Brain asymmetries in autism and developmental language disorder: a nested whole-brain analysis.
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We report a whole-brain MRI morphometric survey of asymmetry in children with high-functioning autism and with developmental language disorder (DLD). Subjects included 46 boys of normal intelligence aged 5.7-11.3 years (16 autistic, 15 DLD, 15 controls). Imaging analysis included grey-white segmentation and cortical parcellation. Asymmetry was assessed at a series of nested levels. We found that asymmetries were masked with larger units of analysis but progressively more apparent with smaller units, and that within the cerebral cortex the differences were greatest in higher-order association cortex. The larger units of analysis, including the cerebral hemispheres, the major grey and white matter structures and the cortical lobes, showed no asymmetries in autism or DLD and few asymmetries in controls. However, at the level of cortical parcellation units, autism and DLD showed more asymmetry than controls. They had a greater aggregate volume of significantly asymmetrical cortical parcellation units (leftward plus rightward), as well as a substantially larger aggregate volume of right-asymmetrical cortex in DLD and autism than in controls; this rightward bias was more pronounced in autism than in DLD. DLD, but not autism, showed a small but significant loss of leftward asymmetry compared with controls. Right : left ratios were reversed, autism and DLD having twice as much right- as left-asymmetrical cortex, while the reverse was found in the control sample. Asymmetry differences between groups were most significant in the higher-order association areas. Autism and DLD were much more similar to each other in patterns of asymmetry throughout the cerebral cortex than either was to controls; this similarity suggests systematic and related alterations rather than random neural systems alterations. We review these findings in relation to previously reported volumetric features in these two samples of brains, including increased total brain and white matter volumes and lack of increase in the size of the corpus callosum. Larger brain volume has previously been associated with increased lateralization. The sizeable right-asymmetry increase reported here may be a consequence of early abnormal brain growth trajectories in these disorders, while higher-order association areas may be most vulnerable to connectivity abnormalities associated with white matter increases. (+info)
Cognitive and neuroimaging findings in physically abused preschoolers.
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AIMS: To characterise the cognitive, motor, and language skills of toddlers and preschoolers who had been physically abused and to obtain concurrent MRIs of the brain. METHODS: A between groups design was used to compare a sample of 19 children, aged 14-77 months, who had been hospitalised for physical abuse with no evidence of neurological injury to a comparison group of 19 children matched for age and socioeconomic status. Children underwent cognitive, language, and motor testing within three months of their discharge from the hospital. Caregivers of the injured children were interviewed and were asked to complete questionnaires to characterise the child's developmental level and behaviour just prior to the hospitalisation. RESULTS: Children who had been physically abused scored significantly lower than the comparison group on measures of cognitive functioning, motor skills, and language skills. The groups did not differ in child behaviour ratings completed by the caregivers. MRI of the brain was performed for 15 children in the physical abuse group; two were found to have significant cerebral atrophy. CONCLUSIONS: Children who have been physically abused are at high risk for delays in cognitive, motor, and language development. Standard of care for these children should include developmental testing as well as neuroimaging of the brain to detect occult brain injury. (+info)
Correlation between brainstem and cortical auditory processes in normal and language-impaired children.
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A functional relationship between brainstem and cortical auditory processing was shown to be abnormal in children with language-based learning problems (LP). Auditory evoked potentials were used to investigate brainstem and cortical responses to the speech sound /da/. The duration of the wave V-V(n) complex of the auditory brainstem response was studied, as was the effect of noise on correlations between cortical responses to repeated stimuli. The group of LP children (n = 11) demonstrated abnormal encoding of speech sounds on both individual measures of brainstem and cortical processing; prolonged wave V-V(n) duration and pronounced susceptibility of cortical correlations to degradation by noise were both interpreted as reflecting diminished synchrony of response generator mechanisms. Furthermore, the LP group as a whole failed to demonstrate a relationship between brainstem and cortical measures that was demonstrated to be quite strong across all normal children (NL, n = 9). However, a subset of roughly three-quarters of the LP children appeared to demonstrate the normal relationship between brainstem and cortical processing, suggesting that they share a common functional connection with NL children. This relatively normal relationship between brainstem and cortical auditory processing in most LP children, as well as the exceptions to this relationship reflected by a smaller portion of LP children, may delineate different subclasses of auditory-language-based learning problems. This suggests the potential for use of these measures as diagnostic tools. (+info)
Developmental impairments following severe falciparum malaria in children.
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OBJECTIVE: Neurological deficits are reported in children after cerebral malaria (CM) but little is known about the prevalence and characteristics of persisting neurocognitive consequences. The prevalence of developmental impairments following other complications of falciparum malaria, such as multiple, prolonged or focal seizures, is not known. Thus, our objective was to investigate the long-term developmental outcome of CM and malaria with complicated seizures (M/S). METHODS: We followed up a cohort of children previously exposed to CM or M/S and children unexposed to either condition. All children between 6 and 9 years of age, exposed to CM, and an equal number of children exposed to M/S were identified from databases of hospital admissions from 1991 to 1998. The unexposed group was randomly selected from a census database. The children's performance was measured using assessments of cognition, motor, speech and language, hearing and vision. A parental questionnaire was used to identify children with epilepsy. RESULTS: CM group scores were significantly lower than unexposed group scores on the assessments of higher level language (adjusted mean difference -1.63, 95% CI: -2.99 to -0.27), vocabulary (-0.02, 95% CI: -0.04 to -0.01), pragmatics (OR 2.81, 95% CI: 1.04-7.6) and non-verbal functioning (-0.33, 95% CI: -0.61 to -0.06). The areas of significantly reduced functioning for the M/S group were concentrated on phonology (OR 2.74, 95% CI: 1.26-5.95), pragmatics (OR 3.23, 95% CI: 1.2-8.71) and behaviour (OR 1.8, 95% CI: 1.0-3.23). The performance of the active epilepsy group was significantly poorer than that of the group without epilepsy on the tests of comprehension, syntax, pragmatics, word finding, memory, attention, behaviour and motor skills. CONCLUSIONS: CM and M/S are associated with developmental impairments. If these impairments persist, this may have implications for least 250,000 children in Sub-Saharan Africa each year. Active epilepsy significantly increases the risk of cognitive and behavioural problems in children with a history of severe malaria. (+info)
Reduced functional connectivity between V1 and inferior frontal cortex associated with visuomotor performance in autism.
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Some recent evidence has suggested abnormalities of the dorsal stream and possibly the mirror neuron system in autism, which may be responsible for impairments of joint attention, imitation, and secondarily for language delays. The current study investigates functional connectivity along the dorsal stream in autism, examining interregional blood oxygenation level dependent (BOLD) signal cross-correlation during visuomotor coordination. Eight high-functioning autistic men and eight handedness and age-matched controls were included. Visually prompted button presses were performed with the preferred hand. For each subject, functional connectivity was computed in terms of BOLD signal correlation with the mean time series in bilateral visual area 17. Our hypothesis of reduced dorsal stream connectivity in autism was only in part confirmed. Functional connectivity with superior parietal areas was not significantly reduced. However, the autism group showed significantly reduced connectivity with bilateral inferior frontal area 44, which is compatible with the hypothesis of mirror neuron defects in autism. More generally, our findings suggest that dorsal stream connectivity in autism may not be fully functional. (+info)
Teaching idiom comprehension to children with mental retardation.
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This study examined the effectiveness of a training program designed to teach children with mild mental retardation the meaning of 12 idiomatic phrases, such as "to hit the sack." Four 9-year-old children participated in the training. A multiple baseline design across subjects and across three sets of idioms was implemented. Training consisted of presenting both literal and idiomatic contexts in the form of story narratives, and asking the children to explain the outcome of the story and to select one picture from an array of four that represented the outcome. All children demonstrated learning, although 1 child required review procedures to facilitate maintenance. Children were able to generalize their receptive learning to an expressive task with varying levels of success. All children demonstrated an ability to understand the learned idioms when presented in unfamiliar contexts. (+info)
Prenatal cocaine exposure and children's language functioning at 6 and 9.5 years: moderating effects of child age, birthweight, and gender.
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OBJECTIVE: To evaluate whether prenatal cocaine exposure (PCE), or the interaction between PCE and contextual variables, is associated with children's language at age 6 and 9.5 years, adjusting for relevant covariates. METHODS: Analyses were based on 160 low-income, urban children from a prospective study who completed a standardized language assessment at 6 and 9.5 years. PCE was determined using neonatal meconium assays and maternal self-report. RESULTS: Significant interaction effects of PCE on language outcomes were found in multivariate longitudinal analyses using generalized estimating equations (GEE). Children with PCE had lower receptive language than unexposed children at 6 but not at 9.5 years, lower expressive language if they had lower birthweight, and lower expressive and total language if they were female. Other risk (e.g., violence exposure) and protective factors (e.g., preschool experience) were related to language outcomes regardless of PCE status. CONCLUSIONS: Age, birthweight, and gender moderated the relation between PCE and school-aged children's language. (+info)
Speech perception and short-term memory deficits in persistent developmental speech disorder.
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Children with developmental speech disorders may have additional deficits in speech perception and/or short-term memory. To determine whether these are only transient developmental delays that can accompany the disorder in childhood or persist as part of the speech disorder, adults with a persistent familial speech disorder were tested on speech perception and short-term memory. Nine adults with a persistent familial developmental speech disorder without language impairment were compared with 20 controls on tasks requiring the discrimination of fine acoustic cues for word identification and on measures of verbal and nonverbal short-term memory. Significant group differences were found in the slopes of the discrimination curves for first formant transitions for word identification with stop gaps of 40 and 20 ms with effect sizes of 1.60 and 1.56. Significant group differences also occurred on tests of nonverbal rhythm and tonal memory, and verbal short-term memory with effect sizes of 2.38, 1.56, and 1.73. No group differences occurred in the use of stop gap durations for word identification. Because frequency-based speech perception and short-term verbal and nonverbal memory deficits both persisted into adulthood in the speech-impaired adults, these deficits may be involved in the persistence of speech disorders without language impairment. (+info)