Resting electroencephalogram alpha-power over posterior sites indexes baseline visual cortex excitability

Variations of oscillatory brain activity have been related to distinct functional states depending on the frequency of oscillations. In the a-band (about 8-14 Hz), decreased oscillatory activity is thought to reflect a state of enhanced cortical excitability, and increased activity to reflect a state of cortical idling or inhibition in which excitability is reduced, but the alpha/excitability link has not been probed directly. Here, we studied the relationship between resting oscillatory activity and visual cortex excitability across participants using electroencephalography and transcranial magnetic stimulation to the occipital pole. We found individual posterior a-band power to correlate with the individual threshold for eliciting illusory, transcranial magnetic stimulation-induced visual percepts. This provides direct support for an a/excitability link and for baseline states of the visual brain to vary across individuals.