Unmasking Language Lateralization in Human Brain Intrinsic Activity

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• Brain lateralization is key, with language typically left-dominant.
• Resting-state fMRI studies have shown limited hemispheric asymmetry.
• The global signal in fMRI is often discarded but may hold crucial information.

Purpose of the Study:

• To investigate hemispheric asymmetries in the global signal during resting-state fMRI.
• To explore the relationship between global signal asymmetry and brain function.
• To validate findings using semantic processing tasks.

Main Methods:

• Analysis of the global signal component in resting-state fMRI data.
• Examination of amplitude modulation of spontaneous fluctuations.
• Comparison with task-based fMRI during semantic tasks (synonym judgment, sentence comprehension).

Main Results:

• Leftward global signal asymmetry observed in left frontal/temporal cortex and right cerebellum (semantic regions).
• Rightward global signal asymmetry detected in right frontal/parietal regions (attention networks).
• Asymmetries correlate with amplitude modulation of spontaneous brain activity.

Conclusions:

• The global signal in resting-state fMRI is a valuable indicator of brain lateralization.
• This method reveals functional asymmetries related to semantic processing and attention.
• Findings enhance understanding of brain signal physiology and lateralization.