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M Erb

Publications and source records attributed to M Erb.

At least 19 recordsLinked to original sources
PubMed2006

Developing somatosensory projections bypass periventricular brain lesions.

The authors studied four hemiparetic patients with large unilateral periventricular brain lesions acquired during the early third trimester of pregnancy. fMRI and magnetoencephalography demonstrated that the primary somatosensory representation of their paretic hands was nevertheless located in the contralateral rolandic cortex. Thus, outgrowing thalamocortical somatosensory projections had apparently bypassed the lesion to reach their original cortical destination. Such somatosensory projections curving around the lesion were effectively visualized by magnetic resonance diffusion tractography.

Adult↗
PubMed2006

Differential cerebral activation during observation of expressive gestures and motor acts.

We compared brain activation involved in the observation of isolated right hand movements (e.g. twisting a lid), body-referred movements (e.g. brushing teeth) and expressive gestures (e.g. threatening) in 20 healthy subjects by using functional magnetic resonance imaging (fMRI). Perception-related areas in the occipital and inferior temporal lobe but also the mirror neuron system in the lateral frontal (ventral premotor cortex and BA 44) and superior parietal lobe were active during all three conditions. Observation of body-referred compared to common hand actions induced increased activity in the bilateral posterior superior temporal sulcus (STS), the left temporo-parietal lobe and left BA 45. Expressive gestures involved additional areas related to social perception (bilateral STS, temporal poles, medial prefrontal lobe), emotional processing (bilateral amygdala, bilateral ventrolateral prefrontal cortex (VLPFC), speech and language processing (Broca's and Wernicke's areas) and the pre-supplementary motor area (pre-SMA). In comparison to body-referred actions, expressive gestures evoked additional activity only in the left VLPFC (BA 47). The valence-ratings for expressive gestures correlated significantly with activation intensity in the VLPFC during expressive gesture observation. Valence-ratings for negative expressive gestures correlated with right STS-activity. Our data suggest that both, the VLPFC and the STS are coding for differential emotional valence during the observation of expressive gestures.

Adult↗
PubMed2006

Humor and smiling: cortical regions selective for cognitive, affective, and volitional components.

BACKGROUND: The interrelationships among humor, smiling, and grinning have fascinated philosophers for millennia and neurologists for over a century. A functional dissociation between emotional facial expressions and those under voluntary control was suggested decades ago. Recent functional imaging studies, however, have been somewhat at odds with older studies with respect to the role of the right frontal cortex in the perception of humor. METHODS: Blood oxygen level-dependent (BOLD) activity was measured in 13 subjects during the presentation of "funny" vs "nonfunny" versions of essentially the same cartoons and compared with BOLD activity associated with "merely grinning" at similar nonfunny cartoons via fMRI. RESULTS: Humor perception was correlated with BOLD activity in the left temporo-occipitoparietal junction and left prefrontal cortex and humor-associated smiling (recorded with an MR-compatible video camera) with bilateral activity in the basal temporal lobes. Unexpectedly, both conditions were also accompanied by a decrease in BOLD activity in the right orbitofrontal cortex. Voluntary "grinning" in the absence of humorous stimuli was accompanied by bilateral activity in the facial motor regions. CONCLUSIONS: These results confirm the clinically derived hypothesis of separate cortical regions responsible for the production of emotionally driven vs voluntary facial expressions. The right orbitofrontal decrease reconciles inconsistencies between clinical and functional imaging findings and may reflect a disinhibition of facial emotional expression.

Adolescent↗
PubMed2005

fMRI reveals two distinct cerebral networks subserving speech motor control.

BACKGROUND: There are few data on the cerebral organization of motor aspects of speech production and the pathomechanisms of dysarthric deficits subsequent to brain lesions and diseases. The authors used fMRI to further examine the neural basis of speech motor control. METHODS AND RESULTS: In eight healthy volunteers, fMRI was performed during syllable repetitions synchronized to click trains (2 to 6 Hz; vs a passive listening task). Bilateral hemodynamic responses emerged at the level of the mesiofrontal and sensorimotor cortex, putamen/pallidum, thalamus, and cerebellum (two distinct activation spots at either side). In contrast, dorsolateral premotor cortex and anterior insula showed left-sided activation. Calculation of rate/response functions revealed a negative linear relationship between repetition frequency and blood oxygen level-dependent (BOLD) signal change within the striatum, whereas both cerebellar hemispheres exhibited a step-wise increase of activation at approximately 3 Hz. Analysis of the temporal dynamics of the BOLD effect found the various cortical and subcortical brain regions engaged in speech motor control to be organized into two separate networks (medial and dorsolateral premotor cortex, anterior insula, and superior cerebellum vs sensorimotor cortex, basal ganglia, and inferior cerebellum). CONCLUSION: These data provide evidence for two levels of speech motor control bound, most presumably, to motor preparation and execution processes. They also help to explain clinical observations such as an unimpaired or even accelerated speaking rate in Parkinson disease and slowed speech tempo, which does not fall below a rate of 3 Hz, in cerebellar disorders.

Adolescent↗
PubMed2004

Identification of emotional intonation evaluated by fMRI.

During acoustic communication among human beings, emotional information can be expressed both by the propositional content of verbal utterances and by the modulation of speech melody (affective prosody). It is well established that linguistic processing is bound predominantly to the left hemisphere of the brain. By contrast, the encoding of emotional intonation has been assumed to depend specifically upon right-sided cerebral structures. However, prior clinical and functional imaging studies yielded discrepant data with respect to interhemispheric lateralization and intrahemispheric localization of brain regions contributing to processing of affective prosody. In order to delineate the cerebral network engaged in the perception of emotional tone, functional magnetic resonance imaging (fMRI) was performed during recognition of prosodic expressions of five different basic emotions (happy, sad, angry, fearful, and disgusted) and during phonetic monitoring of the same stimuli. As compared to baseline at rest, both tasks yielded widespread bilateral hemodynamic responses within frontal, temporal, and parietal areas, the thalamus, and the cerebellum. A comparison of the respective activation maps, however, revealed comprehension of affective prosody to be bound to a distinct right-hemisphere pattern of activation, encompassing posterior superior temporal sulcus (Brodmann Area [BA] 22), dorsolateral (BA 44/45), and orbitobasal (BA 47) frontal areas. Activation within left-sided speech areas, in contrast, was observed during the phonetic task. These findings indicate that partially distinct cerebral networks subserve processing of phonetic and intonational information during speech perception.

Adult↗
PubMed2004

Distinct frontal regions subserve evaluation of linguistic and emotional aspects of speech intonation.

In addition to the propositional content of verbal utterances, significant linguistic and emotional information is conveyed by the tone of speech. To differentiate brain regions subserving processing of linguistic and affective aspects of intonation, discrimination of sentences differing in linguistic accentuation and emotional expressiveness was evaluated by functional magnetic resonance imaging. Both tasks yielded rightward lateralization of hemodynamic responses at the level of the dorsolateral frontal cortex as well as bilateral thalamic and temporal activation. Processing of linguistic and affective intonation, thus, seems to be supported by overlapping neural networks comprising partially right-sided brain regions. Comparison of hemodynamic activation during the two different tasks, however, revealed bilateral orbito-frontal responses restricted to the affective condition as opposed to activation of the left lateral inferior frontal gyrus confined to evaluation of linguistic intonation. These findings indicate that distinct frontal regions contribute to higher level processing of intonational information depending on its communicational function. In line with other components of language processing, discrimination of linguistic accentuation seems to be lateralized to the left inferior-lateral frontal region whereas bilateral orbito-frontal areas subserve evaluation of emotional expressiveness.

Acoustic Stimulation↗
PubMed2004

Proton MR spectroscopy in succinic semialdehyde dehydrogenase deficiency.

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a rare hereditary disorder of the CNS catabolism of gamma-aminobutyric acid (GABA), leading to accumulation of the metabolite 4-hydroxybutyrate (GHB). Here the authors report on 1.5 and 3.0 T proton MR spectroscopy in a patient with SSADH deficiency. A characteristic pattern with clearly elevated GABA levels and traces of GHB was found in both the white and the gray matter of the brain. In vivo spectroscopy may be useful for diagnosis and monitoring SSADH deficiency.

Adult↗
PubMed2004

Directional correlation in white matter tracks of the human brain.

PURPOSE: To describe a technique for the detection of distinct brain fibers in sets of magnetic resonance (MR) diffusion tensor imaging (DTI) data. MATERIALS AND METHODS: MR-DTI can be used for a tractography of brain fibers presuming a data set of high spatial resolution and high signal to noise. A less demanding technique for the visualization of discrete brain fiber bundles involves segmentation. By using a region-growing algorithm, those voxels that have a direction similar to that of the major eigenvector in neighboring voxels of a data set can be marked. It has been shown recently by Mori et al (1) that this technique can be successfully applied to data from a single slice of a mouse brain. In this study, the segmentation technique was applied with modifications to multislice DTI data from the human brain. RESULTS: A distinct segmentation of various brain fiber bundles could be achieved by the use of a two-step algorithm. In the first step, voxels within large fiber tracts-such as corticofugal tracts (e.g., corticospinal tract) and the optic radiation-were segmented by starting the region-growing algorithm in the corpus callosum (CC) and erasing this major structure from the data set. In the second step, remaining voxels were segmented by the same algorithm; this revealed a good assignment of the similarly oriented fibers derived by segmentation to the anatomically given brain lobes. This two-step procedure was successfully applied to DTI data of six healthy volunteers. CONCLUSION: The segmentation technique for DTI data proposed by Mori et al (1) for data from mouse brains can be applied to multislice data from the human brain by using a two-step algorithm including a masking of the major fiber tracts.

Anisotropy↗
PubMed2004

The influence of pulse and respiration on spinal cerebrospinal fluid pulsation.

RATIONALE AND OBJECTIVES: The aim of the study is to elucidate the location and amount of spinal cerebrospinal fluid pulsations and to differentiate and quantify the cardiac and the respiratory influence. MATERIALS AND METHODS: An echo planar imaging sequence was applied to 5 different levels of the spinal canal of 7 healthy volunteers. The amount of maximal flow and respiratory signal variation were determined by a time and frequency domain analysis, respectively. RESULTS: CSF pulsation was high in the anterior cervical and in the thoracolumbar spine. Respiratory influence rose by 19% at C1 and by 28% at T12. The systolic flow was elevated during late expiration and the diastolic upward movement was pronounced by early expiration. CONCLUSION: The pulsation in the lower spine seems to be related to a second motor of CSF movement because there is a rising respiratory influence and a reappearance of pulsation waves. Physiological spinal CSF pulsation contains a relevant respiratory component.

Adult↗
PubMed2003

Differential expression of L- and S-MAG upon cAMP stimulated differentiation in oligodendroglial cells.

Myelin-associated glycoprotein (MAG), an immunoglobulin-like cell signaling protein involved in axon-glial interactions, displays two intracellular C-termini as a result of alternative mRNA splicing. During brain development, the two MAG mRNAs that encode L-MAG and S-MAG differ in their relative abundance. We have investigated the differential expression of L- and S-MAG upon cAMP treatment in the oligodendroglial cell line Oli-neu, a cell line able to differentiate in vitro. We have engineered GFP and VSVG fusions by small insertions into the alternatively spliced exons of the cloned MAG gene and reintroduced them into Oli-neu cells. The individually tagged MAG isoforms were expressed under the control of the MAG promoter and regulatory region. In this system, L-MAG was the predominant isoform before the stimulation of cells with cAMP, whereas upon cAMP treatment the S-MAG isoform was predominantly expressed in cells with a high degree of morphological differentiation. We suggest that the regulation of the MAG alternative splicing and the morphological differentiation in oligodendrocytes are controlled both by the same cAMP-responsive differentiation step.

Animals↗
PubMed2003

Comparison of representational maps using functional magnetic resonance imaging and transcranial magnetic stimulation.

OBJECTIVE: Comparison of functional magnetic resonance imaging (fMRI) representational maps, that were generated during voluntary thumb abduction, hand dorsiflexion and foot elevation to amplitude maps of motor-evoked potentials (MEPs) elicited by single transcranial magnetic stimulation (TMS) administered to cortical motor representation areas of the muscles of the thenar eminence, extensor carpi radialis and tibialis anterior muscles. METHODS: Stimulus locations that produced maximal motor-evoked potential amplitudes were compared to fMRI activation maxima in three-dimensional (3D)-space and in a 2D-projection using a novel technique that allowed fMRI activation sites to be projected onto the surface of the brain. RESULTS AND CONCLUSIONS: When analyzing pooled data from all target muscles, the location of projected fMRI and TMS activation maxima on the cortical surface differed by an average 13.9 mm. The differences in 3D distances were particularly large for representation areas of lower leg muscles. 3D distances between fMRI activation maxima and highest MEP site in TMS correlated significantly with higher TMS thresholds. These observations strongly suggest that higher TMS excitation thresholds and lower MEP amplitudes are largely due to the absolute distance between the stimulation site and the excitable cortical tissue targeting this muscle. After the projection 4 out of 5 representation sites as evaluated by TMS were located anterior to the fMRI activation maxima, an observation which may due to the orientation of the magnetic field induced by the current in the coil. The representation sites as evaluated with both methods were specific for the type of movement: distances between representation maxima of the same movements were significantly smaller than those within different movements. Nevertheless, fMRI and TMS provide complementary information, which is discussed on the basis of the functional map observed with both methods.

Adult↗
PubMed2002

Dynamic brain activation during processing of emotional intonation: influence of acoustic parameters, emotional valence, and sex.

Appreciation of the emotional tone of verbal utterances represents an important aspect of social life. It is still unsettled, however, which brain areas mediate processing of intonational information and whether the presumed right-sided superiority depends upon acoustic properties of the speech signal. Functional magnetic resonance imaging was used to disentangle brain activation associated with (i) extraction of specific acoustic cues and (ii) detection of specific emotional states. Stimulus material comprised pairs of emotionally intonated utterances, exclusively differing either in pitch range or in the length of stressed vowels. Hemodynamic responses showed a dynamic pattern of cerebral activation including sequenced bilateral responses of various cortical and subcortical structures. Activation associated with discrimination of emotional expressiveness predominantly emerged within the right inferior parietal lobule, within the bilateral mesiofrontal cortex and--with an asymmetry toward the right hemisphere--at the level of bilateral dorsolateral frontal cortex. Lateralization did not depend upon acoustic structure or emotional valence of stimuli. These findings might prove helpful in reconciling the controversial previous clinical and experimental data.

Adult↗
PubMed2001

Rate-dependent activation of a prefrontal-insular-cerebellar network during passive listening to trains of click stimuli: an fMRI study.

Eight volunteers underwent fMRI during passive listening to click trains. Using a parametric approach, rate-response profiles across the frequency band considered (2-6 Hz) were determined. Several cerebral structures outside the central-auditory pathways and target areas displayed distinct activation patterns each: rate-response profiles resembling high-pass (left side) or low-pass filtered (right side) signal series emerged at the level of the anterior insula, band-pass like characteristics (center frequency: 3-4 Hz) were observed within the left inferior frontal gyrus, and click train rates > 4 Hz yielded enhanced activation of the right cerebellar hemisphere. A variety of clinical and experimental data indicate that the left and right cerebral hemispheres act as high- and low-pass filters, respectively, on auditory input (double filtering by frequency theory). In light of the present fMRI data, the anterior insula contributes to the assumed double filtering by frequency functions. Furthermore, these intrasylvian areas seem to join up with the right cerebellum and the left inferior frontal gyrus to a network subserving parsing/timing functions within the auditory-verbal domain.

Acoustic Stimulation↗
PubMed2001

Differential activation in parahippocampal and prefrontal cortex during word and face encoding tasks.

Episodic encoding is the first step in the formation of a memory trace. The relation between type of stimulus material and regional brain activation is not fully understood. We measured brain activation using fMRI in 12 healthy subjects during two experiments, word and face encoding. A widespread network of common activations in both tasks was present in the bilateral frontal (BA44/45), occipital (BA17/18/19) and fusiform gyri (BA37) as well as the right hippocampal formation (BA30). A region-of-interest-analysis for the hippocampal formation and dorsolateral prefrontal cortex (DLPFC) was performed additionally. During face encoding the right dorsal and during word encoding the bilateral ventral hippocampal region was activated. In the prefrontal cortex a lateralization to the left side was present only for word encoding. During encoding, activation in the inferior frontal and hippocampal cortex is modulated by the type of stimulus material.

Adult↗
PubMed2001

Early left periventricular brain lesions induce right hemispheric organization of speech.

Right-hemispheric organization of speech has been observed following early left-sided brain lesions involving the language cortex. The authors studied speech organization in hemiparetic patients with pre- and perinatally acquired lesions in the left periventricular white matter using fMRI, and found that right-hemisphere activation correlated with left facial motor tract involvement. This suggests that the impairment of speech motor output from the left hemisphere plays an important role in this alteration of language representation.

Adolescent↗
PubMed2001

Are emotions contagious? Evoked emotions while viewing emotionally expressive faces: quality, quantity, time course and gender differences.

In human interactions, frequently one individual becomes 'infected' with emotions displayed by his or her partner. We tested the predictions by Hatfield et al. (1992) (Primitive emotional contagion. Review of Personal and Social Psychology 14, 151-177) that the automatic, mostly unconscious component of this process, called 'primitive emotional contagion', is repeatable and fast, that stronger facial expressions of the sender evoke stronger emotions in the viewer and that women are more susceptible to emotional contagion than men. We presented photos from the Pictures of Facial Affect (Ekman and Friesen, 1976). (Pictures of Facial Affect. Consulting Psychologists Press, Palo Alto) on a PC varying the affective content (happy and sad), the expressive strength and the duration of presentation. After each photo, subjects rated the strength of experienced happiness, sadness, anger, disgust, surprise, fear and pleasure. Feelings of happiness or sadness were significantly, specifically and repeatedly evoked in the viewer - even with presentations lasting only 500 ms. Stronger expressions evoked more emotion. The gender of the viewer had weak effects. We hypothesize that this fast and repeatable reaction is likely to have a 'prewired' neural basis. We propose that the induction of emotional processes within a subject by the perception of emotionally expressive faces is a powerful instrument in the detection of emotional states in others and as the basis for one's own reactions. Detailed knowledge of emotional reactions to faces is also valuable as a basis for psychiatric studies of disorders in affect and/or communication and in studies using functional imaging (fMRI or PET) where faces are increasingly used as stimuli.

Adult↗
PubMed2001

Sensorimotor mapping of the human cerebellum: fMRI evidence of somatotopic organization.

Functional magnetic resonance imaging (fMRI) was employed to determine areas of activation in the cerebellar cortex in 46 human subjects during a series of motor tasks. To reduce the variance due to differences in individual anatomy, a specific transformational procedure for the cerebellum was introduced. The activation areas for movements of lips, tongue, hands, and feet were determined and found to be sharply confined to lobules and sublobules and their sagittal zones in the rostral and caudal spino-cerebellar cortex. There was a clear symmetry mirroring at the midline. The activation mapped as two distinct homunculoid representations. One, a more extended representation, was located upside down in the superior cerebellum, and a second one, doubled and smaller, in the inferior cerebellum. The two representations were remarkably similar to those proposed by Snider and Eldred [1951] five decades ago. In the upper representation, an intralimb somatotopy for the right elbow, wrist, and fingers was revealed. The maps seem to confirm earlier electrophysiological findings of sagittal zones in animals. They differ, however, from micromapping reports on fractured somatotopic maps in the cerebellar cortex of mammals. We assume that the representations that we observed are not solely the result of spatial integration of hemodynamic events underlying the fMRI method and may reflect integration of afferent peripheral and central information in the cerebellar cortex.

Adolescent↗