Postural effects of imagined leg pain as a function of hypnotizability.
ABSTRACT It has been shown that, in subjects with high hypnotizability (Highs), imagined somatosensory stimulation can involuntarily activate the neural circuits involved in the modulation of reflex action. In this vein, aim of the study was to investigate whether the imagery of nociceptive stimulation in one leg may produce both subjective experience of pain and congruent postural adjustments during normal upright stance. The displacement of the centre of pressure (CoP) was studied during imagery of leg pain (LP) and during the control conditions of imagery of tactile stimulation of the same leg and of throat pain (TP) in 12 Highs and 12 low hypnotizable subjects (Lows). The results showed that the vividness of imagery was higher in Highs than in Lows for all tasks and that only Highs reported actually feeling pain during LP and TP. Congruently, during LP only Highs displaced their CoP towards the leg opposite to the one that was the object of painful imagery and increased their CoP mean velocity and area of excursion. Since the Highs' postural changes were not accounted for only by vividness of imagery and perceived pain intensity, high hypnotizability is apparently responsible for part of the postural effects of pain imagery.
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ABSTRACT: This study examined modulation of corticospinal excitability during both actual and imagined movements. Seven young healthy subjects performed actual (3-50% maximal voluntary contractions) and imagined index finger force production, and rest. Individual responses to focal transcranial magnetic stimulation (TMS) in four fingers (index, middle, ring, and little) were recorded for all three tested conditions. The force increments at the threshold of activation were predicted from regression analysis, representing the TMS-induced response at the threshold activation of the corticospinal pathways. The measured increment in the index finger during motor imagery was larger than that at rest, but smaller than the predicted increment at the threshold of activation. On the other hand, the measured increment in the uninstructed (middle, ring, and little), slave fingers during motor imagery was larger than that at rest, but not different from the predicted increment at the threshold of activation. These contrasting results suggest that the degree of imagery-induced enhancement in corticospinal excitability was significantly less than what could be predicted for threshold levels from regression analysis, but only for the index finger, and not the adjacent slave fingers. It is concluded that corticospinal excitability for the explicitly instructed index finger is specifically enhanced at subthreshold levels during motor imagery.Experimental Brain Research 06/2007; 179(3):517-24. · 2.22 Impact Factor
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ABSTRACT: This study investigated the relationship between acute dissociative reactions to trauma and hypnotizability. Acutely traumatized patients (N=61) with acute stress disorder, subclinical acute stress disorder (no dissociative symptoms), and no acute stress disorder were administered the Stanford Hypnotic Clinical Scale within 4 weeks of their trauma. Although patients with acute stress disorder and patients with subclinical acute stress disorder displayed comparable levels of nondissociative psychopathology, acute stress disorder patients had higher levels of hypnotizability and were more likely to display reversible posthypnotic amnesia than both patients with subclinical acute stress disorder and patients with no acute stress disorder. The findings may be interpreted in light of a diathesis-stress process mediating trauma-related dissociation. People who develop acute stress disorder in response to traumatic experience may have a stronger ability to experience dissociative phenomena than people who develop subclinical acute stress disorder or no acute stress disorder.American Journal of Psychiatry 05/2001; 158(4):600-4. · 14.72 Impact Factor
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ABSTRACT: The authors compared the hypnotizability of 65 Vietnam veteran patients with posttraumatic stress disorder (PTSD) to that of a normal control group and four patient samples using the Hypnotic Induction Profile. The patients with PTSD had significantly higher hypnotizability scores than patients with diagnoses of schizophrenia (N = 23); major depression, bipolar disorder--depressed, and dysthymic disorder (N = 56); and generalized anxiety disorder (N = 18) and the control sample (N = 83). This finding supports the hypothesis that dissociative phenomena are mobilized as defenses both during and after traumatic experiences. The literature suggests that spontaneous dissociation, imagery, and hypnotizability are important components of PTSD symptoms.American Journal of Psychiatry 04/1988; 145(3):301-5. · 14.72 Impact Factor