Showing papers on "Summation published in 1969"

Temporal Summation of Loudness: An Analysis

Abstract: A quantitative psychophysiological theory is developed for loudness level and loudness as a function of stimulus duration. It is based on the psychophysical as well as neurophysiological evidence that the apparent temporal summation of acoustic energy is a result of neural summation at a high level of the auditory system. The theory shows how this can be achieved in spite of a nonlinear relationship between sound intensity and neural excitation. The temporal decay of neural firing preceding the final stage of temporal summation seems to be responsible for overcoming the nonlinearity.

Evoked response correlates of psychophysical magnitude estimates for tactile stimulation in man.

Abstract: Cortical responses evoked by transient sensory stimulation of the index and middle fingers were recorded from the scalp over the contralateral primary somatic projection area in man. Stimulus amplitude and locus were systematically varied. The relationship between stimulus intensity and the magnitude of the evoked response is adequately described by a power function. The exponent of the psychophysical function generated under similar stimulus conditions is of approximately the same size. A mathematical model is presented to describe and predict spatial summation. A complete isomorphism between psychological and neurophysiological events is obtained.

Electrocutaneous stimulation: Psychometric functions and temporal integration

Abstract: Psychometric functions and psychophysical strength-duration curves were obtained with rectangular electro-cutaneous pulses. The slopes of the psychometric functions were much steeper than corresponding functions in other modalities, with the standard deviation of the distribution only about 0.08 times the threshold. Precise monitoring of stimulus current showed that physiological rather than physical variability was involved. Psychophysical strength-duration curves support the contention that large A-fibers are directly stimulated. Data from this study. as well as from comparable I × t experiments in other senses, are well-fit throughout the range of durations by rectangular hyperbolas. The period over which complete temporal summation occurs is only about 0.5 msec.

ON SPATIAL SUMMATION IN THE TACTUAL SENSE A psychophysical and neurophysiological study

Abstract: Franzen, O. On spatial summation in the tactual sense. A psychophysical and neurophysiological study. Scand. 1. Psychol., 1969,10, 193–208.—Individual magnitude estimation scales of apparent intensity of a 300 c/s vibration applied to the volar aspect of the finger-tip as a function of displacement and the number of fingers stimulated were obtained. Spatial summation seems to take place with a lawful increase in perceived intensity as two and three adjacent sensory channels are excited at the same time. Median nerve compound action potentials following electrical stimulation of the index and middle fingers were recorded. A mathematical model is presented to describe and predict spatial summation. The results are interpreted in terms of funneling action of nervous tissue.

Unit activity in inferior colliculus to amplitude-modulated acoustic stimuli

Abstract: 1. Neurons of the inferior colliculus are subdivided into groups on the basis of the type and temporal characteristics of their response to prolonged acoustic stimuli (noise, optimal frequency). Neurons with a prolonged discharge and marked temporal summation (over 10 db), on the one hand, and neurons with an on-discharge to acoustic stimulation and low temporal summation (0–5 db) on the other hand, belong to the extreme groups. An intermediate position is occupied by neurons with prolonged and grouped discharges and temporal summation of 5–10 db and by neurons with a phasic discharge and temporal summation within the same limits. Neurons of the inferior colliculus cover a wide range of response types: from neurons with minimal adaptation and marked temporal summation (up to 45 db) to neurons with an on-discharge of one spike to acoustic stimulation and with absence of temporal summation. 2. Neurons with prolonged and grouped discharge respond to slow modulation frequencies by synchronized spike activity reproducing the rhythm of the modulating wave. They reproduce the modulation frequency up to a certain limit, above which disturbance of reproduction of the rhythm, followed by suppression of spike generation, are observed. 3. Many neurons with on-discharge and low temporal summation (0–5 db) did not respond to the modulation frequencies used in the investigation,. A few neurons with low summation respond selectively within a certain range of high modulation frequencies either by reproduction of the modulation rhythm or by an increase in the general level of spike activity. Neurons of this group with temporal summation higher than 5 db respond to a modulated stimulus with repeated spike generation, starting at a definite modulation frequency not below 5 Hz. Rhythmic activity corresponding to the modulation frequency persists up to a certain limit, beyond which only the initial response arises.