A long-range cortical network emerging with theta oscillation in a mental task.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Imaging

Background:

• Human scalp electroencephalography (EEG) reveals increased global coherence during cognitive tasks.
• This suggests oscillating neural activities form global neuronal assemblies for cognitive functions.
• Frontal midline theta (fm theta) oscillations (4-8 Hz) emerge during mental tasks and are hypothesized to relate to these assemblies.

Purpose of the Study:

• To investigate the relationship between fm theta oscillations and brain activity measured by functional magnetic resonance imaging (fMRI).
• To examine how functional connectivity changes during cognitive tasks, specifically mental calculation.
• To determine if fm theta oscillations coordinate large-scale neural networks involved in cognitive functions.

Main Methods:

• Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) were employed.
• Participants performed a mental calculation task.
• Functional connectivity analyses were conducted on BOLD signals and EEG data.

Main Results:

• EEG-related negative Blood-Oxygen-Level-Dependent (BOLD) signals were prominent in anterior medial regions, linked to fm theta.
• Both negative and positive BOLD signals were observed in distant brain regions.
• Functional connectivity analysis revealed a shift from localized to long-range coherent networks during the task, involving anterior midline, posterior cingulate, and temporal cortices.

Conclusions:

• Negative BOLD in anterior medial regions significantly contributes to fm theta during cognitive tasks.
• A long-range coherent neural network, coordinated by theta oscillations, is established during numerical processing.
• This network, involving specific cortical regions, is crucial for executing cognitive functions.