“Lonely brain” imaging study reveals unexpected neural patterns

A compelling new study examining brain scans from thousands of older adults is suggesting people identifying themselves as lonely can display an unexpectedly unique neural signature. The research found lonely people present with greater volumes of gray and a distinct white matter structure, plus increased functional connectivity in brain regions dedicated to tasks such as daydreaming, reminiscing and imagining.

The new study, led by neuroscientists from McGill University, assessed data from around 40,000 subjects enrolled in the UK Biobank research resource. Instead of looking at a single brain imaging modality, the researchers took a multi-modal approach to the investigation, trying to understand both grey and white matter composition and how different regions of the brain communicate.

“Against our expectations, cortical volumes in several default network regions were larger for lonely than non-lonely individuals,” the scientists report in the newly published study. “A similarly unexpected pattern of positive associations was corroborated for both functional connectivity and white matter structure.”

The default network (also known as the default mode network) is a term used to refer to a collection of several brain regions that are active when we are not explicitly focused on tasks relating to the outside world. Unlike the brain’s attention networks, which spark up when we engage in activities, the default network takes over when we are thinking about the past or the future or daydreaming about an alternative present.

“The default network is well-known to be implicated in mental representations of oneself across time and space, including the reconstruction of one’s personal past, prospecting and planning about an envisioned future, imagination and creative thought as well as simulating thoughts, places, and events,” the researchers write in the study. “The default network is also recognized for its role in representing other people, including their intentions, identity, and affiliation.”

The research concludes this distinctive pattern of brain activity presents a potential “neural signature of loneliness.” However, the researchers also discuss a contrasting 2019 study that associated lower functional connectivity in the default network with young adults reporting loneliness, and suggest reasons for the discordancy of the results.

They hypothesize chronic periods of loneliness over time could generate this shift in the brain’s functional connectivity. The cohort investigated in the new research represent older adults (with an average age in the mid-50s), so it is suggested this change in the brain’s network architecture could be an outcome of constant loneliness over many years.

Lead author on the new study, Nathan Spreng, says it make sense that individuals deprived of social experiences may subsequently increase their levels of internally directed thoughts. Mental simulations of social events would hypothetically increase in the absence of real social activity in the external world, and this would lead to heightened default network connectivity.

“We know these cognitive abilities are mediated by the default network brain regions,” says Spreng. “So this heightened focus on self-reflection, and possibly imagined social experiences, would naturally engage the memory-based functions of the default network.”

Danilo Bzdok, senior author on the new study, notes just how little research there is on the physiological effects of loneliness on the brain. And this is an important void to fill as recent studies are beginning to suggest a kind of epidemic of loneliness building around the world. One 2017 report even went as far as to claim loneliness is a bigger risk factor for premature death than obesity.

“We are just beginning to understand the impact of loneliness on the brain,” says Bzdok. “Expanding our knowledge in this area will help us to better appreciate the urgency of reducing loneliness in today’s society.”

The new study was published in the journal Nature Communications.

Source: McGill University

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