<p>For 200 – 1,0000 msec clusters of neurons assemble into phase synchrony (aka “phase lock”); conversely, for 200-1,000 msec clusters of neurons disassemble into loss of phase synchrony (aka “phase shift”).&nbsp; The dominant acting force for these synchronizatons and desycnhronizations&nbsp; is that of stochastic resonance (“stochasm” is latin for “purposeful randomness”).</p><p>Phase reset is made of phase shift and phase lock, which is the synchronization and desynchronization of neurons. Phase shift is like a “shout out,” where neurons are recruited to synchronize with the action potential activity at the time.</p><p>Thatcher et al. (2008) identified that longer phase shift dynamic is related to superior I.Q., with an optimized balance between phase shift and phase lock being ideal.&nbsp; Phase shift duration is related to the average local inhibitory post synaptic potential duration on cell bodies and the phase lock duration is positively related to the average excitatory post synaptic potential summation on the dendrites of cortical pyramidal cells.</p><p>When phase shift duration is too short then there are fewer neural resources available to be phase locked into a stable dynamic. Longer phase shift duration increases the probability of identifying larger numbers of neurons capable of being phase locked (this is why there is a direct relationship between shift duration and I.Q.). However, when phase shift duration is too long then there is increased noise and reduced number of neurons available for phase locking. When phase lock duration is too long then there is less flexibility and there are reduced resources available to be allocated by the phase shift mechanism. However, too short of phase locking will result in less information processing and less efficiency of the allocated resources with premature release of the resources by a subsequent phase shift.&nbsp; In short, an optimal balance between phase shift duration and phase lock duration is related to higher levels of intelligence because of an optimal balance results in maximum speed and efficiency of information processing.&nbsp;</p><p>The dynamic balance between synchronization and desynchronization is essential for normal brain function and abnormal balance is often associated with pathological conditions such as epilepsy (Lopes da Silva and Pihn, 1995; LeVan Quyen et al, 2001b; Chevez et al, 2003; Netoff and Schiff, 2002), schizophrenia (Lee et al., 2002) and dementia (Stam et al., 2002a; 2002b).</p><p>Phase dynamics are represented in Bob Thatcher’s qEEG analysis as the metric of “Phase Lag.” Phase lag can be normal (no lines presented), hyper phase lag (red lines) or hypo phase lag (blue lines). Hyper phase lag indicates too much phase lag and not enough phase synchrony (i.e. not enough phase lock). This can result in increased neuronal noise and a reduced amount of neurons available for phase locking.</p><p><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/z-fft-phase-lag.png" alt="Hyper Phase Lag in Theta in a 60-year-old man complaining of memory difficulties" width="627" height="467" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center;">Hyper Phase Lag in Theta in a 60-year-old man complaining of memory difficulties<br></p><p style="text-align: center;"><br></p><p>Hypo phase lag indicates not enough phase lag (and too long phase lock) indicating that neuronal assemblies are coming into synchrony too frequently and for longer duration than is ideal. The individual in the following image report difficulty keeping attention on any given task.</p><p><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/z-fft-phase-lag-2.png" alt="" width="528" height="384" role="presentation" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center;">Figure : Hypo Phase Lag in all Frequencies in a 12-year-old&nbsp;<br><span style="font-size: 1rem;">girl who has poor organization skills, focus and concentration</span></p><p><br></p>