Postural Control during the Stroop Test in Dyslexic and Non Dyslexic Teenagers

Postural control in quiet stance although simple still requires some cognitive resources; dual cognitive tasks influence further postural control. The present study examines whether or not dyslexic teenagers experience postural instability when performing a Stroop dual task for which their performances are known to be poor. Fifteen dyslexics and twelve non-dyslexics (14 to 17 years old) were recruited from the same school. They were asked to perform three tasks: (1) fixate a target, (2) perform an interference Stroop test (naming the colour or the word rather than reading the word), (3) performing flexibility Stroop task: the subject performed the interference task as in (2) except when the word was in a box, in which case he had to read the word. Postural performances were measured with a force platform. The results showed a main task effect on the variance of speed of body sway only: such variance was higher in the flexibility task than for the other two tasks. No group effect was found for any of the parameters of posture (surface, mediolateral and anteroposterior sway, variance of speed). Further wavelet analysis in the time-frequency domain revealed an increase in the spectral power of the medium frequency range believed to be related to cerebellum control; an accompanying increase in the cancellation time of the high frequency band related to reflexive loops occurred for non-dyslexics only. These effects occurred for the flexibility task and could be due to its high cognitive difficulty. Dyslexics displayed shorter cancellation time for the medium frequency band for all tasks, suggesting less efficient cerebellar control, perhaps of eye fixation and attention influencing body sway. We conclude that there is no evidence for a primary posture deficit in 15 year old teenagers who come from the general population and who were recruited in schools

Syndrome des ovaires polykystiques et hormone anti-mullérienne

LYON1-BU Santé (693882101) / SudocSudocFranceF

Separation and characterization of antioxidants from Spirulina platensis microalgacombining pressurized liquid extraction, TLC and HPLC-DAD

A new procedure has been developed to separate and characterize antioxidant compounds from Spirulina platensis microalga based on the combination of pressurized liquid extraction (PLE) and different chromatographic procedures, such as Thin-Layer Chromatography (TLC), at preparative scale, and High Performance Liquid Chromatography (HPLC) with a Diode Array Detector (DAD). Different solvents were tested for PLE extraction of antioxidants from Spirulina platensis microalga. An optimized pressurized liquid extraction process using ethanol (generally recognized as safe, GRAS) as extraction solvent has been obtained that provides natural extracts with high yields and good antioxidant properties. TLC analysis of this ethanolic extract obtained at 115°C for 15 min was carried out and the silica layer was stained with a DPPH• (diphenyl-pycril-hydrazyl) radical solution to determine the antioxidant activity of the different chromatographic bands. Next, these coloured bands were collected for their subsequent analysis by HPLC-DAD revealing that the compounds with the most important antioxidant activity present in Spirulina extracts were carotenoids, as well as phenolic compounds and degradation products of chlorophylls.JAM and MH thank MCYT for FPI grants. Authors thank MCYT (project AGL2002-04621- C02-02) for financial support.Peer reviewe

Postural stability measurements in upright stance (25.6 s. duration).

<p>For 15 and 12 control adolescents and for the 27 subjects together. Means and standard errors of surface of CoP, standard deviations of lateral (SDx) and of anteroposterior (SDy) body sway, variance of speed, PII, and PI and CI for each plane (respectively PIy, PIx, CIy and CIx) for each frequency bands (0.05–0.50 Hz, 0.50–1.50 Hz and 1.50–10.00 Hz) for each condition i.e. the quiet fixation task (FT), the Stroop interference test (SIT) and the Stroop flexibility test (SFT).</p

P-values obtained when ANOVA was performed.

<p>On the studied postural parameters for group (dyslexics vs. controls), task (quiet fixation task, Stroop interference test and Stroop flexibility test) and group-task interaction effects. Asterisk indicates significant difference (p<0.05) and circle indicates marginally significant effects.</p

Effects of group in dyslexics vs. controls on the canceling time.

<p>This parameter was elaborated from the wavelet transform applied to CoP displacements, of the second (<b>A</b> - CTx2) and the third (<b>B</b> - CTx3) frequency bands on the mediolateral sway. Asterisk indicates significant difference. Interaction between groups and tasks for the CTx3 (<b>C</b>); asterisk indicates significant difference.</p

Illustration of posturography testing conditions.

<p>The subject viewed the Stroop test on the screen at 100 cm, at the eye level.</p