Biomedical subjects

Wolfgang Grodd

Publications and source records attributed to Wolfgang Grodd.

61 records · Page 4Linked to original sources

PubMed2002

Hemispheric lateralization effects of rhythm implementation during syllable repetitions: an fMRI study.

Rhythm in terms of the modulation of syllable durations represents an information-bearing feature of verbal utterances contributing both to the meaning of a sentence (linguistic prosody) as well as a speaker's emotional expression (affective prosody). In order to delineate the neural structures subserving rhythmic shaping of speech production, functional magnetic resonance imaging (fMRI) was performed during (a) isochronous syllable repetitions and (b) production of syllable triplets with lengthening either of the initial or final unit. A cognitive subtraction approach (rhythmic versus isochronous iterations) revealed activation of right-sided perisylvian areas (superior temporal gyrus, Broca analogue and adjacent premotor cortex) as well as contralateral subcortical structures (putamen and thalamus). Presumably, these responses reflect a right-hemisphere rehearsal mechanism of rhythmic patterns and left-hemisphere monitoring of verbal output.

Acoustic Stimulation↗

PubMed2002

Right-hemispheric organization of language following early left-sided brain lesions: functional MRI topography.

Left-hemispheric (LH) brain lesions acquired early in life can induce language organization in the undamaged right hemisphere (RH). This study addresses the anatomical correlates of language processing in the RH of such individuals. Five hemiparetic patients with left periventricular brain lesions of pre- and perinatal origin were included, in whom fMRI during a word generation task had yielded predominantly RH activation; five age- and sex-matched healthy right-handers served as controls. The patterns of activation in the RH of patients showed a striking similarity with the LH patterns of the normal controls, and voxel-wise comparison failed to detect significant differences. This demonstrates that in patients with early LH damage, RH recruitment for language occurs in brain areas homotopic to the LH regions involved in language processing under normal circumstances.

Adult↗

PubMed2002

Object-selective responses in the human motion area MT/MST.

The perception of moving objects and our successful interaction with them entail that the visual system integrates shape and motion information about objects. However, neuroimaging studies have implicated different human brain regions in the analysis of visual motion (medial temporal cortex; MT/MST) and shape (lateral occipital complex; LOC), consistent with traditional approaches in visual processing that attribute shape and motion processing to anatomically and functionally separable neural mechanisms. Here we demonstrate object-selective fMRI responses (higher responses for intact than for scrambled images of objects) in MT/MST, and especially in a ventral subregion of MT/MST, suggesting that human brain regions involved mainly in the processing of visual motion are also engaged in the analysis of object shape.

Brain Mapping↗

PubMed2002

Reorganization of speech production at the motor cortex and cerebellum following capsular infarction: a follow-up functional magnetic resonance imaging study.

Based on clinical data, Geschwind assumed left hemisphere dominance of speech production to extend to the cortical representation of articulatory and phonatory functions at the motor cortex. This author suggested, furthermore, that the clinical observation of rapid recovery from articulatory impairments after damage to the left-sided corticobulbar tracts reflects compensatory activation of an alternative pathway involving the contralateral pre-central gyrus and its efferent projections. In order to test this hypothesis, functional magnetic resonance imaging (fMRI) was performed 4 and 35 days after stroke in a 38-year-old man who had experienced sudden speech deterioration ('dysarthric speech') concomitant with weakness of the right upper limb and the right side of the face. Computerized tomography demonstrated an ischaemic infarction within the left internal capsule. The patient fully recovered from dysarthria within 9 days. Activation of the right hemisphere analogues of Broca and Wernicke areas has been assumed to contribute to recovery from aphasia. As a further aspect of the reorganization of speech function, the present case study demonstrates for the first time by means of fMRI a selective 'shift' of the cortical representation of speech motor control to the right Rolandic cortex and the left cerebellum during restitution of articulation in a case of transient dysarthria following infarction of the left internal capsule.

Adult↗

PubMed2002

Two types of ipsilateral reorganization in congenital hemiparesis: a TMS and fMRI study.

Reorganization after early brain injuries is not only determined by the maturational stage of the CNS at the time of the insult (timing), but also by the structural properties, location and extent of the lesion. This study addresses the impact of different lesion extents on the type of reorganization induced in a cohort of patients with lesions of uniform structure and location (unilateral periventricular defects) and similar timing (early third trimester of pregnancy). Twelve young adult patients with congenital hemiparesis and 10 age-matched controls were studied. The severity of structural damage to hand motor projections of the cortico-spinal tract was assessed on semi-coronal MRI reconstructions along anatomical landmarks of cortico-spinal tract somatotopy. The functional integrity of these crossed cortico-spinal projections in the affected hemisphere, as well as the presence of any abnormal ipsilateral projections to the paretic hand, was examined by transcranial magnetic stimulation (TMS). Cortical activation during simple voluntary hand movements was studied by functional MRI (fMRI). Patients with small lesions (SL; n = 4) and only mild hand motor impairment possessed intact crossed cortico-spinal projections to the paretic hand, whereas no motor response could be elicited by TMS of the affected hemisphere in those with large lesions (LL; n = 6) and more severe hand motor impairment. Evidence for compensatory recruitment of the unaffected hemisphere was found in both subgroups. In the SL group, fMRI demonstrated ipsilateral activation of premotor areas, without any abnormal projections to the paretic hand originating from these sites. In the LL group, such abnormal ipsilateral projections to the paretic hand were indeed found, and fMRI confirmed cortical activation of an abnormal ipsilateral hand motor representation in the primary sensorimotor region of the unaffected hemisphere. Two patients with intermediate-sized lesions presented combined features of both groups (SL, LL). In conclusion, this study provides evidence that the type of cortico-spinal reorganization depends on the extent of the brain lesion. We propose that involvement of the ipsilateral hemisphere can be (i) of the premotor type, i.e. without ipsilateral motor projections but with significant activation of ipsilateral premotor areas, or (ii) of the primary motor type, i.e. with abnormal ipsilateral cortico-spinal projections to the paretic hand.

Adolescent↗

PubMed1999

Reorganization in the primary motor cortex after spinal cord injury - A functional Magnetic Resonance (fMRI) study.

Activation maps in the primary motor cortex (M1) were investigated in three patients with complete spinal cord injury (SCI) at level TH3, TH7 and TH9 and in one patient with an incomplete spinal cord injury at level L1 during right elbow (4 patients), right thumb (4 patients), bilateral lip (2 patients) and right foot (3 patients during imagined, 1 patient during executed) movements using functional Magnetic Resonance Imaging (fMRI). Compared to controls fMRI activation maps of patients with complete paraplegia showed a cranial displacement of the activation maxima in the contralateral primary motor cortex during elbow movement of 13.3mm, whereas the maxima of thumb and lip movements were not altered. The patient with an incomplete spinal cord injury revealed no displacement of elbow activation maxima. The reorganization is likely to occur on the cortical and not on the spinal level.

Journal Article↗

PubMedDate not supplied

MR imaging and spectroscopy of a tuber cinereum hamartoma in a patient with growth hormone deficiency and hypogonadotropic hypogonadism.

To our knowledge, this is the first report of hypogonadotropic hypogonadism, or growth hormone deficiency, in a patient without non-Pallister-Hall syndrome who had hypothalamic hamartoma diagnosed on the basis of MR imaging and MR spectroscopy findings. On short-TE proton MR spectra, the N-acetylaspartate concentration in the hamartoma was lower than that in the thalamus but similar to that in the amygdala. However, myo-inositol concentration was elevated in the hamartoma compared with that in the amygdala and thalamus. This report stresses the advantages of short-TE spectroscopy and demonstrates that regional variations in spectra should be considered when reference structures are used.

Adolescent↗