Evoked potentials generated by noxious stimulation in the human infant brain

While human infants can display distinctive behavioural and physiological spinal cord and brainstem responses to noxious stimulation, it is not known whether cortical neurons are specifically activated by noxious stimuli in newborns. Here, using a novel approach to time-lock an EEG recording to a clinically required heel lance, we show the presence of a distinct nociceptive-specific potential in newborn infants (35-39 weeks postmenstrual age). The potential can be observed in single trials in the central electrodes (Cz and CPz) and using principal component analysis is characterised by a positivity that occurs at approximately 560 ms post-stimulus (N420-P560; P, positive; N, negative). The magnitude of the nociceptive-specific potential is not dependent on sleep state, whereas an earlier potential (N150-P260-N430), which is sleep-state dependent, is evoked by both noxious and non-noxious stimulation. These results provide the first direct evidence of specific noxious-evoked neural activity in the infant brain and suggest that newborn infants are capable of the sensory-discriminative aspects of pain experience.