Habituation as Parameter for Prediction of Mental Development in Healthy Preterm Infants: An Electrophysiological Pilot Study

Effects of iron supplementation on neural indices of habituation in Bangladeshi children

BACKGROUND

Iron deficiency and anemia have been associated with poor cognition in children, yet the effects of iron supplementation on neurocognition remain unclear.

OBJECTIVE

We aimed to examine the effects of supplementation with iron on neural indices of habituation using auditory event-related brain potentials (ERPs).

METHODS

This substudy was nested within a 3-arm, double-blind, double-dummy, individual randomized trial in Bangladesh, in which 3300 8-mo-old children were randomly selected to receive 3 mo of daily iron syrup (12.5 mg iron), multiple micronutrient powders (MNPs) (including 12.5 mg iron), or placebo. Children were assessed after 3 mo of intervention (mo 3) and 9 mo thereafter (mo 12). The neurocognitive substudy comprised a randomly selected subset of children from the main trial. Brain activity elicited during an auditory roving oddball task was recorded using electroencephalography to provide an index of habituation. The differential response to a novel (deviant) compared with a repeated (standard) sound was examined. The primary outcome was the amplitude of the mismatch response (deviant minusstandard tone waveforms) at mo 3. Secondary outcomes included the deviant and standard tone-evoked amplitudes, N2 amplitude differences, and differences in mean amplitudes evoked by deviant tones presented in the second compared with first half of the oddball sequence at mo 3 and 12.

RESULTS

Data were analyzed from 329 children at month 3 and 363 at mo 12. Analyses indicated no treatment effects of iron interventions compared with placebo on the amplitude of the mismatch response (iron syrup compared with placebo: mean difference (MD) = 0.07μV [95% CI: -1.22, 1.37]; MNPs compared with placebo: MD = 0.58μV [95% CI: -0.74, 1.90]) nor any secondary ERP outcomes at mo 3 or 12, despite improvements in hemoglobin and ferritin concentrations from iron syrup and MNPs in this nested substudy.

CONCLUSION

In Bangladeshi children with >40% anemia prevalence, iron or MNP interventions alone are insufficient to improve neural indices of habituation. This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTRN12617000660381.

A review of the characteristics, mechanisms and clinical significance of habituation in foetuses and newborn infants

Habituation has been a topic of interest since the early 20th century. We summarise the characteristics of habituation, the proposed habituation mechanisms, the associated cortical responses and the link between habituation and cognitive development. Behavioural and neuroimaging studies have highlighted the early sensory abilities of foetuses and newborn infants, with preterm newborn infants exhibiting decreased habituation and dishabituation capabilities that increase their environmental vulnerability. Habituation provides a foundation for the learning and cognition on which higher functions are constructed. It has been suggested that it is efficient for predicting cognitive developmental outcomes in term and preterm newborn infants.

Portable Acquisition of Auditory ERPs: A Pilot Study of Premature Infants

BACKGROUND

Prior work suggests that event-related potential (ERP) studies in infancy may help predict developmental outcome.

METHODS

As part of a longitudinal study of early child development, we used the auditory oddball stimulus paradigm with a portable electroencephalography system to obtain ERP data from two-month-old infants (32 term, six preterm) in Sri Lanka. The mismatch negativity was calculated between 200 and 350 milliseconds after stimulus presentation.

RESULTS

We found a significant correlation between birth weight and mismatch negativity (P = 0.046), and our time-frequency analysis indicated power differences between standard and oddball tones at approximately 5 and 18 Hz. There was no significant difference between mismatch negativity in children undergoing ERP studies in a hospital setting (30) versus in the child's home (eight).

CONCLUSIONS

Although our modest sample size precludes drawing definitive conclusions, these preliminary results show that it is possible to acquire ERP datasets using currently available portable technology in a hospital or home setting, even in a developing nation such as Sri Lanka. Follow-up of this cohort will include developmental assessments, which will add to the growing literature relating early electrophysiology to developmental outcome.

Mismatch response in preterm and asphyxic neonates: a functional electrophysiological investigation of attention and habituation

BACKGROUND AND AIM

There is a lack of diagnostic tools for early risk stratification of cognitive outcome in infants born preterm and infants with asphyxia. Using auditory event-related potentials and mismatch response, we aimed to assess possible differences in early attention and learning, as a marker for brain maturation to subsequently improve the allocation of early neurodevelopmental support.

STUDY DESIGN AND METHODS

This cross-sectional study included 22 very preterm infants (gestational age (GA) < 32 weeks), eight term infants with asphyxia and 35 healthy term infants. An auditory oddball-paradigm with three consecutive stimulation blocks, separated by a two-minute break, was used as a cognitive discrimination task to assess attention and habituation.

RESULTS

The peak-to-peak analysis in the group comparisons showed no significant differences for the first stimulation block. In term healthy infants and term infants after asphyxia, no significant differences were found in amplitudes between block one and three. Preterm infants showed significantly (p = .007) lower amplitudes in the third block for F7 congruent to a positive habituation. The amplitude of the grouped electrodes correlated positively with GA for frontal (R = .271, p= .029) and parietal electrodes (R =.275, p = .027).

CONCLUSION

We found no differences in the auditory attention paradigm between preterm or term asphyxic and control infants when they were evaluated at term corrected age. Most infants did not show any electrophysiologically measurable learning effect indicating habituation or dishabituation. The small sample size of this study is a clear limitation. Therefore, the results must be evaluated with caution, especially regarding their potential predictive value for future cognitive development of infants with a developmental risk. However, our study underlines the possibility of an electrophysiological evaluation as a feasible tool to assess very early cognition in infants.

Reduced brain processing of affective pictures in children with cerebral palsy

Sensory and cognitive deficits are common comorbidities in children with cerebral palsy. This observational study examines if brain processing of affective information is also altered in children with cerebral palsy (CP) in comparison with typically developing peers (TDP).

METHODS

Evoked-related potentials were recorded in 15 children with CP (age = 11.27 ± 4.53 yr, 6 girls) and 14 TDP (age = 10.14 ± 4.29 yr, 5 girls) when viewing pleasant, unpleasant and neutral pictures. The subjective perception of valence and arousal of each one of the pictures was examined.

RESULTS

Children with CP showed a significant amplitude reduction of evoked potentials in the occipital region to the affective stimuli in early brain processing latencies (P100 and N200; all F > 2.9, all p < .05). Children with CP rated pictures with affective content (pleasant and unpleasant) as less arousing (F(2.25) = 46.71, p < .001), and neutral pictures as more pleasant, than their TDP (F(2.25) = 75.56, p < .001).

CONCLUSION

The pictures with emotional content produce less activation, both at the behavioral and brain processing levels in children with CP. These differences were found in early latencies of brain processing which could be related to alterations in the detection of emotionally relevant stimuli.

Changes in event-related brain responses and habituation during child development - A systematic literature review

OBJECTIVE

This systematic review highlights the influence of developmental changes of the central nervous system on habituation assessment during child development. Therefore, studies on age dependant changes in event-related brain responses as well as studies on behavioural and neurophysiological habituation during child development are compiled and discussed.

METHODS

Two PubMed searches with terms "(development evoked brain response (fetus OR neonate OR children) (electroencephalography OR magnetoencephalography))" and with terms "(psychology habituation (fetal OR neonate OR children) (human brain))" were performed to identify studies on developmental changes in event-related brain responses as well as habituation studies during child development.

RESULTS

Both search results showed a wide diversity of subjects' ages, stimulation protocols and examined behaviour or components of event-related brain responses as well as a demand for more longitudinal study designs.

CONCLUSIONS

A conclusive statement about clear developmental trends in event-related brain responses or in neurophysiological habituation studies is difficult to draw. Future studies should implement longitudinal designs, combination of behavioural and neurophysiological habituation measurement and more complex habituation paradigms to assess several habituation criteria.

SIGNIFICANCE

This review emphasizes that event-related brain responses underlie certain changes during child development which should be more considered in the context of neurophysiological habituation studies.