Event-related potentials following contraction of respiratory muscles in pre-term and full-term infants

OBJECTIVE: Involuntary isolated body movements are prominent in pre-term and full-term infants. Proprioceptive and tactile afferent feedback following limb muscle contractions is associated with somatotopic EEG responses. Involuntary contractions of respiratory muscles, primarily the diaphragm – hiccups – are also frequent throughout the human perinatal period during active behavioural states. Here we tested whether diaphragm contraction provides afferent input to the developing brain, as following limb muscle contraction. METHODS: In 13 infants on the neonatal ward (30–42 weeks corrected gestational age), we analysed EEG activity (18-electrode recordings in six subjects; 17-electrode recordings in five subjects; 16-electrode recordings in two subjects), time-locked to diaphragm contractions (n = 1316) recorded with a movement transducer affixed to the trunk. RESULTS: All bouts of hiccups occurred during wakefulness or active sleep. Each diaphragm contraction evoked two initial event-related potentials with negativity predominantly across the central region, and a third event-related potential with positivity maximal across the central region. CONCLUSIONS: Involuntary contraction of the diaphragm can be encoded by the brain from as early as ten weeks prior to the average time of birth. SIGNIFICANCE: Hiccups – frequently observed in neonates – can provide afferent input to developing sensory cortices in pre-term and full-term infants.