Individual differences in hemispheric asymmetry for global-local processing in young and older adults

Area of Science:

• Neuroscience
• Cognitive Psychology
• Human Brain Anatomy

Background:

• The brain's hemispheres exhibit functional asymmetry for global-local processing.
• Global processing is specialized in the right hemisphere, local processing in the left.
• This hemispheric asymmetry is thought to remain intact with age, though older adults may perform worse on global tasks.

Purpose of the Study:

• To investigate hemispheric asymmetry for global-local processing across age groups.
• To examine if individual differences in hemispheric asymmetry exist.
• To explore potential explanations for inconsistent findings in previous group-level studies.

Main Methods:

• A divided visual field design was employed with a hierarchical-figures task.
• Participants (127 young, 58 older) viewed stimuli briefly in either the left or right visual field.
• This design allows initial processing by the contralateral hemisphere, assessing hemispheric specialization.

Main Results:

• Both age groups showed right-hemisphere specialization for global figures (left visual field) and left-hemisphere specialization for local figures (right visual field).
• Older adults performed significantly worse overall on global hierarchical figures compared to younger adults.
• Individual analysis revealed subgroups with varying patterns of hemispheric asymmetry, not just the predicted pattern.

Conclusions:

• Hemispheric asymmetry for global-local processing is present in both young and older adults.
• Individual differences in hemispheric asymmetry patterns were observed in right-handed participants.
• These individual variations may account for inconsistencies found in previous group-level research with smaller sample sizes.