Daijiworld Media Network - New York
New York, Oct 8: A study of fruit flies by researchers at NYU Langone Health has provided new insights into how the brain forms and maintains short-term memories, confirming a long-standing theory about the neural circuits involved in working memory.
Although fruit flies have fewer than 200,000 neurons compared with the tens of billions in the human brain, their neural organisation and communication systems share important similarities with those of humans. Researchers can also study the fruit fly brain in detail because its complete network of neuronal connections, known as the connectome, has been mapped.
The study, published online in the journal Nature on October 7, examined how neurons encode information into working memory while allowing the memory to remain stable for a short period and be activated or switched off quickly.
Researchers exposed fruit flies to the smell of apple cider vinegar and observed that the insects continued moving towards the odour for several seconds after the smell disappeared.
Monitoring their brains revealed similar patterns of electrical activity in two types of neurons, known as PFG and hΔK.
The researchers found that the PFG and hΔK neurons form an attractor network, in which neurons communicate with one another to maintain a stable signal. However, the communication between the two types of neurons is normally blocked.
When the communication is blocked, PFG neurons track the fly's orientation using information from its internal compass system. When the block is removed and the two neuron types begin communicating, the fly can retain a specific location, such as the source of an odour, and move towards it.
Researchers described the mechanism as a “split attractor network”. In this system, PFG neurons carry the content of the memory, hΔK neurons regulate the timing of memory formation, and the communication block acts as a gate.
According to the researchers, the arrangement provides both the stability and flexibility required for working memory, allowing information to be retained temporarily without continuously consuming resources.
Senior investigator Katherine Nagel, associate professor in the Department of Neuroscience at NYU Grossman School of Medicine, said the findings demonstrate how a specific neuronal circuit can create a short-term memory that helps a fly remember a direction and navigate towards an odour.
The researchers plan to investigate how the circuit operates across different time periods and examine what information is tracked by other types of neurons. They also aim to understand why different brain regions can control similar functions simultaneously.