Fourteen and six (14 & 6) positive bursts, as they are often called, are regular, arciform repetitions that are centered in the posterior temporal region with a broad distribution across the adjacent regions. The distribution may be unilateral, bisynchronous, or bilateral asynchronous. When they occur unilaterally, a right-sided predominance in the number of occurrences may be present. The 14 & 6 pattern is common between the ages of 8 and 14 years and rare in early childhood. After adolescence, it declines in incidence (Niedermeyer, 1999b). Drowsiness and light non-REM sleep are the states expected to demonstrate 14 & 6, and it is absent in full wakefulness and deeper sleep (Eeg-Olofsson, 1971). They have been reported to occur in 0.5% to more than 50% of EEGs, depending on the EEG’s montage, duration, inclusion of sleep, and patient age distribution (Cervone and Blum, 2007; Jabbari et al., 2000; Santoshkumar et al., 2009; Velizarova et al., 2011).

The positive spike term in this pattern’s name refers to the arciform appearance and not to surface polarity or any individual spikes. The sharply contoured component of each arciform element is oriented downward in commonly used referential montages, that is, the spikes point in the positive direction according to convention. Although 14 and 6 Hz are the two most common frequencies for the burst of successive spikes, a range of frequencies may be present. Typically, the frequency is between either 13 and 17 Hz or between 5 and 7 Hz, with the faster frequency range occurring in late childhood and adolescence and the slower frequency range in middle childhood. Occasionally, the frequency evolves from the faster to the slower within one burst. Alternatively, the faster frequency form may end with a single, diphasic, high-amplitude, N-shaped potential (Reiher and Carmant, 1991).

The bursts usually last less than 2 seconds and have an amplitude that rarely is greater than 150 μV. More commonly, the duration is 0.5 to 1 second and the amplitude is about 75 μV. Since 14 & 6 bursts have broad, uniformly distributed fields, they are best recorded with long interelectrode distances. Channels generated with short interelectrode distances are expected to depict 14 & 6 as low amplitude because of the near isoelectric distribution over the region recorded by the two electrodes. This reflects the differential amplification of EEG amplifiers. A contralateral ear reference montage provides maximal amplitude waves. An ipsilateral ear reference montage may misrepresent the localization as frontal because the ear region and much of the posterior scalp may be within an isoelectric field, so the channels demonstrating the pattern will include the more anterior electrodes. Posterior skull defects increase the likelihood of observing a 14 & 6 burst because of the breach effect (Beydoun and Drury, 1992).