α Phase-Amplitude Tradeoffs Predict Visual Perception

Area of Science:

• Neuroscience
• Cognitive Science
• Psychophysics

Background:

• Spontaneous alpha oscillations (∼10 Hz) are linked to cognitive functions, particularly visual perception.
• Alpha oscillation phase and amplitude influence cortical excitability and perceptual performance.
• The causal role of alpha phase-amplitude tradeoffs in visual perception is not fully understood.

Purpose of the Study:

• To investigate the causal role of alpha phase-amplitude tradeoffs on visual perception.
• To test predictions from the pulsed inhibition theory regarding alpha oscillations and perception.
• To determine if high alpha amplitude at specific phases leads to reduced perceptual performance.

Main Methods:

• Assessed human cortical excitability using transcranial magnetic stimulation (TMS) to induce phosphene perception.
• Recorded post-pulse evoked activity using simultaneous electroencephalography (EEG).
• Analyzed the modulation of phosphene perception probability by alpha phase and amplitude.

Main Results:

• Pre-pulse alpha phase significantly modulated phosphene perception probability, especially with high alpha amplitude.
• A non-optimal phase (between -π/2 and -π/4) for phosphene perception was identified for high alpha amplitude.
• This non-optimal phase correlated with increased post-pulse evoked activity (event-related potential) in perceived phosphene trials.

Conclusions:

• Alpha oscillations induce periodic inhibitory moments when alpha amplitude is high, decreasing perceptual performance.
• These findings provide strong causal evidence supporting the pulsed inhibition theory of alpha oscillations.
• The study elucidates the mechanism by which alpha oscillations dynamically regulate visual perception.