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Biomedical subjects

C Njiokiktjien

Publications and source records attributed to C Njiokiktjien.

At least 19 recordsLinked to original sources
PubMed2003

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.

Age Factors↗
PubMed2002

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.

Adult↗
PubMed2001

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.

Adult↗
PubMed2000

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.

Activities of Daily Living↗
PubMed1997

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.

Adolescent↗
PubMed1997

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.

Journal Article↗
PubMed1995

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.

Adolescent↗
PubMed1994

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.

Adolescent↗
PubMed1994

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.

Attention↗
PubMed1994

[Pediatric dysphasia. II. The current concepts of its neurobiological mechanisms].

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.

Aphasia↗
PubMed1994

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.

Brain↗
PubMed1993

[Pediatric dysphasia. 1. The concept and clinical aspects].

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.

Aphasia↗
PubMed1991

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.

Arousal↗
PubMed1990

Developmental dysphasia: clinical importance and underlying neurological causes.

This survey deals with two aspects of developmental dysphasia which are relevant to child psychiatry; the early diagnosis and treatment of children with developmental dysphasia, which may prevent the progression of learning and behaviour disorders, and the underlying biological causes of this neuro-developmental disorder. The pathophysiology of developmental dysphasia is complex and age-related. 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. The 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 and learning a 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. These children are very likely to have a genetically determined developmental disorder on a limited neuronal level (no cerebral damage of any kind!) such as an abnormal asymmetry of the hemispheres. In somewhat more than half the patients, this basic syndrome 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. Treatment should not be confined to speech therapy techniques, but should also take into consideration the existence of abnormal motor and affective development and can thus only be optimally given by a highly trained team whose expertise also extends to the schooling aspect.

Aphasia↗
PubMed1989

Late sequelae of a non-optimal neonatal neurological condition in ERPs at the age of 11-13 years.

In a longitudinal study a selective attention task was administered to 11-13-year-old children. During this task (employing a combined filter and selective-set paradigm), event-related brain potentials were recorded to study timing and morphology of early and late selection processes. Task performance was prospectively and retrospectively related to neurological optimality at birth and to flash-evoked potential correlates that were registered at the age of five. The results provided evidence that even after 13 years neonatal neurological suboptimality was reflected in task performance, both in reaction time and in electrophysiological data. Task load interacted with group classification according to optimality to the disadvantage of suboptimals. This implied that load demands differentiated between groups. The event-related brain potentials revealed the existence of a negative shift associated with memory load (search-related negativity) at Fz and Cz, and a positive deflection at Pz (P3b) associated with target detection. Cortical activity, expressed in terms of these deflections, appeared to be less pronounced for the suboptimal group.

Adolescent↗
PubMed1989

[Dysphatic development: clinical importance and neurological background].

The timely treatment of children with developmental dysphasia is important in the prevention of subsequent learning and behaviour disorders. The pathophysiology of developmental dysphasia is complex and depends on age. In the preverbal and early verbal phase the severity of the clinical picture is determined by accompanying motor function pathology (simple motor function, dysarthria, general and oral dyspraxia) and by receptive pathology (hearing, and auditory perception). In the verbal period linguistic problems become more prominent (syntax, morphology, semantics and verbal memory), these problems might be accompanied by oral motor symptoms. The different developmental language syndromes become more apparent with time. After kindergarten age the oral motor and perceptual problems diminish, but the language disorders, that influence communication and scholastic learning, remain. In a small number of children without oral motor, perceptual and memory problems, there exists a 'bare or nuclear syndrome', a so called 'pure dysphasia', without other neurological signs. In these children there is perhaps a genetically determined developmental disorder on a restricted neuronal level (no brain damage!). In more than half of the patients this syndrome is accompanied by other neurological signs, predominantly pointing to the left cerebral hemisphere. Furthermore there can be signs from the right cerebral hemisphere, the corpus callosum and from the afferent fibers systems for auditory perception. The nature and causes of these disorders are extremely variable, so that one cannot speak of the neural substrate or the pathogenesis. The diagnosis and the treatment can optimally only be performed by an experienced team, the expertise of which has to penetrate into the school education system.

Aphasia↗
PubMed1989

[The Kleine-Levin syndrome].

Two boys, aged 12 and 13 years, showed relapsing periods of somnolence and excessive eating, starting after a viral illness. One of them also showed periodic disturbance of sexual impulse control. The symptomatic periods were followed by symptom-free intervals in a highly characteristic pattern. This gave the clue to the diagnosis Kleine-Levin syndrome. The cause of this syndrome is unknown, in some cases a relationship between infectious disease or traumatic brain damage has been postulated. A dysfunction of the hypothalamus and associated structures is suspected. The syndrome has a rather favourable prognosis. The symptoms can be relieved by amphetamines, methylphenidate and probably also by lithium carbonate.

Adolescent↗