Showing papers on "Superior frontal gyrus published in 1997"

Neuropathology of scrapie: a study of the distribution patterns of brain lesions in 222 cases of natural scrapie in sheep, 1982–1991

Abstract: Detailed neuropathological findings in 222 cases of naturally occurring scrapie from Great Britain are described. The material consisted of formalin-fixed brain from eight breeds of sheep submitted between 1982 and 1991. Paraffinembedded histological sections were made from several specified brain areas, including the medulla oblongata, cerebellum, pons, mesencephalon, diencephalon, septal area, basal ganglia and frontal cortex. Sections were examined by conventional and polarised light microscopy and the type and distribution of the lesions were recorded. Histologically, the lesions included vacuolation of neuronal perikarya and grey matter neuropil, neuronal degeneration (especially ‘dark’ neurons) and loss, a reactive glial (predominantly astrocytic) response and amyloidosis. Vacuolar lesions were present in the cerebral cortex of 37 per cent of cases, centred around the superior frontal gyrus. Vacuolar lesions were detected in the neocortex for as long as sections have been taken from the superior frontal gyrus and are thus probably not a new feature of the disease. The distribution of vacuolation in the grey matter neuropil could be classified into seven patterns. Data from individual breeds of sheep showed that in some breeds there were significant differences in the age at which animals with different patterns of vacuolation died from scrapie.

Sensorimotor cerebral activation during optokinetic nystagmus A functional MRI study

Abstract: Self-motion or object motion can elicit optokinetic nystagmus (OKN), which is an integral part of dynamic spatial orientation. We used functional MR imaging during horizontal OKN to study cerebral activation patterns in sensory and ocular motor areas in 10 subjects. We found activation bilaterally in the primary visual cortex, the motion-sensitive areas in the occipitotemporal cortex (the middle temporal and medial superior temporal areas), and in areas known to control several types of saccades such as the precentral and posterior median frontal gyrus, the posterior parietal cortex, and the medial part of the superior frontal gyrus (frontal, parietal, and supplementary eye fields). Additionally, we observed cortical activation in the anterior and posterior parts of the insula and in the prefrontal cortex. Bilateral activation of subcortical structures such as the putamen, globus pallidus, caudate nucleus, and the thalamus traced the efferent pathways of OKN down to the brainstem. Functional MRI during OKN revealed a complex cerebral network of sensorimotor cortical and subcortical activation.

Ictal Speech Arrest and Parasagittal Lesions

Abstract: Lesions in the parasagittal region may cause seizures with speech arrest. To correlate lesion localization within the parasagittal region with ictal speech function we studied 11 patients with parasagittal lesions. The exact lesion localization was assessed with magnetic resonance imaging. In all patients with speech arrest the lesion involved the left superior frontal gyrus (n = 6), in 3 patients the lesion was confined to this gyrus. Speech arrest did not occur in patients with right-sided lesions (n = 4) or left-sided lesions outside the superior frontal gyrus (n = 1). Our data suggest that a small lesion confined to the left superior frontal gyrus (the supplementary motor area) is sufficient to cause speech arrest.

Speech and the dominant superior frontal gyrus: correlation of ictal symptoms, EEG, and results of surgical resection.

Abstract: Two patients with seizures characterized by speech arrest had astrocytoma in the superior frontal gyrus (SFG) of the left hemisphere. Preoperative video EEG monitoring of seizures using subdural electrode arrays showed that comprehension, crude vocalization, and limb and tongue movements were preserved during speech arrest. One patient had difficulty writing during seizures. Ictal EEG onset was localized to the SFG without involvement of Broca's area. Electrical stimulation of SFG electrodes reproduced the speech arrest and writing difficulty. Resection of this region reduced seizures but did not result in lasting speech deficit. Cessation of speech with electrical stimulation of the superior frontal gyrus occurs by interrupting control of muscles required for speaking, which occurs independently of simple 'negative' motor effects. We postulate that functional redundancy is the basis for resection of this region without producing significant speech deficits.

[Proteoglycans in senile dementia of Alzheimer's type].

Abstract: Levels of the proteoglycans hyaluronic acid, heparan sulfate, dermatan sulfate and chondroitin sulfate in brains were measured. The samples were from 25 brains obtained at autopsy from patients who had senile dementia of Alzheimer's type (SDAT) (60 to 97 years old) and 10 brains from non-demented elderly subjects (75 to 101 years old). Proteoglycan levels in the brains of patients with SDAT were twice as high in the hippocampus and four times higher in the superior frontal gyrus than the levels in brains of non-demented elderly subjects. The content of heparan sulfate proteoglycan was greatest nine times higher in the hippocampus and seven times higher in the superior frontal gyrus. By immuno-electronmicroscopic examination, heparan sulfate proteoglycan was found in the basement membranes of capillaries, and in a portion of the cores of the senile plaques.