New technology is allowing researchers to see brain connections working in real time.

The human brain is composed of billions of neurons wired together in intricate webs and communicating through electrical pulses and chemical signals.

Although neuroscientists have made progress in understanding the brain's many functions - such as regulating sleep, storing memories, and making decisions - visualising the entire “wiring diagram” of neural connections throughout a brain has not been possible.

But now, using Drosophila fruit flies, researchers in the US have developed a method to easily see neural connections and the flow of communications in real time within living flies.

The work is a step forward toward creating a map of the entire fly brain's many connections, and helping scientists understand the neural circuits within human brains as well.

When two neurons connect, they link together with a structure called a synapse, a space through which one neuron can send and receive electrical and chemical signals to or from another neuron. Even if multiple neurons are very close together, they need synapses to truly communicate.

The laboratory of Caltech research professor Carlos Lois has developed a method for tracing the flow of information across synapses, called TRACT (Transneuronal Control of Transcription).

Using genetically engineered Drosophila fruit flies, TRACT allows researchers to observe which neurons are ‘talking’ and which neurons are ‘listening’ by prompting the connected neurons to produce glowing proteins.

Using a type of microscope that can peer through a thin window installed on the fly's head, the researchers can observe the colourful glow of neural connections in real time as the fly grows, moves, and experiences changes in its environment.

The image accompanying this article shows olfactory receptor neurons (red) activating the production of a green protein in their synaptically-connected downstream partners.

Many neurological and psychiatric conditions, such as autism and schizophrenia, are thought to be caused by altered connections between neurons.

With technology like TRACT, researchers could one day determine how different diseases perturb the connections within brain circuits.

Additionally, because neural synapses change over time, TRACT allows the monitoring of synapse formation and destruction from day to day.

Being able to see how and when neurons form or break synapses will be critical to understanding how the circuits in the brain assemble during growth, and how they fall apart with age or disease.

A paper on the technology is accessible here.