How Social Isolation Alters the Brain and Behaviour

Over the last 10-20 years, concerns have been growing about how social isolation and loneliness affect people's mental and physical health, particularly among the elderly who are especially vulnerable to isolation. These problems were also exacerbated by the recent COVID-19 pandemic, which resulted in the unintentional consequence of increasing loneliness and isolation. People experiencing social isolation have increased rates of physical and mental health problems, such as cardiovascular disease, depression, anxiety, have a decreased quality of life, and an increased likelihood of death due to any cause. Interestingly, social isolation in both people and in animals cause similar behavioural changes such as reduced sleep, inactivity, and memory problems. Even though social isolation and feelings of loneliness are linked to such negative health outcomes, very little is known about how a lack of social experience changes the brain to cause behavioural and physical changes. Here, we will study the behavioural changes caused by isolation. Using the model organism Drosophila melanogaster, we recently discovered that social isolation reduces the numbers of synapses in their brains by 20-40%, and we find Drosophila exhibit behavioural changes including decreased sleep, reduced activity, and impaired memory, similar to what is seen in people. Through the experiments proposed, we aim to determine how a lack of social experience causes this reduction in synapses, and how it alters information processing in the brain, leading to the behavioural changes we see. Understanding the neurobiological underpinnings of how social interaction alters the nervous system can reveal fundamental properties about our nervous systems and methods to mitigate or reverse the detrimental effects of social isolation in people.