Asymmetric intra- and interhemispheric interactions during covert and overt sentence reading

Area of Science:

• Neuroscience
• Cognitive Science
• Psycholinguistics

Background:

• Sentence reading, both silent (covert) and aloud (overt), engages widespread brain networks with notable lateralization.
• Understanding the principles of functional lateralization in reading is crucial for deciphering brain organization.

Purpose of the Study:

• To investigate the regional lateralization of covert and overt German sentence reading using functional MRI.
• To explore how functional connectivity within and between hemispheres modulates during these reading tasks.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed in 39 healthy participants.
• Psychophysiological interaction (PPI) analyses were used to examine task-dependent functional connectivity changes.

Main Results:

• Covert reading showed left-lateralization linked to enhanced intrahemispheric coupling in the left dorsal stream, not contralateral suppression.
• Overt reading involved right perisylvian cortices for articulation through asymmetric interhemispheric interactions.

Conclusions:

• Functional lateralization in reading arises from a dynamic interplay of intra- and interhemispheric coupling, varying with task demands.
• Asymmetric positive coupling, rather than homotopic anti-correlation, primarily drives functional lateralization in reading.