Brain wave study reveals shifting auditory responses in children with ADHD

Children with attention-deficit/hyperactivity disorder process unexpected sounds differently than their peers, and these brain responses appear to change as they grow older. A recent study measuring brain waves in two distinct age groups found that children with elevated ADHD symptoms exhibit heightened sensitivity to unexpected tones in early childhood, but diminished sensitivity by middle childhood. These findings were published in the journal Developmental Cognitive Neuroscience.

The human brain constantly monitors the environment for new or unexpected sounds. This ability allows people to adapt to their surroundings and focus on important information while tuning out harmless background noise. In typical development, sensory systems refine their ability to categorize sounds through repeated exposure.

Neuroscientists conceptualize this process through a framework called predictive coding. The brain builds a working model of expected sounds based on recent patterns in the environment. When a new sound breaks that established pattern, the brain generates a specific electrical signal known as mismatch negativity. This rapid response happens in a fraction of a second.

Mismatch negativity operates automatically, without requiring conscious thought. If a completely unique or bizarre sound occurs, the brain generates a secondary electrical signal associated with involuntary attention. This later signal is called a novelty response.

Another important feature of sensory processing is habituation. When a person hears the same sound repeatedly, the brain’s electrical response typically shrinks over time. Habituation helps the brain conserve energy by ignoring irrelevant distractions, freeing up mental resources for goal-directed behavior. Without this ability, a person might feel constantly overwhelmed by everyday background noise.

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Researchers Marija Pranjić, Jirapat Likitlersuang, and Anne B. Arnett at Boston Children’s Hospital and Harvard Medical School wanted to understand how these auditory processes operate in children with ADHD. Children with ADHD often struggle with attention regulation and sensory overload. The research team suspected that these everyday challenges might stem from basic differences in how the brain encodes sensory information.

The researchers designed an experiment to test these brain responses across two separate developmental stages. The first part of the study evaluated a group of 115 young children between two and a half and five years old. Participants were excluded if they had a history of seizures, an autism diagnosis, or known genetic syndromes.

Because clinical ADHD diagnoses are rarely given to very young children, the researchers categorized the early childhood group based on comprehensive clinical ratings. Sixty-four children had elevated ADHD symptoms, while 51 children exhibited typical development.

To measure brain activity, the researchers placed a net of harmless sensors on each child’s head to record an electroencephalogram, commonly known as an EEG. The children watched a silent video while listening to a sequence of sounds through speakers. The test required no active behavioral response from the participants. This passive monitoring approach is ideal for studying young children who might struggle with complex instructions.

The sound sequence consisted mostly of a repetitive standard tone. Occasionally, the researchers played a slightly different tone to trigger the brain’s mismatch negativity response. They also mixed in completely unique environmental noises, such as a drum beat or a cricket chirp, to trigger the novelty response.

Pranjić and her colleagues found that young children with elevated ADHD symptoms had a stronger brain response to the unexpected tones. Their mismatch negativity amplitude was larger than that of the children with typical development. This pattern emerged even after the researchers accounted for differences in age and cognitive ability.

The young children with elevated ADHD symptoms also showed differences in habituation. The typically developing children adapted quickly to the repetitive standard tones and the unique environmental noises, showing reduced brain activity over time. In contrast, the brains of the children with elevated ADHD symptoms did not settle down as effectively across the repeated trials.

The researchers then conducted a similar experiment with a separate group of 71 older children. These participants were between seven and eleven years old. In this older group, 53 children had a confirmed ADHD diagnosis, and 18 children were typically developing.

These older participants completed the exact same listening task while the researchers recorded their brain waves. The findings in this older group were quite different from the early childhood group. Children with ADHD in middle childhood exhibited a blunted mismatch negativity response compared to their typically developing peers.

The older children with ADHD showed a weaker brain reaction to unexpected sounds. The researchers did not find evidence of habituation differences between the diagnostic groups in this older cohort. Both the typically developing children and those with ADHD showed similar reductions in brain activity when exposed to the novelty sounds over time.

These age-related differences suggest that sensory processing in ADHD changes over the course of development. In early childhood, the brain might overreact to sensory deviations, while in middle childhood, it might underreact. This shifting pattern aligns with theories that ADHD involves atypical connections between early auditory encoding and later attention selection.

The study design evaluated two distinct age groups at a single point in time, meaning it did not track the same children as they grew older. Because of this cross-sectional approach, researchers cannot say for certain how an individual child’s brain responses evolve. It remains unknown whether the differences seen in middle childhood represent a delayed maturation of the auditory system or an alternative path of sensory development.

Future longitudinal studies, which follow the same participants over many years, are needed to answer these developmental questions. Additionally, the results do not indicate that atypical auditory processing causes ADHD behaviors. The study only demonstrates that altered sensory processing is associated with the condition.

The findings support the idea that ADHD is not exclusively a disorder of higher-order executive functioning. Basic sensory processing differences appear to play an important role in how children experience and interact with the world around them. Understanding exactly how the brain filters sounds could eventually aid in the early detection of attention disorders.

Identifying these biological markers might one day help clinicians design better therapies for children who struggle to tune out distractions. Tracking how sensory adaptation matures across childhood could provide a new window into the developing brain. The study, “Atypical auditory cortical processing in ADHD during early and middle childhood,” was authored by Marija Pranjić, Jirapat Likitlersuang, and Anne B. Arnett.