Influence of Body Position on Cortical Pain-Related Somatosensory Processing: An ERP Study

Background: Despite the consistent information available on the physiological changes induced by head down bed rest, a condition which simulates space microgravity, our knowledge on the possible perceptual-cortical alterations is still poor. The present study investigated the effects of 2-h head-down bed rest on subjective and cortical responses elicited by electrical, pain-related somatosensory stimulation. Methodology/Principal Findings: Twenty male subjects were randomly assigned to two groups, head-down bed rest (BR) or sitting control condition. Starting from individual electrical thresholds, Somatosensory Evoked Potentials were elicited by electrical stimuli administered randomly to the left wrist and divided into four conditions: control painless condition, electrical pain threshold, 30 % above pain threshold, 30 % below pain threshold. Subjective pain ratings collected during the EEG session showed significantly reduced pain perception in BR compared to Control group. Statistical analysis on four electrode clusters and sLORETA source analysis revealed, in sitting controls, a P1 component (40–50 ms) in the right somatosensory cortex, whereas it was bilateral and differently located in BR group. Controls ’ N1 (80–90 ms) had widespread right hemisphere activation, involving also anterior cingulate, whereas BR group showed primary somatosensory cortex activation. The P2 (190–220 ms) was larger in left-central locations of Controls compared with BR group. Conclusions/Significance: Head-down bed rest was associated to an overall decrease of pain sensitivity and an altered pai

The Human Operculo-Insular Cortex Is Pain-Preferentially but Not Pain-Exclusively Activated by Trigeminal and Olfactory Stimuli

Increasing evidence about the central nervous representation of pain in the brain suggests that the operculo-insular cortex is a crucial part of the pain matrix. The pain-specificity of a brain region may be tested by administering nociceptive stimuli while controlling for unspecific activations by administering non-nociceptive stimuli. We applied this paradigm to nasal chemosensation, delivering trigeminal or olfactory stimuli, to verify the pain-specificity of the operculo-insular cortex. In detail, brain activations due to intranasal stimulation induced by non-nociceptive olfactory stimuli of hydrogen sulfide (5 ppm) or vanillin (0.8 ppm) were used to mask brain activations due to somatosensory, clearly nociceptive trigeminal stimulations with gaseous carbon dioxide (75% v/v). Functional magnetic resonance (fMRI) images were recorded from 12 healthy volunteers in a 3T head scanner during stimulus administration using an event-related design. We found that significantly more activations following nociceptive than non-nociceptive stimuli were localized bilaterally in two restricted clusters in the brain containing the primary and secondary somatosensory areas and the insular cortices consistent with the operculo-insular cortex. However, these activations completely disappeared when eliminating activations associated with the administration of olfactory stimuli, which were small but measurable. While the present experiments verify that the operculo-insular cortex plays a role in the processing of nociceptive input, they also show that it is not a pain-exclusive brain region and allow, in the experimental context, for the interpretation that the operculo-insular cortex splay a major role in the detection of and responding to salient events, whether or not these events are nociceptive or painful

Viewing the body modulates both pain sensations and pain responses

Viewing the body can influence pain perception, even when vision is non-informative about the noxious stimulus. Prior studies used either continuous pain rating scales or pain detection thresholds, which cannot distinguish whether viewing the body changes the discriminability of noxious heat intensities or merely shifts reported pain levels. In Experiment 1, participants discriminated two intensities of heat-pain stimulation. Noxious stimuli were delivered to the hand in darkness immediately after participants viewed either their own hand or a non-body object appearing in the same location. The visual condition varied randomly between trials. Discriminability of the noxious heat intensities (d?) was lower after viewing the hand than after viewing the object, indicating that viewing the hand reduced the information about stimulus intensity available within the nociceptive system. In Experiment 2, the hand and the object were presented in separate blocks of trials. Viewing the hand shifted perceived pain levels irrespective of actual stimulus intensity, biasing responses toward ‘high pain’ judgments. In Experiment 3, participants saw the noxious stimulus as it approached and touched their hand or the object. Seeing the pain-inducing event counteracted the reduction in discriminability found when viewing the hand alone. These findings show that viewing the body can affect both perceptual processing of pain and responses to pain, depending on the visual context. Many factors modulate pain; our study highlights the importance of distinguishing modulations of perceptual processing from modulations of response bias

Moving Active Functionality from Centralized to Open Distributed Heterogeneous Environments

Abstract. Active functionality is especially useful for enforcing business rules in applications, such as Enterprise Application Integration (EAI) and e-commerce. It can be used as glue among existing applications, and for data transformations between heterogeneous applications. However, traditional active mechanisms have been designed for centralized systems and are monolithic, thus making it difficult to extend and adapt them to the requirements imposed by distributed, heterogeneous environments. To correct this we present a flexible, extensible, servicebased architecture built on ontologies, services and events/notifications. The main contributions of this work are: i) the homogeneous use of ontologies for a semantically meaningful exchange and combination of events in open heterogeneous environments, and for the infrastructure itself; ii) a flexible architecture for the composition of autonomous, elementary services to provide Event-Condition-Action (ECA) functionality in different configurations; iii) the interaction of these services via notifications using a publish/subscribe mechanism (concept-based addressing).

Engineering Event-Based Systems with Scopes

Event notification services enable loose coupling and they are therefore becoming an essential part of distributed systems' design. However, the development of event services follows the early stages of programming language evolution, disregarding the need for efficient mechanisms to structure event-based applications. In this paper, the well-known notion of scopes is introduced to event-based systems. We show that limiting the visibility of events is a simple yet powerful mechanism that allows to identify application structure and offers a module construct for the loosely coupled components in event-based systems. We are able to customize the semantics of scoped event notification services by binding meta-objects to the application structure that reify important aspects of notification delivery, like interface mappings and transmission policies. The scoping concept facilitates design and implementation by offering encapsulation and adaption of syntax and semantics of eventbased systems

Effect of propofol and remifentanil on a somatosensory evoked potential indicator of pain perception intensity in volunteers

Somatosensory evoked potentials (SEPs) have been linked to noxious activation and stimulus intensity. In this exploratory study we investigated the impact of anaesthetic drugs on SEPs and pain ratings, to assess their applicability as an objective measure of the nociception/anti-nociception balance. Following institutional approval and written informed consent, 10 healthy adult volunteers were enrolled (29.5 ± 9.1 years, 63.0 ± 8.9 kg and 171.4 ± 7.2). Median nerve electrical stimulation was adjusted according to volunteers' sensitive, motor and painful thresholds (PT). Baseline SEPs were registered, and remifentanil and propofol administered using a stair scheme TCI. For each drug combination a 1.3×PT stimulus was administered, and volunteers evaluated pain intensity in a numerical rating scale (0-10). SEPs' amplitudes and latencies were normalized by the baseline values, reducing volunteers' intervariability. Stimulation currents varied between 6-52 mA (1.3×PT) and pain ratings between 0 and 9. Cortical SEPs latencies were decreased for higher stimulus intensities (P < 0.01), accompanied by increased pain ratings (P < 0.01). An individually adjusted/normalized ratio based on cortical SEPs amplitude and interpeak latency is proposed([Formula: see text]): [Formula: see text] and NSR were significantly correlated in three out of nine subjects, and [Formula: see text] and remifentanil Ce were significantly correlated in two (low number of evaluation points). [Formula: see text] was shown to decrease with increasing doses of propofol and remifentanil (P < 0.05). The proposed metric was depressed by anaesthetics and reflected pain evaluations. Further research is necessary to increase the number of volunteers and drugs' combination, to assess its applicability during surgically adequate anesthetic leves.The authors would like to thank the participation of all volunteers and clinical investigators in this study, especially Dr. Francisco Lobo, Dr. Liliana Pinto, Dr. Diana Afonso, Dr. Germano Cardoso, Dr. Helena and Dr. Luı´s Silva (Neurinbloc). The first author was supported by a scholarship from the Portuguese Foundation for Science and Technology (FCT - SFRH/BD/35879/2007). The authors would also like to acknowledge the UISPA-IDMEC Porto.info:eu-repo/semantics/publishedVersio