Hans-Wilhelm Müller-Gärtner

Neurophysiological correlates of the recognition of facial expressions of emotion as revealed by magnetoencephalography

MEG correlates of the recognition of facial expressions of emotion were studied in four healthy volunteers. Subjects performed a facial emotion recognition task and a control task involving recognition of complex objects including faces. Facial emotion recognition activated inferior frontal cortex, amygdala and different parts of temporal cortex in a relatively consistent time sequence. The characteristics of these activations were clearly different from those recorded during the control task. Most interesting was the fact that faces evoked different MEG responses as a function of task demands, i.e., the activations recorded during facial emotion recognition were different from those recorded during simple face recognition in the control task. These findings support the assumption that MEG is able to specifically identify the activation pattern of the brain when recognition of the emotional expression of a face is performed.

Intensity coding of auditory stimuli: an fMRI study

The effect of stimulus intensity (sound pressure level, SPL) of auditory stimuli on the BOLD response in the auditory cortex was investigated in 14 young and healthy subjects, with no hearing abnormalities, using echo-planar, functional magnetic resonance imaging (fMRI) during a verbal and a non-verbal auditory discrimination task. The stimuli were presented block-wise at three different intensities: 95, 85 and 75 dB (SPL). All subjects showed fMRI signal increases in superior temporal gyrus (STG) covering primary and secondary auditory cortex. Most importantly, the spatial extent of the fMRI response in STG increased with increasing stimulus intensity. It is hypothesized that spreading of excitation is associated with the encoding of increasing stimulus intensity levels. In addition, we found bifrontal activation supposedly evoked by the auditory-articulary loop of working memory. The results presented here should assist in the design of optimal activation strategies for studying the auditory cortex with fMRI paradigms and may help in understanding intensity coding of auditory stimuli.

Differential magnetic resonance signal change in human sensorimotor cortex to finger movements of different rate of the dominant and subdominant hand

Functional magnetic resonance tomography (fMRI) analysis of unimanual and bimanual sequential movements in righthanders showed the following effects. First, a rate-dependent activation of the somato-motor cortex was confirmed, with faster movement rates producing higher activation both in terms of signal intensity and number of activated voxels. Second, the right hemisphere showed more activation than the left hemisphere during unimanual tasks. Third, during bimanual movements, the left hemisphere showed greater activation than the right hemisphere. Finally, while the left hemisphere showed a marked change in activation patterns from unimanual to bimanual task, the right hemisphere activation patterns were not sensitive to task changes. The hemispheric asymmetries suggest substantial left hemisphere involvement in the coordination of bimanual tasks.

Functional Imaging of Conditioned Aversive Emotional Responses in Antisocial Personality Disorder

Individuals with antisocial personality disorder (n = 12) and healthy controls (n = 12) were examined for cerebral regional activation involved in the processing of negative affect. A differential aversive classical conditioning paradigm was applied with odors as unconditioned stimuli and faces as conditioned stimuli. Functional magnetic resonance imaging (fMRI) based on echo-planar imaging was used while cerebral activity was studied during habituation, acquisition, and extinction. Individually defined cerebral regions were analyzed. Both groups indicated behavioral conditioning following subjective ratings of emotional valence to conditioned stimuli. Differential effects were found during acquisition in the amygdala and dorsolateral prefrontal cortex. Controls showed signal decreases, patients signal increases. These preliminary results revealed unexpected signal increases in cortical/subcortical areas of patients. The increases may result from an additional effort put in by these individuals to form negative emotional associations, a pattern of processing that may correspond to their characteristic deviant emotional behavior.

Modulation of the neuronal circuitry subserving working memory in healthy human subjects by repetitive transcranial magnetic stimulation

We studied the effect of repetitive transcranial magnetic stimulation (rTMS) on changes in regional cerebral blood flow (rCBF) as revealed by positron emission tomography (PET) while subjects performed a 2-back verbal working memory (WM) task. rTMS to the right or left dorsolateral prefrontal cortex (DLPFC), but not to the midline frontal cortex, significantly worsened performance in the WM task while inducing significant reductions in rCBF at the stimulation site and in distant brain regions. These results for the first time demonstrate the ability of rTMS to produce temporary functional lesions in elements of a neuronal network thus changing its distributed activations and resulting in behavioral consequences.

Dopamine D2 receptor binding before and after treatment of major depression measured by [123I]IBZM SPECT

Fifteen patients fulfilling DSM-IV criteria for major depression were investigated with the specific dopamine D2 receptor antagonist [123I]iodobenzamide (IBZM). Two single photon emission computed tomography (SPECT) examinations were performed before and after 6 weeks of treatment with a selective serotonin re-uptake inhibitor (SSRI). Striatal D2 receptor binding was calculated and normalized to the cerebellum. In a non-psychiatric control group (n = 17), which was investigated once with [123I]IBZM and SPECT, striatal IBZM binding decreased significantly with age (0.092 per decade). The age-dependent correlation was lower in subjects with major depression and did not reach statistical significance. There was no significant difference in mean IBZM binding between depressives and control subjects. Age-corrected baseline IBZM binding in the striatum was significantly lower in treatment responders than in depressed non-responders and control subjects. Furthermore, in the depressive group there was a significant linear correlation between treatment response and change of D2 receptor binding during treatment in the basal ganglia. IBZM binding increased in treatment responders and decreased in non-responders. In accordance with animal studies, the results suggest an association between changes in the dopaminergic system and treatment response in major depression.

Staging of Pelvic Lymph Nodes in Neoplasms of the Bladder and Prostate by Positron Emission Tomography with 2-[18F]-2-Deoxy-D-Glucose

Objectives: The aim of this study was to evaluate whether pelvic lymph node metastases in patients with neoplasms of the bladder or prostate can be detected applying positron emission tomography with 2-[18F]-2-deoxy-D-glucose (FDG-PET). Methods: Eight patients with bladder cancer and 17 patients with prostate cancer were examined with FDG–PET before pelvic lymph node dissection. Results of PET were then compared to histology of pelvic lymph nodes obtained at surgery. Results: Lymph node metastases were detected by histopathological examination in 3 patients with bladder cancer and in 6 patients with prostate cancer. At the sites with histologically proven metastases, increased FDG uptake suspicious of metastatic disease was found in 2/3 and 4/6 patients, respectively. The smallest detected metastasis was a micrometastasis with a diameter of 0.9 cm. In 3 additional patients who all had histopathologically proven micrometastases (∅ ≤0.5 cm), FDG uptake was within the normal range. No false-positive results were obtained. Conclusions: These results suggest that FDG-PET may be a valuable diagnostic tool in the staging of pelvic lymph nodes in bladder and prostate cancer.

In VivoEvidence for the Involvement of Dopamine-D2Receptors in Striatum and Anterior Cingulate Gyrus in Major Depression

The dopaminergic system is a candidate neurotransmitter system thought to be involved in the pathogenesis of depression. This study addresses the issue whether the antidepressant efficacy of serotonin reuptake inhibition is related to changes in the cerebral dopaminergic system. Cerebral dopamine-D2 receptors were characterized in 13 patients with major depression using the dopamine-D2 receptor antagonist iodobenzamide and single photon emission tomography. Dopamine receptor binding was assessed twice, before and during serotonin reuptake inhibition. An increase in dopamine-D2 receptor binding during serotonin reuptake inhibition was found in striatum and anterior cingulate gyrus in treatment responders, but not in nonresponders. The increase in dopamine-D2 receptor binding correlated significantly with clinical recovery from depression as assessed with the Hamilton depression scale (r = 0.59 for right and left striatum respectively, P < 0.05; r = 0.79 for the anterior cingulate gyrus, P < 0.05 after Bonferroni correction). Qualitatively similar correlations were observed in the precentral gyrus, the medial frontal gyrus, the inferior frontal gyrus, and the frontal part of the opercular gyrus, but these correlations failed to reach statistical significance after correction for the effects of multiple testing. No such correlations were found in the superior frontal gyrus, the orbitofrontal gyrus, the gyrus rectus, the superior parietal gyrus, or the superior temporal gyrus. The data strengthen the concept that the striatum and the anterior cingulate gyrus are involved in mood regulation. Dopamine-D2 receptors may constitute a central role in this domain.

Topographic segregation and convergence of verbal, object, shape and spatial working memory in humans

This functional magnetic resonance imaging study investigates commonalties and differences in working memory (WM) processes employing different types of stimuli. We specifically sought to characterize topographic convergence and segregation with respect to prefrontal cortex involvement using verbal, spatial, real object and shape memory items in a two-back WM task. Both the dorsolateral and ventrolateral prefrontal cortices are conjointly activated across all stimulus types. No stimulus-specific differences in the activation patterns of the prefrontal cortex could be demonstrated giving support to the view of an amodal prefrontal involvement during WM processes. However, extra-frontal regions specialized on feature processing and involved in the preprocessing of the stimuli were selectively activated by these different subtypes of WM. These selectively activated regions are assigned to parts of the ventral and dorsal stream.

Network analysis in episodic encoding and retrieval of word-pair associates: a PET study.

The involvement of distributed brain regions in declarative memory has been hypothesized based on studies with verbal memory tasks. To characterize episodic declarative memory function further, 14 right‐handed volunteers performed a visual verbal learning task using paired word associates. The volunteers underwent positron emission tomography. 15O‐butanol was used as a tracer of regional cerebral blood flow (rCBF). Inter‐regional functional interactions were assessed based on within‐task, across‐subject inter‐regional rCBF correlations. Anatomical connections between brain areas were based on known anatomy. Structural equation modelling was used to calculate the path coefficients representing the magnitudes of the functional influences of each area on the ones to which it is connected by anatomical pathways. The encoding and the retrieval network elicit similarities in a general manner but also differences. Strong functional linkages involving visual integration areas, parahippocampal regions, left precuneus and cingulate gyrus were found in both encoding and retrieval; the functional linkages between posterior regions and prefrontal regions were more closely linked during encoding, whereas functional linkages between the left parahippocampal region and posterior cingulate as well as extrastriate areas and posterior cingulate gyrus were stronger during retrieval. In conclusion, these findings support the idea of a global bihemispheric, asymmetric encoding/retrieval network subserving episodic declarative memory. Our results further underline the role of the precuneus in episodic memory, not only during retrieval but also during encoding.