Neural oscillations are rhythmic or repetitive electrochemical activity in the brain and central nervous system. Such oscillations can be characterized by their frequency, amplitude and phase. Neural tissue can generate oscillatory activity driven by mechanisms within individual neurons, as well as by interactions between them. They may also adjust frequency to synchronize with the periodic vibration of external acoustic or visual stimuli.[3]

I wouldn’t personally recommend listening to delta wave frequencies for depression, so I’m not sure who advised you to do that? People with depression usually have a higher ratio of theta and delta wave activity, so I would normally recommend listening to high alpha wave and low beta wave frequencies, to help balance things. I have some 10Hz alpha tracks for serotonin release, which you can try for free on my YouTube channel here: I also recommend you give these SMR (low beta wave) tracks a try: I hope that helps.
Initially the children were entrained to a mu-alpha rhythm (7 to 9 Hz) to decrease theta waves. After the initial mu-rhythm entrainment, they entrained SMR-beta waves for 22 minute sessions. The results as interpreted by TOVA demonstrated significant improvements in: inattentiveness, impulsivity, and variability. Teachers and parents also reported behavioral improvements among the children. Using the right brainwave entrainment protocol may be a potential Adderall alternative for those with attentional deficits.
Gamma waves are the fastest brainwave frequency range. Gamma brain waves are believed to link and process information from all other parts of the brain. A high amount of gamma wave activity in the brain is associated with intelligence, compassion, focus and feelings of happiness. High levels of gamma brain waves have also been linked to improved memory and an increased sensitivity to sensory input. Low amounts of gamma brainwave activity have been linked to learning difficulties, poor memory and impaired mental processing.

The eyes of the participants were closed and the VFP goggles illuminated in alternative manner; first the right eye, then the left. The rate at which the photic stimulation was conducted ranged between 0.5 Hz and 50 Hz. Of the 50 patients with migraines, 49 considered their headache as having been “helped” by the stimulation and 36 noted that their headache had completely “stopped” from the VFP goggles.

AVE is capable of producing situationally appropriate brain wave frequencies through the process of entrainment (the tendency of physiological processes to mirror environmental stimuli). AVE also increases cerebral blood flow (blood flow in the brain) and increases the metabolization of glucose in the brain for improved functioning of the neurons. The combined outcome of these processes is improved mental performance. It is an effective, inexpensive alternative therapy for many disorders such as anxiety, Attention Deficit Disorder (ADD), Seasonal Affective Disorder (SAD), PTSD, Fibromyalgia and chronic pain. Our AVE devices are also used successfully to boost physical performance for athletes, academic performance for students and cognitive performance for seniors.
But especially at this point, I’m on a mission to get as many people using Holosync® as I possibly can—my current goal is 100 million Holosync® users. Because we already have so many people using it, the economy of scale allows me to offer it to you for MUCH less than what my accountant suggested: just $179 if you’d like Awakening PrologueTM on CDs… or $159 if you want the downloadable MP3 version…
The functional role of neural oscillations is still not fully understood;[6] however they have been shown to correlate with emotional responses, motor control, and a number of cognitive functions including information transfer, perception, and memory.[7][8][9] Specifically, neural oscillations, in particular theta activity, are extensively linked to memory function, and coupling between theta and gamma activity is considered to be vital for memory functions, including episodic memory.[10][11][12]