Fiona Moultrie1, Matteo Bastiani1, Sezgi Goksan1, Caroline Hartley1, Rebeccah Slater1
1) United Kingdom
In adults, pain evokes greater activity in the somatosensory cortex contralateral to the stimulus, whereas in newborn infants, activity is observed more bilaterally. Weak lateralisation in infants is likely attributable to immature cortico-cortical inter-hemispheric pathways which exist at this critical neurodevelopmental stage. We hypothesised that the degree of ipsilateral somatosensory activity in response to noxious stimulation in infants relates to the integrity of developing cortico-cortical tracts.
10 healthy term infants were recruited from the John Radcliffe Hospital, Oxford for an MRI scan within the first week of life. A mild experimental noxious stimulus was applied ten times to the left foot of each infant during a functional MRI scan (TR=2300ms; TE=50ms; multiband=4; resolution 2×2×2mm) and diffusion data were acquired (TR=2900ms; resolution 1.8x1.8x1.8mm; multiband=3; directions=152; b=500, 1000, 2000). The average percentage BOLD increase was calculated in the thalami and bilaterally in the paracentral lobule (PCL), which includes somatotopic representation of the foot. We identified white matter tracts from the thalami to the PCLs, and cortico-cortical tracts between the ipsilateral and contralateral PCL, and calculated diffusion metrics.
Bilateral activity was evoked in the PCL, which was highly correlated across hemispheres within individual infants (r2= 0.8675; p= 0.0023). While mean noxious-evoked activity in the contralateral PCL was correlated with the integrity of contralateral thalamo-PCL tracts (r2= 0.6924; p = 0.0202), the ipsilateral PCL activity was not dependent on the integrity of ipsilateral thalamo-PCL tracts. Activity in the ipsilateral PCL was however significantly correlated with the integrity of cortico-cortical tracts between the ipsilateral and contralateral PCL, adjusted for contralateral PCL activity (r2= 0.6043; p= 0.0397).
In newborn infants, the degree of bilateral activity in the somatosensory cortices is related to the integrity of the cortico-cortical association pathways linking these brain structures.
NIHR Biomedical Research Centre (Oxford) and Wellcome Trust Grant 102176.
