Philip G. Grieve

Reduced functional connectivity in visual evoked potentials in children with autism spectrum disorder

OBJECTIVE An analysis of EEG synchrony between homologous early visual areas tested the hypothesis that interhemispheric functional connectivity during visual stimulation is reduced in children with autism compared to controls. METHODS EEG power and coherence within and between two homologous regions of the occipital cortex were measured during long latency flash visual evoked potentials. Measures were compared between two groups of children (5.5-8.5years), one with autism spectrum disorders and the other with typical development. RESULTS In and below the theta band, interhemispheric synchrony was reduced in autistic subjects compared to typical controls by as much as 50%. Above the theta band interhemispheric synchrony in autistic children became indistinguishable from what would occur for uncorrelated cortical activity. Interhemispheric synchrony in autistic subjects was decreased in spite of bilaterally increased power. Wavelet power showed autistic children had a more rapid initial response to stimulation, a slower recovery, and more modulation at longer latencies. CONCLUSIONS Results suggest that the sensory cortices of autistic children are hypersensitive to stimulation with concurrent diminished functional connectivity between hemispheres. SIGNIFICANCE Simultaneously increased intrahemispheric power and decreased interhemispheric synchronization of elementalvisual information suggests either that power increases cause poor interhemispheric connectivity or that processes, such as thalamocortical regulation, impact power and coherence independently.

Spatial correlation of the infant and adult electroencephalogram

OBJECTIVE To examine the effects of volume conduction of current on measurements of spatial correlation in the high-density electroencephalogram (EEG) at extremes of human development: infancy and adulthood. METHODS To calculate theoretical spatial correlation of EEG from volume conduction of uncorrelated cortical sources and compare theory with observations of intra/interhemispheric coherence. RESULTS Result verified prediction of reduced spatial correlation in infants due to volume conduction. Theoretical magnitude of spatial correlation from volume conduction demonstrated as lower bound on observed magnitude of coherence (MC). MC of adults is greater than MC of infants. Adult intrahemispheric MC is greater than interhemispheric MC. Scalp muscle electromyogram (EMG) produces artifactually low values of MC. CONCLUSIONS Volume conduction of current from uncorrelated cortical sources produces an erroneous component of spatial correlation that is smaller in infants than adults. The increased MC in adults is indicative of increased adult neuronal myelination. EMG artifact causes erroneous observations of coherence. SIGNIFICANCE Measured EEG spatial correlation contains contributions from both neural activity and volume conduction of current. This is an important issue when measurements are used to deduce physiological correlates of neuropsychological phenomena. Measurements of the neural component of spatial correlation are more accurate early in life because of reduced volume conduction.

Electroencephalographic activity of preterm infants is increased by Family Nurture Intervention: A randomized controlled trial in the NICU

OBJECTIVE To assess the impact of Family Nurture Intervention (FNI) on electroencephalogram (EEG) activity in preterm infants (26-34 weeks gestation). METHODS Two groups were tested in a single, level IV neonatal intensive care unit (NICU; standard care or standard care plus FNI) using a randomized controlled trial design. The intervention consists of sessions designed to achieve mutual calm and promote communication of affect between infants and their mothers throughout the NICU stay. EEG recordings were obtained from 134 infants during sleep at ∼35 and ∼40 weeks postmenstrual age (PMA). Regional brain activity (power) was computed for 10 frequency bands between 1 and 48 Hz in each of 125 electrodes. RESULTS Near to term age, compared to standard care infants, FNI infants showed robust increases in EEG power in the frontal polar region at frequencies 10 to 48 Hz (20% to 36% with p-values <0.0004). Effects were significant in both quiet and active sleep, regardless of gender, singleton-twin status, gestational age (26-30 or 30-35 weeks) or birth weight (<1500 or >1500 g). CONCLUSION FNI leads to increased frontal brain activity during sleep, which other investigators find predictive of better neurobehavioral outcomes. SIGNIFICANCE FNI may be a practicable means of improving outcomes in preterm infants.

EEG functional connectivity in term age extremely low birth weight infants.

OBJECTIVE The hypothesis is tested that electrocortical functional connectivity (quantified by coherence) of extremely low birth weight (ELBW) infants, measured at term post-menstrual age, has regional differences from that of full term infants. METHODS 128 lead EEG data were collected during sleep from 8 ELBW infants with normal head ultrasound exams and 8 typically developing full term infants. Regional spectral power and coherence were calculated. RESULTS No significant regional differences in EEG power were found between infant groups. However, compared to term infants, ELBW infants had significantly reduced interhemispheric coherence (in frontal polar and parietal regions) and intrahemispheric coherence (between frontal polar and parieto-occipital regions) in the 1-12Hz band but increased interhemispheric coherence between occipital regions in the 24-50Hz band. CONCLUSIONS ELBW infants at term post-menstrual age manifest regional differences in EEG functional connectivity as compared to term infants. SIGNIFICANCE Distinctive spatial patterns of electrocortical synchrony are found in ELBW infants. These regional patterns may presage regional alterations in the structure of the cortex.

Fetal cerebrovascular resistance and neonatal EEG predict 18-month neurodevelopmental outcome in infants with congenital heart disease

The purpose of this study was to investigate early markers of risk for neurobehavioral compromise in survivors with congenital heart disease (CHD).

Cross-frequency phase coupling of brain rhythms during the orienting response

A critical function of the brains orienting response is to evaluate novel environmental events in order to prepare for potential behavioral action. Here, measures of synchronization (power, coherence) and nonlinear cross-frequency phase coupling (m:n phase locking measured with bicoherence and cross-bicoherence) were computed on 62-channel electroencephalographic (EEG) data during a paradigm in which unexpected, highly-deviant, novel sounds were randomly intermixed with frequent standard and infrequent target tones. Low frequency resolution analyses showed no significant changes in phase coupling for any stimulus type, though significant changes in power and synchrony did occur. High frequency resolution analyses, on the other hand, showed significant differences in phase coupling, but only for novel sounds compared to standard tones. Novel sounds elicited increased power and coherence in the delta band together with m:n phase locking (bicoherence) of delta:theta (1:3) and delta:alpha (1:4) rhythms in widespread fronto-central, right parietal, temporal, and occipital regions. Cross-bicoherence revealed that globally synchronized delta oscillations were phase coupled to theta oscillations in central regions and to alpha oscillations in right parietal and posterior regions. These results suggest that globally synchronized low frequency oscillations with phase coupling to more localized higher frequency oscillations provide a neural mechanism for the orienting response.

Behavioral states in the fetal baboon

This study was designed to characterize behavioral states in the fetal baboon. Automated methods were developed and validated to recognize behavioral states based on relationships among three physiologic variables (EEG patterns, eye movements, heart period variability). Data included twelve 16-h records from 3 chronically instrumented fetal baboons at 0.8-0.9 of term. Randomly generated control records were used to differentiate occurrences of state from chance association of the variables. For 41.2 +/- 4.6% (mean +/- S.E.) of the time, the physiologic variables were synchronous and formed cycles of state with a mean duration of 34.4 min. Components of these cycles had mean +/- S.E. durations of 7.2 +/- 0.3 min for state 1FB (the analogue of quiet sleep in the human infant and state 1F in the human fetus), 20.7 +/- 1.2 min for the state 2FB (the analogue of active sleep in the human infant and state 2F in the human fetus), and 3.6 +/- 0.2 min for state transitions. For 24.6 +/- 2.4% of the time, the state variables exhibited coincidental, state-like agreements, that were not part of state cycles. Finally, for 34.3 +/- 2.7% of the time, there was no systematic agreement among the three variables. These data provide convincing evidence that organized behavioral states are present in the fetal baboon as early as 0.8 of term gestation.

Developmental profiles of infant EEG: overlap with transient cortical circuits.

OBJECTIVE To quantify spectral power in frequency specific bands and commonly observed types of bursting activities in the EEG during early human development. METHODS An extensive archive of EEG data from human infants from 35 to 52 weeks postmenstrual age obtained in a prior multi-center study was analyzed using power spectrum analyses and a high frequency burst detection algorithm. RESULTS Low frequency power increased with age; however, high frequency power decreased from 35 to 45 weeks. This unexpected decrease was largely attributable to a rapid decline in the number of high frequency bursts. CONCLUSIONS The decline in high frequency bursting activity overlaps with a developmental shift in GABAs actions on neurons from depolarizing to hyperpolarizing and the dissolution of the gap junction circuitry of the cortical subplate. SIGNIFICANCE We postulate that quantitative characterization of features of the EEG unique to early development provide indices for tracking changes in specific neurophysiologic mechanisms that are critical for normal development of brain function.

Anesthetic‐specific electroencephalographic patterns during emergence from sevoflurane and isoflurane in infants and children

Background:  Devices that monitor the depth of anesthesia are increasingly used to titrate sedation and avoid awareness during anesthesia. Many of these monitors are based upon electroencephalography (EEG) collected from large adult reference populations and not pediatric populations (Anesthesiology, 86, 1997, 836; Journal of Anaesthesia, 92, 2004, 393; Anesthesiology, 99, 2003, 34). We hypothesized that EEG patterns in children would be different from those previously reported in adults and that they would show anesthetic‐specific characteristics.

Family Nurture Intervention in preterm infants alters frontal cortical functional connectivity assessed by EEG coherence

To assess the impact of Family Nurture Intervention (FNI) on cortical function in preterm infants at term age.