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Unilateral hemispheric lesions disrupt parallel processing within the contralateral intact hemisphere: an auditory
Michela Adriani1, Anne Bellmann, Reto Meuli
1Division de Neuropsychologie, CHUV, 1011, Lausanne, Switzerland.
Neuroimage
|November 5, 2003
Summary
Unilateral brain damage can impair sound recognition and localization. Even with normal performance, left hemisphere activation was reduced in patients, suggesting intact networks function at a lower capacity.
Area of Science:
- Neuroscience
- Auditory Perception
- Cognitive Psychology
Background:
- Sound recognition and localization involve distinct bilateral cortical networks.
- Unilateral brain lesions can disrupt auditory processing, indicating hemispheric specialization and interaction are crucial.
- Previous studies suggest potential deficits in sound processing following unilateral brain damage.
Purpose of the Study:
- To investigate the effects of unilateral right hemisphere lesions on sound recognition and localization.
- To examine brain activation patterns using fMRI in patients with varying degrees of auditory processing deficits.
- To correlate psychophysical performance with neural activation in specialized auditory networks.
Main Methods:
- Psychophysical assessment of sound recognition and localization abilities.
- Functional magnetic resonance imaging (fMRI) to measure brain activity during auditory tasks.
- Comparison of activation patterns in patients with unilateral right hemisphere lesions versus healthy control subjects.
Main Results:
- Patients showed varied deficits: combined recognition/localization (2), selective localization (2), selective recognition (1), and normal performance (2).
- Overall left hemisphere activation was reduced in patients compared to controls, regardless of task performance.
- Patients with normal performance showed activation patterns similar to controls, albeit with lower intensity.
- Patients with impaired performance exhibited severely reduced and atypical activation patterns.
Conclusions:
- Specialized brain networks for sound recognition and localization are present in the left hemisphere even after right-sided lesions.
- Normal auditory task performance in patients suggests functional compensation, but with reduced overall activation.
- Impaired performance correlates with a breakdown in parallel processing within these specialized networks.