'Lack of deep sleep led to dinosaurs' demise'

Giant meteorites from outer space, fire storms, tidal waves and an ice age have all been suggested by experts to explain the demise of T-Rex and other giant dinosaurs.

However, the latest theory to explain their extinction claims they did not survive because their reptilian sleeping patterns meant their brains did not learn new skills properly.

Unlike mammals and birds, reptiles are unable to experience slow wave sleep, the type of sleep believed to be responsible for boosting memories, especially those connected to performing new tasks.

As a result, reptiles are much more limited in the type of complex behaviour they can experience than other animals such as mammals and birds.

The implication of new research by Niels Rattenborg, of the Max Planck Institute for Ornithology in Germany, is that the inability of dinosaurs - which are ancestors of modern-day reptiles - to experience slow wave sleep may have been one of the reasons why they became extinct.

Slow wave - or deep - sleep leads to enhancements in both learning and physical performance. It effectively shuts down the parts of the brain that have learned new skills and allows this learning to become consolidated without interruption.

Without this crucial ability it could be that, when the earth experienced huge climatic changes towards the end of the era of the dinosaurs, they were unable to pick up sufficient new tricks to learn their way out of extinction.

The research also shows that, although birds and mammals appear to have developed the same brain structures and, importantly, the same series of connections between structures that allow slow wave sleep to take place, these developments must have happened independently.

Despite the common ancestry of birds and reptiles among the dinosaurs, regarding sleep at least it is in fact birds and mammals that have more in common in terms of brain structure and function.

The paper is published by Elsevier in its journal Brain Research Bulletin.