<p style="text-align: center;"><img src="@@PLUGINFILE@@/frequency-alpha-rhythm.png" alt="Chart of the common speed of alpha rhythm (“AR”) in pediatrics and the elderly (alpha rhythm matures around age 10)" width="394" height="503" class="img-responsive atto_image_button_middle"><br></p><p style="text-align: center;">Figure : Chart of the common speed of alpha rhythm (“AR”) in pediatrics and the elderly (alpha rhythm matures around age 10)<br></p><p style="text-align: center;"><br></p><p>The mean adult frequency was found to be 10.5Hz, and is slightly higher in females than in males (Brazier and Finesinger, 1944; Petersen &amp; Eeg-Olofsson, 1971).&nbsp; Alpha stabilizes at its final peak by the ages of 10 (Niedermeyer, 1999b), although earlier studies have tracked its stability as high as the age 15 (Peterson &amp; Eeg-Olofsson, 1971).&nbsp; Mean alpha below 9 Hz is significantly low, and a mean frequency below 8 Hz “is always abnormal, usually suggestive of a diffuse encephalopathy” (Markand, 1990, p. 181) (e.g., with systemic metabolic disorders like renal or hepatic disorders, hypothyroidism, hypoglycemia, or with cerebral insults).&nbsp; A general rule (Hughes, 1994) is that anyone from age 8 through centenarians should have an alpha background rhythm of at least 8 Hz. Wu and Liu (1995) only found 1% of healthy adults to have a dominant rhythm of 8 Hz. Occasionally a sub-harmonic to alpha is found at ½ the individual’s alpha frequency, and occasionally a fast alpha variant will walk into your clinic, at 13+ Hz. You will know it is alpha, because this 14-15 Hz rhythm will block to eye opening, and it is only found in about 3.6% of the population (Brazier &amp; Finesinger, 1944). Above average mean alpha levels may suggest hypervigilance, high intelligence (Gasser, Von Lucadou-Muller Verleger, &amp; Bacher, 1983) good memory (Klimesch, Doppelmayr, Schimke, &amp; Pachinger, 1996), and a fast processing rate.&nbsp; Worst case, these are the individuals who can spin into delusional thinking and flights of fancy, where their grip on reality is loose.&nbsp;</p><p>The alpha rhythm may also increase with increased body temperature (Gundel, 1984) or hyperthyroidism.&nbsp; The 10-14 Hz range seemed to be important during intellectual activity.&nbsp; Alpha frequency is positively correlated to cognitive performance, speed of information processing, and is significantly higher in individuals with good memory performance (Klimesch, 1999).</p>