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 to thermal stimuli is elevated in women with overactive bladder syndrome.

Abstract: Introduction This study sought to provide a preliminary assessment of whether spinally mediated afferent hyperactivity (i.e., central sensitization) might contribute to manifestations of overactive bladder syndrome (OAB) in women as indexed by elevated temporal summation of evoked heat pain stimuli. Methods We recruited 20 adult women with OAB who were planning to undergo interventional therapy for OAB with either onabotulinumtoxinA injection or sacral neuromodulation and 23 healthy controls without OAB symptoms to undergo quantitative sensory testing with cutaneous thermal pain temporal summation. The primary study outcome was the degree of temporal summation, as reflected in the magnitude of positive slope of the line fitted to the series of 10 stimuli at the 49°C target temperatures. Linear regression and analysis of covariance were utilized to compare the degree of temporal summation between study groups. Results The standardized slope of temporal summation trials for women with OAB was significantly higher than for controls (β = 3.43, 95% confidence interval = 0.6–6.2, P = 0.017). The adjusted means ±SE of the standardized temporal summation slopes for the full OAB and control groups were 3.0 ± 0.5 (95% confidence interval = 2.0, 4.1) and 1.7 ± 0.5 (95% confidence interval = 0.7, 2.7), respectively. Conclusion In this preliminary study, we demonstrated that women with OAB refractory to primary and secondary therapies exhibited greater thermal cutaneous temporal summation than women without OAB symptoms. This suggests that central sensitization, indexed by temporal summation, may be an underlying factor contributing to OAB in some women. Neurourol. Urodynam. © 2016 Wiley Periodicals, Inc.

Repetitive painful stimulation produces an expansion of withdrawal reflex receptive fields in humans.

Abstract: The aims of the present study were to investigate whether temporal summation of the nociceptive withdrawal reflex depends on the stimulation site on the sole of the human foot, and to characterize the reflex receptive fields (RRF) of lower limb muscles to repetitive stimulation. The cutaneous RRFs were assessed in 15 subjects in sitting position by recording the EMG from five lower leg muscles and the kinematic responses (ankle, knee, and hip joints) to repetitive painful electrical stimulation. The stimulus consisted of a series of five stimuli (frequency: 3 Hz) delivered randomly at 10 different sites on the sole of the foot. The size of the reflexes increased generally between the first and the second stimulus, however, the increment depended on the stimulation site. In tibialis anterior, the RRF covered the distal sole of the foot and gradually expanded during the stimulus train. No expansion toward the heel area was detected. In soleus, the reflexes were facilitated after the second stimulus at all sites and remained in this state until the last stimulus. In vastus lateralis, biceps femoris, and iliopsoas a gradual expansion of the RRF was seen, resulting in RRFs covering the lateral, distal foot, and part of the proximal foot (iliopsoas). Knee and hip flexion were evoked at all sites. Ankle dorsiflexion was evoked at the distal foot, while ankle plantarflexion was evoked at the heel. The enlargement of the RRF reflects spinal temporal summation leading to gradually stronger reflex responses. The degree of temporal summation was dependent on stimulation site. The facilitation of the withdrawal reflex responses due to repetitive stimulation might have potential applications in the rehabilitation engineering field, where these reflexes could be used to assist gait of patients with central nervous system injuries.

Experimental knee pain evoke spreading hyperalgesia and facilitated temporal summation of pain.

Abstract: Objectives This study evaluated the deep-tissue pressure pain sensitivity and temporal summation of pain within and around healthy knees exposed to experimental pain. Design The study was designed as a randomized crossover trial, with each subject tested on 1 day. Setting All tests were carried out at the Laboratory for Musculoskeletal Pain and Motor Control, Center for Sensory-Motor Interaction, Department of Health Science and Technology at Aalborg University, Denmark. Subjects Seventeen healthy subjects (10 males) participated in this study. Interventions Experimental pain model. Pain was induced in the infrapatellar fat pad by injection of hypertonic saline and the contralateral infrapatellar fat pad was injected with isotonic saline as control. Outcome Measures Pressure pain thresholds, temporal summation of pressure pain, and cutaneous mechanosensitivity were assessed on three occasions: baseline, immediately after the injection, and when pain had vanished. Assessments sites were located in the peripatellar region, vastus lateralis, and tibialis anterior muscles. Results The experimental knee pain model demonstrated 1) hyperalgesia to pressure stimulation on the infrapatellar fat pad during experimental pain, and 2) facilitated temporal summation of pressure pain at the infrapatellar fat pad and knee-related muscles. Conclusion The increased sensitivity and temporal summation found in this study were exclusive to deep -tissue with no contralateral decreased pain sensitivity. The study showed that acute knee joint pain leads to hyperalgesia and facilitated temporal summation in the infrapatellar fat pad and in muscles located distant to the injection site, in subjects with no history of knee pain.

Estimating the critical duration for temporal summation of standard achromatic perimetric stimuli

Abstract: Purpose: To estimate the critical duration of temporal summation for achromatic Goldmann III stimuli under the conditions of standard automated perimetry (SAP) and quantify response variability for short duration stimuli. Methods: Contrast thresholds were gathered using the method of constant stimuli for seven circular (0.48° diameter) incremental stimuli of varying duration (sum-of-frames equivalent: 8.3-198.3 msec), at an eccentricity of 8.8° along the four principal meridians of the visual field in two healthy, psychophysically experienced observers. Stimuli were presented on a high-resolution CRT display with a background luminance of 10 cd/m2. Psychometric functions were fitted using a probit model and non-parametric local linear analysis. The critical duration was estimated using iterative two-phase regression analysis, the results also being compared with values produced using previously published methods of analysis. Results: The median critical duration estimated using iterative two-phase regression analysis was 27.7 msec (IQR 22.5-29.8). A slight steepening of the psychometric function slope (lower variability) was observed for longer stimulus durations, using both probit and local-linear analysis techniques, but this was not statistically significant. Conclusions: Critical duration estimates in this study are substantially shorter than those previously reported for a Goldmann III stimulus under the conditions of SAP. Further work is required to firmly establish the relationship between measurement variability and the degree of local temporal and spatial summation.