Development of spontaneous activity transients and ongoing cortical activity in human preterm babies

University of Helsinki, Helsinki, Uusimaa, Finland
Neuroscience (Impact Factor: 3.36). 04/2007; 145(3):997-1006. DOI: 10.1016/j.neuroscience.2006.12.070
Source: PubMed


Recent experimental studies have shown that developing cortex in several animals species, including humans, exhibits spontaneous intermittent activity that is believed to be crucial for the proper wiring of early brain networks. The present study examined the developmental changes in these spontaneous activity transients (SAT) and in other ongoing cortical activities in human preterm babies. Full-band electroencephalography (FbEEG) recordings were obtained from 16 babies at conceptional ages between 32.8 and 40 wk. We examined the SATs and the intervening ongoing cortical activities (inter-SAT; iSAT) with average waveforms, their variance and power, as well as with wavelet-based time-frequency analyses. Our results show, that the low frequency power and the variance of the average waveform of SAT decrease during development. There was a simultaneous increase in the activity at higher frequencies, with most pronounced increase at theta-alpha range (4-9 Hz). In addition to the overall increase, the activity at higher frequencies showed an increased grouping into bursts that are nested in the low frequency (0.5-1 Hz) waves. Analysis of the iSAT epochs showed a developmental increase in power at lower frequencies in quiet sleep. There was an increase in a wide range of higher frequencies (4-16 Hz), whereas the ratio of beta (16-30 Hz) and theta-alpha (4-9 Hz) range activity declined, indicating a preferential increase at theta-alpha range activity. Notably, SAT and iSAT activities remained distinct throughout the development in all measures used in our study. The present results are consistent with the idea that SAT and the other ongoing cortical activities are distinct functional entities. Recognition of these two basic mechanisms in the cortical activity in preterm human babies opens new rational approaches for an evaluation and monitoring of early human brain function.

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Available from: Sampsa Vanhatalo,
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    • "The output of this analysis presents the proportion of time covered by each amplitude category, and the estimation of wave amplitudes is mathematical. (B) The event-based EEG analysis begins from detection of brain events called SAT (Vanhatalo et al. 2005; Vanhatalo and Kaila 2006), and the intervals between these detections are called inter-SAT (Tolonen et al. 2007) or IBIs. The detections are performed on a continuous basis, but the metrics are subsequently computed for 5 min epochs as displayed in the lowest graph. "
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    ABSTRACT: Recent experimental studies have shown that early brain activity is crucial for neuronal survival and the development of brain networks; however, it has been challenging to assess its role in the developing human brain. We employed serial quantitative magnetic resonance imaging to measure the rate of growth in circumscribed brain tissues from preterm to term age, and compared it with measures of electroencephalographic (EEG) activity during the first postnatal days by 2 different methods. EEG metrics of functional activity were computed: EEG signal peak-to-peak amplitude and the occurrence of developmentally important spontaneous activity transients (SATs). We found that an increased brain activity in the first postnatal days correlates with a faster growth of brain structures during subsequent months until term age. Total brain volume, and in particular subcortical gray matter volume, grew faster in babies with less cortical electrical quiescence and with more SAT events. The present findings are compatible with the idea that (1) early cortical network activity is important for brain growth, and that (2) objective measures may be devised to follow early human brain activity in a biologically reasoned way in future research as well as during intensive care treatment.
    Cerebral Cortex 05/2014; 25(9). DOI:10.1093/cercor/bhu097 · 8.67 Impact Factor
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    • "Clinically, neonatal brain function or development is assessed predominantly using EEG. EEG spectral power, which reflects rhythmic activity of corticomotor neurons, is known to change gradually after birth (Khazipov & Luhmann, 2006; Biagioni et al., 2007; Tolonen et al., 2007). Moreover, EMG spectral power that reflects the activity of motor units also changes during human development (Hadders-Algra et al., 1992; Gibbs et al., 1997; Farmer et al., 2007; Petersen et al., 2010). "
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    ABSTRACT: Anatomical studies show the existence of corticomotor neuronal projections to the spinal cord before birth, but whether the primary motor cortex drives muscle activity in neonatal 'spontaneous' movements is unclear. To investigate this issue, we calculated corticomuscular coherence (CMC) and Granger causality in human neonates. CMC is widely used as an index of functional connectivity between the primary motor cortex and limb muscles, and Granger causality is used across many fields of science to detect the direction of coherence. To calculate CMC and Granger causality, we used electroencephalography (EEG) to measure activity over the cortical region that governs leg muscles, and surface electromyography (EMG) over the right and left tibialis anterior muscles, in 15 healthy term and preterm neonates, during spontaneous movements without any external stimulation. We found that 17 leg muscles (10 right, seven left) in 12 neonates showed significant CMC, whose magnitude significantly correlated with postnatal age only in the beta frequency band. Further analysis revealed Granger causal drive from EEG to EMG in 14 leg muscles. Our findings suggest that the primary motor cortex drives muscle activity when neonates move their limbs. Moreover, the positive correlation between CMC magnitude and postnatal age suggests that corticomuscular communication begins to develop during the neonatal stage. This process may facilitate sensory-motor integration and activity-dependent development.
    European Journal of Neuroscience 05/2014; 40(3). DOI:10.1111/ejn.12612 · 3.18 Impact Factor
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    • "(m = 6.5; frequency separation 1 standard deviation; see Fig. 3). Wavelet analysis is a routine signal analysis method that allows analysis of spectral changes in the signal at high temporal resolution, which is important when studying features within the SAT transient (for more methodological reasoning of wavelets for this purpose, please see Ref. [34]). Fifth, we analyzed separately the changes of activity at higher frequencies by filtering two specific frequency bands: To analyze changes at about 4–7 Hz, a high pass filter at 4.5 Hz with stop band at 3.0 Hz and low pass filter at 6.5 Hz with stop band at 9 Hz were used. "
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    ABSTRACT: Background: Animal experiments have suggested that the quality of the early intermittent brain activity is important for shaping neuronal connectivity during developmental phase that corresponds to early prematurity. This is a pilot study aiming to assess whether spontaneous activity transients (SAT) in the early preterm babies are affected by drugs that are routinely used in neonatal intensive care. Methods: We collected retrospectively seventeen EEG recordings (15 babies, conceptional age 26-33weeks, no brain lesions) that were divided into groups according to drug administration at the time of EEG: phenobarbital, fentanyl, theophylline, and controls. SATs were extracted from the EEG for further analysis with several advanced time-series analysis paradigms. Results: The visual appearance of SATs was unaffected by drugs. Phenobarbital reduced the total power of the SAT events. Both fentanyl and phenobarbital reduced the length of SATs, and enhanced the oscillations at higher frequencies. Theophylline reduced the oscillatory activity at middle frequencies during SAT, but enhanced oscillations at higher frequencies during time-period prior to SAT. Conclusions: Our findings suggest, that (i) all drugs examined affect brain activity in ways that are not seen in the visual EEG interpretation, and that (ii) both acute and long term (i.e. developmental) effects of these drugs on brain may warrant more attention as a part of optimizing preterm neurological care.
    Brain & development 02/2013; 36(2). DOI:10.1016/j.braindev.2013.01.009 · 1.88 Impact Factor
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