Into the minds of babes :: Anil Ananthaswamy, based on Stanislas Dehaene, Sid Kouider & Robin Carhart-Harris :: New Scientist, 23 August 2014
Summary and review of the above article
Stanislas Dehaene indicates that conscious perception arises through a two stage process. The first stage involves the unconscious processing of an image, and then after about 300 ms a network of brain regions, particularly in the frontal and parietal areas, supports the perception of a conscious image, which can be reported by the subject.
Sid Kouider subsequently worked with Dehaene to investigate if and how infant brains perform this function. Their team discovered that infants had the same activity in the brain networks that gave rise to conscious perception in adults. However, in 5-15 month olds, this activity came 750 ms after the initial stimulus, compared to 300 ms for adults; for 5 month old infants the time lag was even longer at 900 ms.
It is suggested that the greater delay in infants may be due to lack of mylenisation of axons reducing connectivity, and also the immaturity of the prefrontal cortex. In this article, the reduced connectivity in the infant brain is likened to adult brains when attention is less focused, or even to when they enter altered states of consciousness. For instance, the brain is shown to be less controlled when watching an absorbing film, with a lack of planning and a reduced sense of self.
Robin Carhart-Harris’s recent experiment at Imperial College London demonstrated the more pronounced effect of psilocybin (magic mushroom). The function of the default network, which is active when the brain is thinking introspectively as opposed to primarily dealing with signals from the environment, and which is based on the prefrontal, cingulate and temporal cortex, is impaired by psilocybin; in particular the posterior cingulate and medial prefrontal are deactivated and long-range connectivity between brain regions is reduced. One subject in this experiment report difficulty in distinguishing between themselves and the surrounding environment. It is suggested similarly that infants, although they are conscious, may have reduced self-awareness due to lower connectivity and less developed frontal processing.