Scientists 'eavesdrop' on signals and messages sent inside a FRUIT FLY's brain

Reading the mind of a FRUIT FLY: Scientists 'eavesdrop' on signals and messages sent inside the insect's brain

Scientists added fluorescent tags to the neurons in the brains of fruit flies

These lit up when the neurons exchanged messages over their synapses

The colours continued to glow for up to an hour after a message was sent

It gives a long-lasting record of sensory experiences flies had in the past

Published: 06:51 EST, 4 December 2015 | Updated: 08:02 EST, 4 December 2015

Fruit flies really have just two goals in their relatively short lives - to find rotting fruit and to breed.

But now scientists have discovered a way to read the minds of these insects and watch how their tiny brains light up when they get a whiff of a nearby banana.

The researchers used fluorescent molecules to tag the neurons in the flies' brains so that they produced different colours as the cells communicated with each other.

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Neurobiologists have found a way of 'eavesdropping' on the messages sent between neurons in the brains of fruit flies. They used flourescent tags that light up when a signal is exchanged (pictured). It allowed them to see how the brains react to sensory experiences like smelling a banana or changes in temperature

These fluorescent tags continued to glow for between 10 minutes to an hour, meaning the scientists could 'eavesdrop' on what had been going on in the insects' mind.

They were able to see whether a fly had been in a warm or a cold environment earlier on in the test, from the way the brain lit up.

FLIES PRODUCE MONSTER SPERM

Fruit flies have the longest sperm of any creature in the animal kingdom.

Scientists have found its sperm even dwarfs those produced by giants like elephants.

It achieves this by producing sperm that is tightly coiled. When unravelled, a single sperm is 2.2-inches (5.8cm).

That makes the sperm 20 times the length of its body and 1,000 times that of human sperm.

Each sperm looks like a rolled-up ball of twine and is transferred to a female as a large mass that slowly loosens.

Flies develop huge testes that make up almost 11 per cent of its body weight in order to produce the giant sperm.

Producing such sexual organs consumes so much energy that it delays the male insects' sexual maturity.

The insects have about 800 sperm in their reproductive tracts at one time.

However, despite its size, fruit fly sperm is rather sluggish.

This means it needs some help from the female to reach its goal.

They could also see that the scent of a banana produced a different reaction in the olfactory region of the brain compared to when the fly had smelled jasmine, for example.

Dr Marco Gallio, a neurobiologist at Northwestern University in Illinois who led the research, said: 'Our results show we can detect a specific pattern of activity between neurons in the brain, recording instantaneous exchanges between them as persistent signals that can later be visualized under a microscope.'

The researchers, whose work is published in the journal Nature Communications, focused on the communication that occurs between neurons in the brain.

Each neuron sends information to its neighbour over connections known as synapses, where tiny packages of biochemical information are passed between them.

The researchers found that they could split fluorescent tags in half, so one part was in the 'talking' neuron and the other was in the 'listening' neuron.

When a message was sent between the two over the synapse, the two halves came together and lit up.

The researchers were able to use different colours of fluorescent molecule to examine different types of neural synapse.

It allowed them to see multiple colours under a microscope in a single fly's brain, allowing them to effectively eavesdrop on how the animal experienced temperature, odour and vision.

Upon smelling one of their favourite foods - a banana - the synapses lit up brightly.

Fruit flies, also called Drosophila melanogaster (pictured) tend to only live for around 30 days but now scientists have found a way to see what goes on in their brains during this short time

Drosophila melanogaster, as fruit flies are also known, can live for up to 30 days and are commonly used as scientific models for larger animals.

The researchers hope their work could provide new ways of studying how neural networks can rearrange themselves as memories are made, during learning or after brain injury.

But the technology currently only works in fruit flies and can't be used in larger animals or humans. Instead researchers tend to use less invasive techniques by looking at brain activity.

These tend to only record the fleeting electrical signals produced by the brain, however, while the new technique provides a longer lasting record of brain communication.

The researchers divided fluorescent tags in two, dividing them between the 'talking' neuron (pre) and the 'listening' neuron (post). When the two halves of the tag combined, they lit up, illustrating that a message had been exchanged between the neurons (pictured)

The researchers were able to see how the brains of the flies reacted to changes in temperature (pictured). The coloured tags continued to glow for up to an hour, providing scientists with a long-lasting record of the sensory experiences the flies had in the past

Dr Gallio added: 'Much of the brain's computation happens at the level of synapses, where neurons are talking to each other.

'Different synapses are active during different behaviours, and we can see that in the same animal with our three distinct labels.

'Our technique gives us a window of opportunity to see which synapses were engaged in communication during a particular behaviour or sensory experience.

'It is a unique retrospective label.'