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.

The Function of Intensity in the Spatial Summation of Subliminal Stimuli in the Retina

Abstract: (1935). The Function of Intensity in the Spatial Summation of Subliminal Stimuli in the Retina. The Journal of General Psychology: Vol. 12, No. 1, pp. 95-107.

Spatial summation in the warmth sense

Abstract: The warmth sense is characterized by generous spatial summation: perceived strength of warmth sensation increases with increasing areal extent of stimulation as well as with increasing stimulus intensity. When intensity is low, area exerts its greatest effect, in that warmth depends on the product of stimulus area and intensity - i.e., on total power in watts. Response to integrated heat input at low intensity enables the warmth sense to help maintain constant body temperature. As stimulus intensity increases, area’s relative influence on warmth diminishes until the pain threshold is reached, whereupon spatial summation vanishes. Lack of summation at high intensity enables the warmth sense to help protect the skin from potentially damaging heat. The level-dependence of spatial summation is reflected in the way stimulus size influences the psychophysical power functions that relate warmth sensation to stimulus intensity: the larger the areal extent of the stimulus, the smaller the exponent of the power function.

The nonlinear increase of pain in distance-based and area-based spatial summation

Abstract: When nociceptive stimulation affects a larger body area, pain increases. This effect is called spatial summation of pain (SSp). The aim of this study was to describe SSp as a function of the size or distance of a stimulated area(s) and to test how this function is shaped by the intensity and SSp test paradigm. Thirty-one healthy volunteers participated in a within-subject experiment. Participants were exposed to area-based and distanced-based SSp. For area-based SSp, electrocutaneous noxious stimuli were applied by up to 5 electrodes (5 areas) forming a line-like pattern; for distance-based SSp, the same position and lengths of stimuli were used but only 2 electrodes were stimulated. Each paradigm was repeated using pain of low, moderate, and high intensity. It was found that the pattern of pain intensity followed a logarithmic (power) rather than a linear function. The dynamics of the pain increase were significantly different across pain intensities, with more summation occurring when pain was perceived as low. Results indicated that area-based SSp is more painful than distance-based SSp when low and moderate but not when high pain intensity is induced. Presented findings have important implications for all studies in which the spatial dimension of pain is measured. When the area or separation between nociceptive stimulation increases, pain does not increase linearly and the pattern of the pain increase is a result of the interaction between intensity and the number of nociceptive sites. A power function should be considered when predicting the size of a nociceptive source.

On a first passage problem in stochastic storage systems with total release

Abstract: In a previous paper (Ten Hoopen and Reuver, 1965) the selective interaction of two independent sequences of stimuli in time, called excitatory and inhibitory, was considered. An inhibitory stimulus annihilated the next excitatory stimulus. The interval distribution of the distorted excitatory sequence was derived. This concept has been used (Ten Hoopen, 1966a) to characterize unusual spike interval distributions of nerve cells, when it is assumed that every undeleted excitatory stimulus provokes a response. In this case the assumption is open to doubt as it ignores an elementary property of nerve cells, viz., the temporal and spatial summation of excitation. It is generally accepted that a certain minimum amount of excitation is necessary to cause a response. In this note a generalization called the deletion model is proposed, which removes the above drawback. Suppose excitatory stimuli arrive according to a recurrent process and accumulate at the nerve cell. As soon as n of these have arrived a response occurs and the process starts again. Inhibitory stimuli arrive according to a recurrent process also, independently of the other sequence. If in the course of summation of the excitatory stimuli an inhibitory stimulus arrives, all accumulated excitation is wiped out, and summation starts anew. The probability density function of the responses, denoted by p(t), is derived in Section 2. If incoming excitatory stimuli arrive more or less regularly, p(t) has a multi-modal character. This type of interval distribution has frequently been observed in analyzing neurophysiological data. 409