A group of scientists collaborating from Canada, Spain and Italy have published a study in Current Biology on the sleep and waking patterns of chicken embryos and how they can be influenced from outside the shell.
Injecting the chicken embryos with a sugar solution laced with a radioactive tracer, and could therefore study the prenatal chick’s brain activity, while still in the egg. Brain activity uses sugar, and so the sign of any activity would cause the brain to ‘light up’, when viewed through the combined positron emission tomography and structural X-ray computed tomography set up. Sleeping shows less brain activity than waking up.
The scientists tried to wake up the sleeping chicks by exposing them to all manner of sounds, but found little to no reaction, until they turned on a track of a mother hen emitting a danger call. The scans also showed that the chick’s movement in the shell did not show a ‘waking up’ brain response.
The researchers conclude that the waking up state is therefore inducible, and present during the last 20% of embryonic life before hatching.
Source: New Scientist