Theta and Alpha Oscillations Reflect Distinct Control and Stabilization Processes Across Working Memory.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Quantitative Electroencephalography (qEEG)

Background:

• Working memory (WM) stage-specific processing dynamics are not fully understood, especially with varying memory loads.
• Oscillatory brain activity, including theta and alpha bands, is implicated in WM, but its precise temporal and load-dependent roles require further clarification.

Purpose of the Study:

• To investigate the load-dependent modulation of theta, lower alpha, and upper alpha power during distinct WM stages (encoding, maintenance, retrieval).
• To elucidate the functional dissociation of oscillatory bands across temporally separated WM processes.

Main Methods:

• Quantitative EEG was recorded from 45 healthy young adults performing a modified Sternberg task with memory loads of 3, 5, or 6 items.
• Data analysis involved cluster-based permutation testing and regression models to assess brain-behavior relationships.
• Temporal dissociation of encoding, maintenance, and retrieval stages allowed for stage-specific oscillatory analysis.

Main Results:

• Frontocentral theta power increased with memory load and was highest during retrieval, predicting faster reaction times at lower loads.
• Lower alpha power was greater during maintenance than retrieval, with load-dependent effects in occipital regions.
• Upper alpha power peaked during maintenance across all loads and predicted response accuracy under moderate load.

Conclusions:

• Theta and alpha oscillations exhibit distinct functional roles across WM stages.
• Theta activity is primarily associated with retrieval and response speed.
• Alpha activity, particularly upper alpha, is crucial for memory maintenance and accuracy, especially under increased cognitive demand.