Phase-locking and amplitude modulations of EEG alpha: Two measures reflect different cognitive processes in a working...

Area of Science:

• Cognitive Neuroscience
• Neurophysiology

Background:

• Oscillatory electroencephalography (EEG) responses in the alpha frequency band (8-12 Hz) are known to increase with memory load during working memory tasks.
• Previous research shows conflicting results regarding which specific measure of alpha activity is affected by memory processes.

Purpose of the Study:

• To differentiate between evoked and total alpha activity in EEG.
• To investigate the distinct roles of phase-locking and amplitude modulation in alpha activity during working memory.
• To compare alpha EEG responses between perception and memory conditions within a delayed-matching-to-sample task.

Main Methods:

• Utilized a delayed-matching-to-sample (S1-S2) paradigm.
• Compared EEG alpha responses during perception and memory conditions.
• Analyzed both evoked and total alpha activity to distinguish phase-locking and amplitude modulation effects.

Main Results:

• Total alpha activity significantly increased during the retention interval in the memory condition compared to the perception condition.
• Evoked alpha activity did not differ between memory and perception conditions.
• Evoked alpha activity increased with task complexity, specifically when processing non-Kanizsa figures versus Kanizsa figures.

Conclusions:

• Demonstrated a functional differentiation between evoked and total alpha activity in EEG.
• Alpha phase-locking is primarily influenced by task complexity.
• Alpha amplitude modulation clearly reflects memory demands in working memory paradigms.