Hemispheric laterality assessment with dichotic digits testing in dyslexia and auditory processing disorder.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Audiology

Background:

• Cerebral hemisphere functional asymmetry is often assessed using dichotic listening tests, typically showing a right ear advantage.
• Auditory processing disorder (APD) and dyslexia are common conditions that can affect auditory and language processing.
• Understanding hemispheric laterality in these conditions is crucial for targeted interventions.

Purpose of the Study:

• To investigate hemispheric laterality in adults with dyslexia, auditory processing disorder (APD), and comorbid dyslexia and APD.
• To compare laterality patterns against a control group with normal hearing and no learning disabilities.
• To identify specific auditory processing deficits related to hemispheric function.

Main Methods:

• Utilized the dichotic listening test to assess functional asymmetry of cerebral hemispheres.
• Recruited adult participants across four groups: control, dyslexia, APD, and comorbid dyslexia/APD.
• Ensured repeatability and stability of laterality assessment results.

Main Results:

• Control and APD groups exhibited right hemispheric dominance.
• The group with both dyslexia and APD showed left hemispheric dominance.
• Individuals with dyslexia alone displayed no significant hemispheric dominance.
• Auditory performance in competing acoustic signals was deficient across all three clinical groups.

Conclusions:

• Hemispheric laterality differs significantly among individuals with dyslexia, APD, and comorbid conditions.
• Auditory processing deficits, particularly in noisy environments, are prevalent in these groups.
• Laterality of hemispheric functions is altered for auditory-language stimuli in adults with dyslexia and comorbid dyslexia/APD.