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Phase-amplitude coupling of delta brush unveiling neuronal modulation development in the neonatal brain
Takashi Shibata1, Hiroshi Otsubo1
1Division of Neurology, The Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Delta brushes indicate neonatal brain maturity. This study used phase-amplitude coupling (PAC) to show delta brushes peak around 32-36 post-menstrual weeks, primarily in the occipital region, reflecting developing brain activity.
Area of Science:
- Neonatal electroencephalography (EEG)
- Neuroscience
- Developmental neuroscience
Background:
- Delta brushes are a key electroencephalogram (EEG) marker of brain maturity in newborns.
- Understanding the developmental trajectory of delta brushes is crucial for assessing neurological development.
- Phase-amplitude coupling (PAC) offers a method to analyze the interaction between different brainwave frequencies.
Purpose of the Study:
- To investigate the spatiotemporal development of neonatal delta brushes using phase-amplitude coupling (PAC).
- To elucidate the relationship between slow delta waves and superimposed fast (alpha-beta) activity within delta brushes.
- To correlate these findings with post-menstrual age (PMW) in neurologically intact neonates.
Main Methods:
- Analyzed EEG data from 18 neurologically intact neonates across four post-menstrual age groups (≤30, 31-34, 35-38, 39-42 PMW).
- Calculated PAC metrics (modulation index, direct mean vector length, mean phase angle) between slow delta waves (0.5-1.5 Hz) and alpha-beta activity (8-25 Hz).
- Examined PAC in four regions: frontal, central, temporal, and occipital.
Main Results:
- Significant regional differences in direct mean vector length (dMVL) were observed in neonates ≤34 PMW.
- Both modulation index (MI) and dMVL indicated a strengthening of delta brush activity in the occipital region between 32 and 36 PMW.
- The mean phase angle of coupling consistently centered around 0° or 180° across all age groups.
Conclusions:
- PAC analysis successfully revealed the spatiotemporal dynamics of alpha-beta activity modulated by slow delta waves in neonatal delta brushes.
- Delta brush activity appears maximal around 32-36 PMW, with a predominant occipital distribution.
- The observed PAC patterns may reflect the modulation of cortical neuronal fast activity by subcortical slow delta waves during a critical neonatal developmental window.
Introduction:
Delta brushes are an indicator of brain maturity on a neonatal EEG. We investigated phase-amplitude coupling (PAC) between slow delta waves and superimposed alpha-beta activity in delta brushes to elucidate the spatiotemporal developments of the delta brush with post-menstrual weeks (PMW).
Methods:
The subjects were 18 neurologically intact patients (seven girls). We analyzed EEG within 42 PMW. Patients were divided into four age groups as follows: PMW ≤30w; 31-34 w; 35-38 w; and 39-42 w. We selected up to three epochs of 2-minute EEG segments including delta brushes. We calculated the modulation index (MI), direct mean vector length (dMVL), and mean of phase angle of coupling by PAC between slow waves (0.5-1.5 Hz) and fast activities (8-25 Hz) in four regions (F: Fp1 and Fp2, C: C3 and C4, T: T3 and T4, O: O1 and O2).
Results:
We collected data from 18 patients and 31 epochs between 29 and 42 PMW, which comprised one, four, five, and eight patients, and two, seven, eight, and 14 epochs in the ≤30w, 31-34 w, 35-38 w, and 39-42 w groups, respectively. There were significant differences in the dMVL between the four regions in age groups ≤30w (P = 0.033) and 31-34w (0.017). Both MI and dMVL showed that delta brushes became higher in the occipital region from 32 to 36 PMW. The mean phase angle of coupling concentrated around either 0° or 180° for all age groups.
Conclusions:
PAC analysis revealed the spatiotemporal relations of alpha-beta activities that are modulated by slow delta waves in neonatal delta brushes. The delta brushes appeared to be at a maximum around 32-36 PMW with the predominant occipital distribution. The PAC of the delta brush might represent the cortical neuronal fast activity that is modulated by slow delta waves of subcortical regions during a particular neonatal period.
