The specialised regional functionality of the mature human cortex partly emerges through experience-dependent specialisation during early development. Our existing understanding of this process is based on evidence from unitary imaging modalities and has thus focused on isolated changes in spatial or temporal precision of neural or haemodynamic activation alone, giving an incomplete picture of the process. We speculate that neural specialisation of function will be underpinned by better coordinated haemodynamic and metabolic changes in a broader orchestrated physiological response.
Thus, we present a harmonised framework in which specialisation is indexed by the emergence of coupling between neuronal activity and vascular supply of oxygen and energy. Here, we combine simultaneous measures of coordinated neural activity EEG , metabolic rate and oxygenated blood supply broadband near-infrared spectroscopy to measure emerging specialisation in the infant brain.
In 4-tomonth-old infants, we show that social processing is accompanied by spatially and temporally specific increases in coupled activation in the temporal-parietal junction, a core hub region of the adult social brain. During non-social processing coupled activation decreased in the same region, indicating specificity to social processing. Coupling was strongest with high frequency brain activity beta and gamma , consistent with the greater energetic requirements and more localised action of high frequency brain activity.
We conclude that functional specialisation of the brain is a coordinated activity across neural, haemodynamic, and metabolic changes, and our ability to measure these simultaneously opens new vistas in understanding how the brain is shaped by its environment. The adult brain is highly specialised, with core networks coordinating to subserve complex behaviours. This specialised functioning emerges across development through a combination of genetically influenced brain architecture and experience-dependent and experience-expectant learning processes 1.
This interaction between predisposition and change with experience has been closely studied in the domain of social interaction, where neonates attended preferentially to faces 2 but expertise in recognition, communication, and initiation emerge gradually over time 1 , 3. Social communication is core to human interaction, and our ability to live in extended-family groups has been linked to the evolution of advanced cognitive abilities 4.
