Proceedings of The Physiological Society

Future Physiology (Leeds, UK) (2017) Proc Physiol Soc 39, PC63

Poster Communications

Sleep promotes somatosensory cortical development in human newborn infants

K. Whitehead1, J. Meek2, L. Fabrizi1

1. University College London, London, United Kingdom. 2. University College London Hospitals, London, United Kingdom.

Human newborn infants spend more time in active sleep (precursor to REM sleep) than at any other stage of development. During these periods there is profuse motor activity (1). But what is its function? One possibility is that frequent facial and body movements during active sleep provide proprioceptive and tactile input to the immature somatosensory system (2,3). Data from very pre-term human infants indicate that somatosensory information is somatotopically encoded in the cortex by fast alpha-beta neural oscillations (8-20 Hz) (4,5). The aim of this study was to investigate whether movements during active sleep evoke alpha-beta oscillations in late pre-term and full-term infants, and the developmental trajectory of this movement-evoked neural activity. In our study we recorded electrical brain activity using scalp electroencephalography (EEG) in 17 healthy infants (9 female) of corrected gestational age 34+1 - 42+5 weeks+days, and monitored movements of the right hand during active sleep. Alpha-beta energy at electrodes overlying the left somatosensory (C3, CP3), midline somatosensory (Cz, CPz) and right somatosensory (C4, CP4) region was compared between the 1 second pre-movement onset and 1 second post-movement onset using Wilcoxon paired tests. The developmental trajectory of movement-evoked cortical oscillations was evaluated by correlation of the ratio of energy post-movement/pre-movement with the corrected gestational age of the infants (Spearman's correlation coefficients). Right hand movement evoked increased alpha-beta energy over the left lateral somatosensory region specifically (C3 p = .025, CP3 p = .017; median ratio post/pre-movement C3 1.24, CP3 1.30; midline and right somatosensory region n.s.: p ≥ .145) (Fig. 1). Next, we investigated whether right hand movement-evoked left somatosensory alpha-beta energy (normalised by its pre-movement baseline) is affected by age. Movement evokes the greatest increase in alpha-beta energy (approximately two- to three-fold its baseline level) in pre-term and early-term infants (34-38 weeks corrected gestational age) (C3: r -.221 p = .017, CP3: r - .177 p = .055). Our data suggest that the alpha-beta frequency band may serve to anchor representation in primary somatosensory cortex to the physical layout of the body in line with animal models (4). Movement-evoked alpha-beta activity during active sleep is only present in pre-term and early-term infants. The timing of the decrease in evoked alpha-beta activity correlates with the average time of birth (40 weeks), indicating that this mechanism may support intra-uterine somatosensory development, in preparation for entry into the external world at full-term.

Where applicable, experiments conform with Society ethical requirements