of temporal summation of EPSPs. Our findings explain the effect of I h on EPSP shape and temporal summation, and suggest that neurons are provided with two independent degrees of freedom for different functions: the total amount of I h (controlling the degree of temporal summation of dendritic inputs at the soma) and the dendritic spatial distribution of I h (regulating local dendritic processing).

103 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202323
202234
202118
20204
201911
201812