Alpha wave

Alpha waves, or the alpha rhythm, are <a href="/facts/Neural_oscillations/knHbTaxg">neural oscillations</a> in the frequency range of 8–12 <a href="/facts/Hertz/6Wshj5qm">Hz</a> likely originating from the synchronous and coherent (<a href="/facts/Phase_(waves)/cpGtuVll">in phase</a> or constructive) neocortical neuronal electrical activity possibly involving <a href="/facts/Thalamus/UHDtUStc">thalamic</a> pacemaker cells. Historically, they are also called "Berger's waves" after <a href="/facts/Hans_Berger/QqDlmT4P">Hans Berger</a>, who first described them when he invented the <a href="/facts/EEG/XGvpcBl5">EEG</a> in 1924.
Alpha waves are one type of <a href="/facts/Neural_oscillations/knHbTaxg">brain waves</a> detected by <a href="/facts/Electrophysiology/VPd5VYzm">electrophysiological</a> methods, e.g., <a href="/facts/Electroencephalography/XGvpcBl5">electroencephalography</a> (EEG) or <a href="/facts/Magnetoencephalography/epvUfx7A">magnetoencephalography</a> (MEG), and can be quantified using <a href="/facts/Spectral_density/q3Rfs7b0">power spectra</a> and <a href="/facts/Time%25E2%2580%2593frequency_representation/b3BqBScJ">time-frequency representations</a> of power like <a href="/facts/Quantitative_electroencephalography/PYIjRCDm">quantitative electroencephalography</a> (qEEG). They are predominantly recorded over <a href="/facts/Parieto-occipital_sulcus/9Sjq88WV">parieto-occipital brain</a> and were the earliest brain rhythm recorded in humans. Alpha waves can be observed during relaxed wakefulness, especially when there is no mental activity. During the eyes-closed condition, alpha waves are prominent at <a href="/facts/Parietal_lobe/T74NKNTN">parietal locations</a>. Attentional processing or cognitive tasks attenuate (reduce) the alpha waves.
Historically, alpha waves were thought to represent the brain in an idle state as they are strongest during rest and quiet wakefulness. More recently it was found the alpha oscillations increase in demanding task not requiring visual input. In particular, alpha oscillations increase during maintenance (retention) of visually presented information. These findings resulted in the notion that alpha oscillations inhibit areas of the cortex not in use, and they play an active role in network coordination and communication. Whether they are inhibitory or play an active role in attention may link to their direction of propagation. Possibly top-down propagating waves are inhibitory whereas forward propagating waves reflect visual bottom-up attentional processes, but this is still an area of active research.

Alpha wave open-in-new

Alpha wave