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Biomedical subjects

R A Müller

Publications and source records attributed to R A Müller.

25 records · Page 2Linked to original sources
PubMed1998

Brain organization of motor and language functions following hemispherectomy: a [(15)O]-water positron emission tomography study.

The capacity of the developing brain for compensatory reorganization after early hemispherectomy has been previously shown in neurobehavioral studies, above all with regard to language recovery. The present study examines the organization of motor and language areas by means of [(15)O]-water positron emission tomography (PET) in a 6-year-old boy who underwent right functional hemispherectomy at age 3 years. The results suggest that compensatory allocation for movement of the weak hand primarily involves the premotor, inferior frontal, and insular cortices, and the supplementary motor area in the retained hemisphere, as well as the bilateral cerebellum. Receptive language and prosodic functions primarily activated the left perisylvian cortices. However, language and motor activations were also seen in cortical and subcortical remains on the hemispherectomized side suggesting incomplete disconnection by functional hemispherectomy.

Brain↗
PubMed1998

Developmental changes of cortical and cerebellar motor control: a clinical positron emission tomography study with children and adults.

Functional neuroimaging data regarding the development of motor organization in normal children and adolescents are virtually unavailable because of ethical concerns. As an alternative approach, we studied child and adult lesion patients, focusing on movement of the hand ipsilateral to the lesion and on brain activations in the contralesional hemisphere. [15O]-water positron emission tomography was performed during rest and sequential finger-thumb tapping in 10 children (aged 6 to 14 years) and 15 adults (aged 18 to 74 years) with unilateral lesion. We expected more distinct activation/deactivation patterns during movement in adults than in children. While there were no group differences in activation of primary and secondary motor cortices, deactivations in nonmotor cortex were significantly more pronounced in adults than in children. This indirectly supports our hypothesis of developmental focalization of cerebral motor control. Activations in the cerebellum and vermis were significantly stronger in the adults than in the children, possibly reflecting normal developmental patterns.

Adolescent↗
PubMed1997

Receptive and expressive language activations for sentences: a PET study.

Most language mapping studies have focussed on activations for single-word tasks. We examined activations for verbal auditory and generation tasks using sentence stimuli. [15O]-water PET was performed in 4 female and 5 male normal adults. Listening to sentences (minus rest) activated the superior and middle temporal gyri bilaterally, but mean activation was significantly stronger on the left. The strongest activation for sentence generation (minus repetition) was seen in the left middle and inferior frontal gyri (area 46). This focus appears to be anterior to activations reported for single-word generation, possibly due to greater verbal working memory demands of the sentential task. Additional activation of the left inferior temporal lobe can be attributed to lexicosemantic processing.

Acoustic Stimulation↗
PubMed1997

Plasticity of motor organization in children and adults.

We explored the effects of maturational plasticity on motor activations for the affected hand in patients with unilateral lesion involving the rolandic cortex. Ten patients with early lesion (onset < 4 years), seven patients with late lesion (onset > or = 10 years) and eight normal adults underwent [15O]-water positron emission tomography (PET). Rolandic activations in the contralesional hemisphere were enhanced in both patient groups when compared to normal adults. Secondary motor and frontoparietal nonmotor cortices were more activated in the early than in the late lesion group, suggesting a greater potential for reorganization during early development than later in life. Cerebellar activations were similar in late lesion patients and normal adults, but significantly weaker in early lesion patients.

Adolescent↗
PubMed1997

Language and motor functions activate calcified hemisphere in patients with Sturge-Weber syndrome: a positron emission tomography study.

This study examines whether or not in Sturge-Weber syndrome hypoperfused brain areas that are affected by calcification continue to retain some function and participate in language and motor activations. [15O]-Water positron emission tomography (PET) was used for brain mapping of these functions in two patients with extensive unilateral calcification and hypoperfusion and in one patient with calcification and hypoperfusion restricted to the left posterior region. Task-related regional cerebral blood flow changes suggest that (1) hypoperfused areas may become activated during language and motor performance, and (2) progressive calcification in Sturge-Weber syndrome is associated with functional reorganization in the language and motor domains. Interhemispheric reorganization appears to be more pronounced for language than for motor functions.

Adolescent↗
PubMedDate not supplied

Functional brain reorganization in children.

Developmental brain plasticity in association with focal brain injury is dependent on a number of factors, including age of the individual at the time of injury, size and topography of the brain lesion, maturational state of the brain system injured, integrity of brain areas surrounding and contralateral to the lesion, presence and duration of epilepsy, and medication effects. Recently developed functional neuroimaging tools now make it possible to study non-invasively several aspects of human brain functional reorganization in response to injury. Clinical models which are suitable for the study of developmental brain plasticity include patients who have undergone cortical resections for the alleviation of intractable epilepsy, patients who have sustained unilateral cerebrovascular insults at various periods of development, patients with chronic progressive unilateral brain injury such as in the Sturge-Weber syndrome, and patients with early sensory deprivation such as blind or deaf subjects. Although evidence of functional brain reorganization can be demonstrated in these models, it is emphasized that the neurobiological rules that govern intrahemispheric versus interhemispheric reorganization of function in the brain are, at present, poorly understood.

Animals↗