Not All Brains Are Alike: Monash University Dives Deep into the Brain, Reveals Unexpected Changes in Mental Illnesses
An innovative research project that mapped changes in the brains of nearly 1,300 individuals diagnosed with six distinct mental health disorders has shed light on the extraordinary diversity of brain changes associated with disorders such as schizophrenia and major depression.
The research, made public in Nature Neuroscience, was conducted by a team from Monash University’s Turner Institute for Brain and Mental Health and School of Psychological Sciences. It employed brain imaging techniques to gauge the volume of over a thousand distinct brain regions.
“Over the past few decades, researchers have mapped brain areas showing reduced volume in people diagnosed with a wide variety of mental illness, but this work has largely focused on group averages, which makes it difficult to understand what is happening in the brains of individual people” explained Ashlea Segal, a PhD student who led the study.
“For example, knowing that the average height of the Australian population is about 1.7 m tells me very little about the height of my next-door neighbour.”
Utilizing newly designed statistical methods developed by Prof Andre Marquand of the Donders Institute, Netherlands, who also contributed to leading the project, the team was able to highlight areas in the brain with unusually reduced or increased volumes in patients diagnosed with disorders like schizophrenia, depression, bipolar disorder, obsessive-compulsive disorder, attention-deficit hyperactivity disorder, or autism spectrum disorder.
Professor Fornito added, “We used a statistical model to establish expectations about brain size given someone’s age and sex. We can then quantify how much an individual person’s brain volume deviates from these expectations, much like the growth charts commonly used for height and weight in paediatrics,” added Professor Alex Fornito, who led the research team.
“We confirmed earlier findings that the specific brain regions showing large deviations in brain volume vary a lot across individuals, with no more than 7% of people with the same diagnosis showing a major deviation in the same brain area.
“This result means that it is difficult to pinpoint treatment targets or causal mechanisms by focusing on group averages alone. It may also explain why people with the same diagnosis show wide variability in their symptom profiles and treatment outcomes.”
Further investigations into the connections between areas showing large volume variations were conducted by the team.
Ms Segal added, “Because the brain is a network, dysfunction in one area can spread to affect other, connected sites. We found that, while deviations occurred in distinct brain regions across different people, they were often connected to common upstream or downstream areas, meaning they aggregated within the same brain circuits.”
“It’s possible that this circuit-level overlap explains commonalities between people with the same diagnosis, such as, for example, why two people with schizophrenia generally have more symptoms in common than a person with schizophrenia and one with depression.”
By applying this fresh approach, the team was able to pinpoint possible therapeutic targets for various disorders.
Ms. Segal elaborated, “We found that certain specific brain circuits were preferentially involved in some disorders, suggesting that they are potential treatment targets.”
Yet, the research indicates that these targets might only suit a specific group of individuals. For example, the study uncovered that brain circuits connected to the frontal regions seemed to be predominantly associated with depression. While these circuits are often chosen for non-invasive brain stimulation treatments, the data implies they might only benefit roughly one-third of patients, according to her.
The methodology conceived by the team paves the way for new prospects in mapping brain alterations in mental illness.
“The framework we have developed allows us to understand the diversity of brain changes in people with mental illness at different levels, from individual regions through to more widespread brain circuits and networks, offering a deeper insight into how the brain is affected in individual people,” concluded Professor Fornito.
Source: 10.1038/s41593-023-01404-6
Image Credit: Stan Grossfeld/The Boston Globe via Getty Images