Giovanni Ferretti

Visual scanning and reading ability in normal and dyslexic children

Very few studies have investigated the development of visual search of aligned stimuli in relation to normal reading acquisition and in developmental dyslexia. In this study we used a new computerised experimental task which requires a visuo-motor response (RT) to a target appearing unpredictably in one out of seven different spatial positions on a horizontally aligned array of 18 geometrical figures. The aims of the study were to investigate: (1) the visual scanning development in normal children from pre-school to school age; (2) whether visual scanning performance in kindergarten children could predict reading acquisition; (3) the visual scanning abilities in a group of developmental dyslexic children. The main results were: (1) a significant decrement of RTs with age and a progressive increase of the left-to-right gradient with reading experience; (2) visual scanning abilities in kindergarten proved to be a good predictor of reading acquisition; (3) dyslexics were slow scanners and did not present the left-to-right strategy typical of normal readers. The results support the hypothesis of a relationship between visual scanning and reading abilities.

Is interhemispheric transfer time related to age? A developmental study

In simple visuomotor reaction time tasks, the difference between reaction time (RT) in the uncrossed hand/hemifield condition from RT in the crossed hand/hemifield, known as CUD (crossed-uncrossed difference), has been interpreted as reflecting interhemispheric transmission time (IHTT). Several studies in normal adults have found a CUD of a few milliseconds (3-4), while an abnormally long CUD has been reported in patients who underwent a surgical section of the corpus callosum or in congenital acallosal subjects. The corpus callosum, which is the most important structure for interhemispheric transfer of information, completes its myelination approximately by age ten. It has been hypothesized that the functional maturity of the corpus callosum coincides with the termination of the myelination cycle. No developmental study has focused on the development of IHTT, in relation to callosal maturation. The purpose of our study has been to investigate the development of interhemispheric transfer of visuomotor information in children aged seven to eleven, using a simple RT task with lateralized visual stimuli. The results indicate an age-related decrease of CUD, which we interpret as reflecting the maturation of the corpus callosum during childhood years.

Treatment with l-Arginine improves neuropsychological disorders in a child with Creatine transporter defect

Creatine transporter deficit (CT1) is an inherited metabolic disorder that causes mental retardation, epilepsy, speech, language and behavioral deficits. Until now, no treatment has been proven to be successful for this condition. We describe 1-year follow-up study of a child, aged 9.6 years, with CT1 defect, on oral supplementation with l-arginine, a precursor of creatine synthesis. Under supplementation, he showed a noticeable improvement of neurological, language and behavioral status and an increase of brain creatine and phosphocreatine documented with magnetic resonance spectroscopy. The results suggest that children with CT1 disorder show some residual adaptive plasticity for certain functions even at quite an advanced age. Further trials with higher l-arginine dosages and more protracted treatment are encouraged.

Mental retardation and verbal dyspraxia in a new patient with de novo creatine transporter (SLC6A8) mutation

We report on a 9.5‐year‐old Italian boy affected by creatine transporter deficit (CT1), due to a de novo mutation in SLC6A8 gene. The patient was investigated by means of a comprehensive neuropsychological protocol and presented with an unusual alteration of speech and expressive‐language function, associated with mental retardation, that differed from CT1 patients described to date. In particular, he exhibited a developmental apraxia of speech (DAS) with motor planning and execution deficit, while receptive language was consistent with his mental age.

TACTILE DISCRIMINATION OF DIRECTION OF LINES IN RELATION TO HEMISPHERIC SPECIALIZATION

The role of the right hemisphere in a task of haptic discrimination of line orientation was studied in 16 children aged 7–6 and 16 adults aged 25 yr. The exploratory movements were limited to hand and wrist, since it has been shown that distal movements are mediated by the contralateral hemisphere. A comparison of the performance of the two hands shows a clear superiority of the left hand and inferred right hemisphere in both children and adults. An especial emphasis in the discussion is given to the role of the experimental procedure in enhancing the effect of the hemispheric functional asymmetries.

Visual information processing in infants with focal brain lesions

Abstract Visual information processing for faces were tested by means of the Fagan test of infant intelligence (FTII) in six infants of approximately 12 months of age affected by congenital unilateral brain lesions. Magnetic resonance imaging (MRI) was used to determine the side and size of the lesions. In addition to the FTII, all infants were submitted to a psychometric evaluation using the Griffiths scales. Visual acuity, visual field, and ocular motility were also assessed. Three infants showed damage in the left hemisphere and three in the right. The severity of the lesions, as revealed by MRI scan, was similar in the two groups. All infants except one had normal or borderline cognitive scores on the Griffiths scales. Conversely, four infants showed abnormal results on the FTII, which were not associated with the severity of the lesions, psychometric scores, or the presence of visual deficits. A preference for stimuli presented on the left side of the screen was found, independent of the side of the lesions. This effect was stronger for novel stimuli. The results of this study confirm the importance of early assessment of neuropsychological functions in infants with focal brain lesions.

Neuropsychological assessment of a case of early right hemiplegia: Qualitative and quantitative analysis

Evidence for normal development of linguistic but poor visuo-perceptual skills has been obtained with the neuropsychological assessment of a case of early left-brain injury. Data suggest the transfer of linguistic functions from the left to the right hemisphere at the expense of visuo-perceptual capacities for which the right hemisphere is potentially specialized.