Fruit fly offers insight into human ‘space issues’

Paul Mayne // Western NewsBiology professor Anne Simon said looking at fruit flies and their ‘personal space’ issues may lead to learning more about individuals with autism spectrum disorder or schizophrenia, among others, which present abnormal social spacing issues.

The need for ‘personal space’ among fruit flies has Biology professor Anne Simon buzzing when it comes to potentially learning more about individuals with autism spectrum disorder or schizophrenia.

“How does the brain decide there is another individual of the same species? That type of basic response is conserved because it’s important to know who is from your species,” Simon said. “It is a ‘conserved behaviour’ to try to go towards a group of the same individuals. Then, in that group, there are clues, and an exchange of information, and you have to decide what’s okay and what’s not.

“Social spacing is going to be a very basic conserved behaviour. It makes sense you’re not going to stand right next to someone, but how do we decide how far? That would have a conserved mechanism.”

Using genetic and pharmacological manipulations of fruit flies, Simon’s research showed dopamine levels contributed to the response to others in a social group, specifically social spacing. In the brain, dopamine functions as a neurotransmitter – a chemical released by neurons to send signals to other nerve cells. The brain includes several distinct dopamine pathways, one of the more common plays a major role in reward-motivated behaviour.

Simon added the dopamine system was proposed to underlie a conserved network for social decision-making from eusocial insects such as bees, through birds and rodents, to humans. The study was recently published in the scientific journal The Royal Society (Biology Letters).

Without any sort of manipulation, fruit flies typically interact one or two body lengths apart. But when dopamine levels were amplified, personal space shrunk as the male fruit flies began to crowd closer together. When dopamine levels were lowered, the need for more personal space increased. For female fruit flies, who generally have higher dopamine content than males, social distance increased with both lowered and increased dopamine levels.

“If you have an alteration in your dopamine pathway, then you don’t know if another (pathway) is more important,” Simon said. “Males and females respond differently – we want to see what that difference is. If social response to others is sex-specific, it could help us understand how certain disorders, that have hallmarks of abnormal social interaction, could also be the same.

“Understanding the normal variation in any group, including humans, could potentially help alleviate some of the symptoms where people have issues at the molecular level, such as schizophrenia and autism.”

Simon is working on putting “pieces of the puzzle together” by looking at neuroligin, a protein that mediates the formation and maintenance of synapses between neurons, which has been associated with cases of autism.

“We know it’s affecting social space. So we’re trying to figure out what starts first, what one (synapse) is activated first. What happens in terms of the mechanism,” she said. “Where do we start and what is being activated by the social cue, with the understanding the social response will be specific to what is important for that species. It’s about looking at basic molecules and then realizing that a particular pathway is important for understanding neurodisorders.”

Simon added there are still a lot of “black boxes” in understanding how the brain, in both humans and fruit flies, responds to social cues. She looks forward to further collaboration with other researchers.

“It’s a very selfish endeavour, intellectually” she said of research, but “research can be far reaching and I’m convinced it will have far reaching affects. It’s just putting the puzzle together.”