Imaging nociceptive brain activity in the newborn infant

In this thesis electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are used to investigate the temporal and spatial patterns of noxious-evoked brain activity in newborn infants. EEG was used to investigate responses to graded intensities of experimental noxious stimulation, and evoked brain activity was compared with behavioural and spinal cord activity constituting common surrogate measures of pain in infants. Nociceptive-specific brain activity was elicited in response to all forces of experimental noxious stimulation (applied forces: 32 - 128 mN). In addition, the magnitude of the noxious-evoked response was positively correlated with the magnitude of reflex leg withdrawal, and this relationship was observed in the absence of changes in facial expression. As fMRI had not previously been used to investigate nociceptive processing in infants at 3 Tesla, initial experiments were conducted to optimise the acquisition parameters. The results from optimisation showed that an echo time of approximately 50 ms should be used in future fMRI studies in infants. Experiments conducted alongside this optimisation used fMRI to investigate the cortical and subcortical structures activated by experimental noxious stimulation (applied forces: 32 - 128 mN) in newborn infants (0 - 11 days old). This was compared with noxious-evoked brain activity in adults (applied forces: 32 - 512 mN). Experimental noxious stimulation evoked a widespread pattern of brain activity in newborn infants that overlapped with the network of brain regions activated by nociceptive processing in adults.