Texte remanié de l'éd. allemande de: Th. Ph. D.--Philosophical faculty--Münster--Münster university, 1989.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Thèse présentée en vue de l’obtention du grade de Philosophiae Doctor (Ph.D.) en Psychologie, option Neuropsychologie clinique / La douleur est un enjeu central dans le domaine médical. La gestion efficace de la douleur aiguë est cruciale pour prévenir la douleur chronique. Parmi les diverses conditions cliniques, la douleur est prédominante chez les patients ayant subi un trauma orthopédique, persistant plusieurs jours après la blessure, avec un risque élevé de complications. Cependant, les traitements pharmacologiques, comme les opiacés et les anti-inflammatoires non stéroïdiens, bien que couramment utilisés, peuvent avoir des effets négatifs sur la consolidation osseuse et la santé générale. Dans ce contexte, il apparaît pertinent d’explorer des méthodes d’intervention alternatives, telles que la stimulation magnétique transcrânienne répétitive (SMTr). Bien que cette technique soit prometteuse pour le traitement de la douleur chronique, son efficacité dans les douleurs aiguës reste incertaine. De plus, l’effet placebo, qui joue un rôle dans les traitements de la douleur, a souvent été sous-estimé dans les études antérieures sur la SMTr. Par ailleurs, le taux de réponse à la SMTr varie beaucoup chez les individus. Ainsi, mieux comprendre les effets spécifiques de la SMTr et de l’effet placebo associé pourrait améliorer son efficacité. Cette thèse visait donc à combler ces lacunes en poursuivant deux objectifs principaux. Le premier était d’explorer l’effet placebo associé à l’utilisation d’un protocole multisessions de SMTr en phase aiguë chez des patients ayant subi une fracture du membre supérieur. Dans cette étude, un groupe a reçu une intervention de SMTr sham, tandis que l’autre a uniquement bénéficié des soins orthopédiques usuels. Les résultats ont révélé un effet significatif du placebo dans le groupe ayant reçu la SMTr sham, suggérant des bénéfices de l’intervention sur la guérison en termes d’intensité douloureuse et de récupération fonctionnelle. Il est donc impératif que les études futures incluent des groupes témoins pour distinguer les effets spécifiques de la SMTr des effets non spécifiques (p. ex., évolution naturelle de la condition) et de l’effet placebo. Cette étude met aussi en lumière la nécessité d’améliorer les soins en orthopédie, tout en appelant à des recherches supplémentaires pour comprendre le rôle des différents facteurs impliqués (p. ex., utilisation du placebo, cadre thérapeutique, etc.). Le second objectif portait sur la faisabilité et l’efficacité d’un protocole de SMTr (actif vs sham), bonifié par une procédure de conditionnement, dans le cadre d’une douleur expérimentale induite chez des individus en bonne santé. Ce protocole visait à optimiser la réponse à la SMTr en modulant à la fois le seuil de douleur et les attentes de soulagement des participants, un facteur clé influençant la réponse aux interventions analgésiques. Néanmoins, les résultats se sont révélés peu concluants en raison de limitations méthodologiques (p. ex., la procédure de conditionnement utilisée, absence de suggestions verbales, etc.). Ainsi, des études futures pourraient apporter des améliorations au protocole et l’appliquer auprès d’une population souffrant de douleurs cliniques, dont l’expérience douloureuse et les attentes diffèrent de celles des individus en bonne santé. En effet, les individus souffrant de douleurs chroniques ou aiguës sont plus souvent réceptifs aux interventions thérapeutiques, ce qui pourrait améliorer les résultats futurs. / Pain is a common issue in the medical field, and optimal management during the acute phase is critical to preventing chronic pain. Among various clinical conditions, pain is a predominant symptom in orthopedic trauma patients, which persists for several days after the injury, with a high risk of complications. However, managing pain in this population proves to be a significant challenge, as pharmacological treatments such as opioids and non-steroidal anti-inflammatory drugs are frequently used despite their potential adverse effects on bone healing and patients’ overall health. Therefore, exploring alternative intervention methods, such as repetitive transcranial magnetic stimulation (rTMS), is necessary. While rTMS has shown analgesic potential in chronic and experimental pain, its effectiveness in managing acute pain remains uncertain. Moreover, the analgesic placebo effect involved in all pain interventions seems to have been underestimated, if not neglected, in previous rTMS studies. Additionally, the response rate to rTMS varies widely among individuals, such that any endeavour aiming to deepen our understanding of the specific effects of rTMS and associated placebo effects could reveal to be fruitful in optimizing its efficacy. Therefore, this thesis aimed to address these gaps through two main objectives. The first study investigated the placebo effect of a multi-session sham rTMS protocol in the context of acute pain in patients with an upper limb fracture, by comparing their clinical outcomes to a group receiving standard orthopedic care. The results showed a significant placebo effect in the group receiving sham rTMS, suggesting that the placebo intervention benefited the healing trajectory in terms of pain level and functional recovery. This underscores the importance of including control groups in future rTMS studies to better distinguish between the specific effects of rTMS, non-specific effects (such as natural recovery), and the placebo effect. Furthermore, the study indicates that current orthopedic care models could be enhanced by subacute, multi-session interventions, although further validation is needed. The second study focused on the feasibility and effectiveness of an rTMS protocol (active vs sham) enhanced with a conditioning procedure in healthy individuals experiencing experimental pain. This protocol aimed to optimize the response to rTMS by modulating participants' pain thresholds and their expectations of pain relief, a factor known to influence outcomes in analgesic interventions. However, the results of this study were inconclusive, likely due to various methodological limitations (e.g., ineffective conditioning procedure, number of rTMS sessions, crossover design, absence of verbal suggestions, etc.). Although the design of our protocol did not prove effective, future studies could make methodological adjustments and apply this protocol to a population suffering from clinical pain. Thus, it is important to bear in mind that the painful experience of a clinical population differs from that of healthy individuals. Indeed, patients with clinical pain may have different expectations regarding treatments, which could influence their responsiveness to interventions.

People have always been fascinated by the extent to which belief or will may influence<p>behavior. Proverbs, like “we tend to get what we expect,” and concepts, such as optimistic<p>thinking or self-fulfilling prophecy, reflect this intuition of an important link between one’s<p>dispositions and subsequent behavior. In other words, one’s predictions directly or<p>indirectly cause them to become true. In a similar manner, every culture, country or<p>religion has their own words for ‘expectation,’ ‘belief,’ ‘disappointment,’ ‘surprise,’ and<p>generally all have the same meaning: under uncertainty, what one expects or believes is the<p>most likely to happen. This relation between what caused a reaction in the past will<p>probably cause it again in the future might not be realistic. If the expected outcome is not<p>confirmed, it may result in a personal ‘disappointment’, and if the outcome fits no<p>expectations, it will be a ‘surprise’. Our brain is hardwired with this heuristic capacity of<p>learning the cause-effect relationship and to project its probability as the basis for much of<p>our behavior, as well as cognitions. This experience-based expectation is a form of<p>learning that helps the brain to bypass an exhaustive search in finding a satisfactory<p>solution. Expectations may thus be considered an innate theory of causality; that is, a set of<p>factors (causes) generating a given phenomenon (effects) influence the way we treat<p>incoming information but also the way we retrieve the stored information. These<p>expectancy templates may well represent one of the basic rules of how the brain processes<p>information, affecting the way we perceive the world, direct our attention and deal with<p>conflicting information. In fact, expectations have been shown to influence our judgments<p>and social interactions, along with our volition to individually decide and commit to a<p>particular course of action. However, people’s expectations may elicit the anticipation of<p>their own automatic reactions to various situations and behaviors cues, and can explain that<p>expecting to feel an increase in alertness after coffee consumption leads to experiencing<p>the consequent physiologic and behavioral states. We call this behavior-response<p>expectancy. This non-volitional form of expectation has been shown to influence<p>cognitions such as memory, pain, visual awareness, implicit learning and attention, through<p>the mediation of phenomena like placebo effects and hypnotic behaviors. Importantly,when talking about expectations, placebo and hypnosis, it is important to note that we are<p>also talking about suggestion and its modulating capability. In other words, suggestion has<p>the power to create response expectancies that activate automatic responses, which will, in<p>turn, influence cognition and behavior so as to shape them congruently with the expected<p>outcome. Accordingly, hypnotic inductions are a systematic manipulation of expectancy,<p>similar to placebo, and therefore they both work in a similar way. Considering such<p>assumptions, the major question we address in this PhD thesis is to know if these<p>expectancy-based mechanisms are capable of modulating more high-level information<p>processing such as cognitive conflict resolution, as is present in the well-known Stroop<p>task. In fact, in a recent series of studies, reduction or elimination of Stroop congruency<p>effects was obtained through suggestion and hypnotic induction. In this PhD thesis, it is<p>asked whether a suggestion reinforced by placebos, operating through response-expectancy<p>mechanisms, is able to induce a top-down cognitive modulation to overcome cognitive<p>conflict in the Stroop task, similar to those results found using suggestion and hypnosis<p>manipulation. / Doctorat en Sciences Psychologiques et de l'éducation / info:eu-repo/semantics/nonPublished