Fruit flies expand understanding of how brains work

Scientists at the University of Sheffield have gained a new insight into how our brains work after studying the inner workings of fruit fly equivalents.

The new research investigates the parts of the flies' brains – which work just like our human equivalents but are much less complicated – that enable them to perceive the visual world in detail.

The study, which is published in the journal Science, set out to challenge a 30-year old belief that in insect brains colour and motion information are processed independently. A team of scientists separated the colour sensitivity of the flies’ inner and outer receptors to discover how colour and motion signals interact in the brain. The scientists use a fly flight simulator which enables them to measures the insect’s response to motion.

The team leader, Dr Mikko Juusola, of the University’s Department of Biomedical Science, said: “Important processes happen at the level of neural circuits all the time. Collectively these computations make us who we are.

“They enable us to respond to changes in the real world appropriately, learn new things, recall old memories, and to think, dream and play. Understanding how these neural computations happen helps us to understand how the brain works.”

Dr Trevor Wardill and Dr Olivier List, who were post-doctoral scientists in the Juusola laboratory during this work, said: “Our understanding of the neural circuit computations is very limited at best. Our report looks into the mechanisms, information processing and consequences of such computations within the well-defined circuits in the fly brain. The level of microcircuits, our brain and the fly brain are likely to work pretty much the same way.”

Dr Xiaofeng Li, who performed recordings from individual brain cells for this study as a part of his PhD work. Dr Li added: "The results demonstrate that the fly brain uses inputs from photoreceptors that are sensitive to different colours to improve its motion perception." Brain facts: Fly brains have just 200,000 brain cells where as the human brain has billions of neurones, each with an average of 7,000 synaptic connections to other neurones.

The neural networks - at a microscopic level - are very similar across humans and the fruit flies species, making it much easier to study the brain processes.

Fly brains have just 200,000 brain cells, each of which can be identified, and in some cases scientists know their neural neighbours and connections to the level of individual synapses.

In comparison, the human brain has billions of neurones, each with on average 7,000 synaptic connections to other neurones, making studying the exact functions of precise microcircuits in the human brain much more complicated.

Dr Juusola added: “We thought that combining colour and motion information in the microcircuits of the fly brain should improve motion perception, making it easier for a fly to see colourful objects and other flies when flying around in the blossoming fields of summer.

“We used genetic manipulation, combined with electrophysiological, optical and behavioural assays, and information theoretical analysis to show how and why colour and motion information is combined in neural circuit processes, explaining flies' behaviour.”

Additional information The University of Sheffield's Department of Biomedical Science

Department of Biomedical Science The University of Sheffield

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