Asymmetrical hemisphere activation enhances global–local processing

• Manipulated hemisphere activity using contra-lateral hand contractions.
• Right (vs. left) hand contractions caused greater relative left cortical activity.
• Activation of left (right) hemisphere caused more local (global) attentional scope.
• Left-hemisphere activation increased left-hemisphere N1 amplitudes to local targets.
• Manipulations of hemisphere activity facilitates global or local processing.

Decades of research focusing on the neurophysiological underpinnings related to global–local processing of hierarchical stimuli have associated global processing with the right hemisphere and local processing with the left hemisphere. The current experiment sought to expand this research by testing the causal contributions of hemisphere activation to global–local processing. To manipulate hemisphere activation, participants engaged in contralateral hand contractions. Then, EEG activity and attentional scope were measured. Right-hand contractions caused greater relative left-cortical activity than left-hand contractions. Participants were more narrowly focused after left-hemisphere activation than after right-hemisphere activation. Moreover, N1 amplitudes to local targets in the left hemisphere were larger after left-hemisphere activation than after right-hemisphere activation. Consistent with past research investigating hemispheric asymmetry and attentional scope, the current results suggest that manipulating left (right) hemisphere activity enhanced local (global) attentional processing.