Are human brains unique?

New research shows that properties thought to be unique to the human brain are also shared by the mouse brain.

Researchers at the University of Sydney have analysed intricate whole-brain maps in mice to show that neural architecture varies along the path of information flow in a similar way in mouse and human brains, pointing to fundamental neural mechanisms for information processing.

Published in the Proceedings of the National Academy of Sciences of the United States, their finding calls into question the uniqueness of human consciousness and the anatomical structures that have evolved to support it.

“Lots of research has focused on how the brain’s circuits are specialised for different functions in the human brain — for example, how the properties of visual processing areas differ from brain areas that integrate diverse types of information,” said Dr Ben Fulcher, in the School of Physics at the University of Sydney, lead author of the study.

“This was thought to be something that might be unique to humans, following the large expansion of the human cortex, that may therefore be responsible for our distinct cognitive capabilities. By contrast, the brain’s cellular properties in animals like mice were thought to be relatively uniform,” Dr Fulcher said.

Recent work has revealed the main properties of brain circuits vary along the path that information flows through the human brain.

“We wanted to test whether this principle of brain organisation is unique to humans, or whether it may apply across species,” said Dr Fulcher. “To do this, we leveraged intricate, modern brain-mapping experiments, performed only in the past few years, that have yielded unprecedented whole-brain maps of neural circuits.”

Thanks to a new emphasis on data sharing in modern neuroscience, the research team was able to synthesise diverse high-quality datasets from around the world. Their findings demonstrate that various properties of neural circuits vary together; the path of information in the mouse brain flows the same way as in highly specialised human brains.

“While the dominant structure was surprisingly similar, we also found key interspecies differences, with a weaker overall variation in mouse compared to human,” said Dr Fulcher. “This suggests that while mouse and human brains may share a common organisational structure, the degree of specialisation differs between the two species.”

Understanding how biological brains process information is crucial to refining the artificial intelligence algorithms that have an ever-increasing role in our lives.

Dr Fulcher said the next step is to understand how these common brain structures lead to efficient information processing, and the incredible array of thoughts, feelings, and behaviours we are capable of.

“We know very little about how the complex web of interconnected brain cells somehow gives rise to the incredible array of cognitive functions that we can perform,” Dr Fulcher said. “Our results provide clues to how the brain’s structure has evolved to facilitate efficient information processing.”