A glimpse of consciousness emerging in the brains of babies has been recorded for the first time. Insights gleaned from the work may aid the monitoring of babies under anaesthesia, and give a better understanding of awareness in people in vegetative states – and possibly even in animals.
The human brain develops dramatically in a baby’s first year, transforming the baby from being unaware to being fully engaged with its surroundings. To capture this change, Sid Kouider at the Ecole Normale Supérieure in Paris, France, and colleagues used electroencephalography (EEG) to record electrical activity in the brains of 80 infants while they were briefly shown pictures of faces.
In adults, awareness of a stimulus is known to be linked to a two-stage pattern of brain activity. Immediately after a visual stimulus is presented, areas of the visual cortex fire. About 300 milliseconds later other areas light up, including the prefrontal cortex, which deals with higher-level cognition. Conscious awareness kicks in only after the second stage of neural activity reaches a specific threshold. “It’s an all-or-nothing response,” says Kouider.
Adults can verbally describe being aware of a stimulus, but a baby is a closed book. “We have learned a lot about consciousness in people who can talk about it, but very little in those who cannot,” says Tristan Bekinschtein at the University of Cambridge, who was not involved in the work.