Neural bases of language switching in high and early proficient bilinguals.

The left inferior frontal cortex, the caudate and the anterior cingulate have been proposed as the neural origin of language switching, but most of the studies were conducted in low proficient bilinguals. In the present study, we investigated brain areas involved in language switching in a sample of 19 early, high-proficient Spanish-Catalan bilinguals using a picture naming task that allowed contrasting switch and non-switch trials. Compared to the non-switching condition, language switching elicited greater activation in the head of the left caudate and the pre-SMA/ACC. When the direction of the switching was considered, the left caudate was more associated with forward switching and the pre-SMA/ACC with backward switching. The discussion is focused on the relevance of these brain structures in language control in early, high-proficient bilinguals, and the comparison with previous results in late bilinguals.

Bridging language and attention: brain basis of the impact of bilingualism on cognitive control.

Using two languages on an everyday basis appears to have a positive effect on general-purpose executive control in bilinguals. However, the neural correlates of this effect remain poorly understood. To investigate the brain bases of the bilingual advantage in executive control, we tested 21 Spanish monolinguals and 19 Spanish-Catalan early bilinguals in a non-verbal task-switching paradigm. As expected based on previous experiments on non-verbal task switching, we found activation in the right inferior frontal cortex and the anterior cingulate of monolingual participants. While bilingual participants showed a reduced switching cost, they activated the left inferior frontal cortex and the left striatum, a pattern of activation consistent with networks thought to underlie language control. Overall, these results support the hypothesis that bilinguals' early training in switching back and forth between their languages leads to the recruitment of brain regions involved in language control when performing non-linguistic cognitive tasks.

Evaluation of white matter damage in patients with Alzheimer's disease and in patients with mild cognitive impairment by using diffusion tensor imaging.

PURPOSE: The objective of this study was to evaluate white matter tissue damage in patients with Alzheimer's disease (AD) and in patients with mild cognitive impairment (MCI) using diffusion tensor imaging (DTI). MATERIALS AND METHODS: Forty-seven subjects were evaluated: 14 patients with AD, 15 with MCI and 18 healthy volunteers. All subjects were studied using conventional magnetic resonance imaging (MRI) and DTI (32 directions) with a 1.5 T magnet. Fractional anisotropy (FA) was measured in the following regions: frontal, occipital, parietal and temporal white matter and in the genu and splenium of the corpus callosum. The results were compared between the different groups and correlated with the Mini-Mental State Evaluation (MMSE) scores. RESULTS: A statistically significant difference was obtained between controls and MCI patients (p < 0.007) and between controls and AD patients (p < 0.05) with regard to FA of the white matter in the splenium. A statistically significant difference was obtained between controls and AD patients with regard to FA in the genu (p < 0.016). Moreover, there was a statistically significant difference between controls and AD patients considering the genu (p < 0.016) and the frontal white matter on the right side (p < 0.024). The MMSE scores correlated with the FA values measured in the genu, the splenium and frontal white matter on the right side. No significant differences were identified between patients with AD and those with MCI. CONCLUSIONS: DTI could be of value in the early detection of white-matter damage in patients with MCI and AD. The DTI values correlate with the neuropsychological tests.

Functional MRI in the assessment of cortical activation in subjects with Parkinson's disease.

PURPOSE: The purpose of this study was to evaluate cortical activation patterns in patients with Parkinson's disease during a relatively complex motor task. MATERIALS AND METHODS: Seven patients (six men and one woman) with lateralised akinetic-rigid Parkinson's disease underwent functional magnetic resonance imaging (MRI) of the brain with a 1.5-T magnet. Finger tapping was chosen as a motor task. The control group included 11 volunteers (six men and five women) with no neurological disease. RESULTS: Patients showed hyperactivity of the ipsilateral and contralateral motor cortex associated with bilateral over-activation of the parietal cortex during movement of the affected hand. In some cases, there was a lack of activation of the pre-motor and supplementary motor areas whereas, when present, activation in these areas was greater during movement of the healthy hand. Finally, activation of the occipital cortex was found in all patients as a result of their tendency to control movement visually. CONCLUSIONS: Results of this study confirm a re-organisation of cortical circuits due to subcortical damage in patient's with Parkinson's disease.

Age-related chemical changes in human elastins from non-atherosclerotic areas of thoracic aorta.

Elastins from normal appearing areas of human thoracic aortae with varying degrees of mineralization were taken from subjects of different ages and purified by autoclaving their amino acid compositon, Ca and P contents and N terminal profiles were determined before and after EDTA decalcification. (1) Decrease in desmosine concentration with increasing age was accounted for by dilution of the elastin by autoclave-resistant polar glycoproteins. (2) The appearance and growth of a mineral phase with a Ca/P molar ratio typical of apatites was accompanied by an increased association of polar contaminants with elastin. (3) After 24 h EDTA treatment, small and constant amounts of Ca were still apparent although P was absent, in elastins from all age groups. (4) The undialyzable fraction of the material solubilised by EDTA consisted mainly of elastin fragments, glycoproteins and Ca. (5) All the elastin samples showed the same type of N-terminal amino acids. In low and medium mineralized samples the concentration of amino end-groups was slightly increased, while in highly mineralized elastin the content of N-terminal residues was three times greater than in normal young elastin. Extraction with EDTA reduced the amount of end-groups to a normal level. It is suggested that in the initial stages of elastin fibre mineralization, an increased amount of autoclave-resistant glycoproteins becomes associated with elastin; and that with ageing, degradative changes involving peptide-bond cleavage may occur. However, evidence of degradation is found only in old and highly mineralized elastin samples.

The application of collagenase, purified by affintiy chromatography, to the isolation of insoluble elastin from bovine aorta.

Clostridium histolyticum collagenase (clostridiopeptidase A, EC 3.4.4.16), purified by affinity chromatography, was applied to the isolation of insoluble elastin from bovine aorta. The extremely low level of N-terminal residues (1.6 mol per 10(6) g of protein) present in this preparation indicated the almost complete lack of hydrolytic damage caused by the isolation procedure. The amino acid profile of the aortic elastin was found to be almost identical to that of insoluble elastin prepared from bovine ligamentum nuchae by the same method.