Frontal and Parietal Cortices Show Different Spatiotemporal Dynamics across Problem-solving Stages

Area of Science:

• Neuroscience
• Cognitive Science
• Cognitive Neuroscience

Background:

• Arithmetic problem-solving involves multiple stages, from encoding to execution.
• Previous fMRI studies indicated a frontal-parietal network for complex tasks, but temporal contributions remain unclear.
• Understanding the precise timing of frontal and parietal roles in arithmetic is crucial.

Purpose of the Study:

• To investigate the time-resolved contributions of frontal and parietal cortices during arithmetic problem-solving.
• To differentiate brain dynamics associated with retrieval versus multistep procedural strategies.
• To explore the roles of theta, alpha, and beta frequencies in memory and executive functions during arithmetic.

Main Methods:

• Combined electroencephalography (EEG) and magnetoencephalography (MEG) for time-resolved analyses.
• Trial-by-trial evaluation of arithmetic strategies: retrieval vs. multistep procedural.
• Evoked source analyses and time-frequency source power analyses.

Main Results:

• Right frontal cortex showed early strategy selection effects (around 300 msec) for procedural strategies.
• Parietal cortex activation occurred later (around 700 msec).
• Procedural strategies elicited stronger beta and alpha desynchronization in frontal, parietal, and temporal regions, linked to executive demands.
• Arithmetic fact retrieval was associated with increased theta power in the right prefrontal cortex.

Conclusions:

• Frontal and parietal brain regions exhibit distinct temporal activation patterns during arithmetic problem-solving.
• Different frequency bands (theta, alpha, beta) reflect distinct cognitive processes, namely memory retrieval and executive control.
• The findings elucidate the dynamic interplay within the frontal-parietal network during numerical cognition.