Cortical processing of pain: the role of habituation

Pain is a subjective, multidimensional experience that depends on many factors, including pain stimulus intensity, expectations and mood. Compared to questionnaires, pain event-related potentials (pain ERP) allow pain to be evaluated more objectively. Pain ERP means that people receive pain stimuli, for instance electrical stimuli applied to the finger, with simultaneous registration of electrical brain activity. Habituation is an important phenomena following repeated exposure to pain stimuli, describing the progressive decrease of brain signal amplitude. Habituation occurs less in people with chronic pain and is considered a potential key mechanism in the development of chronic pain. Pain hypervigilance, i.e. heightened vigilance for pain sensations, has an impact on pain experience as well. This dissertation examines the relationship between habituation, hypervigilance and chronic pain. We used a new analysis method called the Event-Related Fixed-Interval Area (ERFIA) multilevel method, which not only evaluates ERP peaks, but also examines the pain ERP in closer detail. We showed that stimulus intensity, habituation and hypervigilance had an impact on large sections of the ERP. People with chronic pain showed reduced habituation independent of hypervigilance. Both chronic pain and hypervigilance were independently associated with reduced habituation of the pain ERP. These findings are relevant to the development of future treatment strategies

Time Effect on Acute Postoperative Pain After Total Knee Replacement Surgery:An Exploratory Study Using the Experience Sampling Method

OBJECTIVES: Acute postoperative pain (APP) is the main cause of postoperative dissatisfaction; however, traditional methods of pain assessment provide limited insights into the dynamics and development of APP. This study used the experience sampling method (ESM) to understand the dynamics of APP over time in relation to various patient factors. METHODS: Forty patients scheduled to undergo total knee replacement surgery were recruited in this study. Following an initial assessment, a short report questionnaire was sent to the patients via 10 digital alerts per day to assess the pain levels during two preoperative and the first 6 postoperative days. The data were analyzed using multilevel regression including random intercept and slope. RESULTS: Thirty-two patients submitted the pre-specified minimum of 30% of their short reports, yielding 1217 records. The analysis revealed significant (P<0.001) linear and quadratic decreases in APP and a quadratic time effect. The lowest between-days and within-day pain levels were observed on postoperative day 4.8 and during the time slot 3.8 or approximately 19:15, respectively. Significant random intercepts and slopes were noted, indicating variations in the mean pain level between patients and a decrease in pain. None of the 10 patient factors had any confounding effect. DISCUSSION: Using ESM data combined with multilevel analysis, we were able to evaluate the postoperative pain course while considering inter-individual differences in the baseline pain level and non-linear pain course over time. The findings of this study could aid clinicians in personalizing the treatment for APP

A mosaic monoploid reference sequence for the highly complex genome of sugarcane.

Sugarcane (Saccharum spp.) is a major crop for sugar and bioenergy production. Its highly polyploid, aneuploid, heterozygous, and interspecific genome poses major challenges for producing a reference sequence. We exploited colinearity with sorghum to produce a BAC-based monoploid genome sequence of sugarcane. A minimum tiling path of 4660 sugarcane BAC that best covers the gene-rich part of the sorghum genome was selected based on whole-genome profiling, sequenced, and assembled in a 382-Mb single tiling path of a high-quality sequence. A total of 25,316 protein-coding gene models are predicted, 17% of which display no colinearity with their sorghum orthologs. We show that the two species, S. officinarum and S. spontaneum, involved in modern cultivars differ by their transposable elements and by a few large chromosomal rearrangements, explaining their distinct genome size and distinct basic chromosome numbers while also suggesting that polyploidization arose in both lineages after their divergence