Spatio-Temporal Decoding of the Navon Task Challenges Rigid Hemispheric Asymmetries in Global-Local Processing

Area of Science:

• Cognitive Neuroscience
• Neuroimaging

Background:

• Global precedence effects demonstrate faster perception of global forms over local details.
• Functional hemispheric asymmetries are linked to variability in global precedence effects, but findings are inconsistent due to methodological limitations.

Purpose of the Study:

• To develop a detailed model of global-local processing using high temporal and spatial resolution.
• To investigate the temporal and spatial dynamics of global-local processing and identify involved neural networks.

Main Methods:

• Magnetoencephalography (MEG) and Multivariate Pattern Analysis (MVPA) were used on 63 participants.
• A divided visual field, divided attention Navon paradigm assessed hierarchical letter form perception.
• Linear Discriminant Analysis (LDA) and searchlight analysis mapped decoding accuracies.

Main Results:

• Decoding accuracy revealed a temporal precedence of global over local letter form processing.
• Spatial mapping confirmed known regions (lingual gyrus for local, inferior occipital gyrus for global) and identified integration areas.
• Significant interindividual variation in lateralization patterns was observed, contradicting typical assumptions.

Conclusions:

• This study provides novel temporal and spatial data on global-local processing from a single MEG measurement.
• Interindividual variability in brain lateralization is proposed as a key factor explaining past inconsistencies in global precedence effect research.