Arthur Wunderlich | Universität Ulm (original) (raw)
Papers by Arthur Wunderlich
Rofo Fortschr Rontgenstrahl, 2006
Journal of Computer Assisted Tomography, 2001
Conventional postoperative evaluation of patients following carotid thromboendarterectomy (TEA) c... more Conventional postoperative evaluation of patients following carotid thromboendarterectomy (TEA) consists of a clinical neurologic examination to assess neurologic deficits, color duplex ultrasound to document the surgically reestablished patency of the carotid artery, and CT for exclusion of postoperative ischemic infarctions. Recent studies prove that diffusion-weighted MRI is more sensitive in the detection of fresh insults than conventional MRI and CT. The objective of the study was to ascertain the incidence of clinically asymptomatic peri-and postoperative ischemic infarctions visualized at MRI. We included 52 patients in the study. Fifty-one patients (31 men, 20 women; average age 68 years) underwent cranial MR examination including a diffusion-weighted sequence at 24 h prior to carotid TEA and again 24 h following the procedure. One patient did not agree to participate. In 29 of 51 patients (56%), neither the pre-nor the postoperative MR scans showed any diffusion abnormalities. In 16 patients (31%), however, preoperative MRI detected fresh ischemic insults. In nine patients (17.6%), the size of the insult resulted in surgery being postponed for 4 weeks. In six patients (11.8%), postoperative MRI returned findings of fresh disturbances of diffusion suggestive of ischemia that were not visualized on preoperative scans. Discrete neurologic deficits were observed in only two (3.9%) of these patients. Deficits were transient and disappeared within 72 h. Our findings underscore MRI's capacity for visualizing perioperative ischemic events. Moreover, MRI provides evidence of clinically asymptomatic embolisms that occur perioperatively.
Recently, we have reported studies of transport and sorption of heavy metal ions in watersaturate... more Recently, we have reported studies of transport and sorption of heavy metal ions in watersaturated quartz sand columns under relatively fast water flow. In these experiments, clear indications for a fast and strong adsorption of the ions to the sediment could be found. Here we report the findings in a series of other experiments performed under static conditions. In this case, much higher concentrations of ions are adsorbed to the sand and remain immobile over time scales of more than a year. Changes in the MRI contrast observed for the sediment areas with the adsorbed ions indicate rearrangements in the distribution of the ions during the first days after administration to the sediment. EDX-studies of the ion distribution after several days indicate a spatially inhomogeneous distribution of adsorbed ions on the surface of the quartz sand. If the adsorbed ions are subjected to flow, a part of adsorbed ions moves away with the water flow. Also all ions are rapidly accessible to acid leaching.
Auditory verbal hallucinations in schizophrenia may be due to dysfunctional inner speech-related ... more Auditory verbal hallucinations in schizophrenia may be due to dysfunctional inner speech-related cortical areas. Repetitive transcranial magnetic stimulation (rTMS) has been reported to be an effective treatment of hallucinations. In a cross-over sham controlled study, we guided rTMS stereotactically to inner speech-related cortical areas in hallucinating patients. These areas were identified individually prior to rTMS using fMRI in a subgroup of our patients. Active stimulation was applied over Broca's area and over the superior temporal gyrus as determined by fMRI, or according to structural images in the remaining patients. rTMS did not lead to a significant reduction of hallucination severity. Conclusively, rTMS has to be regarded critically as a possible novel tool for the treatment of hallucinations.
Neuroreport, Jun 13, 2001
We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the a... more We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the active condition they steered the car themselves (driving), in the passive condition a person from outside the scanner was steering the car (passive driving). Common activations in both conditions were found in occipital and parietal regions bilaterally. Activity specifically associated with driving was found only in the sensorimotor cortex and the cerebellum. Compared to passive driving, activity during driving was reduced in numerous brain regions including MT/MST. It is concluded that simulated driving requires mainly perceptual-motor integration and that the limited cognitive capacity model of driving has to be revised.
Egs General Assembly Conference Abstracts, 2002
While the transport of heavy metal ions at high concentrations through an aquifer usually occurs ... more While the transport of heavy metal ions at high concentrations through an aquifer usually occurs without notable concentration changes due to sorption, sorption is the dominating phenomenon in the transport of dilute heavy metal solutions in the concen- tration range of 100 µM and below which is typical for many contamination situations. In our work we mapped the distribution of sorptive paramagnetic heavy metal ions in aquifer columns filled with sandy material in images with relaxation time contrast. The relaxation time change is brought about by the increase in the wall relaxivity experienced by the pore water in the aquifer upon adsorption of the paramagnetic ions. The presented study focusses on the sorption of heavy metal ions at the pore walls from a dilute solution, on the propagation of heavy metal ions from a point source with high concentration, and on the remobilization of adsorbed heavy metal ions due to changing hydrochemical conditions. The heavy metal concentrations typically were in the lower mg/L and mg/kg range. Heavy metal species under study up to now were mainly Cr3+ and Gd3+. While the former ion is a relatively common contaminant in many industrial effluents, Gd3+ was mainly studied due to its possible relevance as a model ion for actinoid ions with the same valence and similar chemical properties. The sorption processes of the heavy metal ions could be visualized and quantified in three dimensional images at high temporal and spatial resolution. Once adsorbed, the localization of the heavy metal ions remained rather stable during flushing with water of pH 3.5 or higher. After decreasing the pH-value to 2, the contaminations were remobilized. Neither the small scale propagation nor the remobilization are accessible with con- ventional column tests. It could also be shown that the propagation of the heavy metal ions is strongly influenced by local heterogeneities. Without MRI these effects would not be recognisable.
Rofo Fortschr Rontgenstrahl, 2007
Alcohol flooding has been studied macroscopically as an approach for active remediation of NAPL c... more Alcohol flooding has been studied macroscopically as an approach for active remediation of NAPL contaminations in aquifer sediments in pilot scale and field scale experiments previously. A direct, time-resolved observation of the interaction between the NAPL phase and the alcohol in the sediment has not been reported up to now. In our contribution, we will present results from MRI studies on column setups with dimensions in the 10 cm range. In the MRI experiments, different contrast modes were used to distinguish between water phase and NAPL. The time resolution in the experiments is about 10 s for the acquisition of a 3D image dataset with a voxel volume of ≈ 10 μL, thus enabling the visualization of fast interactions. Using slower imaging protocols, the spatial resolution could be increased to voxel volumes of ≈ 1 μL. As the signal intensity recorded in a voxel is an average value over the whole voxel, even smaller quantities of residual NAPL can be localized in such images. The experiments were carried out in steady state columns filled with sandy material. The alcohol phase was injected below the NAPL contamination. Like that, the alcohol is moving upwards by the density difference between alcohol and water. After contact with the NAPL it takes dissolved NAPL with it to the surface. The observation of a water-rich zone around the NAPL contamination during the passage of the flooding alcohol indicates that the contact zone between NAPL and flooding alcohol is crucial for the efficiency the remediation.
Magnetic Resonance Imaging, 2004
In recent years, a rising number of different table waters supersaturated with oxygen have hit th... more In recent years, a rising number of different table waters supersaturated with oxygen have hit the market with claims of both positive health effects and an increase in athletic performance. A scientific validation of these claims needs additional knowledge on the fate of the oxygen supersaturation in the human digestive tract. Taking advantage of the fact that molecular oxygen is paramagnetic, MRI can be applied to observe the behavior of oxygen-supersaturated water after oral uptake. In this contribution we report results obtained on several healthy volunteers. On the basis of these results we can conclude that oral uptake of oxygen-supersaturated drinking water with a low content in CO 2 leads to a considerable increase in the oxygenation in the lumen of the oral cavity and of the stomach. Comparing the observed contrast changes with those brought about by conventional contrast agents, even the highly oxygen-supersaturated waters still perform rather poorly.
Environmental Science and Technology, Oct 1, 2003
The exploration of the transport and matrix interactions of heavy metal ions in the subsurface en... more The exploration of the transport and matrix interactions of heavy metal ions in the subsurface environment under natural conditions is an important field of research in environmental science and technology. Most commonly, column tests are used for a first assessment of the transport behavior. Classical column tests fall short with regard to the spatial and temporal resolution; however, these detailed data are needed for proper upscaling. Hence, providing spatially and temporally resolved data on the distribution of environmentally relevant concentrations of heavy metal ions in a water-wet aquifer matrix poses a major challenge to analytical chemistry. In this contribution, we present the results of Magnetic Resonance Imaging (MRI) studies in which submilligram quantities of heavy metal ions where either fed conventially through the column or locally injected into saturated sand packings. The subsequent transport and mobilization was monitored at a high spatial and temporal resolution. The results from a local injection show that the test design of column tests has not yet come to an end and that column tests under MRI-control may be used as a model system for, e.g., remediation techniques.
Magnetic Resonance Imaging, Apr 1, 2003
In this contribution, we report results from MRI studies of the propagation of heavy metal ions t... more In this contribution, we report results from MRI studies of the propagation of heavy metal ions through columns packed with sandy aquifer materials. Both sorption of low concentrations of heavy metal ions from water flowing through the column and the formation of sorption traces produced from initially localized higher concentrations of heavy metal ions, and the remobilisation of adsorbed ions with time and changing hydrochemical conditions were studied. Multislice spin-echo and FLASH techniques were used for the imaging experiments. Advantages and problems of the different imaging protocols for the study of aquifer materials are discussed.
Schizophrenia Research, 2003
Hypofrontality and decreased lateralization have been two major, albeit controversial, results fr... more Hypofrontality and decreased lateralization have been two major, albeit controversial, results from functional neuroimaging studies of schizophrenia. We used fMRI to study cortical activation during a verbal and spatial working memory (WM) task (2-back) in 15 inpatients acutely ill with schizophrenia and 15 matched control subjects. We hypothesized (i) hypofrontality in patients in both tasks and (ii) decreased lateralization of prefrontal activation in patients under the assumption that, in controls, left prefrontal cortex (PFC) is engaged preferentially in the verbal task (verbal domain dominance) and the right prefrontal cortex is engaged preferentially in the spatial task (spatial domain dominance). Our results showed no significant differences in frontal activation between controls and patients, i.e. no hypofrontality in patients, even at a very liberal threshold (p<0.01). This may be explained by the fact that nearly all patients studied received atypical neuroleptics. Nonetheless, we found evidence for more subtle, domain-related prefrontal dysfunction. Whereas controls showed verbal WM domain dominance in left inferior frontal cortex and spatial WM domain dominance in right prefrontal cortex, these domain dominance effects were absent in the patient group, i.e. there were no lateralization effects. Finally, only patients showed an inverse correlation between performance and right prefrontal activation in verbal WM. We conclude that the finding of hypofrontality may depend on the medication of the patients and that there is prefrontal dysfunction even in the absence of hypofrontality.
NeuroImage, 2003
Emotions have been shown to modulate memory processes. However, the neuronal substrate underlying... more Emotions have been shown to modulate memory processes. However, the neuronal substrate underlying these modulatory effects is largely unknown. Using event-related functional magnetic resonance imaging (fMRI), we investigated whether the context of emotional encoding modulates brain activation predictive for subsequent recall of emotionally neutral material. While inferior frontal activation predicted recall in general, our data show that in a positive encoding context, recall was predicted by activation of right anterior parahippocampal and extrastriate visual brain areas, whereas in a negative encoding context, recall was predicted by activation of the amygdala. Thus, we could demonstrate that successful episodic encoding is differentially modulated by emotional context. These results contribute to the understanding of the interaction of emotion and cognition and moreover are of general relevance for studies of episodic memory.
Neuroreport, 2001
We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the a... more We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the active condition they steered the car themselves (driving), in the passive condition a person from outside the scanner was steering the car (passive driving). Common activations in both conditions were found in occipital and parietal regions bilaterally. Activity specifically associated with driving was found only in the sensorimotor cortex and the cerebellum. Compared to passive driving, activity during driving was reduced in numerous brain regions including MT/MST. It is concluded that simulated driving requires mainly perceptual-motor integration and that the limited cognitive capacity model of driving has to be revised.
RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2012
Liver iron content (LIC) measurement plays a central role in the management of patients with tran... more Liver iron content (LIC) measurement plays a central role in the management of patients with transfusional iron overload. Calculating the LIC with data obtained from standardized MRI sequences represents an attractive alternative diagnostic possibility. The purpose of this study was to compare the LIC measurement obtained with gradient-echo (GRE) sequences to the mean liver proton transverse relaxation (R2) acquired with SE sequences. 68 patients with iron overload (median age: 24, range: 3-88) underwent 1.5 T MRI for liver iron content measurement. All patients received spin-echo (SE) and gradient-echo (GRE) sequences. The two MRI methods revealed different liver iron content results although a significant correlation was found (r=0.85, p<0.001). Values evaluated using GRE sequences (median: 260 μmol/g dry weight [d. w.], range: 6-732) were generally higher than those obtained by SE examinations (median: 161 μmol /g d. w., range: 5-830). In conclusion, our study revealed different results for both MRI measurements, which could lead to different decisions concerning the management of chelation therapy in individual patients.
NeuroReport, 2002
Using event-related fMRI we investigated the rewarding properties of cultural objects (cars) sign... more Using event-related fMRI we investigated the rewarding properties of cultural objects (cars) signaling wealth and social dominance. It has been shown recently that reward mechanisms are involved in the regulation of social relations like dominance and social rank. Based on evolutionary considerations we hypothesized that sports cars in contrast to other categories of cars, e.g. limousines and small cars, are strong social reinforcers and would modulate the dopaminergic reward circuitry. Twelve healthy male subjects were studied with fMRI while viewing photographs of di¡erent car classes followed by an attractivity rating. Behaviorally sports cars were rated signi¢cantly more attractive than limousines and small cars.Our fMRI results revealed signi¢cantly more activation in ventral striatum, orbitofrontal cortex, anterior cingulate and occipital regions for sports cars in contrast to other categories of cars.We could thus demonstrate that arti¢cial cultural objects associated with wealth and social dominance elicit activation in reward-related brain areas. NeuroReport 13:2499^2503
Neuropharmacology, 2001
In a randomised double-blind trial the subjective, neuropsychological and brain activation effect... more In a randomised double-blind trial the subjective, neuropsychological and brain activation effects of the two enantiomers of the MDMA (ecstasy-) like drug N-ethyl-3,4-methylenedioxyamphetamine (MDE) were studied in five normal subjects using functional magnetic resonance imaging (fMRI). (S)-MDE produced elevated mood, impairments in conceptually driven cognition and marked right frontal activation. In contrast, (R)-MDE produced increased depression, enhanced visual feature processing, and activation of visual cortical and left frontal areas. Plasma concentrations were higher for the (R)-enantiomer. The so-called entactogenic effects of MDE are likely to be caused by the (S)-enantiomer, whereas (R)-MDE appears to be responsible for neurotoxic effects.
Rofo Fortschr Rontgenstrahl, 2006
Journal of Computer Assisted Tomography, 2001
Conventional postoperative evaluation of patients following carotid thromboendarterectomy (TEA) c... more Conventional postoperative evaluation of patients following carotid thromboendarterectomy (TEA) consists of a clinical neurologic examination to assess neurologic deficits, color duplex ultrasound to document the surgically reestablished patency of the carotid artery, and CT for exclusion of postoperative ischemic infarctions. Recent studies prove that diffusion-weighted MRI is more sensitive in the detection of fresh insults than conventional MRI and CT. The objective of the study was to ascertain the incidence of clinically asymptomatic peri-and postoperative ischemic infarctions visualized at MRI. We included 52 patients in the study. Fifty-one patients (31 men, 20 women; average age 68 years) underwent cranial MR examination including a diffusion-weighted sequence at 24 h prior to carotid TEA and again 24 h following the procedure. One patient did not agree to participate. In 29 of 51 patients (56%), neither the pre-nor the postoperative MR scans showed any diffusion abnormalities. In 16 patients (31%), however, preoperative MRI detected fresh ischemic insults. In nine patients (17.6%), the size of the insult resulted in surgery being postponed for 4 weeks. In six patients (11.8%), postoperative MRI returned findings of fresh disturbances of diffusion suggestive of ischemia that were not visualized on preoperative scans. Discrete neurologic deficits were observed in only two (3.9%) of these patients. Deficits were transient and disappeared within 72 h. Our findings underscore MRI's capacity for visualizing perioperative ischemic events. Moreover, MRI provides evidence of clinically asymptomatic embolisms that occur perioperatively.
Recently, we have reported studies of transport and sorption of heavy metal ions in watersaturate... more Recently, we have reported studies of transport and sorption of heavy metal ions in watersaturated quartz sand columns under relatively fast water flow. In these experiments, clear indications for a fast and strong adsorption of the ions to the sediment could be found. Here we report the findings in a series of other experiments performed under static conditions. In this case, much higher concentrations of ions are adsorbed to the sand and remain immobile over time scales of more than a year. Changes in the MRI contrast observed for the sediment areas with the adsorbed ions indicate rearrangements in the distribution of the ions during the first days after administration to the sediment. EDX-studies of the ion distribution after several days indicate a spatially inhomogeneous distribution of adsorbed ions on the surface of the quartz sand. If the adsorbed ions are subjected to flow, a part of adsorbed ions moves away with the water flow. Also all ions are rapidly accessible to acid leaching.
Auditory verbal hallucinations in schizophrenia may be due to dysfunctional inner speech-related ... more Auditory verbal hallucinations in schizophrenia may be due to dysfunctional inner speech-related cortical areas. Repetitive transcranial magnetic stimulation (rTMS) has been reported to be an effective treatment of hallucinations. In a cross-over sham controlled study, we guided rTMS stereotactically to inner speech-related cortical areas in hallucinating patients. These areas were identified individually prior to rTMS using fMRI in a subgroup of our patients. Active stimulation was applied over Broca&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s area and over the superior temporal gyrus as determined by fMRI, or according to structural images in the remaining patients. rTMS did not lead to a significant reduction of hallucination severity. Conclusively, rTMS has to be regarded critically as a possible novel tool for the treatment of hallucinations.
Neuroreport, Jun 13, 2001
We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the a... more We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the active condition they steered the car themselves (driving), in the passive condition a person from outside the scanner was steering the car (passive driving). Common activations in both conditions were found in occipital and parietal regions bilaterally. Activity specifically associated with driving was found only in the sensorimotor cortex and the cerebellum. Compared to passive driving, activity during driving was reduced in numerous brain regions including MT/MST. It is concluded that simulated driving requires mainly perceptual-motor integration and that the limited cognitive capacity model of driving has to be revised.
Egs General Assembly Conference Abstracts, 2002
While the transport of heavy metal ions at high concentrations through an aquifer usually occurs ... more While the transport of heavy metal ions at high concentrations through an aquifer usually occurs without notable concentration changes due to sorption, sorption is the dominating phenomenon in the transport of dilute heavy metal solutions in the concen- tration range of 100 µM and below which is typical for many contamination situations. In our work we mapped the distribution of sorptive paramagnetic heavy metal ions in aquifer columns filled with sandy material in images with relaxation time contrast. The relaxation time change is brought about by the increase in the wall relaxivity experienced by the pore water in the aquifer upon adsorption of the paramagnetic ions. The presented study focusses on the sorption of heavy metal ions at the pore walls from a dilute solution, on the propagation of heavy metal ions from a point source with high concentration, and on the remobilization of adsorbed heavy metal ions due to changing hydrochemical conditions. The heavy metal concentrations typically were in the lower mg/L and mg/kg range. Heavy metal species under study up to now were mainly Cr3+ and Gd3+. While the former ion is a relatively common contaminant in many industrial effluents, Gd3+ was mainly studied due to its possible relevance as a model ion for actinoid ions with the same valence and similar chemical properties. The sorption processes of the heavy metal ions could be visualized and quantified in three dimensional images at high temporal and spatial resolution. Once adsorbed, the localization of the heavy metal ions remained rather stable during flushing with water of pH 3.5 or higher. After decreasing the pH-value to 2, the contaminations were remobilized. Neither the small scale propagation nor the remobilization are accessible with con- ventional column tests. It could also be shown that the propagation of the heavy metal ions is strongly influenced by local heterogeneities. Without MRI these effects would not be recognisable.
Rofo Fortschr Rontgenstrahl, 2007
Alcohol flooding has been studied macroscopically as an approach for active remediation of NAPL c... more Alcohol flooding has been studied macroscopically as an approach for active remediation of NAPL contaminations in aquifer sediments in pilot scale and field scale experiments previously. A direct, time-resolved observation of the interaction between the NAPL phase and the alcohol in the sediment has not been reported up to now. In our contribution, we will present results from MRI studies on column setups with dimensions in the 10 cm range. In the MRI experiments, different contrast modes were used to distinguish between water phase and NAPL. The time resolution in the experiments is about 10 s for the acquisition of a 3D image dataset with a voxel volume of ≈ 10 μL, thus enabling the visualization of fast interactions. Using slower imaging protocols, the spatial resolution could be increased to voxel volumes of ≈ 1 μL. As the signal intensity recorded in a voxel is an average value over the whole voxel, even smaller quantities of residual NAPL can be localized in such images. The experiments were carried out in steady state columns filled with sandy material. The alcohol phase was injected below the NAPL contamination. Like that, the alcohol is moving upwards by the density difference between alcohol and water. After contact with the NAPL it takes dissolved NAPL with it to the surface. The observation of a water-rich zone around the NAPL contamination during the passage of the flooding alcohol indicates that the contact zone between NAPL and flooding alcohol is crucial for the efficiency the remediation.
Magnetic Resonance Imaging, 2004
In recent years, a rising number of different table waters supersaturated with oxygen have hit th... more In recent years, a rising number of different table waters supersaturated with oxygen have hit the market with claims of both positive health effects and an increase in athletic performance. A scientific validation of these claims needs additional knowledge on the fate of the oxygen supersaturation in the human digestive tract. Taking advantage of the fact that molecular oxygen is paramagnetic, MRI can be applied to observe the behavior of oxygen-supersaturated water after oral uptake. In this contribution we report results obtained on several healthy volunteers. On the basis of these results we can conclude that oral uptake of oxygen-supersaturated drinking water with a low content in CO 2 leads to a considerable increase in the oxygenation in the lumen of the oral cavity and of the stomach. Comparing the observed contrast changes with those brought about by conventional contrast agents, even the highly oxygen-supersaturated waters still perform rather poorly.
Environmental Science and Technology, Oct 1, 2003
The exploration of the transport and matrix interactions of heavy metal ions in the subsurface en... more The exploration of the transport and matrix interactions of heavy metal ions in the subsurface environment under natural conditions is an important field of research in environmental science and technology. Most commonly, column tests are used for a first assessment of the transport behavior. Classical column tests fall short with regard to the spatial and temporal resolution; however, these detailed data are needed for proper upscaling. Hence, providing spatially and temporally resolved data on the distribution of environmentally relevant concentrations of heavy metal ions in a water-wet aquifer matrix poses a major challenge to analytical chemistry. In this contribution, we present the results of Magnetic Resonance Imaging (MRI) studies in which submilligram quantities of heavy metal ions where either fed conventially through the column or locally injected into saturated sand packings. The subsequent transport and mobilization was monitored at a high spatial and temporal resolution. The results from a local injection show that the test design of column tests has not yet come to an end and that column tests under MRI-control may be used as a model system for, e.g., remediation techniques.
Magnetic Resonance Imaging, Apr 1, 2003
In this contribution, we report results from MRI studies of the propagation of heavy metal ions t... more In this contribution, we report results from MRI studies of the propagation of heavy metal ions through columns packed with sandy aquifer materials. Both sorption of low concentrations of heavy metal ions from water flowing through the column and the formation of sorption traces produced from initially localized higher concentrations of heavy metal ions, and the remobilisation of adsorbed ions with time and changing hydrochemical conditions were studied. Multislice spin-echo and FLASH techniques were used for the imaging experiments. Advantages and problems of the different imaging protocols for the study of aquifer materials are discussed.
Schizophrenia Research, 2003
Hypofrontality and decreased lateralization have been two major, albeit controversial, results fr... more Hypofrontality and decreased lateralization have been two major, albeit controversial, results from functional neuroimaging studies of schizophrenia. We used fMRI to study cortical activation during a verbal and spatial working memory (WM) task (2-back) in 15 inpatients acutely ill with schizophrenia and 15 matched control subjects. We hypothesized (i) hypofrontality in patients in both tasks and (ii) decreased lateralization of prefrontal activation in patients under the assumption that, in controls, left prefrontal cortex (PFC) is engaged preferentially in the verbal task (verbal domain dominance) and the right prefrontal cortex is engaged preferentially in the spatial task (spatial domain dominance). Our results showed no significant differences in frontal activation between controls and patients, i.e. no hypofrontality in patients, even at a very liberal threshold (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01). This may be explained by the fact that nearly all patients studied received atypical neuroleptics. Nonetheless, we found evidence for more subtle, domain-related prefrontal dysfunction. Whereas controls showed verbal WM domain dominance in left inferior frontal cortex and spatial WM domain dominance in right prefrontal cortex, these domain dominance effects were absent in the patient group, i.e. there were no lateralization effects. Finally, only patients showed an inverse correlation between performance and right prefrontal activation in verbal WM. We conclude that the finding of hypofrontality may depend on the medication of the patients and that there is prefrontal dysfunction even in the absence of hypofrontality.
NeuroImage, 2003
Emotions have been shown to modulate memory processes. However, the neuronal substrate underlying... more Emotions have been shown to modulate memory processes. However, the neuronal substrate underlying these modulatory effects is largely unknown. Using event-related functional magnetic resonance imaging (fMRI), we investigated whether the context of emotional encoding modulates brain activation predictive for subsequent recall of emotionally neutral material. While inferior frontal activation predicted recall in general, our data show that in a positive encoding context, recall was predicted by activation of right anterior parahippocampal and extrastriate visual brain areas, whereas in a negative encoding context, recall was predicted by activation of the amygdala. Thus, we could demonstrate that successful episodic encoding is differentially modulated by emotional context. These results contribute to the understanding of the interaction of emotion and cognition and moreover are of general relevance for studies of episodic memory.
Neuroreport, 2001
We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the a... more We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the active condition they steered the car themselves (driving), in the passive condition a person from outside the scanner was steering the car (passive driving). Common activations in both conditions were found in occipital and parietal regions bilaterally. Activity specifically associated with driving was found only in the sensorimotor cortex and the cerebellum. Compared to passive driving, activity during driving was reduced in numerous brain regions including MT/MST. It is concluded that simulated driving requires mainly perceptual-motor integration and that the limited cognitive capacity model of driving has to be revised.
RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2012
Liver iron content (LIC) measurement plays a central role in the management of patients with tran... more Liver iron content (LIC) measurement plays a central role in the management of patients with transfusional iron overload. Calculating the LIC with data obtained from standardized MRI sequences represents an attractive alternative diagnostic possibility. The purpose of this study was to compare the LIC measurement obtained with gradient-echo (GRE) sequences to the mean liver proton transverse relaxation (R2) acquired with SE sequences. 68 patients with iron overload (median age: 24, range: 3-88) underwent 1.5 T MRI for liver iron content measurement. All patients received spin-echo (SE) and gradient-echo (GRE) sequences. The two MRI methods revealed different liver iron content results although a significant correlation was found (r=0.85, p<0.001). Values evaluated using GRE sequences (median: 260 μmol/g dry weight [d. w.], range: 6-732) were generally higher than those obtained by SE examinations (median: 161 μmol /g d. w., range: 5-830). In conclusion, our study revealed different results for both MRI measurements, which could lead to different decisions concerning the management of chelation therapy in individual patients.
NeuroReport, 2002
Using event-related fMRI we investigated the rewarding properties of cultural objects (cars) sign... more Using event-related fMRI we investigated the rewarding properties of cultural objects (cars) signaling wealth and social dominance. It has been shown recently that reward mechanisms are involved in the regulation of social relations like dominance and social rank. Based on evolutionary considerations we hypothesized that sports cars in contrast to other categories of cars, e.g. limousines and small cars, are strong social reinforcers and would modulate the dopaminergic reward circuitry. Twelve healthy male subjects were studied with fMRI while viewing photographs of di¡erent car classes followed by an attractivity rating. Behaviorally sports cars were rated signi¢cantly more attractive than limousines and small cars.Our fMRI results revealed signi¢cantly more activation in ventral striatum, orbitofrontal cortex, anterior cingulate and occipital regions for sports cars in contrast to other categories of cars.We could thus demonstrate that arti¢cial cultural objects associated with wealth and social dominance elicit activation in reward-related brain areas. NeuroReport 13:2499^2503
Neuropharmacology, 2001
In a randomised double-blind trial the subjective, neuropsychological and brain activation effect... more In a randomised double-blind trial the subjective, neuropsychological and brain activation effects of the two enantiomers of the MDMA (ecstasy-) like drug N-ethyl-3,4-methylenedioxyamphetamine (MDE) were studied in five normal subjects using functional magnetic resonance imaging (fMRI). (S)-MDE produced elevated mood, impairments in conceptually driven cognition and marked right frontal activation. In contrast, (R)-MDE produced increased depression, enhanced visual feature processing, and activation of visual cortical and left frontal areas. Plasma concentrations were higher for the (R)-enantiomer. The so-called entactogenic effects of MDE are likely to be caused by the (S)-enantiomer, whereas (R)-MDE appears to be responsible for neurotoxic effects.