At the Infant Consciousness Conference held recently in the United States and sponsored by New York University, researchers explored when and how consciousness might arise, and how to spot the signs. They also considered clues from recent brain imaging studies that suggest the capacity for consciousness may arise before birth, toward the end of pregnancy.
The definition of consciousness itself is controversial and is generally considered to be the ability to have subjective experiences. However, a baby's consciousness may differ from that of an adult, and may develop gradually rather than all at once. Most researchers believe that the connection between the thalamus and cortex in the brain, which is critical to consciousness, does not begin to form until about 24 weeks of fetal development.
Researchers use techniques such as functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) to look for possible signs of consciousness. One study found alternating activity between the default mode network, dorsal attention network, and executive control network in the brains of full-term newborns and preterm infants of the same age, which has been hypothesized to be a potential marker of consciousness. However, in premature infants scanned between 32 and 37 weeks, these networks had not yet formed. Another study found a "small-world network" in the brains of premature infants, a pattern of neural connections that is disrupted by anesthesia or brain injury and may support conscious perception.
Additionally, MEG studies have shown that fetuses aged 35 weeks and older are able to respond to changes in sound patterns, similar to conscious adults. These findings suggest that fetuses may begin to develop some form of consciousness late in pregnancy.