Ontogenesis of laterality in 3- to 10-yr.-old children: increased unimanual independence grounded on improved bimanual motor function.

Underlying sensorimotor factors, such as intermanual coupling, contributing to optimal laterality, long remain immature. Using the handmotor laterality blackboard, developmental change in symmetric bimanual motor function for 413 children in groups of 3 to 10 years of age shows synchronicity increased between groups 3 and 5 years of age; but between groups 5 and 7 years of age, given immature coupling, one hand may still disturb the movements of the other one. Between groups 7 and 9 years of age, the hands gradually stop disturbing each other and move independently and fluently. Changes in intermanual coupling with increasing unimanual independence represent expression of changing interhemispheric integration across groups. This promotes optimal laterality and task distribution between the hands. Maturation of the corpus callosum is inferred to be a factor in these ontogenetic changes which ultimately lead to optimal left hemisphere specialization for actions such as fluent writing.

Ontogenetic trends in gnostic hand function in 3- to 12-yr-old children.

The intimate relation between the sensory and motor functions of the hands during object manipulation and exploratory touch, the well-known improvement in object handling and constructive performance in ontogenesis and the emergent laterality thereof, assume changes in morphognostic capabilities in children. In this study we tried to corroborate the hypothesis of Mesker that mature and lateralized finger-thumb opposition is preceded by a stage of two-sided manual form agnosia in preschool children, followed by acquisition of morphognosis of the fingers and, finally, the thumbs. This study examined the development of gnostic hand function in 290 children from 3 to 11 years of age who drew the outlines of a meaningless wooden object passively felt with each hand without visual control. Analysis showed a clear ontogenetic change across the two age groups of increasing morphognostic function: 48% of the 6-yr.-olds drew correctly what the fingers of both left and right hands had perceived (thumbs, 14%). Of the 11-yr.-olds 91% and 61% performed perfectly with the right and left hands, respectively. The fingers preceded the thumbs in reproduction by most children, and the correct reproduction by the left thumb precedes that of the right thumb. The ontogenesis of bimanual sensorimotor functioning is discussed in the light of cortical and callosal development.

Facial identity and facial emotions: speed, accuracy, and processing strategies in children and adults.

As yet, nearly all studies in face and facial affect recognition typically provide only data on the accuracy of processing, invariably also in the absence of reference data on abstract information processing. In this study, accuracy and speed of abstract visuo-spatial processing, face recognition, and facial emotion recognition were investigated in normal school children (7-10 years) and adults (25+/-4 years). In the age range of 7-10 years, accuracy of facial processing hardly increased, while speed did substantially increase with age. Adults, however, were substantially more accurate and faster than children. Differences between facial and abstract information processing were related to type of processing strategy, that is, configural or holistic processing versus featural or piecemeal processing. Improvement in task performance with age is discussed in terms of an enhanced efficiency of the configural organization of facial knowledge (facial information processing tasks), together with a further increase in processing capacity (all tasks). The differential developmental course of speed and accuracy levels indicates that speed is a more sensitive measure when children get older. Moreover, it also suggests that speed of performance, in addition to accuracy, might be successfully used in the assessment of clinical deficits, as has recently been demonstrated in children with autistic disorders of social contact.

Children with non-verbal learning disabilities (NLD): coherence values in the resting state may reflect hypofunctional long distance connections in the right hemisphere.

EEG intrahemispheric coherences (HCohs) in the resting state in twenty-four 4 Hz frequency windows between 1 and 51 Hz were studied in 18 children with "non-verbal learning disorder" (NLD) and compared to a group of 18 children with "verbal learning disorder" (VLD). New facts were found in the NLD group. These concern hemispheric balance, expressed as left minus right (L-R) homologous HCohs: 1a). In the high frequencies (25-51 HZ) the number of long-distance HCohs, higher in the right hemisphere (RH), is lower than HCohs, which are higher in the left hemisphere (LH). A reversed interhemispheric asymmetry is seen for short distance HCohs in that band. These asymmetries are not found in the VLD group, and the tendency is even reversed. 1b). In the low frequencies (1-27 Hz) all higher HCohs are more numerous in the RH, irrespective of interelectrode distance (IED). In these bands there are no NLD-VLD group differences; 2). In NLD there is a significant inverse relationship between IED and (L-R)HCoh values (designated as LRDif) in the high frequencies: the larger the IED, the higher the LRDif. In the lower frequencies there is no such tendency. In the VLD group these relationships were absent. These preliminary results suggest long distance gamma band hypoconnectivity in the RH of NLD children, in line with the hypothesis of an RH long distance connectivity problem in NLD. This may explain difficulties with mtermodal perception (gestalt function). Finally in the NLD group some gamma band interhemispheric (ICohs) over F7/F8 and T3/T4 were lower than in VLD children and some gamma band ICohs were higher in NLD compared to VLD over O1/O2. This is possibly connected with the cognitive differences subserved by these areas, i.e., language, respectively visuospatial function.

Disordered recognition of facial identity and emotions in three Asperger type autists.

In this report we aim to explore severe deficits in facial affect recognition in three boys all of whom meet the criteria of Asperger's syndrome (AS), as well as overt prosopagnosia in one (B) and covert prosopagnosia in the remaining two (C and D). Subject B, with a familially-based talent of being highly gifted in physics and mathematics, showed no interest in people, a quasi complete lack of comprehension of emotions, and very poor emotional reactivity. The marked neuropsychological deficits were a moderate prosopagnosia and severely disordered recognition of facial emotions, gender and age. Expressive facial emotion, whole body psychomotor expression and speech prosody were quasi absent as well. In all three boys these facial processing deficits were more or less isolated, and general visuospatial functions, attention, formal language and scholastic performances were normal or even highly developed with the exception of deficient gestalt perception in B. We consider the deficient facial emotion perception as an important pathogenetic symptom for the autistic behaviour in the three boys. Prosopagnosia, the absent facial and bodily expression, and speech prosody were important but varying co-morbid disorders. The total clinical picture of non-verbal disordered communication is a complex of predominantly bilateral and/or right hemisphere cortical deficits. Moreover, in B, insensitivity to pain, smells, noises and internal bodily feelings suggested a more general emotional anaesthesia and/or a deficient means of expression. It is possible that a limbic component might be involved, thus making affective appreciation also deficient.

Development of ideomotor praxis representation.

To create a short screening instrument to investigate the development of ideomotor praxis representation (IPR), 357 normally developing children between the ages of 2 1/2 and 9 1/2 years were investigated. The IPR screening consisted of six mimed actions which had to be performed on verbal request. The greatest change in the representational style is the transition from performing the action using the body as the object to performing with an imaginary object (i.e. symbolic representation). This transition suggests a development from a concrete and egocentric level of performance to an abstract and allocentric level. Before the age of 6 years differences are evident between self-directed and externally directed gestures. The level of symbolic representation has to be dissociated from the degree of motor precision, which shows hardly any improvement after 6 years of age. With the proposed model one may interpret the level of IPR in clinical practice. IPR screening is clinically relevant from the age of 4 1/2 years onwards.

Attention deficits in children with low performance IQ: arguments for right hemisphere dysfunction.

The attentional component of cognitive functioning in children might be viewed from several interrelated angles that nearly all point to right hemisphere (RH) neural circuits, subserving nonverbal attention. Neuropsychological aspects indicative of RH brain dysfunction are one aspect, studied here. Among children with learning disabilities (LD) we distinguish between LD with emphasis on nonverbal cognitive deficits and LD with verbal dysfunction. We approached this dichotomy by studying the extremes of these two LD categories (89 ss) with respect to attention deficit disorder with (ADHD) or without hyperactivity (ADD). We examined 44 children with at least average verbal IQ (VIQ > or = 95) and lower performance IQ (PIQ at least 25 points lower than VIQ), i.e. the nonverbal group, and 45 children with at least average performance IQ (PIQ > or = 95) and lower verbal IQ (VIQ at least 25 points lower than PIQ). The percentage of AD(H)D among the nonverbal LD group was more than twice as high as among the verbal LD group. Although a convincing right hemisphere (RH) syndrome could not be shown on a neurological basis in most subjects of the non-verbal LD group, a large body of evidence points on the one hand to RH dysfunction associated with nonverbal LD and on the other hand to an association between RH dysfunction and ADD. However, on clinical grounds, discussed here, we consider ADD and low visuospatial cognition, being the most important component of low PIQ, as dissociated functions, largely subserved by the RH.

Unimanual and bimanual simultaneous fingertapping in schoolchildren: developmental aspects and hand preference-related asymmetries.

Computerised analysis of finger tapping was performed in 233 normal 5- to 12-year-old children whose hand preference was assessed with six demonstration actions. Performance with both hands became more rapid with age when tapping unimanually or simultaneously in phase with two hands as quickly as possible. There were no differences between the sexes. Performance with both hands also acquired more tapping regularity with age during unimanual tapping, whereas only the left hand did so during bimanual tapping. There was no age effect on the dexterity (speed) difference between unimanually tapping hands, nor on the relative time lag and the degree of synchrony between the hands in bimanual tapping. The degree of synchrony, however, becomes more stable in older children. The more righthanded children are, the faster the right hand is in unimanual tapping, and the more the right hand is ahead of the left hand during bimanual tapping. However, there is a right shift for both of these variables which makes them poor predictors of hand preference. These results suggest that there is a strong bias towards the right hand in complete righthanders as well as--to a lesser extent--in all others, which might be connected to the leading role of the left hemisphere for the performance aspects of hand motor function under study.

EEG coherence changes during finger tapping in acallosal and normal children: a study of inter- and intrahemispheric connectivity.

The EEG inter- and intrahemispheric coherences (ICoh and HCoh) in the theta, alpha and beta bands were studied in an acallosal group (ACCG) of five children and a normal group of 30 sex- and age-matched children (NG) during resting and tapping conditions. Being functionally deficient, tapping in the ACCG was characterized by increased intertap intervals and variability (in right-hand tapping) and by variability together with decreased synchronization (in bimanual tapping). In the ACCG, frontal, central and parietal ICohs were shown to be smaller, while temporal ICohs were larger under all conditions (see also Koeda, T., Knyazeva, M., Jonkman, J., Njiokiktjien, C., De Sonneville, L., Vildavsky, V., 1995. The resting EEG in acallosal children: compensatory left hemisphere mechanisms? Electroencephalogr. Clin. Neurophysiol. 95, 397-407). The effect was most pronounced in the EEG beta band. The sagittal HCohs, including fronto-central, fronto-parietal, and centro-parietal HCohs within both hemispheres, were larger in the ACCG, whereas temporal HCoh (fronto-temporal, centro-temporal, parieto-temporal and occipito-temporal) were smaller, suggesting rearrangement of intracortical activity associated with callosal agenesis. Tapping induced an increase in ICoh and HCoh between frontal, central and parietal areas in the NG, and weak enhancement only in the left temporal HCoh in the ACCG. The beta band, the most reactive band in the NG, was 'silent' in the ACCG, suggesting deviant cortical function during motor activity as well.

Relation of early neuromotor and cranial signs with neuropsychological outcome at 4 years.

The persistence and predictive value at 3-5 years of age of three signs detected within the first 18 months of life were investigated: phasic stretch reflex in one or both gastrocnemius muscles, imbalance in passive axial tone with an excess of dorsal extension, and a ridge on the squamous sutures. Phasic stretch reflex and at least one of the other signs were found in 14 children during repeated assessments within the first 18 months. The progress of these children was compared with that of 14 matched controls who had repeatedly normal neurological assessments during the first 18 months in the same clinic in Paris. At the age 3-5 years all the children were then assessed blindly by the second author from a pediatric neurological viewpoint and by two psychologists and two psychomotor therapists as well. The parents of the affected children reported significantly more problems in motor/praxis skills, language development and attention. Abnormal neurological signs were also significantly more frequent than in the controls. Suboptimal cognition did not reach significance. The neurological inclusion criteria were still present at 3-5 years old in 86% (vs. respectively 100% and 93% during the first 18 months of life) of this small group of children, while the cranial suture sign was still present in only 28% (vs. 64%). Findings of these three signs during the first 18 months of life may help in predicting long-term neurobehavioral or long-term neuropsychological problems.

The EEG in acallosal children. Coherence values in the resting state: left hemisphere compensatory mechanism?

Resting EEG interhemispheric and intrahemispheric coherences (ICoh and HCoh) in the theta, alpha and beta bands were studied in 7 patients with agenesis of the corpus callosum (5 children, aged 10-14 years, and 2 adults) and 2 groups of sex- and age-matched normal children and adults (42 subjects). In patients the ICohs (F3/F4, C3/C4, P3/P4, O1/O2) were lower than in the normal sample. The ICoh decrease, corresponding with the completeness of commissural agenesis, showed the essential role of the corpus callosum in interhemispheric EEG synchronization. A remarkable new fact was found, namely lower right hemisphere HCoh in the acallosal patients in comparison to the normals, suggesting reduced connectivity of the right hemisphere. It is assumed that the deviant HCoh patterns in the patients, most pronounced in the beta band, are indicative of compensatory left hemisphere mechanisms, accounting for a specific brain plasticity phenomenon in acallosal subjects.

Methylphenidate and information processing. Part 1: Differentiation between responders and nonresponders; Part 2: Efficacy in responders.

Part 1 of this study attempted to discriminate clinical responders and nonresponders to methylphenidate (MPH) on the basis of neuropsychological deficit profiles. Part 2 addressed the question to what extent MPH might ameliorate these deficits. Hyperactive clinical responders (n = 30) and nonresponders (n = 28) to MPH, were compared to normal controls (n = 27) on selective and sustained attention tasks and on conventional psychological and neurological measures. The responders took part in a randomized double-blind placebo-controlled crossover study. They ingested a placebo (PL) or MPH (0.3-0.6 mg/kg/day) during 4 weeks, and were then tested. After crossover, another period of 4 weeks was concluded by a second test series. Compared to controls, both responders and nonresponders showed attention deficits in encoding, memory search, and decision operations, as well as in focused and sustained attention, vigilance, and use of feedback. These deficits were the most severe in the responders. Anamnestic data, IQ scores, and neurological variables did not discriminate between groups. MPH selectively alleviates attention deficits. MPH did not affect divided attention, except for an increased accuracy of response organization. The drug, however, greatly improved focused and sustained attention, vigilance, impulsivity, and the behavioral adaptivity to feedback.

Callosal size in children with learning disabilities.

The corpus callosum (CC), the main structure subserving hemispheric collaboration, that is necessary for efficient cognitive functioning, undergoes developmental processes such as axonal retraction and myelination. Callosal growth therefore is vulnerable for adverse events such as perinatal asphyxia, but there are also genetic and epigenetic factors that determine form and thickness. MRI scans of 110 children, either with specific learning disabilities (LD), i.e. dysphasia/dyslexia, or with several degrees of general LD, showed callosa that were highly variable in size. The callosal size corrected for brain size did not vary significantly according to the severity of the LD, although it tended to be smaller in severe LD, i.e. mental retardation. Callosal size varied however, due to the likely presence of genetic influences or of adverse perinatal events. Children with familial dysphasia/dyslexia, had a thicker CC, possibly reflecting a poorly understood neurodevelopmental mechanism that inhibits the establishment of cerebral dominance. LD children (all subgroups together) with perinatal adverse events had a smaller CC than the familial cases, suggesting CC damage. Despite a multitude of developmental factors influencing the final size, this study suggests that total callosal size, supposedly linked to interhemispheric function, may contribute to the pathophysiological mechanisms that give rise to LD.

Interhemispheric interaction in children of 7-8: analysis of EEG coherence and finger tapping parameters.

To investigate interhemispheric interaction (IHI), the EEGs of 42 children between the ages of 7-8 years were recorded while they were performing, as fast as possible, both unimanual and bimanual rhythmic tapping tasks. As an EEG index of IHI we used coherence values (Coh) in the alpha band in the pairs of leads F3/F4, C3/C4, P3/P4, O1/O2, and T3/T4 during resting and tapping. The difference between left hand (L-L) and right hand (R-R) intertap intervals in comparable conditions was though to reflect IHI. Interhemispheric alpha Coh increase was only evident in bimanual rhythmic tasks, and was confined to the C3/C4 and P3/P4 regions. Coh in these brain areas correlated negatively with the time difference between the L-L and R-R intertap intervals. The results show that interhemispheric alpha Coh. can be regarded as an index of IHI during bimanual tapping, and support the clinical hypothesis that bimanual versus unimanual tapping might reflect interhemispheric or callosal function.

Dyslexia: a neuroscientific puzzle.

The initial assumptions as to the existence of neurodevelopmental disorders have been confirmed by almost a century of studies focused on the nature and causes of reading disability. Dyslexia is an umbrella term for the various manifestations of reading disabilities, each of which is related to its own complex of neuropsychological dysfunctions, sometimes accompanied by neurological symptoms that can be indicative of the specific location involved. Electro-physiology and neuro-imaging in relation to metabolic activity have also confirmed that, to some extent, there is dysfunction in various cerebral areas, more frequently in the left than in the right hemisphere, less often between the hemispheres (corpus callosum) and outside the classical language areas. The rather rare subtype referred to as visual dyslexia and the inter-modal disconnection type resembling alexia are eclipsed by dyslexias related to spoken language: the dysphonemic (auditory-phonological) subtype and the subtypes that are concerned with the production of speech (fluency, word-finding, syntax, sequences), semantics (language comprehension) and linguistic memory. Although it is considered that there are basic brain dysfunctions in dyslexics such as deficits in sequential information processing, there is no "grand unified theory" of dyslexia. There are some new insights as regards the aetiology. In addition to indications of such possible causes as perinatal brain damage, genetic or chromosomal anomalies that manifest themselves in the substrate in an unclear manner, there is also the possibility that the cortical language areas can be disturbed in their development (migration disorders and abnormal asymmetry) due to genetic or epigenetic hormonal and/or immunological factors, so that the normal left hemispheric dominance does not develop. The diagnosis and treatment of dyslexia should begin at an early age and should be acknowledged as being of great social importance.

[Pediatric dysphasia. II. The current concepts of its neurobiological mechanisms]. / Detskaia disfaziia: soobshchenie II. Sovremennye predstavleniia o neirobiologicheskikh mekhanizmakh.

This survey deals with the underlying biological causes and pathogenetic mechanisms of developmental dysphasia. There can be a basic syndrome of "pure dysphasia"; these children are very likely to have a genetically determined developmental disorder on a limited neuronal level (no cerebral damage of any kind) on a developmental disorder by other factors such as an abnormal cortical architecture and abnormal symmetry of the hemispheres. In somewhat more than half the patients, the basic syndrome of pure dysphasia is accompanied by other neurological signs, most of which are indicative of functional disorders of the left hemisphere. There can also be symptoms of the right hemisphere, of the corpus callosum and of the afferent pathway systems for auditory perception. The nature and causes of these anomalies can be multifarious, so that it is unfeasible to speak of the substrate or the pathogenesis.

[Pediatric dysphasia. 1. The concept and clinical aspects]. / Detskaia disfaziia, Soobshchenie 1. Kontseptsiia i klinicheskie aspekty.

This survey deals with the early diagnosis and treatment of children with developmental dysphasia, which may prevent the progression of learning and behavior disorders. In the pre-verbal and early verbal stage, the severity of the clinical picture is primarily determined by concomitant motor pathology (motor dysfunction, dysarthria, general and oral dyspraxia) and by receptive pathology (hearing and auditory perception). In the verbal period, linguistic problems start to play a role, and often combine with oral motor symptoms to present a mixed picture. Various language syndromes do not become clear until some time later. After the kindergarten period, the oral motor and perceptual problems decrease and the language disorders continue to play a role and influence the child's conversation, internal speech reading and spelling at school. In a relatively small number of children without oral motor, perceptual or memory problems, there can be a basic syndrome of "pure dysphasia" without any other neurological signs. In somewhat more than half the patients, the basic syndrome of pure dysphasia is accompanied by other neurological signs. Treatment should not be confined to speech therapy techniques, but can only be optimally given by a highly trained team whose expertise also extends to the schooling aspect.

Methylphenidate-induced changes in ADDH information processors.

In a randomized double-blind placebo-controlled crossover study, 17 hyperactives, clinically considered as drug responders, were administered a battery of information processing tasks to assess the efficacy of methylphenidate. The investigation concentrated on sustained attention, and, following a linear stage model of information processing (divided and focused attention), encoding, filtering, selective set and response organization operations. Methylphenidate did not affect short-term memory or visual retention, baseline motor speed and encoding. Methylphenidate improved vigilance aspects of sustained attention. The drug did not improve filtering but did enhance selective set (target search) operations. The decline in speed and speed variability as a result of medication could not readily be explained in terms of response organization processes. An attempt was made to unite the experimental results through the concept of signal-response frequency.