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.

Temporal summation of muscle pain evoked by very fast pressure sequences and rotation

Abstract: Background: Pressure evoked temporal summation of pain has been described with slow repetitions ( 1 Hz). This study examined temporal summation of pain by repeated computer-controlled pressure stimulation at high repetition rates with and without simultaneous active probe rotations for potential better efficiency.Methods: In 15 healthy subjects, 15 pressure stimuli (300 and 500 ms durations) were delivered at the pressure pain threshold intensity with and without rotation of a rounded probe (1 cm2) at three repetition frequencies (1.5, 1, 0.5 Hz). The pressure pain intensity was continuously rated on a visual analogue scale (VAS) and scores after each stimulus were extracted and normalized to the first score.Results: The peak VAS score was larger for rotational (p < 0.001), longer stimulus duration (p < 0.02), and lower frequencies (p < 0.05) compared with non-rotational, shorter stimulus duration, and highe...

Systematic changes in temporal summation across human visual cortex

Abstract: The visual system analyzes image properties across multiple spatial and temporal scales. Population receptive field ("pRF") models have successfully characterized spatial representations across the human visual pathways. Here, we studied temporal representations, measuring fMRI and electrocorticographic ("ECoG") responses in posterior, lateral, ventral, and dorsal visual areas to briefly viewed contrast patterns. We built a temporal pRF model employing linear summation and time-varying divisive normalization. Our model accurately predicts the fMRI amplitude and ECoG broadband time-course, accounting for two phenomena - accumulation of stimulus information over time (summation), and response reduction with prolonged or repeated exposure (adaptation). We find systematic differences in these properties: summation periods are increasingly long and adaptation more pronounced in higher compared to earlier visual areas. We propose that several features of temporal responses - adaptation, summation, and the timescale of temporal dynamics - can be understood as resulting from a small number of canonical neuronal computations.

Temporal summation in hearing-impaired listeners.

Abstract: A study was conducted to explore variations in auditory temporal summation in listeners with normal hearing, and impairment due to otosclerosis, sensori-neural hearing loss and acoustic neuroma. Using a two-interval forced-choice procedure the detection threshold was measured for one-third octave noise bands centered at either 1000 or 4000 Hz, in combination with eight signal durations (2.5, 5, 10, 20, 40, 80, 160, and 640 ms). The results indicated that for normal listeners: (1) the slope of the function relating the detection threshold and the signal duration varied inversely with the frequency tested, and (2) the variability in the detection threshold was greater for 4000 Hz than for 1000 Hz. A comparison of performance across groups showed that the magnitude of the slope of the temporal integration function decreased as the site of lesion moved from middle ear to eighth nerve. For listeners with normal hearing and those with otosclerosis, temporal integration appeared to be incomplete at 640 ms.