Chemosensory processing in children with attention-deficit/hyperactivity disorder

Area of Science:

• Neuroscience
• Psychiatry
• Olfactory Research

Background:

• Attention-deficit/hyperactivity disorder (ADHD) is associated with dopamine-related cognitive deficits and altered olfactory sensitivity.
• Previous research indicates a lower dopamine-sensitive olfactory threshold in individuals with ADHD.
• The role of neuroplasticity and cortical mechanisms in ADHD-related olfactory changes requires further investigation.

Purpose of the Study:

• To investigate whether olfactory sensitivity, but not trigeminal sensitivity, is increased in children with ADHD.
• To examine the relationship between olfactory bulb (OB) volume and olfactory performance in ADHD.
• To explore cortical functional connectivity patterns in the primary olfactory cortex during chemosensory stimulation in ADHD.

Main Methods:

• Structural and functional magnetic resonance imaging (fMRI) were employed in 18 boys with ADHD and 17 healthy controls (aged 7-12).
• Olfactory and trigeminal detection thresholds were assessed.
• Olfactory bulb (OB) volumes were measured, and functional connectivity of the frontal piriform cortex (fPIR) with other brain regions was analyzed.

Main Results:

• Individuals with ADHD exhibited significantly increased olfactory sensitivity and larger olfactory bulb (OB) volumes compared to controls.
• No significant group differences were observed in trigeminal stimulus sensitivity.
• The fPIR in ADHD showed stronger positive functional coupling with salience network structures during olfactory and trigeminal stimulation.

Conclusions:

• Superior olfactory functioning is a characteristic of individuals with ADHD.
• Increased OB volume in ADHD may be attributed to heightened olfactory sensitivity and neuroplasticity.
• Altered functional connectivity patterns suggest a top-down influence on OB structure and function during chemosensory processing in ADHD.