Brain activity exhibits a mixture of frequencies at any given time. But the dominant frequency varies depending on the state of consciousness (ie: awake, anxious, angry, calm, relaxed) and on individual differences.

The normal brainwave in the encephalogram of a person who is awake and alert; occurs with a frequency between 12 and 30 hertz. Brainwaves have diferent frecuencies along the spectrum and receive the name

This is the most predominant brain frequency during deep sleep.

In the heart a delta wave in the ECG is seen in Wolff-Parkinson-White syndrome.

Tare delta . These are less than 4 Hz and occur in deep sleep and also during experiences of empathy state. Delta waves are involved with our ability to integrate and let go and reflects unconscious mind.

It is the dominant rhythm in infants up to one year of age and it is present in stages 3 and 4 of sleep.

It tends to be the highest in amplitude and the slowest waves. We increase Delta waves in order to decrease our awareness of the physical world. We also access information in our unconscious mind through Delta.

Peak performers decrease Delta waves when high focus and peak performance are required.

However, most individuals diagnosed with Attention Deficit Disorder, naturally increase rather than decrease Delta activity when trying to focus. the inappropriate Delta response often severely restricts the ability to focus and maintain attention. It is as if the brain is locked into a perpetual drowsy state.

Another way to look at Delta is to imagine you are driving in a car and you shift into 1st gear.you're not going to get anywhere very fast. So Delta would represent 1st gear.

Delta (0.1-3 Hz): Distribution: generally broad or diffused may be bilateral, widespread
Subjective feeling states: deep, dreamless sleep, non-REM sleep, trance, unconscious
Associated tasks and behaviors: lethargic, not moving, not attentive
Physiological correlates: not moving, low- Level of arousal
Effects of training: can induce drowsiness, trance, deeply relaxed states

Brainwaves of 12 to 15 Hz represent Sensory Motor Rhythm (SMR). This is associated with bodily relaxation.

Beta waves center around cortical activity and our ability to think and access.

Beta wave is the term used to designate the frequency range of brain activity above 12 Hz (12 transitions or cycles per second). Beta states are the states associated with normal waking consciousness.
Low amplitude beta with multiple and varying frequencies is often associated with active, busy or anxious thinking and active concentration.
Rhythmic beta with a dominant set of frequencies is associated with various pathologies and drug effects.

By one definition, gamma waves are manifest at 24 Hz and higher, though researchers have recognized that higher level cognitive activities occur when lower frequency gamma waves suddenly double into the 40 Hz range.

Research has shown gamma waves are continuously present during low voltage fast neocortical activity (LVFA), which occurs during the process of awakening and during active rapid eye movement (REM) sleep.

Some researchers do not distinguish gamma waves as a distinct class but include them in beta brain waves.

Gamma waves are involved in higher mental activity and are related with higher reasoning faculties.
Transient periods of synchronized firing over the gamma waveband, of entire banks of neurons from different parts of the brain, have been proposed as a mechanism for bringing a distributed matrix of cognitive processes together to generate a coherent, concerted cognitive act, such as perception.

Gamma waves are associated with solving the binding problem. Recent studies have shown that recognition of new insights occur when patterns jump from 20 to 40 Hz. It is believed by neuroscientists that gamma activity occurs when various chemical messengers foster efficient communications across large swaths of brain tissue.

Brainwave synchronization is a private case of functional brain connectivity concept, whereas functional connectivity is defined as the temporal correlation between spatially-remote neurophysiological events, expressed as deviation from statistical independence (temporal correlation) across these events in distributed neuronal groups and areas, which produce the brainwaves (for the recent review see Fingelkurts An.A., Fingelkurts Al.A., Kaa S. Functional connectivity in the brain – is it an elusive concept? Neuroscience & Biobehavioral Reviews. 2005, 28(8):827-836). As authors have stated, "the functional brain connectivity has become one of the most influential concepts in modern cognitive neuroscience, especially given the current shift in emphasis from studies of functional segregation to studies of functional integration."

Frequencies that might be used in brainwave synchronization and the related brain waves and mind states.

Although some studies have shown that these frequencies do provide help in treating certain medical conditions, [citation needed] there is not a wide acceptance by the medical community to adopt the practice of brainwave synchronization for emotional/mental disorders. the fixed, constant frequency of the synchronization is less helpful than techniques such as classical neurofeedback or learning meditation, which naturally generate brain wave frequencies that differ from person to person and may vary from minute to minute.