<p>The highest amplitude of alpha is found in the occipital area and is generally below 50 microvolts (µV).&nbsp; Amplitudes of 20-60 µV have been found in 66% of people, while amplitudes below 20 µV are found in 28%, and above 60 µV in 6% (Simonova et al., 1967).&nbsp; Children have higher amplitudes than adults (50-60 µV) and 9% of children (ages 1-15) have amplitudes of 100 µV or higher (Petersen &amp; Eeg-Olofsson, 1971).&nbsp;&nbsp;</p><p>An inverse relationship exists between the frequency of alpha and alpha amplitude (Brazier &amp; Finesinger, 1944).&nbsp; About 7%-9% of adults have a “low-voltage record,” consisting of amplitudes under 20 µV (Markand, 1990), which may or may not display alpha activity.</p><p>Klimesch (1999) has found that upper band alpha power (10-12Hz) decreases during semantic processing (i.e. talking)&nbsp; and theta power increases during episodic memory retrieval. Klimesch (1999) also found that a low theta/alpha ratio during resting state predicts good cognitive and memory performance, while , while under task, a large increase in theta power (synchronization) and a significant decrease in alpha power (desynchronization) is associated with good cognitive/memory performance.&nbsp; In relation to theta activity, it should be noted that Klimesch finds that theta synchronization occurs in a narrow frequency band in the range of the peak theta frequency, whereas there is a second, inefficient form of theta synchronization associated with large, but irregular activity.&nbsp; Klimesch (1999) concluded:</p><div class="editor-indent" style="margin-left: 30px;"><p><i>Large scale alpha synchronization blocks information processing because very large populations of neurons oscillate with the same phase and frequency.&nbsp; In contrast, alpha desynchronization reflects actual cognitive processes because different neuronal networks start to oscillate at different frequencies and with different phases (p. 190).</i></p></div><p>Synchronous, persistent alpha is expected with eyes closed—this is effectively the brain “twiddling its thumbs.“ However, when eyes are open, alpha ought to diminish. If it does not, especially if it is predominantly seen on one side, the individual ought to consult a neurologist.</p>