g., Vigneau et al. 2006, 2011) in these same children. With regard to our first aim, we tested the hypothesis that there is an increase in lateralization with age. This could be both in terms of direction (left-lateralized vs. right-lateralized) or in terms of strength, by which we mean the amount
of lateralization irrespective of direction of lateralization. With regard to our second aim, the functional crowding hypothesis clearly predicts that GABA antagonist drugs children with functions Inhibitors,research,lifescience,medical lateralized to different hemispheres (i.e., left-lateralized for language and right-lateralized for visuospatial memory or vice versa) should outperform children with both functions lateralized to the same hemispheres (either the left or the right hemisphere) on psychometric tests. Methods Participants Participants were 60 typically developing Inhibitors,research,lifescience,medical children (34 girls, 26 boys) across three age bands 6–8 (M= 6.94 years, SD= 0.40 years), 10–11 (M= 10.79 years, SD= 0.43 years), and 13–16 years of age (M= 14.33 years,
SD= 0.94 years) recruited from schools around Oxfordshire, UK. Two additional children (one 8-year-old and one 10-year-old) were dropped from the study because of noisy fTCD recordings for both tasks. Data on the language production task were obtained for 58 children, and on the visuospatial memory task for 57 children. In 55 children, data Inhibitors,research,lifescience,medical were obtained on both tasks. Results on the visuospatial memory Inhibitors,research,lifescience,medical task from 20 six- to eight-year-olds have previously been reported on in a paper describing the development of that task (Groen et al. 2011). Participants were without any history of neurological disorder and with normal or corrected-to-normal vision. Parents of the participants confirmed that no child had a diagnosis
of a neurodevelopmental disorder, such as autism, specific language impairment, or dyslexia, and that English was the main language spoken at home. Hand preference was assessed with the Edinburgh Handedness Inventory1 (Oldfield 1971), with scores of 40 or above denoting right-handedness, 40 or below denoting Inhibitors,research,lifescience,medical left-handedness, and scores in between denoting mixed-handedness. The sample included 47 right-handed (28 girls), four left-handed (three girls) and eight mixed-handed (three girls) children. No hand preference data were available for aminophylline one boy. Parental consent and child assent were obtained for all participants. The project was approved by the Central University Research Ethics Committee of the University of Oxford and is in accordance with the WMA Declaration of Helsinki for experiments involving humans. Cognitive and language tests Nonverbal cognitive ability Two subtests (Sequential Order and Repeated Patterns) of the nonverbal IQ test, Leiter International Performance Scale-Revised (Roid and Miller 1997), were used to derive a “Fluid Reasoning IQ” score (M= 100, SD= 15).
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