Functional neuroimaging with magnetic resonance imaging (fMRI) or positron emission tomography (P... more Functional neuroimaging with magnetic resonance imaging (fMRI) or positron emission tomography (PET) provides the methodology to unravel some of the fascinating, but hitherto largely unresolved interactions between physical exercise and brain function. Phenomena such as raised mood, pain modulation, and sport addiction associated with physical exercise are highly interesting psychophysical models that require further in depth understanding at the neurotransmitter
Pineal cysts have been suggested to be linked to headache pathogenesis. However, no systematic st... more Pineal cysts have been suggested to be linked to headache pathogenesis. However, no systematic studies on this topic have been performed so far. The aim of this study was to investigate the relationship between pineal cysts and headache and to determine the relevance of the cyst size in this context. We conducted a case-control study of patients who consulted the neurological department between 1999 and 2006 to investigate the relationship between pineal cysts and headache and to determine the relevance of the cyst size. A total of 51 patients with pineal cyst were identified, thereby 51% were suffering from headache (half of them had migraine), whereas in the control group, only 25% had headache (thereof 31% suffered from migraine). There was a significant relationship between headache (as well as migraine) and pineal cysts (chi-square test), but no significant difference in pineal cyst diameter between the patient group with headache versus without headache (t-test). Our data provide evidence for a causal relationship between pineal cysts and headache, respectively, migraine in this patient cohort.
Zusammenfassung In den letzten Jahrzehnten haben funktionelle Bildgebungsstudien unser Verständn... more Zusammenfassung In den letzten Jahrzehnten haben funktionelle Bildgebungsstudien unser Verständnis hinsichtlich der zentralnervösen Schmerzverarbeitung beim Menschen deutlich verbessert. Besonderes Interesse wurde dabei auf opioiderge Mechanismen der Schmerztransmission und Inhibition gerichtet. Hierdurch stehen heute umfassende Erkenntnise zur In-vivo-Verteilung von Opioidrezeptoren beim Menschen zur Verfügung, und geschlechtsspezifische Unterschiede konnten gezeigt werden. Eine zunehmende Anzahl von Studien hat zudem über veränderte Opioidrezeptorverteilungsmuster bei klinischen
Voxel-based morphometry (VBM) has proved a powerful method to detect subtle changes of grey matte... more Voxel-based morphometry (VBM) has proved a powerful method to detect subtle changes of grey matter (GM) at the group level but the detection of GM changes in single subjects has not been investigated systematically. We tested two parametric approaches based on either the one-sample or two-sample t-test with a „pooled “estimate of variance. Moreover, we tested two corrections for multiple statistical tests, namely, the family wise error correction predicated on Gaussian random fields (FWE) and the false discovery rate predicated on ...
In Huntington's disease (HD), the distribution of pathological changes throughout the brain i... more In Huntington's disease (HD), the distribution of pathological changes throughout the brain is incompletely understood. Some studies have identified leftward-biased lateralization, whereas others did not. We performed mag- netic resonance imaging and a voxel-based asymmetry analysis in 44 right-handed HD gene carriers (presymptom- atic, n 5; stage I, n 28; stage II, n 11) and 44 right-handed healthy controls. The
Opioids modulate the affective component of pain and in vivo data indicate that opioids induce ac... more Opioids modulate the affective component of pain and in vivo data indicate that opioids induce activation changes in the rostral ACC, insula and other brain areas. Hence, opioidergic release is to be expected in these brain regions following experimental pain stimulation. We examined healthy volunteers during heat pain and control subjects during rest using [18F]fluorodiprenorphine-PET. Pain stimulation led to significant
Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) is... more Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) is a primary head-pain syndrome, which is often refractory to any medical treatment. Concerning the pathophysiology of SUNCT, hypothalamic involvement ipsilaterally to the pain has been suggested based on the clinical features and one functional imaging case report. Here we now report a new case with SUNCT and the concomitant
Functional neuroimaging methods such as positron emission tomography (PET) or functional magnetic... more Functional neuroimaging methods such as positron emission tomography (PET) or functional magnetic resonance imaging (fMRI) provide fascinating insights into the cerebral processing of pain. Neuroimaging studies have shown that no clearly defined "pain centre" exists. Rather, an entire network of brain regions is involved in the processing of nociceptive information, which leads to the subjective impression of "pain". Sophisticated study designs nowadays permit the characterisation of different components of pain processing. In this review, we summarise neuroimaging studies, which contributed to the characterisation of these different aspects of cerebral pain processing, such as somatosensory (discrimination of different stimulus modalities, noxious vs non-noxious, summation), emotional, cognitive (attention, anticipation, distraction), vegetative (homeostasis) and motor aspects.
To investigate whether the functional changes in pain disorder might be reflected by structural b... more To investigate whether the functional changes in pain disorder might be reflected by structural brain changes. Pain disorder assessed with the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria is characterized by persistent and distressing chronic pain at one or more body sites which cannot be fully explained by a physiological process or somatic disorder. Psychological factors are thought to play a major role. Recent neuroimaging studies evidenced altered pain processing in patients suffering from this disorder. Fourteen right-handed women fulfilling the DSM-IV criteria for pain disorder and 25 healthy age-matched women were investigated with magnetic resonance imaging. In the voxel-based morphometry analysis, we compared both groups for changes of gray-matter density. We included age and Beck Depression Inventory scores as nuisance variables to minimize possible confounding effects of age or depressive comorbidity. In the patient group, we found significant gray-matter decreases in the prefrontal, cingulate, and insular cortex. These regions are known to be critically involved in the modulation of subjective pain experiences. In the context of similar results in patients with other functional pain syndromes, such as fibromyalgia and chronic back pain, we suggest that structural changes in fronto-limbic brain circuits represent not only an objective marker of these pain syndromes but also constitute a critical pathophysiological element. These findings represent a further proof of the important role of central changes in pain disorder.
Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance im... more Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have delineated a human pain network in vivo. Despite the recognition of cerebral structures engaged in pain transmission, the cerebral mechanisms involved in pain modulation are still not well understood. Here, we investigated healthy volunteers using fMRI during experimental heat pain and distraction induced by a visual incongruent color-word Stroop task. A factorial design permitted categorical and covariation analysis of four conditions, namely innocuous and noxious heat; with and without distraction. Pain without distraction evoked an activation pattern similar to that observed in previous neuroimaging pain studies. Distraction was associated with a significant reduction of the visual analogue scale (VAS) ratings for pain intensity and unpleasantness and a reduction of pain-related activation in multiple brain areas, particularly in the so-called 'medial pain system'. Distraction significantly increased the activation of the cingulo-frontal cortex including the orbitofrontal and perigenual anterior cingulate cortex (ACC), as well as the periaquaeductal gray (PAG) and the posterior thalamus. Covariation analysis revealed functional interaction between these structures during pain stimulation and distraction, but not during pain stimulation per se. According to our results, the cingulo-frontal cortex may exert top-down influences on the PAG and posterior thalamus to gate pain modulation during distraction.
Functional neuroimaging with magnetic resonance imaging (fMRI) or positron emission tomography (P... more Functional neuroimaging with magnetic resonance imaging (fMRI) or positron emission tomography (PET) provides the methodology to unravel some of the fascinating, but hitherto largely unresolved interactions between physical exercise and brain function. Phenomena such as raised mood, pain modulation, and sport addiction associated with physical exercise are highly interesting psychophysical models that require further in depth understanding at the neurotransmitter
Pineal cysts have been suggested to be linked to headache pathogenesis. However, no systematic st... more Pineal cysts have been suggested to be linked to headache pathogenesis. However, no systematic studies on this topic have been performed so far. The aim of this study was to investigate the relationship between pineal cysts and headache and to determine the relevance of the cyst size in this context. We conducted a case-control study of patients who consulted the neurological department between 1999 and 2006 to investigate the relationship between pineal cysts and headache and to determine the relevance of the cyst size. A total of 51 patients with pineal cyst were identified, thereby 51% were suffering from headache (half of them had migraine), whereas in the control group, only 25% had headache (thereof 31% suffered from migraine). There was a significant relationship between headache (as well as migraine) and pineal cysts (chi-square test), but no significant difference in pineal cyst diameter between the patient group with headache versus without headache (t-test). Our data provide evidence for a causal relationship between pineal cysts and headache, respectively, migraine in this patient cohort.
Zusammenfassung In den letzten Jahrzehnten haben funktionelle Bildgebungsstudien unser Verständn... more Zusammenfassung In den letzten Jahrzehnten haben funktionelle Bildgebungsstudien unser Verständnis hinsichtlich der zentralnervösen Schmerzverarbeitung beim Menschen deutlich verbessert. Besonderes Interesse wurde dabei auf opioiderge Mechanismen der Schmerztransmission und Inhibition gerichtet. Hierdurch stehen heute umfassende Erkenntnise zur In-vivo-Verteilung von Opioidrezeptoren beim Menschen zur Verfügung, und geschlechtsspezifische Unterschiede konnten gezeigt werden. Eine zunehmende Anzahl von Studien hat zudem über veränderte Opioidrezeptorverteilungsmuster bei klinischen
Voxel-based morphometry (VBM) has proved a powerful method to detect subtle changes of grey matte... more Voxel-based morphometry (VBM) has proved a powerful method to detect subtle changes of grey matter (GM) at the group level but the detection of GM changes in single subjects has not been investigated systematically. We tested two parametric approaches based on either the one-sample or two-sample t-test with a „pooled “estimate of variance. Moreover, we tested two corrections for multiple statistical tests, namely, the family wise error correction predicated on Gaussian random fields (FWE) and the false discovery rate predicated on ...
In Huntington's disease (HD), the distribution of pathological changes throughout the brain i... more In Huntington's disease (HD), the distribution of pathological changes throughout the brain is incompletely understood. Some studies have identified leftward-biased lateralization, whereas others did not. We performed mag- netic resonance imaging and a voxel-based asymmetry analysis in 44 right-handed HD gene carriers (presymptom- atic, n 5; stage I, n 28; stage II, n 11) and 44 right-handed healthy controls. The
Opioids modulate the affective component of pain and in vivo data indicate that opioids induce ac... more Opioids modulate the affective component of pain and in vivo data indicate that opioids induce activation changes in the rostral ACC, insula and other brain areas. Hence, opioidergic release is to be expected in these brain regions following experimental pain stimulation. We examined healthy volunteers during heat pain and control subjects during rest using [18F]fluorodiprenorphine-PET. Pain stimulation led to significant
Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) is... more Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) is a primary head-pain syndrome, which is often refractory to any medical treatment. Concerning the pathophysiology of SUNCT, hypothalamic involvement ipsilaterally to the pain has been suggested based on the clinical features and one functional imaging case report. Here we now report a new case with SUNCT and the concomitant
Functional neuroimaging methods such as positron emission tomography (PET) or functional magnetic... more Functional neuroimaging methods such as positron emission tomography (PET) or functional magnetic resonance imaging (fMRI) provide fascinating insights into the cerebral processing of pain. Neuroimaging studies have shown that no clearly defined "pain centre" exists. Rather, an entire network of brain regions is involved in the processing of nociceptive information, which leads to the subjective impression of "pain". Sophisticated study designs nowadays permit the characterisation of different components of pain processing. In this review, we summarise neuroimaging studies, which contributed to the characterisation of these different aspects of cerebral pain processing, such as somatosensory (discrimination of different stimulus modalities, noxious vs non-noxious, summation), emotional, cognitive (attention, anticipation, distraction), vegetative (homeostasis) and motor aspects.
To investigate whether the functional changes in pain disorder might be reflected by structural b... more To investigate whether the functional changes in pain disorder might be reflected by structural brain changes. Pain disorder assessed with the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria is characterized by persistent and distressing chronic pain at one or more body sites which cannot be fully explained by a physiological process or somatic disorder. Psychological factors are thought to play a major role. Recent neuroimaging studies evidenced altered pain processing in patients suffering from this disorder. Fourteen right-handed women fulfilling the DSM-IV criteria for pain disorder and 25 healthy age-matched women were investigated with magnetic resonance imaging. In the voxel-based morphometry analysis, we compared both groups for changes of gray-matter density. We included age and Beck Depression Inventory scores as nuisance variables to minimize possible confounding effects of age or depressive comorbidity. In the patient group, we found significant gray-matter decreases in the prefrontal, cingulate, and insular cortex. These regions are known to be critically involved in the modulation of subjective pain experiences. In the context of similar results in patients with other functional pain syndromes, such as fibromyalgia and chronic back pain, we suggest that structural changes in fronto-limbic brain circuits represent not only an objective marker of these pain syndromes but also constitute a critical pathophysiological element. These findings represent a further proof of the important role of central changes in pain disorder.
Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance im... more Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have delineated a human pain network in vivo. Despite the recognition of cerebral structures engaged in pain transmission, the cerebral mechanisms involved in pain modulation are still not well understood. Here, we investigated healthy volunteers using fMRI during experimental heat pain and distraction induced by a visual incongruent color-word Stroop task. A factorial design permitted categorical and covariation analysis of four conditions, namely innocuous and noxious heat; with and without distraction. Pain without distraction evoked an activation pattern similar to that observed in previous neuroimaging pain studies. Distraction was associated with a significant reduction of the visual analogue scale (VAS) ratings for pain intensity and unpleasantness and a reduction of pain-related activation in multiple brain areas, particularly in the so-called 'medial pain system'. Distraction significantly increased the activation of the cingulo-frontal cortex including the orbitofrontal and perigenual anterior cingulate cortex (ACC), as well as the periaquaeductal gray (PAG) and the posterior thalamus. Covariation analysis revealed functional interaction between these structures during pain stimulation and distraction, but not during pain stimulation per se. According to our results, the cingulo-frontal cortex may exert top-down influences on the PAG and posterior thalamus to gate pain modulation during distraction.
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Papers by Michael Valet