Roger Luechinger - Academia.edu (original) (raw)

Papers by Roger Luechinger

PLoS ONE, 2013

Abundant behavioral evidence suggests that the ability to self-control is limited, and that any e... more Abundant behavioral evidence suggests that the ability to self-control is limited, and that any exertion of self-control will increase the likelihood of subsequent self-control failures. Here we investigated the neural correlates underlying the aftereffects of self-control on future control processes using functional magnetic resonance imaging (fMRI). An initial act of self-control (suppressing emotions) impaired subsequent performance in a second task requiring control (Stroop task). On the neural level, increased activity during emotion suppression was followed by a relative decrease in activity during the Stroop task in a cluster in the right lateral prefrontal cortex (PFC) including the dorsolateral prefrontal cortex (DLPFC), an area engaged in the effortful implementation of control. There was no reliable evidence for reduced activity in the medial frontal cortex (MFC) including the anterior cingulate cortex (ACC), which is involved in conflict detection processes and has previously also been implicated in self-control. Follow-up analyses showed that the detected cluster in the right lateral PFC and an area in the MFC were involved in both the emotion suppression task and the Stroop task, but only the cluster in the right lateral PFC showed reduced activation after emotion suppression during the Stroop task. Reduced activity in lateral prefrontal areas relevant for the implementation of control may be a critical consequence of prior self-control exertion if the respective areas are involved in both self-control tasks.

Parallel imaging techniques are useful for fMRI studies in light of the increasing susceptibility... more Parallel imaging techniques are useful for fMRI studies in light of the increasing susceptibility effects at high magnetic field strength. Yet, spatially varying noise amplification constitutes a challenge for the application of these techniques. The medial temporal lobe is particularly vulnerable to susceptibility effect with increasingly strong signal reduction. We present two fMRI studies comparing SENSE single-shot (ssh) echo planar imaging (EPI) at acceleration factors of 2.0, 2.4, 2.7, and 3.0 with conventional sshEPI at TE of 22 and 35 ms. Data were acquired during a learning task which activates the medial temporal lobe bilaterally. Susceptibility related image distortion was markedly reduced with increasing SENSE acceleration. Moreover, in the group results, statistical power increased in the whole brain with SENSE compared to conventional imaging and with a TE of 35 ms compared to 22 ms. Higher SENSE acceleration factors further improved image quality and increased statistical power in the occipital lobe and fusiform gyrus, but not in the medial temporal lobe. We therefore conclude that an sshEPI acquisition protocol with a moderate SENSE acceleration factor of R = 2.0 and TE 35 ms is suitable for the detection of medial temporal activation at 3T.

Neurobiology of Aging, 2015

The biomarker potential of the inhibitory neurotransmitter g-aminobutyric acid (GABA) for the in ... more The biomarker potential of the inhibitory neurotransmitter g-aminobutyric acid (GABA) for the in vivo characterization of preclinical stages in Alzheimer's disease has not yet been explored. We measured GABA, glutamate þ glutamine (Glx), and N-acetyl-aspartate (NAA) levels by single-voxel MEGA-PRESS magnetic resonance spectroscopy in the posterior cingulate cortex of 21 elderly subjects and 15 patients with amnestic mild cognitive impairment. Participants underwent Pittsburgh Compound B positron emission tomography, apolipoprotein E (APOE) genotyping, and neuropsychological examination. GABA, Glx, and NAA levels were significantly lower in patients. NAA was lower in Pittsburgh Compound Bpositive subjects and APOE ε4 allele carriers. GABA, Glx, and NAA levels were positively correlated to CERAD word learning scores. Reductions in GABA, Glx, and NAA levels may serve as metabolic biomarkers for cognitive impairment in amnestic mild cognitive impairment. Because GABA and Glx do not seem to reflect amyloid b deposition or APOE genotype, they are less likely biomarker candidates for preclinical Alzheimer's disease.

Frontiers in Behavioral Neuroscience, 2014

Analogies may arise from the conscious detection of similarities between a present and a past sit... more Analogies may arise from the conscious detection of similarities between a present and a past situation. In this functional magnetic resonance imaging study, we tested whether young volunteers would detect analogies unconsciously between a current supraliminal (visible) and a past subliminal (invisible) situation. The subliminal encoding of the past situation precludes awareness of analogy detection in the current situation. First, participants encoded subliminal pairs of unrelated words in either one or nine encoding trials. Later, they judged the semantic fit of supraliminally presented new words that either retained a previously encoded semantic relation ("analog") or not ("broken analog"). Words in analogs versus broken analogs were judged closer semantically, which indicates unconscious analogy detection. Hippocampal activity associated with subliminal encoding correlated with the behavioral measure of unconscious analogy detection. Analogs versus broken analogs were processed with reduced prefrontal but enhanced medial temporal activity. We conclude that analogous episodes can be detected even unconsciously drawing on the episodic memory network.

Background: In accordance with the Theory of Structural Dissociation of the Personality (TSDP), s... more Background: In accordance with the Theory of Structural Dissociation of the Personality (TSDP), studies of dissociative identity disorder (DID) have documented that two prototypical dissociative subsystems of the personality, the ''Emotional Part'' (EP) and the ''Apparently Normal Part'' (ANP), have different biopsychosocial reactions to supraliminal and subliminal trauma-related cues and that these reactions cannot be mimicked by fantasy prone healthy controls nor by actors.

Pacing and Clinical Electrophysiology, 2002

MRI is established as an important diagnostic tool in medicine. However, the presence of a cardia... more MRI is established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. The aim of this study was to investigate the state of a pacemaker reed switch in different orientations and positions in the main magnetic field of 0.5-, 1.5-, and 3.0-T MRI scanners. Reed switches used in current pacemakers and ICDs were tested in 0.5-, 1.5-, and 3.0-T MRI scanners. The closure of isolated reed switches was evaluated for different orientations and positions relative to the main magnetic field. The field strengths to close and open the reed switch and the orientation dependency of the closed state inside the main magnetic field were investigated. The measurements were repeated using two intact pacemakers to evaluate the potential influence of the other magnetic components, like the battery. If the reed switches were oriented parallel to the magnetic fields, they closed at 1.0 +/- 0.2 mT and opened at 0.7 +/- 0.2 mT. Two different reed switch behaviors were observed at different magnetic field strengths. In low magnetic fields (< 50 mT), the reed switches were closed. However, in high magnetic fields (> 200 mT), the reed switches opened in 50% of all tested orientations. No difference between the three scanners could be demonstrated. The reed switches showed the same behavior whether they were isolated or an integral part of the pacemakers. The reed switch in a pacemaker or an ICD does not necessarily remain closed in strong magnetic fields at 0.5, 1.5, or 3.0 T and the state of the reed switch may not be predictable with certainty in clinical situations.

NMR in Biomedicine, 2012

The aim of this study was to quantitatively assess the field strength dependence of the transvers... more The aim of this study was to quantitatively assess the field strength dependence of the transverse relaxation rate (R(2) *) change in cortical gray matter induced by hyperoxia and hyperoxic hypercapnia versus normoxia in an intra-individual comparison of young healthy volunteers. Medical air (21% O(2) ), pure oxygen and carbogen (95% O(2) , 5% CO(2) ) were alternatively administered in a block-design temporal pattern to induce normoxia, hyperoxia and hyperoxic hypercapnia, respectively. Local R(2) * values were determined from three-dimensional, multiple, radiofrequency-spoiled, fast field echo data acquired at 1.5, 3 and 7 T. Image quality was good at all field strengths. Under normoxia, the mean gray matter R(2) * values were 13.3 ± 2.7 s(-1) (1.5 T), 16.9 ± 0.9 s(-1) (3 T) and 29.0 ± 2.6 s(-1) (7 T). Both hyperoxic gases induced relaxation rate decreases ΔR(2) *, whose magnitudes increased quadratically with the field strength [carbogen: -0.69 ± 0.20 s(-1) (1.5 T), -1.49 ± 0.49 s(-1) (3 T), -5.64 ± 0.67 s(-1) (7 T); oxygen: -0.39 ± 0.20 s(-1) (1.5 T), -0.78 ± 0.48 s(-1) (3 T), -3.86 ± 1.00 s(-1) (7 T)]. Carbogen produced larger R(2) * changes than oxygen at all field strengths. The relative change ΔR(2) */R(2) * also increased with the field strength with a power between 1 and 2 for both carbogen and oxygen. The statistical significance of the R(2) * response improved with increasing B(0) and was higher for carbogen than for oxygen. For a sequence with pure T(2) * weighting of the signal response to respiratory challenge, the results suggested a maximum carbogen-induced signal difference of 19.3% of the baseline signal at 7 T and TE = 38 ms, but a maximum oxygen-induced signal difference of only 3.0% at 1.5 T and TE = 76 ms. For 3 T, maximum signal changes of 4.7% (oxygen) and 8.9% (carbogen) were computed. In conclusion, the R(2) * response to hyperoxic respiratory challenge was stronger for carbogen than for oxygen, and increased quadratically with the static magnetic field strength for both challenges, which highlights the importance of high field strengths for future studies aimed at probing oxygen physiology in clinical settings.

Journal of Clinical Periodontology, 2012

Dentine hypersensitivity (DH) is characterized by a short, sharp pain arising from exposed dentin... more Dentine hypersensitivity (DH) is characterized by a short, sharp pain arising from exposed dentin. Most published literature reports on peripheral neural aspects of this pain condition. The current investigation focused on differential cerebral activity elicited by stimulation of sensitive and insensitive teeth by means of natural air stimuli. Five graded stimulus strengths were randomly applied by means of a multi-injector air jet delivery system, each followed by an individual rating of perceived stimulus intensity. Brain activity was analysed by functional magnetic resonance imaging (fMRI). Stimulation of sensitive teeth induced significant activation in the thalamus, somatosensory cortices (SI & SII), anterior, middle and posterior insular cortices, anterior mid cingulate cortex, perigenual anterior cingulate cortex and frontal regions (BA10 and BA46). Differential responses to DH and painless perceptions were observed in the anterior insula and anterior midcingulate cortex. For the first time, this fMRI study demonstrates the feasibility of investigating cerebral processes related to DH evoked by natural (air) stimuli. Our neuroimaging data additionally provide evidence that differential activity in the anterior Insula (aIC) and anterior midcingulate cortex (aMCC) may represent clinically relevant pain experienced by DH patients.

Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2007

Human Brain Mapping, 2014

Imaging studies have identified a wide network of brain areas activated by nociceptive stimuli an... more Imaging studies have identified a wide network of brain areas activated by nociceptive stimuli and revealed differences in somatotopic representation of highly distinct stimulation sites (foot vs. hand) in the primary (S1) and secondary (S2) somatosensory cortices. Somatotopic organization between adjacent dermatomes and differences in cortical coding of similarly perceived nociceptive stimulation are less well studied. Here, cortical processing following contact heat nociceptive stimulation of cervical (C4, C6, and C8) and trunk (T10) dermatomes were recorded in 20 healthy subjects using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Stimulation of T10 compared with the C6 and C8 revealed significant higher response intensity in the left S1 (contralateral) and the right S2 (ipsilateral) even when the perceived pain was equal between stimulation sites. Accordingly, contact heat evoked potentials following stimulation of T10 showed significantly higher N2P2 amplitudes compared to C6 and C8. Adjacent dermatomes did not reveal a distinct somatotopical representation. Within the assessed cervical and trunk dermatomes, nociceptive cortical processing to heat differs significantly in magnitude even when controlling for pain perception. This study provides evidence that controlling for pain perception is not sufficient to compare directly the magnitude of cortical processing [blood oxygen level dependence (BOLD) response and amplitude of evoked potentials] between body sites. Hum Brain Mapp 00:000-000, 2013. V C 2013 Wiley-Periodicals Inc.

European Heart Journal, 2005

Magnetic resonance imaging (MRI) is well established as an important diagnostic tool in medicine.... more Magnetic resonance imaging (MRI) is well established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. In this study, heating effects at the myocardium-pacemaker lead tip interface have been investigated in a chronic animal model during MRI at 1.5 Tesla. Pacemaker leads with additional thermocouple wires as temperature sensors were implanted in nine animals. Temperature increases of up to 20 degrees C were measured during MRI of the heart. Significant impedance and minor stimulation threshold changes could be seen. However, pathology and histology could not clearly demonstrate heat-induced damage. MRI may produce considerable heating at the lead tip. Changes of pacing parameters due to MRI could be seen in chronic experiments. Potential risk of tissue damage cannot be excluded even though no reproducible alterations at the histological level could be found.

American Heart Journal, 2011

Recent studies suggest that magnetic resonance (MR) imaging of the brain and spine may safely be ... more Recent studies suggest that magnetic resonance (MR) imaging of the brain and spine may safely be performed in patients with pacemakers (PMs) and implantable cardioverter/defibrillators (ICDs), when taking adequate precautions. The aim of this study was to investigate safety, feasibility, and diagnostic value (DV) of MR imaging in cardiac applications (cardiac MR [CMR]) in patients with PMs and ICDs for the first time. Thirty-two PM/ICD patients with a clinical need for CMR were examined. The specific absorption rate was limited to 1.5 W/kg. Devices were reprogrammed pre-CMR to minimize interference with the electromagnetic fields. Devices were interrogated pre-CMR and post-CMR and after 3 months. Troponin I levels were measured pre-CMR and post-CMR; image quality (IQ) and DV of CMR were assessed. All devices could be reprogrammed normally post-CMR. No significant changes of pacing capture threshold, lead impedance, and troponin I were observed. Image quality in patients with right-sided devices (RSD) was better compared with that in patients with left-sided devices (LSD) (P < .05), and less myocardial segments were affected by device-related artefacts (P < .05). Diagnostic value was rated as sufficiently high, allowing for diagnosis, or better in 12 (100%) of 12 patients with RSD, and only in 7 (35%) of 20 patients with LSD. Cardiac MR may be performed safely when limiting specific absorption rate, appropriately monitoring patients, and following device reprogramming. Cardiac MR delivers good IQ and DV in patients with RSD. Cardiac MR in patients with RSD may therefore be performed with an acceptable risk/benefit ratio, whereas the risk/benefit ratio is rather unfavorable in patients with LSD.

Background: Magnetic Resonance Imaging (MRI) of patients with implanted cardiac devices is curren... more Background: Magnetic Resonance Imaging (MRI) of patients with implanted cardiac devices is currently considered hazardous due to potential for electromagnetic interference to the patient and pacemaker system. With approximately 60 million MRI scans performed worldwide per year, an estimated majority of pacemaker patients may develop an indication for an MRI during the lifetime of their pacemakers, suggesting that safe use of pacemakers in the MRI environment would be clinically valuable. A new pacing system (Medtronic EnRhythm MRI™ SureScan™ and CapSureFix MRI™ leads) has been designed and pre-clinically tested for safe use in the MRI environment. The EnRhythm MRI study is designed to confirm the safety and efficacy of this new pacing system.

PLoS ONE, 2013

Abundant behavioral evidence suggests that the ability to self-control is limited, and that any e... more Abundant behavioral evidence suggests that the ability to self-control is limited, and that any exertion of self-control will increase the likelihood of subsequent self-control failures. Here we investigated the neural correlates underlying the aftereffects of self-control on future control processes using functional magnetic resonance imaging (fMRI). An initial act of self-control (suppressing emotions) impaired subsequent performance in a second task requiring control (Stroop task). On the neural level, increased activity during emotion suppression was followed by a relative decrease in activity during the Stroop task in a cluster in the right lateral prefrontal cortex (PFC) including the dorsolateral prefrontal cortex (DLPFC), an area engaged in the effortful implementation of control. There was no reliable evidence for reduced activity in the medial frontal cortex (MFC) including the anterior cingulate cortex (ACC), which is involved in conflict detection processes and has previously also been implicated in self-control. Follow-up analyses showed that the detected cluster in the right lateral PFC and an area in the MFC were involved in both the emotion suppression task and the Stroop task, but only the cluster in the right lateral PFC showed reduced activation after emotion suppression during the Stroop task. Reduced activity in lateral prefrontal areas relevant for the implementation of control may be a critical consequence of prior self-control exertion if the respective areas are involved in both self-control tasks.

Parallel imaging techniques are useful for fMRI studies in light of the increasing susceptibility... more Parallel imaging techniques are useful for fMRI studies in light of the increasing susceptibility effects at high magnetic field strength. Yet, spatially varying noise amplification constitutes a challenge for the application of these techniques. The medial temporal lobe is particularly vulnerable to susceptibility effect with increasingly strong signal reduction. We present two fMRI studies comparing SENSE single-shot (ssh) echo planar imaging (EPI) at acceleration factors of 2.0, 2.4, 2.7, and 3.0 with conventional sshEPI at TE of 22 and 35 ms. Data were acquired during a learning task which activates the medial temporal lobe bilaterally. Susceptibility related image distortion was markedly reduced with increasing SENSE acceleration. Moreover, in the group results, statistical power increased in the whole brain with SENSE compared to conventional imaging and with a TE of 35 ms compared to 22 ms. Higher SENSE acceleration factors further improved image quality and increased statistical power in the occipital lobe and fusiform gyrus, but not in the medial temporal lobe. We therefore conclude that an sshEPI acquisition protocol with a moderate SENSE acceleration factor of R = 2.0 and TE 35 ms is suitable for the detection of medial temporal activation at 3T.

Neurobiology of Aging, 2015

The biomarker potential of the inhibitory neurotransmitter g-aminobutyric acid (GABA) for the in ... more The biomarker potential of the inhibitory neurotransmitter g-aminobutyric acid (GABA) for the in vivo characterization of preclinical stages in Alzheimer's disease has not yet been explored. We measured GABA, glutamate þ glutamine (Glx), and N-acetyl-aspartate (NAA) levels by single-voxel MEGA-PRESS magnetic resonance spectroscopy in the posterior cingulate cortex of 21 elderly subjects and 15 patients with amnestic mild cognitive impairment. Participants underwent Pittsburgh Compound B positron emission tomography, apolipoprotein E (APOE) genotyping, and neuropsychological examination. GABA, Glx, and NAA levels were significantly lower in patients. NAA was lower in Pittsburgh Compound Bpositive subjects and APOE ε4 allele carriers. GABA, Glx, and NAA levels were positively correlated to CERAD word learning scores. Reductions in GABA, Glx, and NAA levels may serve as metabolic biomarkers for cognitive impairment in amnestic mild cognitive impairment. Because GABA and Glx do not seem to reflect amyloid b deposition or APOE genotype, they are less likely biomarker candidates for preclinical Alzheimer's disease.

Frontiers in Behavioral Neuroscience, 2014

Analogies may arise from the conscious detection of similarities between a present and a past sit... more Analogies may arise from the conscious detection of similarities between a present and a past situation. In this functional magnetic resonance imaging study, we tested whether young volunteers would detect analogies unconsciously between a current supraliminal (visible) and a past subliminal (invisible) situation. The subliminal encoding of the past situation precludes awareness of analogy detection in the current situation. First, participants encoded subliminal pairs of unrelated words in either one or nine encoding trials. Later, they judged the semantic fit of supraliminally presented new words that either retained a previously encoded semantic relation ("analog") or not ("broken analog"). Words in analogs versus broken analogs were judged closer semantically, which indicates unconscious analogy detection. Hippocampal activity associated with subliminal encoding correlated with the behavioral measure of unconscious analogy detection. Analogs versus broken analogs were processed with reduced prefrontal but enhanced medial temporal activity. We conclude that analogous episodes can be detected even unconsciously drawing on the episodic memory network.

Background: In accordance with the Theory of Structural Dissociation of the Personality (TSDP), s... more Background: In accordance with the Theory of Structural Dissociation of the Personality (TSDP), studies of dissociative identity disorder (DID) have documented that two prototypical dissociative subsystems of the personality, the ''Emotional Part'' (EP) and the ''Apparently Normal Part'' (ANP), have different biopsychosocial reactions to supraliminal and subliminal trauma-related cues and that these reactions cannot be mimicked by fantasy prone healthy controls nor by actors.

Pacing and Clinical Electrophysiology, 2002

MRI is established as an important diagnostic tool in medicine. However, the presence of a cardia... more MRI is established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. The aim of this study was to investigate the state of a pacemaker reed switch in different orientations and positions in the main magnetic field of 0.5-, 1.5-, and 3.0-T MRI scanners. Reed switches used in current pacemakers and ICDs were tested in 0.5-, 1.5-, and 3.0-T MRI scanners. The closure of isolated reed switches was evaluated for different orientations and positions relative to the main magnetic field. The field strengths to close and open the reed switch and the orientation dependency of the closed state inside the main magnetic field were investigated. The measurements were repeated using two intact pacemakers to evaluate the potential influence of the other magnetic components, like the battery. If the reed switches were oriented parallel to the magnetic fields, they closed at 1.0 +/- 0.2 mT and opened at 0.7 +/- 0.2 mT. Two different reed switch behaviors were observed at different magnetic field strengths. In low magnetic fields (< 50 mT), the reed switches were closed. However, in high magnetic fields (> 200 mT), the reed switches opened in 50% of all tested orientations. No difference between the three scanners could be demonstrated. The reed switches showed the same behavior whether they were isolated or an integral part of the pacemakers. The reed switch in a pacemaker or an ICD does not necessarily remain closed in strong magnetic fields at 0.5, 1.5, or 3.0 T and the state of the reed switch may not be predictable with certainty in clinical situations.

NMR in Biomedicine, 2012

The aim of this study was to quantitatively assess the field strength dependence of the transvers... more The aim of this study was to quantitatively assess the field strength dependence of the transverse relaxation rate (R(2) *) change in cortical gray matter induced by hyperoxia and hyperoxic hypercapnia versus normoxia in an intra-individual comparison of young healthy volunteers. Medical air (21% O(2) ), pure oxygen and carbogen (95% O(2) , 5% CO(2) ) were alternatively administered in a block-design temporal pattern to induce normoxia, hyperoxia and hyperoxic hypercapnia, respectively. Local R(2) * values were determined from three-dimensional, multiple, radiofrequency-spoiled, fast field echo data acquired at 1.5, 3 and 7 T. Image quality was good at all field strengths. Under normoxia, the mean gray matter R(2) * values were 13.3 ± 2.7 s(-1) (1.5 T), 16.9 ± 0.9 s(-1) (3 T) and 29.0 ± 2.6 s(-1) (7 T). Both hyperoxic gases induced relaxation rate decreases ΔR(2) *, whose magnitudes increased quadratically with the field strength [carbogen: -0.69 ± 0.20 s(-1) (1.5 T), -1.49 ± 0.49 s(-1) (3 T), -5.64 ± 0.67 s(-1) (7 T); oxygen: -0.39 ± 0.20 s(-1) (1.5 T), -0.78 ± 0.48 s(-1) (3 T), -3.86 ± 1.00 s(-1) (7 T)]. Carbogen produced larger R(2) * changes than oxygen at all field strengths. The relative change ΔR(2) */R(2) * also increased with the field strength with a power between 1 and 2 for both carbogen and oxygen. The statistical significance of the R(2) * response improved with increasing B(0) and was higher for carbogen than for oxygen. For a sequence with pure T(2) * weighting of the signal response to respiratory challenge, the results suggested a maximum carbogen-induced signal difference of 19.3% of the baseline signal at 7 T and TE = 38 ms, but a maximum oxygen-induced signal difference of only 3.0% at 1.5 T and TE = 76 ms. For 3 T, maximum signal changes of 4.7% (oxygen) and 8.9% (carbogen) were computed. In conclusion, the R(2) * response to hyperoxic respiratory challenge was stronger for carbogen than for oxygen, and increased quadratically with the static magnetic field strength for both challenges, which highlights the importance of high field strengths for future studies aimed at probing oxygen physiology in clinical settings.

Journal of Clinical Periodontology, 2012

Dentine hypersensitivity (DH) is characterized by a short, sharp pain arising from exposed dentin... more Dentine hypersensitivity (DH) is characterized by a short, sharp pain arising from exposed dentin. Most published literature reports on peripheral neural aspects of this pain condition. The current investigation focused on differential cerebral activity elicited by stimulation of sensitive and insensitive teeth by means of natural air stimuli. Five graded stimulus strengths were randomly applied by means of a multi-injector air jet delivery system, each followed by an individual rating of perceived stimulus intensity. Brain activity was analysed by functional magnetic resonance imaging (fMRI). Stimulation of sensitive teeth induced significant activation in the thalamus, somatosensory cortices (SI & SII), anterior, middle and posterior insular cortices, anterior mid cingulate cortex, perigenual anterior cingulate cortex and frontal regions (BA10 and BA46). Differential responses to DH and painless perceptions were observed in the anterior insula and anterior midcingulate cortex. For the first time, this fMRI study demonstrates the feasibility of investigating cerebral processes related to DH evoked by natural (air) stimuli. Our neuroimaging data additionally provide evidence that differential activity in the anterior Insula (aIC) and anterior midcingulate cortex (aMCC) may represent clinically relevant pain experienced by DH patients.

Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2007

Human Brain Mapping, 2014

Imaging studies have identified a wide network of brain areas activated by nociceptive stimuli an... more Imaging studies have identified a wide network of brain areas activated by nociceptive stimuli and revealed differences in somatotopic representation of highly distinct stimulation sites (foot vs. hand) in the primary (S1) and secondary (S2) somatosensory cortices. Somatotopic organization between adjacent dermatomes and differences in cortical coding of similarly perceived nociceptive stimulation are less well studied. Here, cortical processing following contact heat nociceptive stimulation of cervical (C4, C6, and C8) and trunk (T10) dermatomes were recorded in 20 healthy subjects using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Stimulation of T10 compared with the C6 and C8 revealed significant higher response intensity in the left S1 (contralateral) and the right S2 (ipsilateral) even when the perceived pain was equal between stimulation sites. Accordingly, contact heat evoked potentials following stimulation of T10 showed significantly higher N2P2 amplitudes compared to C6 and C8. Adjacent dermatomes did not reveal a distinct somatotopical representation. Within the assessed cervical and trunk dermatomes, nociceptive cortical processing to heat differs significantly in magnitude even when controlling for pain perception. This study provides evidence that controlling for pain perception is not sufficient to compare directly the magnitude of cortical processing [blood oxygen level dependence (BOLD) response and amplitude of evoked potentials] between body sites. Hum Brain Mapp 00:000-000, 2013. V C 2013 Wiley-Periodicals Inc.

European Heart Journal, 2005

Magnetic resonance imaging (MRI) is well established as an important diagnostic tool in medicine.... more Magnetic resonance imaging (MRI) is well established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. In this study, heating effects at the myocardium-pacemaker lead tip interface have been investigated in a chronic animal model during MRI at 1.5 Tesla. Pacemaker leads with additional thermocouple wires as temperature sensors were implanted in nine animals. Temperature increases of up to 20 degrees C were measured during MRI of the heart. Significant impedance and minor stimulation threshold changes could be seen. However, pathology and histology could not clearly demonstrate heat-induced damage. MRI may produce considerable heating at the lead tip. Changes of pacing parameters due to MRI could be seen in chronic experiments. Potential risk of tissue damage cannot be excluded even though no reproducible alterations at the histological level could be found.

American Heart Journal, 2011

Recent studies suggest that magnetic resonance (MR) imaging of the brain and spine may safely be ... more Recent studies suggest that magnetic resonance (MR) imaging of the brain and spine may safely be performed in patients with pacemakers (PMs) and implantable cardioverter/defibrillators (ICDs), when taking adequate precautions. The aim of this study was to investigate safety, feasibility, and diagnostic value (DV) of MR imaging in cardiac applications (cardiac MR [CMR]) in patients with PMs and ICDs for the first time. Thirty-two PM/ICD patients with a clinical need for CMR were examined. The specific absorption rate was limited to 1.5 W/kg. Devices were reprogrammed pre-CMR to minimize interference with the electromagnetic fields. Devices were interrogated pre-CMR and post-CMR and after 3 months. Troponin I levels were measured pre-CMR and post-CMR; image quality (IQ) and DV of CMR were assessed. All devices could be reprogrammed normally post-CMR. No significant changes of pacing capture threshold, lead impedance, and troponin I were observed. Image quality in patients with right-sided devices (RSD) was better compared with that in patients with left-sided devices (LSD) (P < .05), and less myocardial segments were affected by device-related artefacts (P < .05). Diagnostic value was rated as sufficiently high, allowing for diagnosis, or better in 12 (100%) of 12 patients with RSD, and only in 7 (35%) of 20 patients with LSD. Cardiac MR may be performed safely when limiting specific absorption rate, appropriately monitoring patients, and following device reprogramming. Cardiac MR delivers good IQ and DV in patients with RSD. Cardiac MR in patients with RSD may therefore be performed with an acceptable risk/benefit ratio, whereas the risk/benefit ratio is rather unfavorable in patients with LSD.

Background: Magnetic Resonance Imaging (MRI) of patients with implanted cardiac devices is curren... more Background: Magnetic Resonance Imaging (MRI) of patients with implanted cardiac devices is currently considered hazardous due to potential for electromagnetic interference to the patient and pacemaker system. With approximately 60 million MRI scans performed worldwide per year, an estimated majority of pacemaker patients may develop an indication for an MRI during the lifetime of their pacemakers, suggesting that safe use of pacemakers in the MRI environment would be clinically valuable. A new pacing system (Medtronic EnRhythm MRI™ SureScan™ and CapSureFix MRI™ leads) has been designed and pre-clinically tested for safe use in the MRI environment. The EnRhythm MRI study is designed to confirm the safety and efficacy of this new pacing system.