673 - Resting-State Functional Connectivity During Wakefulness in Preterm Infants and Healthy Term Infants: An EEG-fNIRS Study

Publication Number: 2656.673

Hiroyuki Kidokoro, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan; Anna Shiraki, University of Geneva, Geneve, Geneve, Switzerland; Hama Watanabe, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Gentaro Taga, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Takafumi Ushida, Nagoya University, Nagoya, Aichi, Japan; Yuki Kunisawa, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan; Ayano Yanagisawa, Department of Pediatrics, Nagoya University Graduate School of Medicine, Nagoya, Japan, Nagoya, Aichi, Japan; Misa Hashimoto, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan; Misae Yamada, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan; Takamasa Mitsumatsu, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan; Masahiro Kawaguchi, Nagoya University Hospital, Nagoya, Aichi, Japan; Yuji Ito, Nagoya University Hospital, Nagoya, Aichi, Japan; Tomohiko Nakata, Nagoya Graduate School of Medicine, Nagoya, Aichi, Japan; Yoshiaki Sato, Nagoya University Hospital, Nagoya, Aichi, Japan; Jun Natsume, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan

Background: Resting-state functional connectivity (FC) differs between active sleep (AS) and quiet sleep (QS) in neonates, but FC during wakefulness (W) remains less well characterized.

Objective: We compared FC during W with AS and QS in preterm and healthy term-born infants using simultaneous video-EEG and functional near-infrared spectroscopy (fNIRS).

Design/Methods: We prospectively enrolled preterm and healthy term-born infants born at Nagoya University Hospital who underwent combined EEG-fNIRS recording between 2020 and 2024. Video-EEG with electrooculography, respiration, and behavioral monitoring was acquired for ≥40 minutes and scored in 30-second epochs to classify AS, QS and W. An eight-channel NIRS array (frontal, left/right temporal, occipital) measured changes in oxy-hemoglobin concentration. From low-frequency ( < 0.1 Hz) oxy-hemoglobin fluctuations, we computed average FC and the phase synchronization index (PSI) across 28 pairs within the same records. Recordings were included if all three states were captured for at least 3 minutes each with acceptable signal quality and, for preterm infants, no severe brain injury.

Results: Thirty-seven recordings from 28 preterm infants and 9 recordings from 9 term-born infants met inclusion criteria. For preterm infants, median (range) gestational age at birth was 32.1 (24.6-34.9) weeks, postnatal day 35 (5-113) and postmenstrual age at recording 37.9 (33.6-41.1) weeks. Corresponding values for term-born infants were 39.0 (37.6-40.7) weeks, 3 (1-6) days, and 39.0 (37.9-39.6) weeks. In preterm infants, mean average FC and PSI during W was higher than during QS (P < 0.001) and did not differ from AS. In term infants, FC and PSI during W did not differ from AS or QS (Figure 1). Group-level FC topographies in preterm infants were similar for W and AS, exhibiting stronger short- and long-range coupling, whereas QS showed weaker fronto-occipital connectivity (Figure 2). In term infants, FC during W resembled QS and was lower than AS, and overall FC values were lower than those in preterm infants. In preterm infants, PSI during W did not correlate with postnatal age, whereas in term infants, it increased with postnatal days (P=0.01, Figure 3).

Conclusion(s): Preterm infants show organized resting-state FC during W that resembles AS, supporting neonatal wakefulness as an active, integrative cortical state. In term newborns, PSI during W increase over the first postnatal days, potentially reflecting maturation of arousal systems (e.g., noradrenergic locus coeruleus). Early postnatal age should be considered when interpreting neonatal resting-state FC.

Figure1: Comparisons of FC metrics among AS, QS and W in preterm (n=37) and healthy term infants (n= 9).
Plots depict 28-channel average functional connectivity (FC) and phase synchronization index (PSI) across active sleep (AS), quiet sleep (QS), and wakefulness (W) in 37 preterm recordings and 9 term-born recordings. In preterm infants, repeated-measures ANOVA with Bonferroni correction shows significant differences between AS and QS (P <0.001) and between QS and W (P <0.001); PSI showed the same pattern. In term infants, average FC does not differ across AS, QS, and W, whereas PSI differs significantly between AS and QS.


Figure 2. Group-level functional connectivity maps across behavioral states.
(a) Schematic of the eight-channel fNIRS probe layout. (b-d) Functional connectivity (FC) during active sleep (AS), quiet sleep (QS), and wakefulness (W) in preterm infants, respectively. (e-g) Corresponding FC maps during AS, QS, and W in term infants.


Figure 3. Association between functional connectivity indices and postnatal day in healthy term infants.
Panels (a) and (b) show the associations of average functional connectivity (FC) and phase synchronization index (PSI), respectively, with postnatal age (days). Active sleep (AS), quiet sleep (QS), and wakefulness (W) are indicated in red, blue, and black, respectively, for both scatter points and fitted trend lines.