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.

Effects of manipulating the interstimulus interval on heat-evoked temporal summation of second pain across the age span.

Abstract: This study examined the effects of interstimulus interval (ISI) on heat-evoked temporal summation of second pain (TSSP) and tested whether greatest maintenance of TSSP would occur at longer ISIs in older adults Several lines of evidence support that TSSP is associated with central sensitization and is centrally mediated The participants were 198 community-dwelling adults divided into 3 age cohorts (18-39, 40-59, and 60-78 years of age) Six TSSP trials used a train of 10 contacts with a preheated probe that made repetitive contact with the volar forearm Participants completed 2 trials at each ISI of 25, 35, and 45 seconds The intraclass correlations for each pair of trials support the reliability of the current methodology Temporal summation of second pain scores declined in a time-dependent manner across ISI In addition, greater maintenance of TSSP at longer ISIs was observed in middle-aged and older age groups compared with the younger cohort Significant associations were found between TSSP and measures of recent pain Greater summation at longer ISIs in older adults would suggest slower decay of excitability in spinal neurons and infer increased risk for central sensitization with advancing age

Dynamic Functional Brain Connectivity Underlying Temporal Summation of Pain in Fibromyalgia

Abstract: Abnormal central pain processing is a leading cause of pain in fibromyalgia (FM) and is perceptually characterized with the psychophysical measure of temporal summation of pain (TSP). TSP is the perception of increasingly greater pain in response to repetitive or tonic noxious stimuli. Previous neuroimaging studies have used static (i.e., summary) measures to examine the functional magnetic resonance imaging (fMRI) correlates of TSP in FM. However, functional brain activity rapidly and dynamically reorganizes over time, and, similarly, TSP is a temporally evolving process. This study was undertaken to demonstrate how a complete understanding of the neural circuitry supporting TSP in FM thus requires a dynamic measure that evolves over time.We utilized novel methods for analyzing dynamic functional brain connectivity in patients with FM in order to examine how TSP-associated fluctuations are linked to the dynamic functional reconfiguration of the brain. In 84 FM patients and age- and sex-matched healthy controls, we collected high-temporal-resolution fMRI data during a resting state and during a state in which sustained cuff pressure pain was applied to the leg.FM patients experienced greater TSP than healthy controls (mean ± SD TSP score 17.93 ± 19.24 in FM patients versus 9.47 ± 14.06 in healthy controls; P = 0.028), but TSP scores varied substantially between patients. In the brain, the presence versus absence of TSP in patients with FM was marked by more sustained enmeshment between sensorimotor and salience networks during the pain period. Furthermore, dynamic enmeshment was noted solely in FM patients with high TSP, as interactions with all other brain networks were dampened during the pain period.This study elucidates the dynamic brain processes underlying facilitated central pain processing in FM. Our findings will enable future investigation of dynamic symptoms in FM.

Differential channeling of sensory stimuli onto a motor neuron in the leech.

Abstract: We studied a specific sensory-motor pathway in the isolated leech ganglia. Pressure-sensitive mechanosensory neurons were stimulated with trains of action potentials at 5–20 Hz while recording the responses of the annulus erector motorneurons that control annuli erection. The response of the annulus erector neurons was a succession of excitatory postsynaptic potentials followed by inhibitory postsynaptic potentials. The excitatory postsynaptic potentials had a brief time-course while the inhibitory postsynaptic potentials had a prolonged time-course that enabled their temporal summation. Thus, the net effect of pressure-sensitive neuron stimulation on the annulus erector neurons was inhibitory. Both phases of the response were mediated by chemical transmission; the excitatory postsynaptic potentials were transmitted via a monosynaptic pathway, and the inhibitory postsynaptic potentials via a polysynaptic one. The pattern of expression of this dual response depended on the field of innervation of the sensory neuron and it was under the influence of cell 151, a non-spiking interneuron, that could regulate the expression of the hyperpolarization. The interaction between pressure-sensitive neurons and annulus erector neuron reveals how sensory specificity, connectivity pattern and regulatory elements interplay in a specific sensory-motor network.