Social Isolation Causes Behavioural Abnormalities and Reduces Synaptic Proteins in the Brains of Drosophila

Social isolation is known to cause a variety of behavioural abnormalities in many different species. Here we perform a detailed behavioural analysis of how chronic social deprivation alters behaviours in the fruit fly, Drosophila melanogaster, within an arena. We identify specific, quantifiable measures to capture behaviours of interest using the previously established cTrax and MATLAB BehavioralMicroarray toolkits. Socially isolated Drosophila exhibited behavioural changes in almost all measures assessed, identifying a surprisingly wide range of behavioural deficits. We observe that both male and female isolated flies demonstrate reduced locomotion (walk distance and speed), are more avoidant of other same-sex individuals (increased social distancing), and show reduced clustering into same-sex groups. Because these measures of sociality are assessed in same-sex groups, they are independent of sexual motivations. For the majority of measures taken, we observe the same behavioural changes in isolated male and female flies. In the brain, we observe that social isolation leads to a reduction in synaptic proteins specifically within dopamine neurons, as well as across the whole brain in both sexes, consistent with the varied behavioural abnormalities observed upon social isolation.