New slant on chicken-and-egg puzzle may hold key to pre-birth learning

CHICKEN embryos can be “woken up” in the egg long before hatching, by rousing them with the sound of clucking hens.

The discovery may have important implications for premature babies, researchers believe.

“This work showed that embryo brains can function in a waking-like manner earlier than previously thought – well before birth,” said study leader Dr Evan Balaban, from McGill University in Montreal, Canada.

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“Like adult brains, embryo brains also have neural circuitry that monitors the environment to selectively wake the brain up during important events.”

Dr Balaban’s team devised experiments in which brain activity in unhatched chick embryos was monitored using an advanced Pet (positron emission tomography) scanning technique.

The researchers found that during the final 20 per cent of life before hatching, the chicks displayed brain activity that mirrored being asleep or awake.

Wakefulness was only induced by “meaningful” recorded sounds of chickens clucking. “Non-vocal” noises had no effect.

Prior to this point in development, embryos were in a state that was “neither like sleep nor waking”, said Dr Balaban. It was more akin to being comatose, or under anaesthetic.

Another surprise was that while their higher brain regions were inactive, the chicks showed increasing spontaneous movement.

Once they reached the threshold of 80 per cent of development, movement ceased as they entered a “sleep-like state”. At the same time, their higher brain regions burst into activity.

“The last 30 per cent of foetal brain development is a more interesting time than we previously thought, because it’s when complex whole-brain functions that depend on co-ordination of widely separated brain areas first emerge,” said Dr Balaban.

The findings, published in the journal Current Biology, may explain instances of complex foetal and pre-birth learning, he said.

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