Event-related desynchronization (ERD)
Event-related desynchronization (ERD) is the short-lasting attenuation or blocking of rhythms within the alpha (beta) band. ERD is found during but also before visual stimulation. [1]
alpha activity serves to functionally disengage a given region by means of “pulsed inhibition.”
Two different types of ERD can be differentiated:
- Shorter lasting, localized to occipital areas and involving upper alpha components (Alpha 2) (most likely reflects primary visual processing and feature extraction);
- Longer lasting, more widespread, most prominent over parietal areas and maximal for lower alpha components (related to cognitive processing and mechanisms of attention)
Pre-Stimulus Oscillatory Activity Modulates Subsequent Processing
We have presented a working hypothesis postulating that information is gated through the brain by functional inhibition of task-irrelevant areas. Further, the functional inhibition is reflected by oscillatory activity in the alpha band. Our hypothesis provides a general framework for understanding how the functional architecture of the brain is shaped.
Our hypothesis provides a putative explanation for why the alpha activity is the strongest electrophysiological signal measured from the human brain:
- optimal performance requires and
- effective inhibition of task-irrelevant regions.
While several studies support this framework more empirical work is required in order to substantiate the principle of gating by inhibition.
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