How Can Brain Imaging Help Us Understand ADHD and Autism?

What you need to know

• This study will use brain imaging to look for differences in brain structure and function between children with ADHD, autism, and typical development.
• The researchers will collect genetic, biochemical, and behavioral data in addition to brain scans to get a more complete picture.
• By using a large sample size and scanning at multiple sites, the study aims to overcome limitations of previous smaller studies.

A Large-Scale Study of ADHD and Autism

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are common neurodevelopmental conditions that affect many children. While we know these disorders involve differences in how the brain develops and functions, many questions remain about the exact nature of these brain differences.

Previous brain imaging studies have found some differences in brain structure and activity in people with ADHD and autism compared to typically developing individuals. However, the results have often been inconsistent across studies. This may be due to small sample sizes in individual studies, differences in brain scanning equipment between research sites, and the natural variation between people with these complex disorders.

To address these challenges, researchers in Japan are launching a large multi-site brain imaging study called the Child Developmental MRI (CDM) project. This ambitious study aims to scan the brains of 300 children - 100 with ADHD, 100 with autism, and 100 with typical development. The researchers will also analyze over 1000 existing brain scans from previous studies.

A Multi-Dimensional Approach

In addition to detailed brain scans, the CDM project will collect a wealth of other data from participants:

• Genetic information
• Epigenetic data (which looks at how genes are switched on or off)
• Biochemical markers from urine samples
• Cognitive test results
• Eye-tracking measures
• Questionnaires on behavior and symptoms

By gathering this multi-dimensional data, the researchers hope to uncover connections between brain structure/function, genetics, biochemistry, and behavior in ADHD and autism. This comprehensive approach may provide new insights into the underlying biology of these disorders.

Overcoming Technical Challenges

A key challenge in multi-site imaging studies is accounting for differences between brain scanners at different locations. Even MRI machines of the same model can produce slightly different results. To address this, the CDM project will use a technique called the “traveling subject” approach.

This involves having 15 healthy adult volunteers travel to each of the study sites to have their brains scanned. By comparing these repeated scans of the same individuals, the researchers can mathematically adjust for scanner differences when analyzing the full dataset.

What Will the Study Look At?

The CDM project will examine several aspects of brain structure and function:

Brain Structure

The researchers will measure the volume of gray matter (the outer layer of the brain containing neuron cell bodies) in different regions. They will also look at the thickness of the cortex (the brain’s outer surface) and the size of its folds and grooves.

Previous studies have found some structural differences in ADHD and autism, but results have been mixed. For example, some studies found decreased gray matter volume in certain regions in ADHD, while others found increases. By using a large sample size, the CDM project hopes to clarify these conflicting findings.

White Matter Connections

The study will examine the brain’s white matter - the “wiring” that connects different regions. A technique called diffusion tensor imaging will measure the integrity and organization of white matter tracts. Some previous research has found differences in white matter structure in ADHD and autism.

Brain Network Activity

When the brain is at rest, different regions show coordinated patterns of activity. The CDM project will use resting-state functional MRI to map these intrinsic brain networks. Prior studies have found altered connectivity in the “default mode network” and other networks in ADHD and autism.

Linking Brain, Genes, and Behavior

A key goal of the CDM project is to connect brain imaging findings with genetic, biochemical, and behavioral measures. Some examples of what the researchers will investigate:

• Whether certain gene variants are associated with brain structure or connectivity differences
• If levels of neurotransmitters and their metabolites in urine samples correlate with brain activity patterns
• How performance on cognitive tests relates to brain network connectivity
• Whether eye gaze patterns during social tasks are linked to activity in social brain regions

By integrating these diverse types of data, the researchers hope to gain new insights into the biological underpinnings of ADHD and autism. This could potentially lead to better ways of diagnosing these disorders or predicting which treatments may work best for individual patients.

Conclusions

• This large multi-site brain imaging study aims to clarify inconsistent findings from previous smaller studies on brain differences in ADHD and autism.
• By collecting genetic, biochemical, and behavioral data alongside brain scans, the project hopes to uncover links between brain structure/function and underlying biology.
• The study’s comprehensive approach and large sample size may lead to new insights into the neurobiology of ADHD and autism.

While the results of this study are still to come, this type of large-scale, multi-dimensional research represents an important step forward in understanding neurodevelopmental disorders. By examining the brain in conjunction with genes, biochemistry, and behavior, we may gain a more complete picture of how these complex conditions arise and how we can better help those affected.