Working Memory Load-related Theta Power Decreases in Dorsolateral Prefrontal Cortex Predict Individual Differences in...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Electrophysiology

Background:

• Working memory (WM) maintenance is effortful, marked by sustained, load-dependent brain activity changes.
• Theta band oscillations are implicated, with EEG studies often showing frontal midline power increases.
• Intracranial recordings present varied findings across different brain regions.

Purpose of the Study:

• Investigate theta power changes during WM maintenance across key WM areas.
• Compare load-dependent theta patterns in dorsolateral prefrontal cortex (DLPFC), dorsal anterior cingulate cortex (dACC), and hippocampus.
• Determine the behavioral relevance of observed theta power modulations.

Main Methods:

• Intracranial EEG recordings from depth electrodes in 13 epilepsy patients.
• Patients performed a Sternberg WM task under varying memory loads.
• Analysis focused on theta frequency power changes during the maintenance phase.

Main Results:

• Theta power increased during maintenance in the hippocampus and dACC.
• Theta power decreased during maintenance in the DLPFC, proportional to memory load.
• Only DLPFC theta power decreases predicted trial-by-trial behavioral performance (reaction times).

Conclusions:

• Theta power changes serve distinct cognitive roles across brain regions.
• Load-dependent theta power decreases in DLPFC are crucial for WM maintenance.
• DLPFC theta activity explains individual differences in WM capacity.