A preliminary neuroimaging study of preschool children with ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a developmental disorder that, by current definition, has onset prior to age 7 years. MRI studies have provided some insight into brain differences associated with ADHD, but thus far have almost exclusively focused on children ages 7 years and older. To better understand the neurobiological development of ADHD, cortical and subcortical brain development should be systematically examined in younger children presenting with symptoms of the disorder. High-resolution anatomical (MPRAGE) images, acquired on a 3.0T scanner, were analyzed in a total of 26 preschoolers, ages 4-5 years (13 with ADHD, 13 controls, matched on age and sex). The ADHD sample was diagnosed using DSM-IV criteria, and screened for language disorders. Cortical regions were delineated and measured using automated methods in Freesurfer; basal ganglia structures were manually delineated. Children with ADHD showed significantly reduced caudate volumes bilaterally; in contrast there were no significant group differences in cortical volume or thickness in this age range. After controlling for age and total cerebral volume, left caudate volume was a significant predictor of hyperactive/impulsive, but not inattentive symptom severity. Anomalous basal ganglia, particularly caudate, development appears to play an important role among children presenting with early onset symptoms of ADHD.

Quantifying excessive mirror overflow in children with attention-deficit/hyperactivity disorder

OBJECTIVES

Qualitative observations have revealed that children with attention-deficit/hyperactivity disorder (ADHD) show increased overflow movements, a motor sign thought to reflect impaired inhibitory control. The goal of this study was to develop and implement methods for quantifying excessive mirror overflow movements in children with ADHD.

METHODS

Fifty right-handed children aged 8.2-13.3 years, 25 with ADHD (12 girls) and 25 typically developing (TD) control children (10 girls), performed a sequential finger-tapping task, completing both left-handed (LHFS) and right-handed finger sequencing (RHFS). Phasic overflow of the index and ring fingers was assessed in 34 children with video recording, and total overflow in 48 children was measured by calculating the total angular displacement of the index and ring fingers with electrogoniometer recordings.

RESULTS

Phasic overflow and total overflow across both hands were greater in children with ADHD than in TD children, particularly during LHFS. Separate gender analyses revealed that boys, but not girls, with ADHD showed significantly more total phasic overflow and total overflow than did their gender-matched control children.

CONCLUSIONS

The quantitative overflow measures used in this study support past qualitative findings that motor overflow persists to a greater degree in children with ADHD than in age-matched TD peers. The quantitative findings further suggest that persistence of mirror overflow is more prominent during task execution of the nondominant hand and reveal gender-based differences in developmental neural systems critical to motor control. These quantitative measures will assist future physiologic investigation of the brain basis of motor control in ADHD.

Age-related changes in motor subtle signs among girls and boys with ADHD

OBJECTIVE

To examine differences in age-related improvement in motor speed and neurologic subtle signs (overflow and dysrhythmia) among boys and girls with and without attention-deficit hyperactivity disorder (ADHD).

METHOD

Diagnosis of ADHD was determined by structured parent interview and administration of ADHD-specific and broad behavior rating scales. Motor function was assessed using the revised Physical and Neurological Assessment of Subtle Signs. Three primary outcome variables were obtained: 1) total time, 2) total overflow, and 3) total dysrhythmia. Effects of age, group, and sex were assessed.

RESULTS

Both control and ADHD groups showed improvement on timed tasks with age; however, controls were consistently faster across the age span. Controls and girls with ADHD showed steady age-related reduction of overflow and dysrhythmia, whereas boys with ADHD had little improvement in these signs through age 14 years.

CONCLUSION

Results indicated that girls with attention-deficit hyperactivity disorder (ADHD) performed similarly to age-matched controls on a quantified motor examination. These results parallel patterns of findings from neuroimaging studies, in which neurologic anomalies in areas related to motor control are present in boys with ADHD, but more equivocal in girls with ADHD. Sex-related differences observed in children with ADHD likely extend beyond symptom presentation to development of motor control, and are likely related to earlier brain maturation in girls.

Dyspraxia in autism: association with motor, social, and communicative deficits

Impaired performance of skilled gestures, referred to as dyspraxia, is consistently reported in children with autism; however, its neurological basis is not well understood. Basic motor skill deficits are also observed in children with autism and it is unclear whether dyspraxia observed in children with autism can be accounted for by problems with motor skills. Forty-seven high-functioning children with an autism spectrum disorder (ASD), autism, or Asperger syndrome (43 males, four females; mean age 10y 7m [SD 1y 10m], mean Full-scale IQ (FSIQ) 99.4 [SD 15.9]), and 47 typically developing (TD) controls (41 males, six females; mean age 10y 6m [SD 1y 5m], mean FSIQ 113.8 [SD 12.3], age range 8-4y) completed: (1) the Physical and Neurological Assessment of Subtle Signs, an examination of basic motor skills standardized for children, and (2) a praxis examination that included gestures to command, to imitation, and with tool-use. Hierarchical regression was used to examine the association between basic motor skill performance (i.e. times to complete repetitive limb movements) and praxis performance (total praxis errors). After controlling for age and IQ, basic motor skill was a significant predictor of performance on praxis examination. Nevertheless, the ASD group continued to show significantly poorer praxis than controls after accounting for basic motor skill. Furthermore, praxis performance was a strong predictor of the defining features of autism, measured using the Autism Diagnostic Observation Schedule, and this correlation remained significant after accounting for basic motor skill. Results indicate that dyspraxia in autism cannot be entirely accounted for by impairments in basic motor skills, suggesting the presence of additional contributory factors. Furthermore, praxis in children with autism is strongly correlated with the social, communicative, and behavioral impairments that define the disorder, suggesting that dyspraxia may be a core feature of autism or a marker of the neurological abnormalities underlying the disorder.

Sex differences in cerebral laterality of language and visuospatial processing

Sex differences on language and visuospatial tasks are of great interest, with differences in hemispheric laterality hypothesized to exist between males and females. Some functional imaging studies examining sex differences have shown that males are more left lateralized on language tasks and females are more right lateralized on visuospatial tasks; however, findings are inconsistent. Here we used functional magnetic resonance imaging to study thirty participants, matched on task performance, during phonological and visuospatial tasks. For each task, region-of-interest analyses were used to test differences in cerebral laterality. Results indicate that lateralization differences exist, with males more left lateralized during the phonological task and showing greater bilateral activity during the visuospatial task, whereas females showed greater bilateral activity during the phonological task and were more right lateralized during the visuospatial task. Our data provide clear evidence for differences in laterality between males and females when processing language versus visuospatial information.

Subtle executive impairment in children with autism and children with ADHD

BACKGROUND

The executive functions of inhibition, planning, flexible shifting of actions, and working memory are commonly reported to be impaired in neurodevelopmental disorders.

METHOD

We compared these abilities in children (8-12 years) with high functioning autism (HFA, n = 17), attention deficit-hyperactivity disorder (ADHD, n = 21) and healthy controls (n = 32). Response inhibition was assessed using the Stroop Color and Word Test (Golden, 1978). Problem solving, set-shifting, and nonverbal memory were assessed using three tasks, respectively, from the CANTAB (Cambridge Cognition, 1996): the Stockings of Cambridge task; the Intra-Dimensional/Extra-Dimensional set-shifting task; and the Spatial Working Memory task (SWM) with tokens hidden behind 3, 4, 6, and 8 boxes.

RESULTS

There were no group differences on the response inhibition, planning, or set-shifting tasks. On the SWM task, children with HFA made significantly more between-search errors compared with controls on both the most difficult problems (8-box) and on the mid-difficulty problems (6-box); however, children with ADHD made significantly more errors compared to controls on the most difficult (8-box) problems only.

CONCLUSION

Our findings suggest that spatial working memory is impaired in both ADHD and HFA, and more severely in the latter. More detailed investigation is needed to examine the mechanisms that differentially impair spatial working memory, but on this set of tasks there appears to be sparing of other executive functions in these neuropsychiatric developmental disorders.

Cortical correlates of neuromotor development in healthy children

OBJECTIVE

To examine the relationship between acquisition of fine motor skills in childhood and development of the motor cortex.

METHODS

We measured finger tapping speed and mirror movements in 43 healthy right-handed subjects (6-26 years of age). While recording surface electromyographic activity from right and left first dorsal interosseus, we delivered focal transcranial magnetic stimulation (TMS) over the hand areas of each motor cortex. We measured motor evoked potential (MEP) threshold, and ipsilateral (iSP) and contralateral (CSP) silent periods.

RESULTS

As children got older, finger speeds got faster, MEP threshold decreased, iSP duration increased and latency decreased. Finger tapping speed got faster as motor thresholds and iSP latency decreased, but was unrelated to CSP duration. In all subjects right hemisphere MEP thresholds were higher than those on the left and duration of right hemisphere CSP was longer than that on the left. Children under 10 years of age had higher left hand mirror movement scores, and fewer left hemisphere iSPs which were of longer duration.

CONCLUSIONS

Maturation of finger tapping skills is closely related to developmental changes in the motor threshold and iSP latency. Studies are warranted to explore the relationship between these measures and other neuromotor skills in children with motor disorders.

SIGNIFICANCE

TMS can provide important insights into certain functional aspects of neurodevelopment in children.

Megalencephaly in NF1: predominantly white matter contribution and mitigation by ADHD

BACKGROUND

Megalencephaly is a frequent CNS manifestation in neurofibromatosis type 1 (NF1); however, its tissue composition, modification by attention deficit hyperactivity disorder (ADHD), and relationship with unidentified bright objects (UBO) remain controversial.

METHODS

Eighteen male patients with NF1, seven of whom had ADHD (NF1+ADHD), were compared with 18 age- and sex-matched controls in terms of MRI-, Talairach-based brain, cerebral, lobar, and sublobar gray and white matter volumes. Twelve subjects with NF1 had UBO in the centrencephalic region, whereas six had no UBO or exclusively infratentorial lesions.

RESULTS

Patients with NF1 without ADHD (NF1-pure) had the largest total cerebral, gray, and white matter volumes with larger parietal/somatosensory white matter volumes than controls, particularly if UBO were present in the basal ganglia. All subjects with NF1 (including NF1+ADHD) had larger total and frontal white matter volumes than controls. Smaller frontal/right prefrontal gray matter volumes were found in NF1+ADHD when compared with NF1-pure patients.

CONCLUSIONS

The increase in frontal and parietal white matter volumes in male patients with NF1, including the preferential centrencephalic distribution, supports the hypothesis that NF1's white matter pathology encompasses but is not limited to visible UBO. Male patients with NF1+ADHD, as compared with NF1-pure patients, showed frontal reductions that are largely consistent with those found in idiopathic ADHD.

Disproportionate increases of white matter in right frontal lobe in Tourette syndrome

OBJECTIVE

Based on previous findings implicating abnormalities of cortico-striatal-thalamo-cortical circuitry in Tourette syndrome (TS), the authors performed a volumetric analysis of frontal and nonfrontal tissue (gray + white matter) in boys with TS, with and without attention deficit hyperactivity disorder (ADHD).

METHODS

Frontal and nonfrontal gray and white matter compartment volumes, obtained by a MRI protocol, were analyzed with a 2 x 2 factorial multivariate analysis of variance approach for associations with a TS or ADHD factor in 11 boys with TS only, 14 with TS + ADHD, 12 with ADHD only, and 26 healthy boys.

RESULTS

In subjects with TS, the right frontal lobe showed a larger proportion of white matter. In addition, results were consistent with previous reports of reduced frontal lobe volumes associated with ADHD. Our analyses suggested these reductions to be mainly the consequence of smaller gray matter volumes, particularly on the left.

CONCLUSIONS

These findings, suggesting the volumetric composition of frontal lobe tissue to be different in TS, support the hypothesis proposing frontostriatal pathway involvement in the pathophysiology of the disorder. Differences in composition of right frontal lobe attributable to white matter do not definitively implicate the hypothesized fiber pathways; however, considered in the context of the unilateral directionality of frontal-striatal circuitry, these results suggest the white matter connections as one explanation for basal ganglia anomalies (loss of normal left > right asymmetry) in TS.

Oculomotor abnormalities in boys with tourette syndrome with and without ADHD

OBJECTIVE

To assess saccadic eye movements in boys with Tourette syndrome (TS) with and without attention-deficit hyperactivity disorder (ADHD), comparing performance with that of an age-matched group of male controls.

METHOD

Three different saccade tasks (prosaccades, antisaccades, and memory-guided saccades) were used to examine functions necessary for the planning and execution of eye movements, including motor response preparation, response inhibition, and working memory. The study included 14 boys with TS without ADHD (TS-only), 11 boys with TS and ADHD (TS+ADHD), and 10 male controls.

RESULTS

Latency of prosaccades was prolonged in boys with TS (both with and without ADHD) compared with controls. Variability in prosaccade latency was greater in the groups of boys with TS+ADHD compared with both the TS-only and control groups. Response inhibition errors on both the antisaccade task (directional errors) and memory-guided saccade task (anticipatory errors) were increased in boys with TS+ADHD compared with those with TS-only. There were no significant differences among the three groups in accuracy of memory-guided saccades.

CONCLUSIONS

Oculomotor findings suggest that TS is associated with delay in initiation of motor response as evidenced by excessive latency on prosaccades. Signs of impaired response inhibition and variability in motor response appear to be associated with the presence of ADHD.

Oculomotor abnormalities in attention deficit hyperactivity disorder: a preliminary study

BACKGROUND

Prevailing hypotheses suggest that attention deficit hyperactivity disorder (ADHD) is secondary to dysfunction of motor intentional systems mediated by prefrontal circuitry. Oculomotor paradigms provide a mechanism for examining and localizing dysfunction at the interface between movement and cognition.

OBJECTIVE

Three different saccade tasks (reflexive or prosaccades, antisaccades, and memory-guided saccades) were used to examine functions necessary for the planning and the execution of eye movements, including motor response preparation, response inhibition, and working memory.

METHODS

The study included 19 children with ADHD, divided into two groups: a group of 8 children on methylphenidate at the time of testing and a group of 11 children not taking any psychoactive medication. Results from the two groups were compared with those from 25 age- and gender-matched normal control children.

RESULTS

Both groups of children with ADHD made significantly more directional errors than did controls on the antisaccade task and significantly more anticipatory errors than did controls on the memory-guided saccade task, findings that are consistent with deficits in response inhibition. There were no significant differences in prosaccade latency, although unmedicated children with ADHD showed significantly greater variability in latency on the prosaccade task than did controls. On the memory-guided saccade task there were no significant differences in saccade accuracy; however, unmedicated children with ADHD showed longer saccade latency than did either controls or medicated children with ADHD.

CONCLUSIONS

Oculomotor findings suggest that deficits in prefrontal functions, in particular response inhibition, contribute to behavioral abnormalities observed in ADHD. Findings also suggest that the administration of methylphenidate is associated with improvements in the consistency of motor response. Although there were no observed improvements in response inhibition with methylphenidate, conclusions await a design in which subjects complete testing both on and off medication.

Depth of lesion model in children and adolescents with moderate to severe traumatic brain injury: use of SPGR MRI to predict severity and outcome

OBJECTIVES

The utility of a depth of lesion classification using an SPGR MRI sequence in children with moderate to severe traumatic brain injury (TBI) was examined. Clinical and depth of lesion classification measures of TBI severity were used to predict neurological and functional outcome after TBI.

METHODS

One hundred and six children, aged 4 to 19, with moderate to severe TBI admitted to a rehabilitation unit had an SPGR MRI sequence obtained 3 months afterTBI. Acquired images were analyzed for location, number, and size of lesions. The Glasgow coma scale (GCS) was the clinical indicator of severity. The deepest lesion present was used for depth of lesion classification. Speed of injury was inferred from the type of injury. The disability rating scale at the time of discharge from the rehabilitation unit (DRS1) and at 1 year follow up (DRS2) were functional outcome measures.

RESULTS

The depth of lesion classification was significantly correlated with GCS severity, number of lesions, and both functional measures, DRS1 and DRS2. This result was more robust for time 1, probably due to the greater number of psychosocial factors impacting on functioning at time 2. Lesion volume was not correlated with the depth of lesion model. In multivariate models, depth of lesion was most predictive of DRS1, whereas GCS was most predictive of DRS2.

CONCLUSIONS

A depth of lesion classification of TBI severity may have clinical utility in predicting functional outcome in children and adolescents with moderate to severe TBI.

Executive function in fluency and recall measures among children with Tourette syndrome or ADHD

This study assessed two relevant aspects of executive dysfunction in children with either Tourette syndrome (TS) or ADHD. Process variables derived from existing neuropsychological measures were used to clarify the executive function construct. Clustering of responses on measures of verbal fluency, figural fluency, and verbal learning was examined to assess strategic response organization. Rule breaks, intrusions, and repetition errors were recorded to assess inhibition errors. No significant differences were found among the three groups (TS, ADHD, and controls) on tasks of response organization (clustering). In our sample, both the ADHD and the TS groups were largely free from executive function impairment, and their performance on the fluency and list learning tasks was in the average range. There was a significant group difference on one of the disinhibition variables, with both TS and ADHD groups showing significantly more intrusions on verbal list learning trials than controls. When more traditional total score variables were analyzed among the three groups, there were no significant differences; however, analysis of effect size revealed medium-to-large effect sizes for Letter Word Fluency total score differences (ADHD vs. controls), and for Semantic Word Fluency total score differences (ADHD vs. TS), with the ADHD group having weaker performance in both comparisons. Results provide some support for the use and analysis of process variables-particularly those related to inhibition and intrusion errors, in addition to the total score variables when assessing executive function deficits in children with ADHD and TS. While group differences may be found, children with uncomplicated TS should not routinely be considered to have significant executive function impairments, and when deficits are found, they may be attributable to other comorbid disorders.

Evidence for a deficit in procedural learning in children and adolescents with autism: implications for cerebellar contribution

To examine the hypothesis that abnormalities in those cognitive functions for which cerebellar components have been implicated contribute to the pathophysiology of autism, tests of judgment of explicit time intervals and procedural learning were administered to 11 participants with autism and 17 age-and-IQ-matched controls. Results indicated that the group with autism demonstrated significant impairments in procedural learning compared with the group of controls. No significant difference in judgment of explicit time intervals was found. The data suggest that deficits in procedural learning may contribute to the cognitive and behavioral phenotype of autism; these deficits may be secondary to abnormalities in cerebellar-frontal circuitry.

The association of neurofibromatosis type 1 and attention deficit hyperactivity disorder

Some research and clinical observations have linked Neurofibromatosis Type 1 (NF-1) and Attention Deficit Hyperactivity Disorder (ADHD). In order to investigate whether ADHD is part of the phenotype of NF-1 or is a separate, unrelated disorder within families, we compared the ADHD status of children affected with NF-1 to that of their unaffected-NF-1 siblings and to that of their biological parents. Results of matched-pair analyses were calculated and revealed a significant with-in pair discordance, when comparing children with NF-1 and their siblings and when comparing children with NF-1 and their biological parents (in families with a sporadic, non-familial NF-1 child). These findings suggest that ADHD may occur as a component of the NF-1 phenotype.

Judgment of duration in individuals with ataxia-telangiectasia

Several clinical investigations with adults suggest that the cerebellum may be critical for judgment of explicit time intervals; however, little work has been done in populations with lesions of the cerebellum acquired during development. We evaluated 17 individuals with ataxia-telangiectasia (AT), an autosomal recessive disorder with on-set in early childhood characterized by diffuse, almost selective, degeneration of the cerebellar cortex, and 21 normal controls, matched for age. Because patients with AT have motor impairment, verbal IQ (VIQ) was used to estimate intelligence; VIQ was significantly lower in the group with AT (p < .0001). Participants were tested using a test of judgment of duration that has been found to be impaired in adults with cerebellar lesions and a contrasting auditory control task (not impaired in adults with cerebellar lesions) involving judgment of pitch. After statistically controlling for VIQ, the 2 groups did not differ significantly on judgment of pitch, but those with AT performed significantly worse than controls on judgment of duration (p = .01). Children and adolescents with AT show deficits in judgment of duration but not of pitch, suggesting that the cerebellum may be critical for judgment of explicit time intervals at all ages.

How children with neurofibromatosis type 1 differ from "typical" learning disabled clinic attenders: nonverbal learning disabilities revisited

To further investigate cognitive deficits in children with Neurofibromatosis Type 1 (NF-1), children with NF-1 were compared to typical learning disabled clinic attenders (LD-clinic), all of whom had reading disabilities, as well as to a group with no disabilities (NoDx). Results indicated that both the NF-1 group and LD-clinic group had reading and reading-related deficits when compared to the NoDx group; however, the NF-1 group was more globally language impaired than the LD-clinic group. In addition, the NF-1 group scored significantly lower than the LD-clinic group, but not the NoDx group, on the visuospatial measures, thus confirming that children with NF-1 have visuospatial deficits not typical of a general LD-clinic population. The NF-1 group was not impaired in comparison to the NoDx group on certain language and visuospatial tasks that were previously found to be deficits in sibling pairwise matched designs; thus, the importance of considering genetic and familial context when studying the impact of genetic disorders on cognition was demonstrated.

Language-based cognitive functioning in parents of offspring with ADHD comorbid for Tourette syndrome or learning disabilities

The parents of children diagnosed with attention deficit hyperactivity disorder (ADHD) were examined for characteristics symptomatic of 2 comorbidities (Co) within their offspring with ADHD: Tourette syndrome (TS) and language-based learning disabilities (LD). A 2 x 2 multivariate analysis of variance design was used; the parents were divided according to whether the offspring with ADHD had TS (Co-TS) or not (No Co-TS) and whether offspring had LD (Co-LD) or not (No Co-LD). Parents (86 mothers and 70 fathers) were administered the short form of the Wechsler Adult Intelligence Scale--Revised (WAIS-R; Wechsler, 1981), subtests of the Woodcock-Johnson Cognitive and Achievement Batteries (Woodcock & Johnson, 1989), and word fluency (semantic and letter; Benton & Hamsher, 1989; Wiig & Semel, 1987). The fathers of offspring with Co-TS were more likely to be diagnosed with LD and had lower WAIS-R Vocabulary, Arithmetic, and Picture Arrangement scores. In addition, when the WAIS-R full scale IQ was used as a covariate, these fathers had lower Woodcock-Johnson Oral Vocabulary, Spelling, and Reading scores (as measured by Letter-Word Identification). The mothers of children with Co-TS had lower WAIS-R Vocabulary scores. Parents of the children with No Co-TS showed a higher proportion of error patterns on the word fluency tasks involving repetitions and rule breaks. The findings show that it was the parents of the children with Co-TS, not the parents of the children with Co-LD, who showed language-based learning problems. In separate discriminant analyses for the fathers and mothers, when the aforementioned significant parental measures were used as predictors, 81% of offspring with Co-TS were correctly classified as having a diagnosis of TS, solely on the basis of characteristics in their parents.

Subcortical volumes in girls with tourette syndrome: support for a gender effect

OBJECTIVE

To test whether girls with Tourette syndrome (TS) show subcortical morphology that differentiates them from control subjects.

METHODS

MRI-based subcortical assessment was completed on 19 girls with TS age 7 to 15 years, 11 with TS only, and 8 with TS plus attention deficit hyperactivity disorder (TS + ADHD), and on 21 age- and sex-matched controls. The structures measured were the caudate, putamen, globus pallidus, and lateral ventricle volumes. Whole-brain-corrected volumes and asymmetry indices were compared using two- and three-group designs (i.e., TS versus control; TS-only versus TS + ADHD versus control).

RESULTS

Two-group comparisons demonstrated no robust significant differences between girls with TS and gender-matched controls. Three-group comparisons demonstrated that TS-only subjects had significantly small lateral ventricles compared with TS + ADHD and control subjects. Because the two-group comparisons of the current study differed from previous reports of putamen asymmetry index as a marker for TS, retrospective comparisons with data from boys were performed. These additional comparisons showed that girls with TS had putamen asymmetry indices similar to those of boys with TS; however, control girls also showed those same patterns.

CONCLUSIONS

Basal ganglia volume and asymmetry differences do not distinguish the girls with TS from matched controls. Gender differences confound the association between putamen asymmetry and TS. Although the numbers are small and the clinical significance is unclear, this study further indicates that girls with TS-only have smaller lateral ventricular volumes than control subjects and those with TS + ADHD.

Thalamic involvement in neurofibromatosis type 1: evaluation with proton magnetic resonance spectroscopic imaging

Neurofibromatosis type 1 is a common autosomal dominant disorder associated with learning disabilities. In addition to gliomas and other tumors, T2 hyperintense lesions (unidentified bright objects or UBOs) are frequently found in the globus pallidus, cerebellum, and white matter regions. To better characterize supratentorial UBO functional significance, we studied by quantitative magnetic resonance spectroscopic imaging (MRSI) 9 male subjects with neurofibromatosis type 1 (age, 6-19 years) and 9 age-matched and sex-matched controls. Maps of the anatomical distribution of the metabolites choline (Cho), N-acetylaspartate (NAA), and creatine were calculated in four axial 15-mm slices. Absolute metabolite concentrations within UBOs, unaffected globus pallidus, and thalami demonstrated an age-related pattern, characterized by elevated Cho and relatively preserved NAA in younger subjects (<10 years) and reduced NAA and normal Cho in older subjects. These changes were found in both UBOs and thalami but were only significant for NAA, NAA/creatine, and NAA/Cho in the latter region. Decreases in NAA ratios were most severe in the thalami of subjects with UBOs in the globus pallidus, whereas UBOs showed similar but milder abnormalities than those in the thalamus. We speculate that the MRSI metabolic abnormality may represent a more generalized phenomenon, without a T2 signal counterpart in the affected brain regions. Based on the neuropathological study by DiPaolo and colleagues (1995), we postulate that Cho elevations reflect increased myelin turnover in areas of intramyelinic edema, which is followed by neuropil injury (reduced NAA). Temporal progression and behavioral correlates of these MRSI changes deserve further exploration.

Relationship of cognitive functioning, whole brain volumes, and T2-weighted hyperintensities in neurofibromatosis-1

Using quantitative magnetic resonance imaging morphometry, we report that the whole brain volumes of patients with neurofibromatosis-1 are significantly larger than normal, confirm the prevalence of macrocephaly as about 50%, and report that macrocephaly in patients with neurofibromatosis-1 does not appear to be related to the familial or sporadic origin of the neurofibromatosis-1 or to the presence or absence of T2-weighted hyperintensities. No strong relationship emerged between the extent of neurofibromatosis-1-associated impairment of cognitive functions and degree of macrocephaly; however, the macrocephalic neurofibromatosis-1 group did have a significant verbal impairment relative to the nonmacrocephalic neurofibromatosis-1 group in vocabulary (P < .009).

Neuroimaging variables related to development of Secondary Attention Deficit Hyperactivity Disorder after closed head injury in children and adolescents

OBJECTIVE

To characterize children who develop Secondary Attention Deficit Hyperactivity Disorder (S-ADHD) after severe and moderate closed head injury (CHI) according to neuroimaging variables.

METHOD

Ninety-nine children from 4-19 years who suffered severe and moderate CHI were prospectively followed for a year after injury. Premorbid psychiatric status was determined by administration to the parent of a structured psychiatric interview. This interview was readministered 1 year after injury to determine the presence of post-closed head injury S-ADHD. An MRI was performed 3 months after injury to define lesion locations and volumes.

RESULTS

A set of multiple logistic regression models determined that the odds of developing S-ADHD were 3.64 times higher among children with thalamus injury, and 3.15 times higher among children with basal ganglia injury. There was no significant difference in lesion volumes in any of the locations of interest between the group who developed S-ADHD and the group who did not develop S-ADHD.

CONCLUSION

The data support an association between S-ADHD and injury in either or both the thalamus and basal ganglia, but they do not definitively demonstrate whether injury in either structure has an effect on S-ADHD in the absence of injury in the other.

Corpus callosum measurements in girls with Tourette syndrome

The objective of this study was to examine whether abnormalities in corpus callosum morphology, previously reported in boys with Tourette syndrome (TS), were also present in girls with this disorder. Among the three groups of girls-TS, TS and attention deficit hyperactivity disorder, and controls-there were no significant differences in the size of the corpus callosum or any of five individual subregions. The findings suggest that abnormalities in corpus callosum morphology in TS are a gender-related phenomenon.

Evaluation of cerebellar size in attention-deficit hyperactivity disorder

Evidence from animal and human research suggests that the cerebellum may play a role in cognition. This includes domains of executive function that are normally attributed to the prefrontal cortex and are typically deficient in individuals with attention-deficit hyperactivity disorder (ADHD). To investigate cerebellar structure in ADHD, magnetic resonance imaging morphometry was used to measure the area of the cerebellar vermis in 12 males with ADHD and 23 male controls matched for age and Wechsler Full-Scale IQ. Analyses were conducted to evaluate group differences, as well as differences between matched pairs of subjects with ADHD and those without ADHD. All measurements were corrected for overall brain size. Both analyses revealed that the size of the posterior vermis was significantly decreased in males with ADHD (P < .05 in both analyses), and that within the posterior vermis, the inferior posterior lobe (lobules VIII-X) was involved in this reduction (P < .05 for group analysis, P < .005 for matched pair analysis), while the superior posterior lobe (lobules VI/VII) was not involved in the reduction. The finding of abnormal inferior posterior vermal size suggests that dysfunction within this region of the cerebellum may underlie clinical deficits seen in individuals with ADHD.

Gender study of neuropsychological and neuromotor function in children with Tourette syndrome with and without attention-deficit hyperactivity disorder

Neuropsychological and neuromotor functions were compared between boys and girls with Tourette syndrome (TS only), attention-deficit hyperactivity disorder (ADHD only), Tourette syndrome with ADHD (TS+ADHD), and a comparison group, in an age (mean = 10 years) and IQ (Wechsler Full-Scale mean = 111) matched sample (n = 116). There were no timed-task neuromotor differences among the groups. Analyses of variance revealed a group x gender interaction for Letter Word Fluency and the Rapid Automatized Naming test. Girls with ADHD only were faster than boys on both tasks. When data for girls only were analyzed, girls with Tourette syndrome with ADHD had the greatest variability of reaction time on the Test of Variables of Attention, and were slowest on Letter Word Fluency. Girls with TS only were slower than girls in the other three groups on Letter Word Fluency. Poor Letter Word Fluency is explained as a linguistic executive dysfunction involving speed and efficiency of memory search in this bright group of girls with Tourette syndrome, not otherwise at risk for linguistic difficulties.

Premorbid prevalence of ADHD and development of secondary ADHD after closed head injury

OBJECTIVE

To determine premorbid prevalence of attention-deficit hyperactivity disorder (ADHD) in children with moderate and severe closed head injury (CHI), to determine incidence of ADHD 1 year after injury, and to characterize children who develop ADHD by demographic, neuropsychiatric, and outcome variables.

METHOD

Ninety-nine children who had severe and moderate CHI were followed up for 1 year. Premorbid and 1-year postinjury psychiatric status were ascertained by parent and child structured interviews and questionnaires measuring affective lability, aggression, apathy, and social judgment.

RESULTS

Premorbid prevalence of ADHD was 0.20, significantly higher than in a reference population (0.045). Fifteen of the remaining 80 children (0.19) developed full ADHD criteria (except for age of onset) by the end of the first year. Children who developed secondary ADHD (S-ADHD) had significantly greater premorbid psychosocial adversity, posttraumatic affective lability and aggression, posttraumatic psychiatric comorbidity, and overall disability than children who did not develop S-ADHD.

CONCLUSIONS

There is an excess prevalence of premorbid ADHD among children who present with moderate and severe CHI. Children with high psychosocial adversity are more likely to develop S-ADHD after CHI. S-ADHD has criteria in common with personality change due to CHI, a deficit in behavioral inhibition being the major overlapping feature.

Decreased cerebellar posterior vermis size in fragile X syndrome: correlation with neurocognitive performance

We examined whether posterior vermis size is smaller in individuals with fragile X syndrome (fra X) than in control subjects and whether this decreased size is associated with cognitive performance. Cognitive and behavioral dysfunctions have been identified in fra X; however, underlying neuropathogenic mechanisms remain unclear. MRI was used to investigate the posterior fossa in 32 males with fra X, 28 males with other causes of cognitive disability (CD), and 38 males with normal development (ND) as well as and in 37 females with fra X and 53 female control subjects. Among females with fra X, neurocognitive correlates of posterior vermis size were examined. Posterior vermis size (cross-sectional area) in males with fra X was significantly smaller compared with CD and ND groups, particularly when corrected for intracranial area. Posterior vermis size corrected for intracranial area was significantly smaller in females with fra X compared with control subjects. Compared with males with fra X and non-fra X control subjects, posterior vermis size in females with fra X was intermediate. After statistically removing the effect of mean parental IQ, posterior vermis size predicted a significant proportion of the variance (10 to 23%) of performance on full-scale, verbal, and performance IQ; block design; categories achieved on the Wisconsin Card Sorting Test; and the Rey inventory score. The size of the posterior vermis is significantly decreased in fra X, more so in males than in females. In females with fra X, posterior vermis size predicts performance on selected cognitive measures.

Neuromotor functioning in children with Tourette syndrome with and without attention deficit hyperactivity disorder

Neuromotor function was assessed in 94 children of normal intelligence with Tourette syndrome, Tourette syndrome and attention-deficit hyperactivity disorder (ADHD), or ADHD only, using the Physical and Neurological Examination of Subtle Signs (PANESS). Time to complete six motor movements was analyzed separately by side (left and right) and complexity (simple and patterned). All groups performed faster on their preferred, dominant side. Although all groups took longer to complete patterned versus simple movements, the group with ADHD had a larger discrepancy for complexity than the other two groups. The speed for simple and patterned tasks was at or faster than age expectations for 54% of tasks in the group with Tourette syndrome but only 15% of tasks in the other two groups. More children in the group with Tourette syndrome (76%) than the groups with Tourette syndrome with ADHD (54%) or ADHD (54%) or ADHD only (65%) performed movements within normal time limits for age. Findings suggest that Tourette syndrome is not associated with motor slowing.

The Children's Affective Lability Scale: a psychometric evaluation of reliability

The Children's Affective Lability Scale (CALS) is a 20-item parent report measure developed to assess affect regulation in children aged 6-16. It was normed with school children in regular education classrooms and with children hospitalized in a psychiatric facility. Internal-consistency reliability, split-half reliability, and two-week test-retest reliability were excellent. Staff interrater reliability in the psychiatric sample was acceptable. Higher CALS scores were observed in an in-patient psychiatric sample than in either an out-patient or a normative sample. A principal components factor analysis yielded two components for the normative sample.

Brain development, gender and IQ in children. A volumetric imaging study

Normal brain development during childhood is a complex and dynamic process for which detailed scientific information is lacking. MRI techniques, combined with methods for advanced image analysis, offer the potential to begin to construct a quantitative map of normal paediatric brain development in vivo. In this study we utilize volumetric analysis of high resolution brain images obtained from MRI to describe cerebral development and morphology in 85 normal children and adolescents ranging in age from 5 to 17 years. The results show that total cerebral volume is 10% larger in boys compared with girls. However, both boys and girls show little change in total cerebral volume after the age of 5 years. Increased cortical grey matter is the primary contributor to larger brain volume in boys, thus supporting the hypothesis that gender associated differences in brain size are related to differences in cortical neuronal density. Prominent, age-related changes in grey matter, white matter and CSF volumes are evident during childhood and appear to reflect ongoing maturation and remodelling of the CNS. Both boys and girls show a similar pattern of cerebral asymmetry; a rightward prominence of cortical and subcortical grey matter and a leftward prominence of CSF is observed. IQ is positively correlated with total cerebral volume in children, in particular, with the volume of cortical grey matter in the prefrontal region of the brain. Subcortical grey matter also contributes to the variance in IQ, although to a lesser extent than cortical grey volume. Quantitative knowledge of the developing human brain will play an increasingly greater role in improving sensitivity and specificity in the interpretation of brain abnormalities in patients within the clinical environment, as well as in groups of children with suspected brain dysfunction in the research setting.

Corpus callosum morphology in children with Tourette syndrome and attention deficit hyperactivity disorder

The aim of this study was to investigate the morphology of the corpus callosum (CC) in Tourette syndrome (TS) and attention deficit hyperactivity disorder (ADHD) to determine whether these conditions affect distinct regional differences. Seventy-seven children and adolescents, aged 6 to 16 years, comprised the four research groups--16 patients with TS, 21 patients with TS plus ADHD, 13 patients with ADHD, and 27 unaffected control subjects. A semiautomated, computer-assisted procedure was used to measure the total area, five subregions, centerline length, perimeter, and bending angle of the CC. MRI data were analyzed using several statistical methods, primarily two-tailed analysis of variance to test the effects of TS and ADHD status, while controlling for the influence of age, gender, and total intracranial area (an estimate of brain size). TS was associated with significant increases in the area of four of five subdivisions, the total area, and the perimeter of the CC. ADHD was associated with a significant decrease in the area of the rostral body. There were no interactions between TS and ADHD factors. These findings suggest that the area of the CC is larger in children with TS, and that this difference is independent of age, handedness, intracranial area, and the diagnosis of ADHD. Our findings support hypotheses that the neurobiologic mechanisms in TS and ADHD involve frontal/subcortical circuits.

Psychometric characteristics of the Children's Motivation Scale

A 16-item Children's Motivation Scale (CMS) was developed to evaluate level of motivation in children and adolescents. The study population consisted of a normative sample of 290 school children and a clinical sample of 165 child and adolescent psychiatric patients. Test-retest, internal consistency, and interrater reliability were fair to good for both samples. Validity of the CMS was demonstrated by its ability to differentiate clinical from normative samples according to the level of motivation, by a significant correlation of the CMS with an independent measure of withdrawal, and by its lack of correlation with an independent measure of depression. Principal components analysis identified a three-component structure. These findings support the conclusion that the CMS accesses a clinically important but often overlooked psychiatric construct.

Biological correlates of learning and attention: what is relevant to learning disability and attention-deficit hyperactivity disorder?

Advances in the related fields of cognitive neuroscience and neuropsychology offer intriguing reformulations of the clinical entities of attention-deficit hyperactivity disorder (ADHD) and learning disabilities (LD). The definition of such terms as attention and learning used in cognitive neuroscience differ from their use in clinical practice and emphasize such processes as intention, working memory, and executive function. Research suggests that neither attention nor long-term memory are the critical cognitive correlates of ADHD or LD. Rather, encoding processes, particularly working memory, are identified as deficiencies for children with these conditions. Furthermore, intention and inhibition appear to be particularly impaired in children with ADHD, who exhibit broader deficits in so-called executive function. Findings from cognitive neuroscience offer explanations of the neuroanatomical and neurophysiological underpinnings of learning problems and the frequent comorbidity of LD and ADHD.

Neuropsychological status of children with Tourette's syndrome with and without attention deficit hyperactivity disorder

To determine the frequency of learning disabilities (LD) and describe the neuropsychological profile of children with Tourette's syndrome (TS) with and without attention deficit hyperactivity disorder (ADHD), we analyzed psychosocial, psychoeducational, and neuropsychological data from 65 children between the ages of 6 and 14 years selected from a larger study of LD. Three groups were formed: TS only, TS+ADHD, and TS +/- ADHD. The third group was composed of children whose ADHD status was not as strongly confirmed by the three different instruments used for ADHD diagnosis. From other (non-TS) research projects in the Center, a comparison group of 27 unaffected siblings who had no diagnosis of ADHD was formed. All children were unmedicated at the time of assessment and had the full set of data available for analysis. LDs were present in 23% of the total TS sample, but LD was not present in the TS-only group. All TS groups had scores at or below 1 SD from the mean on measures of choice reaction time, but the TS-only group was significantly poorer on a measure of executive function (letter word fluency). We discuss the implication of the finding in the TS-only group in terms of a slowing of linguistic productivity.

Basal ganglia volumes in children with attention-deficit hyperactivity disorder

Previous research has demonstrated volume reduction of the left globus pallidus in children with the codiagnoses of Tourette syndrome and attention-deficit hyperactivity disorder (ADHD), in comparison with children who have Tourette syndrome alone and with normal controls. The purpose of this study was to determine whether children with ADHD alone also had volume reduction of the globus pallidus or other basal ganglia structures. Subjects were 10 boys with ADHD, 16 boys with Tourette syndrome and ADHD, and 11 normal control boys. Groups were matched for age. Boys with ADHD were individually matched for age, handedness, and IQ to 10 of the 16 boys with Tourette syndrome and ADHD. Volumes of caudate, putamen, and globus pallidus were measured and corrected for brain volume. The boys with ADHD had significantly smaller left globus pallidus volume and total globus pallidus volume (corrected for brain volume) than the normal controls. The Tourette syndrome plus ADHD group did not differ from the ADHD group on any of the measures. We conclude that small globus pallidus volume, particularly on the left side, is associated with ADHD.

Relationship between T2-weighted hyperintensities (unidentified bright objects) and lower IQs in children with neurofibromatosis-1

To address the controversy regarding the relationship between cognitive impairment (lowering of IQ) and magnetic resonance imaging (MRI) characteristics (T2-weighted hyperintensities or unidentified bright objects [UBOs]) in children with neurofibromatosis-1 (NF-1), we used a pairwise NF-1/ sibling design; we set out to predict the lowering of IQ in each child with NF-1 as a discrepancy from the IQ of an unaffected sibling (D-SIQ). Our multiple regression model included the age of the child with NF-1, familial or sporadic nature of the NF-1, number of locations in the child's brain occupied by T2-weighted hyperintensities (UBOs), and the volumetric percentage of brain tissue occupied by T2-weighted hyperintensities (UBOs). Only the number of locations occupied by UBOs accounted for IQ lowering (D-SIQ) in children with NF-1 (42% of the variance in D-SIQ). This is the first report to confirm that a continuum of lowered IQs in NF-1-affected children exists in relation to the distribution of UBOs (range 0-7), not just presence (vs. absence) of any UBOs.

Executive function in children with Tourette syndrome and/or attention deficit hyperactivity disorder

Tourette Syndrome (TS) in children is associated with various neurobehavioral disorders including attention deficit hyperactivity disorder (ADHD). Children with TS and ADHD show some difficulties with neuropsychological tasks, but we do not know if children with TS alone have neuropsychological deficits. To assess specific cognitive differences among children with TS and/or ADHD, we administered a battery of neuropsychological tests, including 10 tasks related to executive function (EF), to 10 children with TS-only, 48 with ADHD-only, and 32 with TS + ADHD. Children in all groups could not efficiently produce output on a timed continuous performance task [Test of Variables of Attention (TOVA) mean reaction time and reaction time variability]. Children with TS-only appeared to have fewer EF impairments and significantly higher perceptual organization scores than children with TS + ADHD or ADHD-only. These findings suggest that deficiencies in choice reaction time and consistency of timed responses are common to all three groups, but children with TS-only have relatively less EF impairment than children with TS + ADHD or ADHD-only.

Contribution of the FMR1 gene mutation to human intellectual dysfunction

The degree to which genetic factors influence human intelligence remains a matter of some controversy. However, there is little doubt that single gene mutations can significantly alter brain development and function. For example, mutations affecting the FMR1 gene cause the fragile X syndrome, the most prevalent known inherited cause of intellectual dysfunction. The most common mutation occurring in the FMR1 locus involves expansion of a trinucleotide (CGG)n repeat sequence within the promoter region of the gene. Between 6 and 54 repeats are typically observed in individuals from the general population. When > or = 200 CGG repeats are present, the expanded repeat sequence and an adjacent CpG island are usually hypermethylated, Aa phenomenon associated with transcriptional silencing of the gene and commonly referred to as the FMR1 full mutation. The intermediate range of repeats (approximately 50 to 200 CGGs), referred to as the premutation, is characterized by the absence of hypermethylation within the promoter region and normal phenotype. Some individuals have a combination of methylated and unmethylated alleles of differing size and are referred to as having mosaic status. Most males with the FMR1 full mutation function in the mentally retarded range of intelligence; in contrast, females with the FMR1 full mutation show a broader range of intelligence, from mental retardation to normal IQ.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurodevelopmental effects of the FMR-1 full mutation in humans

Brain dysfunction is the most important sequelae of the fragile X (FMR-1) mutation, the most common heritable cause of developmental disability. Using magnetic resonance imaging (MRI) and quantitative morphometry, we have compared the neuroanatomy of 51 individuals with an FMR-1 mutation with matched controls and showed that subjects with an FMR-1 mutation have increased volume of the caudate nucleus and, in males, the lateral ventricle. Both caudate and lateral ventricular volumes are correlated with IQ. Caudate volume is also correlated with the methylation status of the FMR-1 gene. Neuroanatomical differences between two monozygotic twins with an FMR-1 mutation who are discordant for mental retardation are localized to the cerebellum, lateral ventricles and subcortical nuclei. These findings suggest that the FMR-1 mutation causing the fragile X syndrome leads to observable changes in neuroanatomy that may be relevant to the neurodevelopmental disability and behavioural problems observed in affected individuals.

Learning difficulties in children with Tourette syndrome

Children with Tourette syndrome have been shown to have a variety of school difficulties. These difficulties, however, may be related to a single factor or to a combination of problems including tic severity, the use of tic-suppressing medication, executive dysfunction, a direct consequence of having a stigmatizing disorder, and coexisting attention deficit disorder, hyperactivity, obsessive-compulsive behaviors, or other psychopathologies. The goals for the treating health care team are to identify the presence of these factors, to clarify which are the major source of distress, and to develop an individualized multimodal treatment program. The prompt diagnosis of underlying problems and the prescription of appropriate therapy can play an important role in preventing school failure in children with Tourette syndrome.

The treatment of attention-deficit hyperactivity disorder in Tourette's syndrome: a double-blind placebo-controlled study with clonidine and desipramine

OBJECTIVES

Because psychostimulants can exacerbate preexisting motor/phonic tics in individuals with Tourette's syndrome (TS), a clinical trial was performed to examine the ability of clonidine and desipramine to modify attention-deficit hyperactivity disorder (ADHD) behaviors in children with TS + ADHD.

METHODS

A double-blind, placebo-controlled protocol was used in which each subject served as his or her own control and received, in a randomly assigned fashion, 6-week medication cycles with clonidine (0.05 mg four times daily), desipramine (25 mg four times daily), and placebo.

RESULTS

Thirty-seven children with TS+ADHD between the ages 7 to 13 years and of normal intellect were recruited, and 34 (31 males, 3 females) completed the entire protocol. Outcome measures for ADHD included Parent and Teacher Child Behavior Checklists (CBCL), continuous performance tests, and neuropsychologic tests of executive function. Several markers for ADHD were shown to improve significantly (P < .05) after treatment with desipramine (parent linear analogue rating, parent CBCL "hyperactivity" subscale, and teacher CBCL subscales "nervous/overactive," "anxious," and "unpopular"). Improvement with desipramine was always superior to that noted with clonidine. Clinical improvement did not correlate with drug blood levels. On measures of tic severity, neither drug made tics worse. Desipramine showed a statistically significant improvement on a global linear analogue scale, but not on the Hopkins Motor/Vocal Tic Severity Scale, the Tourette Syndrome Severity Scale, or the Yale Global Tic Severity Scale. Clonidine did not significantly alter tic severity on any measure.

CONCLUSION

The results of this study suggest that desipramine may be a useful alternative for the treatment of symptoms of ADHD in children with TS.

An analysis of two discrepancy-based models and a processing-deficit approach in identifying learning disabilities

The incidence of learning disabilities (LD) in a research center sample of 107 boys and 103 girls between 6 and 12 years of age was calculated using Wechsler IQ and Woodcock-Johnson cluster scores in a regression model (REG) and a reliability model (REL). The REL method identified LD three times more often than the REG method, and all those identified by REG were also identified by REL. When stratified by IQ, REG and REL identified similar percentages in the lowest IQ group; however, REG identified at a lower rate as IQ increased. All 87 children identified with reading disabilities (both REL-RD and REG-RD) were weak to a similar extent on phonemic awareness. Comorbid elevated attention ratings were found in 62% of children with RD; 26% had elevated attention ratings but no linguistic processing deficits, and 21% had at least one linguistic processing deficit but no attentionally suspect rating.

Neurofibromatosis type 1: the evolution of deep gray and white matter MR abnormalities

PURPOSE

To investigate the evolution of deeply located high-signal-intensity abnormalities of the brain on T2-weighted MR images of patients with neurofibromatosis type 1 (NF-1).

METHODS

The study consists of two patient groups: 1) retrospective evaluation of MR scans of 24 symptomatic NF-1 patients, 10 of whom were sequentially studied, and 2) prospective MR evaluations of 20 asymptomatic NF-1 subjects from 14 families; 2 of these families were sequentially studied.

RESULTS

Deeply located, high-signal-intensity abnormalities on T2-weighted images were noted in 34 of 44 NF-1 subjects (77%). If NF-1 patients are grouped according to age, 28 of 30 subjects (93%) younger than 15 years had the lesions, whereas 4 of 7 subjects (57%) between 16 and 30 years, and 2 of 7 subjects (29%) older than 31 years had lesions. High-signal lesions in basal ganglia and brain stem were demonstrated in all decades with relatively high frequency. Lesions in the cerebellar white matter and dentate nuclei were mainly found in the patients younger than 10 years, and never found after the third decade. In 13 sequential studies (mean interval, 24 months), lesions appeared to increase in size in 3, remain unchanged in size in 2, and decrease in size in 7. One subject showed a mixed pattern of lesion size change.

CONCLUSIONS

Deeply located high-signal-intensity lesions on T2-weighted MR images are more evident in young NF-1 patients. The underlying brain abnormality, while pathologically unproved, is probably transient.

Molecular-neurobehavioral associations in females with the fragile X full mutation

In this study, young females with the fragile X [fra(X)] full mutation (fM) were assessed using quantitative measures of mutation amplification size (Amp) as well as the ratio of active normal X chromosome to total normal X chromosome (activation ratio-AR). Neurobehavioral assessments of females with the fM were performed and included specific and general measures of cognitive and behavioral/developmental functioning. To investigate molecular-behavioral associations, Amp and AR were used as independent variables, while cognitive and behavioral scores were used as dependent variables. Significant correlations were observed between both molecular variables (Amp and AR) and measures of cognitive functioning, with AR showing the most consistent and robust correlations. As AR increased, overall IQ and specific subtest and area scores from the cognitive tests increased. Conversely, as Amp increased, the overall IQ and specific subtest and area cognitive scores decreased. No significant associations were observed between AR or Amp and measures of behavior or development. The molecular-cognitive associations were generally consistent with the cognitive profile previously described in studies comparing females with fra(X) to age-matched controls. Amp and AR were not associated with one another, nor were they associated with the same cluster of cognitive measures. Though this report does not conclusively show that AR and Amp can be used to clinically assess the risk of a female with the fM for cognitive disability, the evidence presented does suggest that these molecular variables, especially AR, reflect important underlying genetic factors contributing to the fra(X) phenotype.

Developmental dyslexia and attention dysfunction in adults: brain potential indices of information processing

Event-related brain potentials (ERPs) were recorded from a group of 13 men with severe developmental dyslexia and 15 matched normal controls. Auditory and visual stimuli, presented in separate reaction time tasks of graded difficulty, were used to elicit ERPs. No group differences in P300 were seen under relatively undemanding task conditions. However, as task demands increased, visual P300 was reduced in the dyslexic men as compared with the normal readers. An Abbreviated Conners Parent Rating Scale was used to assess retrospectively childhood symptoms of attention-deficit hyperactivity disorder (ADHD). Additional analyses revealed that the dyslexics with a history of many symptoms of ADHD in childhood (high ADHD) accounted for the group differences in P300; the dyslexics with a history of few or no such symptoms (low ADHD) were indistinguishable from the controls at all electrode sites. Furthermore, whereas the low-ADHD dyslexics showed the same hemispheric asymmetry in auditory P300 as did the controls (right > left), auditory P300 was more symmetrically distributed in the high-ADHD dyslexics. The results are interpreted as suggesting that a distinct brain organization may characterize dyslexic men with a history of concomitant deficits in attention.