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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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TL;DR: In cells with strong PICs, nonlinear summation of excitation and inhibition does occur, but this nonlinearity results in a more consistent relationship between membrane potential and the summed excitatory and inhibitory current.
Abstract: We investigated summation of steady excitatory and inhibitory inputs in spinal motoneurons using an in vivo preparation, the decerebrate cat, in which neuromodulatory input from the brain stem facilitated a strong persistent inward current (PIC) in dendritic regions. This dendritic PIC amplified both excitatory and inhibitory synaptic currents two- to threefold, but within different voltage ranges. Amplification of excitatory synaptic current peaked at voltage-clamp holding potentials near spike threshold (about -55 to -50 mV), whereas amplification of inhibitory current peaked at significantly more depolarized levels (about -45 to -40 mV). Thus the linear sum of excitatory and inhibitory currents tended to vary from net excitatory to net inhibitory as holding potential was depolarized. The actual summed currents, however, diverged from the predicted linear currents. At the peak of excitation, summation averaged about 15% sublinear (actual sum was less positive than the linear sum). In contrast, at the peak of inhibition, summation averaged about 18% supralinear (actual more positive than linear). Moreover, these nonlinear effects were substantially larger in cells where the variation from peak excitation to peak inhibition for linear summation was larger. When descending neuromodulatory input was eliminated by acute spinalization, PIC amplification was not observed and summation tended to be either sublinear or approximately linear, depending on input source. Overall, in cells with strong PICs, nonlinear summation of excitation and inhibition does occur, but this nonlinearity results in a more consistent relationship between membrane potential and the summed excitatory and inhibitory current.

34 citations

Journal ArticleDOI
TL;DR: The results show that when halving the stimulus duration the sound pressure must be increased 3 dB to maintain the threshold, thus keeping the acoustic energy constant, and a clear frequency dependence in temporal integration is demonstrated.
Abstract: The relation between stimulus duration and stimulus intensity in perception of acoustic energy generally referred to as the temporal integration, i.e. temporal summation is investigated. In previous studies a wide variety of methods has been used, and accordingly, different results have been obtained. To establish a normal material for later comparison of temporal integration in hearing impaired ears 30 normal persons were investigated. Temporal integration was measured as monoaural threshold determinations for the frequencies 500, 1 kHz, 2 kHz, 4 kHz, and 8 kHz using stimulus durations varying from 1 to 1 000 msec. The results show that when halving the stimulus duration the sound pressure must be increased 3 dB to maintain the threshold, thus keeping the acoustic energy constant. A clear frequency dependence in temporal integration is demonstrated. We hope that the method of calculating temporal integration in this trial will facilitate the comparison of results of different investigators and thereby ex...

34 citations

Journal ArticleDOI
TL;DR: It is demonstrated that sex differences in spatial summation of heat pain are unlikely and result mainly in a shift of the pain threshold on the ordinate and not a change of slope of the stimulus-response function in the pain range.
Abstract: Sex differences in pain sensitivity have been found to vary between considerable and negligible. It has appeared that the pain stimulation method is critical in this context. It was assumed this might be due to the different degrees of spatial summation associated with the different pain stimulus modalities. Hence, sex differences were investigated in spatial summation of heat pain in 20 healthy women and 20 healthy men of similar age. Pain thresholds were assessed by a tracking procedure and responses to supra-threshold pain stimulation by numerical ratings. Heat stimuli were administered by a thermode with contact areas of 1, 3, 6 and 10 cm2. Pain thresholds were significantly higher with smaller areas stimulated than with larger ones. No significant effect of area was found for the ratings of the supra-threshold stimuli, the intensities of which were tailored to the individual pain threshold. Consequently, spatial summation of heat pain appeared to result mainly in a shift of the pain threshold on the ordinate and not a change of slope of the stimulus-response function in the pain range. In neither of the two pain parameters were there any sex differences. Therefore, the present study demonstrated that sex differences in spatial summation of heat pain are unlikely.

34 citations

Journal ArticleDOI
TL;DR: It is concluded that the caudal medulla constitutes a key region for the expression of negative feed-back mechanisms triggered by both spatial summation of noxious inputs and heterotopicNoxious inputs.
Abstract: Gall, Olivier, Didier Bouhassira, Djamel Chitour, and Daniel Le Bars. Involvement of the caudal medulla in negative feedback mechanisms triggered by spatial summation of nociceptive inputs. J. Neur...

34 citations

Journal ArticleDOI
TL;DR: Analysis of the time constants and Bode plots obtained from current injection leads to the development of an equivalent model circuit describing the functional relationships of the individual neuronal elements, which will act as a framework on which active properties such as burst form, timing, and termination can be tested.
Abstract: This paper deals with a quantitative analysis of a network of electrically coupled neurons (cyberchrons) in the snail Helisoma trivolvis. This network produces regular bursts of activity which drive the motoneurons controlling the feeding musculature. Analysis of the time constants and Bode plots obtained from current injection leads to the development of an equivalent model circuit describing the functional relationships of the individual neuronal elements. The equivalent model is used to demonstrate compensation of the frequency response of an individual neuron by the effective loading of the rest of the network. However, the current observed in a postsynaptic neuron is intergrated across the long cell time constant resulting in increased temporal and spatial summation. This frequency compensation and long duration of the postsynaptic response are both believed to be instrumental in the maintenance of a high frequency burst. This model will act as a framework on which active properties such as burst form, timing, and termination can be tested.

34 citations


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