Kunst som drivkraft for byutvikling : En studie av beslutningsprosessen om etablering av Kunstsilo i Kristiansand

Master's thesis in Political science and management (ME502

Entropy of random coverings and 4D quantum gravity

We discuss the counting of minimal geodesic ball coverings of $n$-dimensional riemannian manifolds of bounded geometry, fixed Euler characteristic and Reidemeister torsion in a given representation of the fundamental group. This counting bears relevance to the analysis of the continuum limit of discrete models of quantum gravity. We establish the conditions under which the number of coverings grows exponentially with the volume, thus allowing for the search of a continuum limit of the corresponding discretized models. The resulting entropy estimates depend on representations of the fundamental group of the manifold through the corresponding Reidemeister torsion. We discuss the sum over inequivalent representations both in the two-dimensional and in the four-dimensional case. Explicit entropy functions as well as significant bounds on the associated critical exponents are obtained in both cases.Comment: 54 pages, latex, no figure

Timing is everything: Exploring the psychophysiology of affective touch through subjective reports, physiological responses and behaviour

Stroking someone’s skin activates a group of slow-conducting, unmyelinated low-threshold mechanoreceptors considered integral in affective behaviour involving touch. These afferent fibres are referred to as C-tactile (CT) fibres and they respond vigorously to slow stroking of the skin at velocities between 1-10 cm/s and the firing of these fibres correlates with the perceived pleasantness of the touch. Moreover, field studies have shown that people become more prosocial and friendly after being touched, however, laboratory studies investigating potential mechanisms are lacking. This thesis attempted to investigate the psychophysiology of affective touch using a combination of subjective reports and physiological and behavioural responses. In study 1, forty-five participants received touch targeting CT fibres, control touch and a visual control condition and rated the perceived pleasantness and intensity of the stimulation. Skin conductance level was recorded and facial electromyography (EMG) was recorded from two facial muscles related to negative and positive affect. Additionally, we investigated if the participants’ level of prosocial behaviour changed following tactile stimulations using two economic games. In study 2, forty-eight participants received slow stroking touch to the arm at two separate sessions whilst we collected facial EMG and heart rate variability. Our findings corroborate previous studies that report the pleasantness of CT targeted touch as a hallmark finding. However, although we were able to document consistent and coherent responses to affective touch, touch targeting CT fibres did not change the level of prosocial behaviour when measured in a laboratory setting. A novel finding is that we demonstrated that the activation of the corrugator muscle decreased during CT targeted touch and increased during control touch. We propose that this activation is timed to the arrival of CT afferent input, which can be measured precisely using facial EMG

Shift work and pain : a quantitative EEG investigation into the effects of shift work and nocebo on pain perception

Introduction: Shift work is associated with increased prevalence of pain and shift workers commonly report reduced sleep, which is related to increased pain sensitivity. Thus, night shift work (NSW) may potentially lead to increased pain sensitivity. This study investigates electroencephalogram (EEG) recordings in response to nociceptive electrical stimuli following NSW and habitual sleep (HS) with and without negative expectation (nocebo). Methods: 53 nurses participated in the study. They received nociceptive electrical stimuli following NSW and HS that were either correctly signalled or signalled as higher than the actual intensity delivered (in the case of nocebo). Pain scores were recorded using a visual analogue scale (1-10). EEG measurements were recorded from 32 electrodes and analysed in the time-frequency domain using Analyzer, EEGlab and Matlab. Linear Mixed Models in SPSS was used for statistical analysis. Results: Following NSW, the participants exhibited increased event-related synchronisation (ERS) in response to nociceptive stimuli in the 1-400 ms/1-25 Hz, post stimulus interval across several electrodes, which was significant at p < 0.05 level. Nocebo was significantly associated with lower ERS magnitude than correctly signalled stimuli (p < 0.05). Finally, there was a significant effect of NSW and nocebo on pain scores (p < 0.05), in which the participants rated the electrical stimuli as more painful following NSW and nocebo, however, nocebo was not facilitated by NSW (p = 0.438). Conclusion: NSW leads to sleep induced hyperalgesia accompanied by increased ERS across several electrodes following exposure to nociceptive electrical stimuli. There is also hyperalgesia in response to nocebo, which is accompanied by reduced ERS compared to correctly signalled stimuli. However, the present study does not find support for nocebo as a principal underlying factor in SIH, but rather, SIH and NIH appear to stem from cortical processes that do not overlap

Kunst som drivkraft for byutvikling : En studie av beslutningsprosessen om etablering av Kunstsilo i Kristiansand

Master's thesis in Political science and management (ME502

Dynamics of affective habituation to touch differ on the group and individual level

Slow stroking touch activates C-tactile (CT) fibres in the human skin and is typically described as pleasant. Over a longer duration of stroking, affective habituation sets in, indicated by a reduction in rated pleasantness. However, it is not clear whether the group level effect is represented on an individual level. We analyse the stability of individual ratings of slow stroking touch and their relationship to behavioural and physiological measures. Forty-eight participants (23 women) were repeatedly stroked with a velocity maximally activating CT fibres. The perceived pleasantness was rated on a visual analogue scale. In order to examine the stability of pleasantness ratings, the experiment was repeated after a couple of days. During the experiment, electrocardiogram (ECG) and facial-electromyography (EMG) data were recorded. On the group-level, previous results of affective habituation to touch were replicated and stable across sessions. On the individual level, however, less than half of the participants showed a significant reduction of pleasantness in the course of the experiment. Moreover, the remaining participants showed either no change, random rating behaviour or even an increase in pleasantness ratings during the course of the experiment. The individual response patterns were variable across sessions but stable above the chance level. Furthermore, the response patterns could not be explicitly associated with any of the behavioural or physiological measures. Our findings indicate a lack of group-to-individual generalizability for affective habituation to touch. The variability of rating patterns over time indicates that they are not conclusively determined by stable individual characteristics. Future research investigating touch should favour a more individual approach to the more commonly applied group analysis

Right between the eyes: Corrugator muscle activity tracks the changing pleasantness of repeated slow stroking touch

Subjective reports and physiological responses provide different appraisals of sensory input. The coherence between subjective and physiological responses to repeated pleasant stimuli remains largely unexplored, and is particularly important in situations where subjective responses are prone to cognitive or contextual bias. Here, we investigate how subjective and physiological responses to repeated gentle touch correspond at two separate sessions and compare these to responses obtained when smelling an odorant. Forty-eight participants underwent 60 trials of skin-to-skin slow stroking touch directed to the forearm. We collected subjective pleasantness reports, recorded facial electromyography (EMG) of the corrugator and zygomaticus muscles and heart-rate variability (HRV). With increasing touch repetitions, mean ratings of pleasantness decreased and corrugator muscle activity increased during session 1, whereas zygomaticus activity remained largely unchanged during both sessions. HRV was significantly higher during the first session, but did not increase from baseline during either sessions. Touch was rated as more pleasant than odor, and demonstrated greater resilience to satiety than the odor responses. Facial EMG recordings of the corrugator muscle appear to be a relevant measure for capturing satiety effects in skin-to-skin touch. Zygomaticus and HRV responses were independent of the subjective appraisal of the gentle touch. Rather than being blueprints of the subjective reports, physiological responses appear to reflect different parts of the subjective experience. As such, an improved understanding of the subjective and physiological responses to pleasant stimuli may improve our understanding of the dynamic interactions that take place in shaping complex emotional phenomena, such as aversion and pleasantness

Sleep restriction does not potentiate nocebo‐induced changes in pain and cortical potentials

Background: The increased pain sensitivity following reduced sleep may be related to changes in cortical processing of nociceptive stimuli. Expectations shape pain perception and can inhibit (placebo) or enhance (nocebo) pain. Sleep restriction appears to enhance placebo responses; however, whether sleep restriction also affects nocebo responses remains unknown. The aim of the present study was to determine whether sleep restriction facilitates nocebo‐induced changes in pain and pain‐evoked cortical potentials. Methods: In an experimental study with a crossover design, the sensitivity to electrically induced pain was determined in 53 nurses under two sleep conditions, after habitual sleep and after two consecutive nights at work. Nocebo was induced by conditioning one‐third of the pain stimuli. Pain‐elicited cortical event‐related potentials were recorded by electroencephalography (EEG). Data were analysed both in the time‐domain (N2P2 amplitude) and in the time‐frequency domain (ERP magnitude). Sleepiness and vigilance were also assessed. Results: Both nocebo alone and sleep restriction alone increased the sensitivity to electrically induced pain. However, no interaction effect was found. Moreover, the magnitude of the pain‐elicited responses increased after sleep restriction and decreased after nocebo expectation, suggesting that nocebo is probably not an underlying mechanism for the commonly observed hyperalgesia induced by sleep restriction. Conclusions: The present work addresses whether sleep restriction, known to increase the sensitivity of the pain system, facilitates nocebo‐induced hyperalgesia. Our findings suggest that this is not the case, indicating that the increased sensitivity of the pain system following nocebo and sleep restriction are mediated by different cortical mechanisms

Sleep restriction does not potentiate nocebo‐induced changes in pain and cortical potentials

Background: The increased pain sensitivity following reduced sleep may be related to changes in cortical processing of nociceptive stimuli. Expectations shape pain perception and can inhibit (placebo) or enhance (nocebo) pain. Sleep restriction appears to enhance placebo responses; however, whether sleep restriction also affects nocebo responses remains unknown. The aim of the present study was to determine whether sleep restriction facilitates nocebo‐induced changes in pain and pain‐evoked cortical potentials. Methods: In an experimental study with a crossover design, the sensitivity to electrically induced pain was determined in 53 nurses under two sleep conditions, after habitual sleep and after two consecutive nights at work. Nocebo was induced by conditioning one‐third of the pain stimuli. Pain‐elicited cortical event‐related potentials were recorded by electroencephalography (EEG). Data were analysed both in the time‐domain (N2P2 amplitude) and in the time‐frequency domain (ERP magnitude). Sleepiness and vigilance were also assessed. Results: Both nocebo alone and sleep restriction alone increased the sensitivity to electrically induced pain. However, no interaction effect was found. Moreover, the magnitude of the pain‐elicited responses increased after sleep restriction and decreased after nocebo expectation, suggesting that nocebo is probably not an underlying mechanism for the commonly observed hyperalgesia induced by sleep restriction. Conclusions: The present work addresses whether sleep restriction, known to increase the sensitivity of the pain system, facilitates nocebo‐induced hyperalgesia. Our findings suggest that this is not the case, indicating that the increased sensitivity of the pain system following nocebo and sleep restriction are mediated by different cortical mechanisms

Using Facial Electromyography to Assess Facial Muscle Reactions to Experienced and Observed Affective Touch in Humans

"Affective" touch is believed to be processed in a manner distinct from discriminatory touch and to involve activation of C-tactile (CT) afferent fibers. Touch that optimally activates CT fibers is consistently rated as hedonically pleasant. Patient groups with impaired social-emotional functioning also show disordered affective touch ratings. However, relying on self-reported ratings of touch has many limitations, including recall bias and communication barriers. Here, we describe a methodological approach to study affective responses to touch via facial electromyography (EMG) that circumvents the reliance on self-report ratings. Facial EMG is an objective, quantitative, and non-invasive method to measure facial muscle activity indicative of affective responses. Responses can be assessed across healthy and patient populations without the need for verbal communication. Here, we provide two separate datasets demonstrating that CT-optimal and non-optimal touch elicit distinct facial muscle reactions. Moreover, facial EMG responses are consistent across stimulus modalities, e.g. tactile (experienced touch) and visual (observed touch). Finally, the temporal resolution of facial EMG can detect responses on timescales that supersede that of verbal reporting. Together, our data suggest that facial EMG is a suitable methodology for use in affective tactile research that can be used to supplement, or in some cases, supplant, existing measures