Left hemispheric deficit in the sustained neuromagnetic response to periodic click trains in children with ASD

BACKGROUND

Deficits in perception and production of vocal pitch are often observed in people with autism spectrum disorder (ASD), but the neural basis of these deficits is unknown. In magnetoencephalogram (MEG), spectrally complex periodic sounds trigger two continuous neural responses-the auditory steady state response (ASSR) and the sustained field (SF). It has been shown that the SF in neurotypical individuals is associated with low-level analysis of pitch in the 'pitch processing center' of the Heschl's gyrus. Therefore, alternations in this auditory response may reflect atypical processing of vocal pitch. The SF, however, has never been studied in people with ASD.

METHODS

We used MEG and individual brain models to investigate the ASSR and SF evoked by monaural 40 Hz click trains in boys with ASD (N = 35) and neurotypical (NT) boys (N = 35) aged 7-12-years.

RESULTS

In agreement with the previous research in adults, the cortical sources of the SF in children were located in the left and right Heschl's gyri, anterolateral to those of the ASSR. In both groups, the SF and ASSR dominated in the right hemisphere and were higher in the hemisphere contralateral to the stimulated ear. The ASSR increased with age in both NT and ASD children and did not differ between the groups. The SF amplitude did not significantly change between the ages of 7 and 12 years. It was moderately attenuated in both hemispheres and was markedly delayed and displaced in the left hemisphere in boys with ASD. The SF delay in participants with ASD was present irrespective of their intelligence level and severity of autism symptoms.

LIMITATIONS

We did not test the language abilities of our participants. Therefore, the link between SF and processing of vocal pitch in children with ASD remains speculative.

CONCLUSION

Children with ASD demonstrate atypical processing of spectrally complex periodic sound at the level of the core auditory cortex of the left-hemisphere. The observed neural deficit may contribute to speech perception difficulties experienced by children with ASD, including their poor perception and production of linguistic prosody.

Syndromе associated with multiple venous malformations (Bean syndrome)

Blue rubber bleb nevus syndrome (BRBNS) also called Bean's syndrome is a rare disorder characterized by mucocutaneous angiomatose multiple cutaneous venous malformations. Pathogenesis of the BRBNS is caused by the somatic mutations in angiopoietin receptor gene TEK. These mutations cause ligand-independent activation of the tyrosine kinase receptor and the PI3K / AKT pathway and involve the mTOR in the pathological process in a specific way. There are no universally effective methods for treating systemic forms of vascular malformations currently. However, recent numerous reports have shown the advantages of rapamycin, an mTOR inhibitor, as a well-tolerated and effective therapy in patients with vascular abnormalities, in particular with diffuse angiomatose. This article presents a clinical case of a 5-years old patient with a diagnosis of iron deficiency anemia, who has been treated for a long time and received iron supplements therapy without achieving any effect. The diagnosis of Bean's syndrome was established after 5 years from the first clinical manifestation and based on clinical, laboratory and instrumental methods. The cause of iron deficiency anemia was established. It was repeated chronic bleedings from multiple sites of the gastrointestinal mucosa vessels. Prescribed rapamycin therapy allowed to contain gastrointestinal bleeding, to reduce the size of vascular lesions and to prevent the formation of new ones. Parents gave their consent to use information about the child in the article.

[Developmental continuity of working memory from infancy to preschool age]

The objective of the paper was to study the developmental continuity of working memory function from infancy to preschool age. At the age of 10 to 11 months 44 participants completed delayed response task (A-not-B) that measures working memory function. Between 5 and 7 years of age the same participants performed three tasks assessing working memory for temporal order in auditory and visual modalities and a control task measuring short-term visuospatial memory. The dependence of temporal-order memory at preschool age on individual level of infant working memory was found for all methods of measurement despite the differences in way of presentation and reproducing of the stimuli order. Results indicate direct continuity in the development of working memory function from infancy to preschool age.

The right hemisphere fails to respond to temporal novelty in autism: evidence from an ERP study

OBJECTIVE

This study aimed to investigate electrophysiological correlates of initial attention orienting to temporally novel sound in children with autism (CWA).

METHODS

Twenty-one CWA (4-8 years) and 21 age-matched typically developing children (TDC) were presented with pairs of clicks separated by a 0.5s intra-pair interval, with longer (7-9s) intervals between pairs. Children watched a silent movie during click presentation. We assessed EEG perturbations and event-related potentials (ERP) in response to sounds of different temporal novelty - first (S1) and second (S2) clicks in the pair.

RESULTS

In TDC, the early attention-modulated midtemporal N1c wave evoked by S1 and corresponding EEG phase locking and power increase were right-lateralized and were bilaterally higher than those evoked by S2. CWA demonstrated abnormal S1 responses, characterized by reduced N1c amplitude and EEG phase locking in the right midtemporal region, reversed leftward lateralization of the phase locking, and diminished later frontal N2 wave. Their brain responses to S2 were essentially normal.

CONCLUSIONS

The impaired right hemispheric processing of temporary and contextually novel information and suboptimal lateralization of normally right-lateralized attention networks may be important features of autistic disorder.

SIGNIFICANCE

Results of this study contribute to the understanding of autism neurobiology.

EEG theta rhythm in infants and preschool children

OBJECTIVE

To study behavioral correlates of theta oscillations in infants and preschool children.

METHODS

EEG was recorded during baseline (visual attention) and two test conditions--exploration of toys and attention to 'social' stimulation. Age specific frequency boundaries of theta and mu rhythms were assessed using narrow bin analysis of EEG spectra.

RESULTS

Theta spectral power increased whereas mu power decreased under test conditions in both age groups. In preschoolers theta rhythm increased predominantly over anterior regions during exploratory behavior and over posterior regions during attention to social stimulation. Theta frequency range changed with age from 3.6 to 5.6 Hz in infants to 4-8 Hz in children, and mu range from 6.4-8.4 Hz to 8.4-10.4 Hz.

CONCLUSIONS

In early life, theta oscillations are strongly related to behavioral states with substantial attentional and emotional load. The scalp distribution of theta spectral power depends on age and behavioral condition and may reflect engagement of different brain networks in control of behavior.

SIGNIFICANCE

The findings contribute to the scanty knowledge about the developmental course of theta rhythm. Data on behavioral correlates of theta rhythm in early life may improve our understanding of cognitive and mental processes in healthy and neuropsychiatrically diseased children.

Age-related and individual differences in the performance of a delayed response task (the A-not-B task) in infant twins aged 7-12 months

The aim of the present work was to analyze the age-related dynamics and nature of interindividual differences in performing the A-not-B task, which addresses working memory in children aged 7-12 months. The cohort consisted of 150 children aged 7-12 months from mono- and dizygotic twin pairs. Working memory was assessed in terms of the maximum delay which the children could tolerate in a delayed response test (the A-not-B task). Performance of the task improved with age, such that a sharp change in the ability to tolerate the delay occurred between nine and ten months of age. Mental development as assessed using the Bayley scale showed a significant correlation with the duration of the delay in the task only after a threshold period (9-10 months of age) in the development of working memory. Analysis of intrapair correlations in mono- and dizygotic twins showed that interindividual differences in the A-not-B task delay at age 7-9 months were completely determined by individual environmental factors (including measurement errors), while at age 10-12 months the leading role in the interindividual variability in this measure was taken by the systematic environment. These results show that the abilities to tolerate delays at the beginning and end of the second six months of life are based on different mechanisms.

[Developmental and individual differences in delayed response task performance (A-not-B task) in 7- to 12-month-old infant twins]

The purpose of the study was to explore developmental and individual differences in the working memory that was assessed by performance of the A-not-B task in 7- to 12-month-old infant twins. The sample included 150 infant twins participating in genetic project, 18 of them were tested at 8 and 11 months of age. Information concerning birth weight and gestational age was collected from birth records. All infants were tested using Bayley Scales of Mental and Psychomotor Development. The infant's working memory (WM) was tested during A-not-B task performance, which was shown to depend on the maturity of the prefrontal cortex. The behavioral data were analyzed off-line using videotape records. The one-way ANOVA revealed that the AB performance improves with age. A highly significant improvement of the ability to tolerate the delay in A-not-B task was observed between 9 and 10 months of life. There was no longitudinal stability in individual infant performance of A-not-B across the period of 7-12 months of age. The AB delay was significantly correlated with psychomotor and mental development only after the crucial period of the rapid increase in the AB delay (9-10 months). The analysis of intraclass mono- and dizygotic correlations showed that individual differences in the WM (tolerance to AB delay) at 7-9 months and at 10-12 months are of different nature. There was a significant effect of shared environment on AB delay variance in 10-12-month-old group, whereas down to this age no systematic influence on individual variability was observed. These findings suggest that the ability to tolerate the AB delay can be provided by different brain mechanisms in 7-9 and 10-12-month-old infants.

Alpha activity as an index of cortical inhibition during sustained internally controlled attention in infants

OBJECTIVES

The study examined the suggestion that infant ability to maintain attention in anticipatory task and to sustain interference is related to the active inhibitory processes in cortical neural networks.

METHODS

The extent of selective EEG synchronization in the alpha range has been taken as a measure of cortical inhibition. EEG was registered in 60 infants aged 8-11 months during: (1) attention to an object in the visual field (externally controlled attention); (2) anticipation of the person in the peek-a-boo game (internally controlled attention).

RESULTS

The infants who demonstrated longer periods of anticipatory attention had higher absolute spectral amplitude in the broad frequency range under both experimental conditions. It was suggested that the effect of 'overall' EEG synchronization is related to some stable individual differences in psychophysiological traits. To control for the effect of overall EEG synchronization the relation between relative alpha amplitudes in 6.4-10 Hz range and the duration of internally controlled attention was analyzed. The infants with longer compared to shorter anticipatory attention spans had relatively higher 6.8 Hz alpha synchronization at posterior parietal sites under this experimental condition.

CONCLUSIONS

It was suggested that alpha synchronization over posterior parietal cortex reflects an active inhibition of certain parietal networks involved in maintaining attention to peripheral visual field rather than merely an 'idle' state of this cortical area. Such an inhibition appears to allow infants to avoid interference of concurrent visual stimulation at the periphery of the visual field.

EEG alpha rhythm in infants

The 'functional topography' approach has been applied to study alpha rhythms in infant twins during the second half-year of life. The experimental sample included 154 normal infants born at 32-41 weeks of gestational age. Their chronological age varied from 7.4 to 12.4 months. EEG was registered during wakefulness under two experimental conditions: sustained visual attention and dark homogenous visual field. During darkness as compared with visual attention the sharp increase of spectral amplitudes within 5.2-9.6 Hz band was observed over the occipital-parietal cortex. The properties of the 5.2-9.6 Hz occipital rhythmic activity comply with the classical properties of alpha rhythm. The distinct spectral peak in 6.0-8.8 Hz band at precentral recording sites was observed during sustained visual attention. This rhythmic component was suppressed under the condition of total darkness. Arguments in favour of homology between the infant central rhythm and adult sensorimotor mu rhythm are advanced. The group mean of alpha peak frequency increased from 6.24 +/- 0.45 Hz at 8 months to 6.78 +/- 0.38 Hz at 11 months of chronological age. The frequency of infant alpha rhythm depended only on the period of extrauterine experience, regardless of gestational age at birth. This result points to the critical role of early visual experience in alpha rhythm development. The group mean of the peak frequency of mu rhythm also increased during the second half-year of life, from 7.03 +/- 0.47 Hz at 8 months to 7.42 +/- 0.46 Hz at 11 months. Unlike alpha rhythm, the peak frequency of mu rhythm depended on duration of both intra- and extrauterine development. We speculate that the development of sensorimotor mu rhythm is influenced by somatosensory stimulation, which, in sharp contrast to the visual input, is present in the uterus.

Theta synchronization during sustained anticipatory attention in infants over the second half of the first year of life

The neurophysiological basis of attention control has been investigated in infants during the second half of the first year of life. The marked improvement of voluntary control of attention and action is known to occur during this age period. EEG was registered in 60 infants aged 8-11 months under three experimental conditions: (1) attention to an object in the visual field (externally controlled attention or the 'baseline'); (2) anticipation of the person in the peek-a-boo game (internally controlled attention); and (3) attention to the 'reappeared' person in the peek-a-boo game ('control' condition). Spectral analysis of the data revealed sharp increase of the EEG theta activity (3.6-6.0 Hz) during internally controlled attention as compared to the 'baseline' and the 'control' conditions. The theta1 (3.6-4.8 Hz) increase was maximal at frontal electrode sites. The reactivity of the frontal theta1 during internally controlled attention differentiated subjects with different ability to maintain this type of attention. The theta2 (5.2-6.0 Hz) reactivity was maximal at right temporal electrode site and did not depend on the ability to maintain anticipatory attention. The data point to different functional significance of theta1 and theta2 rhythms in infants. It was suggested that the frontal theta1 synchronization in infants reflects activity of the anterior attention system subserving executive control of attention. The ability to maintain anticipatory attention increased, whereas the frontal theta1 synchronization decreased during the studied age period. There was the direct relationship between frontal theta1 synchronization and persistence of internally controlled attention in 8-month-olds. On the contrary, at 9 and 10 months, these variables were inversely-related. There was no link between theta1 reactivity and persistence of anticipatory attention in 11-month-olds. It was suggested that the age-dependant dynamic of the relationship between frontal theta1 reactivity and attention behaviour reflects the maturational shift in the functioning of anterior attention system. The shift leads to more economic and more efficient functioning of this system.

Externally and internally controlled attention in infants: an EEG study

This work was designed to investigate EEG indices of Internally and Externally Controlled Attention in infancy. EEG was recorded in 15 infants aged 7-8 months under three experimental conditions: (1) visual attention to a new stimulation (Externally Controlled Attention or baseline condition); (2) attention guided by internal cognitive schemata during 'anticipatory' phase of the peek-a-boo game (Internally Controlled Attention); and (3) 'reappearance' phase of the peek-a-boo game when the experimenter talked and smiled to an infant (reappearance). The relative power (RP) in 4-5 single-Hz theta sub-band increased under both phases of the peek-a-boo game. The reactive changes of 4-5 single-Hz RP at prefrontal and frontal leads under the Internally Controlled Attention condition positively correlated with the total time during which an infant was able to maintain ICA. The RP in 5-6 single-Hz theta sub-band significantly increased only under the Internally Controlled Attention condition and did not correlate with the total time of this type of attention. The results support the concept of 'Diffuse Theta-Response System' that is active during expectancy and effortfully focused attention. In contrast to theta, the RP in 6-7, 7-8, and 8-9 single-Hz bands decreased during both phases of the game. The decrease was maximal at precentral leads and most probably reflected blockage of the sensorimotor (mu) rhythm due to higher motility and muscular tension in the game situation. It is concluded that EEG is an adequate vehicle for investigation of brain mechanisms of attention and voluntary control in infants.

[The theta rhythm of the infant EEG and the development of the mechanisms of voluntary control of attention in the 2nd half of the first year of life]

The neurophysiological basis of attention control was studied in infants at the second half-year of life, i.e. in the period when the capability for voluntary control over behavior fundamentally improves. EEG was recorded in 60 infants aed 8-11 months in three experimental conditions: 1) attention to an object in the visual field (externally controlled attention, or the baseline state), 2) anticipation of a person in the peek-a-boo game (internally controlled attention), 3) attention to the reappeared person in the peek-a-boo game (control condition). The spectral analysis of the EEG data revealed a sharp increase in the EEG theta (3.6-6.0 Hz) during internally controlled attention as compared to the baseline and control conditions. The theta1 (3.6-4.8 Hz) increase was maximal in the frontal derivations. The reactivity of the frontal theta1 during internally controlled attention discriminated infants with different abilities to maintain this type of attention. The reactivity of the theta2 (5.2-6.0 Hz) was maximal in the right temporal derivation (T6) and did not depend on stability of the anticipatory attention. The findings point to different functional significance of the theta1 and theta2 rhythms in infants. It is suggested that synchronization of the frontal theta1 rhythm in infants reflects the activity of the anterior attention system which realizes the executive attention control. The ability to maintain anticipatory attention increased with age, whereas the frontal theta1 synchronization decreased and totally disappeared at the age of 11 months. At the age of 8 months there was a positive correlation between the frontal theta1 synchronization and behavioral index of stability of the internally controlled attention. On the contrary, this correlation was negative at the age of 9 and 10 months. It is suggested that the age-dependent dynamics of the relationship between the frontal theta1 reactivity and attention reflects a leap in maturation of the anterior attention system resulting in its more economic and efficient functioning.

[The age-dependent dynamics of brain potentials related to movement in 9- to 12-year-old children]

Movement-related brain potentials (MRBP) were recorded from F3, F4, C3, C4, and Cz in 47 children aged 9-10 and 49 children aged 11-12 in simple button-push task. Difference in MRBP parameters between the two groups was revealed. Amplitude of readiness potential in the left frontal derivation was higher in the older group than in the younger one. In the right frontal and central regions the readiness potential had definitive characteristics in both age groups. Two subcomponents (P2a and P2b) of P2 postmovement positivity were found in both groups. The amplitude of P2b subcomponent and the latency of N3 component increased from 9-10 to 11-12 years.