Have you ever wondered why we react the way we do to certain situations or why some people seem more adept at focusing on tasks than others? Scientists from Australia have shed light on these questions through a groundbreaking study, which investigated the relative influences of genetics and the environment in shaping our brain’s functionality.
Their research, published in Human Brain Mapping, provides evidence that variations in brain function can, to some extent, be traced back to a person’s genetic makeup. This suggests that our ability to process emotions, sustain attention, and remember information is not solely shaped by our experiences but also by the genes passed down to us from our parents.
While previous research has extensively explored the influence of genetics and environment on brain structure, less is known about their impact on brain function. By examining these aspects, researchers aimed to uncover the underlying mechanisms that influence our mental health and cognitive abilities, potentially paving the way for personalized interventions to enhance mental well-being.
“There has been quite a lot of research looking at genetic versus environmental influences on brain structure. But it’s a lot harder to understand the function of our brains,” explained lead author Haeme Park, a postdoctoral research fellow at the Gatt Resilience Group at Neuroscience Research Australia (NeuRA).
For their study, the researchers analyzed data collected from the TWIN-E project, or the Twin Study of Wellbeing using Integrative Neuroscience of Emotion, a comprehensive research initiative designed to explore the genetic and environmental contributions to emotional well-being and mental health.
“In this study, we wanted to bridge lots of gaps in the literature and provide a more robust and thorough picture of how our genetics and environmental factors impact the expression of brain activity during emotional and cognitive tasks, by analysing twins,” Park said.
Participants in the study were subjected to functional magnetic resonance imaging (fMRI), a non-invasive technology that captures brain activity by detecting changes associated with blood flow. This method provides a window into the brain’s activity as it engages in specific tasks. The chosen tasks for the participants were designed to probe both emotional processing — such as reactions to facial expressions — and cognitive functions like memory and attention.
“We get participants set up on the fMRI scanner bed which is fitted with goggles that enable them to see the tasks in front of them. The functional tasks involve them viewing different images, different stimuli, through the goggles,” explained Justine Gatt, an associate professor at the University of New South Wales and head of the Gatt Resilience Group.
The sample consisted of 263 participants, made up of both monozygotic (identical) twins, who share virtually all their genes, and dizygotic (non-identical) twins, who share about half their genetic material. This distinction is crucial for the study’s design, as comparing the similarities and differences in brain function between these two groups can illuminate the roles of genetic and environmental influences.
“With twin studies, it’s important to recruit both identical and non-identical twins,” Gatt said. “Identical twins share 100 per cent of their genetics and if they’re grown up together, they share the same environment. Whereas with the non-identical twins, they only have 50 percent shared genetics, but they also have that common environment.”
The researchers discovered that certain emotional and cognitive tasks are influenced by genetics, while others are more significantly shaped by the environment.
“We know that we use different brain networks for different processes – for example, processing either a crying face or a happy face is going to use different regions in the brain compared to trying to remember someone’s phone number,” Gatt said. “But we found that for some of these networks, genetics plays a small to moderate, but significant role. And for other processes, it’s only the environment that determines brain function.”
One of the standout revelations from the study was the significant genetic contribution to the processing of nonconscious emotional stimuli. Specifically, networks within the brain that responded to nonconscious expressions of disgust and fear showed a clear genetic influence, with heritability estimates suggesting that 23% to 26% of the variation in these responses could be attributed to genetics. This finding highlights the potential for inherited predispositions in how we subconsciously react to certain emotional cues, particularly those associated with negative emotions.
In addition to emotional processing, the study delved into cognitive functions, revealing genetic contributions to tasks involving working memory and selective attention. For instance, specific networks associated with working memory displayed moderate heritability, indicating that genetic factors partly determine our capacity to retain and manipulate information.
Similarly, the study identified genetic influences on our ability to process novel stimuli (as seen in the Oddball task) and maintain focused attention on relevant tasks, with heritability estimates ranging from 27% to 34% for these cognitive processes.
Interestingly, the research also uncovered significant genetic correlations between different brain networks, suggesting that common genetic factors may underlie multiple aspects of brain function. For example, a notable genetic correlation was found between networks involved in nonconscious emotion processing and those engaged during sustained attention tasks. This indicates that the same genetic influences can impact both our emotional and cognitive processing capabilities.
“We discovered that how the brain processes fear and happiness (which was measured in the emotional tasks) and our ability to sustain attention (which was measured in the cognitive tasks), have some shared genetic factors,” explained Park. “This suggests that some common genetic features may underpin these very different processes.”
However, not all findings pointed towards genetic determinism. The study revealed areas of brain function that appeared more heavily influenced by environmental factors. Notably, conscious processing of emotions and the ability to inhibit responses (as required in the Go-NoGo task) did not show significant heritability, suggesting that these aspects of brain function may be more malleable and shaped by individual experiences and interactions with the environment.
“All these results paint a complex picture of the relationship between genes and environment that give rise to the brain activity underlying our cognition and emotion,” Gatt said.
However, the study is not without its limitations. The exclusion of participants due to quality control issues and the reliance on a twin sample may limit the generalizability of the findings to the broader population. Furthermore, the study’s design could not capture all the nuances of individual environmental experiences, which play a crucial role in shaping brain function. This highlights the need for further research to explore the intricate balance between genetics and environment in brain development and function.
Nevertheless, the implications of this study are vast, offering new insights into the genetic and environmental underpinnings of our mental processes. By understanding the factors that influence our brain’s response to emotions and tasks, researchers can develop more targeted approaches to promoting mental health and cognitive well-being.
“What we’re using this data for, beyond looking at genes and environment, is actually predicting mental wellbeing and resilience trajectories over time, and seeing how differences in markers like brain function and structure might profile people who are a bit more resilient or at more risk to a mental health problem,” Gatt explained.
“If someone has a tendency to attend to negative stimuli more than positive, and we know that there’s an element of environment contributing to that, with intervention or training, it’s potentially something we can target and improve for the better.”
The study, “Heritability of cognitive and emotion processing during functional MRI in a twin sample,” was authored by Haeme R. P. Park, Miranda R. Chilver, Yann Quidé, Arthur Montalto, Peter R. Schofield, Leanne M. Williams, and Justine M. Gatt.
