The extended reticular-thalamic activating system model suggests a neural mechanism responsible for regulating generalized levels of arousal (basic rest-activity cycle, sleep cycles, ultradian rhythms, etc.) as well as behavior- or cognition-specific patterns of arousal. The cortical attributes or contents of consciousness are the result of social-psychological conditioning and elemental cognitive acuity. These ambient factors of consciousness (arousal and content) provide us with a first-person experience or awareness. Effective induction of propitious states of consciousness, therefore, requires a multidimensional approach involving sensory-information stimuli, social-psychological conditioning, and education. Binaural beating, a sensory-information stimulus, provides potential consciousness-altering information to the reticular-thalamic activating system which in turn alters arousal states, attentional focus, and level of awareness (crucial elements of consciousness itself). Integrated with other sensory-information techniques, social-psychological conditioning tools, and educational curriculum, binaural beats can provide access to a variety of beneficial applications and first-person experiences of expanded states of consciousness.
Binaural beating is associated with an electoencephalographic (EEG) frequency-following response in the brain that has been demonstrated by Oster (1973) and in the context of hearing-acuity research (Hink et al. 1980). Many other studies have demonstrated the presence of a frequency-following response to auditory stimuli, recorded at the vertex of the human brain (top of the head). This EEG activity was termed "frequency-following response" because its period (cycles per second) corresponds to the fundamental frequency of the stimulus (Smith, Marsh, & Brown 1975). Stated plainly, if the audio stimulus is 24 Hz the resulting measured EEG will show a 24 Hz frequency-following response using appropriate time-domain averaging protocols. This frequency-following response signal is, however, very small and represents only a small portion of the overall EEG and is not, in and of itself, representative of a change in consciousness.
Brainwaves and related states of consciousness are said to be regulated by the brain's reticular formation stimulating the thalamus and cortex. This extended reticular-thalamic activation system (ERTAS) is implicated in a variety of functions associated with consciousness (Newman 1997). The word reticular means "net-like" and the neural reticular formation itself is a large, net-like diffuse area of the brainstem (Anch et al. 1988). The reticular activating system (RAS) interprets and reacts to information from internal stimuli, feelings, attitudes, and beliefs as well as external sensory stimuli by regulating arousal states, attentional focus, and the level of awareness - critical elements of consciousness itself (Empson 1986; Tice & Steinberg 1989). How we interpret, respond, and react to information then, is managed by the brain's reticular formation stimulating the thalamus and cortex, and controlling attentiveness and level of arousal (Empson 1986). "It would seem that the basic mechanisms underlying consciousness are closely bound up with the brainstem reticular system..." (Henry 1992). In the ERTAS model, binaural beats engender changes in rhythmic EEG patterns throughout the cortex and our first-person experience of consciousness as cortico-thalamic projections adapt to information (the binaural-beat waveform) coming to the midbrain reticular formation.
Binaural beats were discovered in 1839 by a German experimenter, H. W. Dove. The human ability to "hear" binaural beats appears to be the result of evolutionary adaptation. Binaural beats can be detected by humans when carrier tones are below approximately 1000 Hz (Oster 1973). The sensation of "hearing" binaural beats occurs when two coherent sounds of nearly similar frequencies (the carrier tones) are presented, one to each ear, and the brain detects phase differences between these sounds. This phase difference normally provides directional information to the listener but when presented with stereo headphones or speakers the brain integrates the two signals, producing a sensation of a third sound called the binaural beat.
Perceived binaural beating appears to originate in the brainstem's superior olivary nucleus, the site of contralateral integration of auditory input (Oster 1973). This auditory sensation is neurologically routed to the reticular formation (Swann et al. 1982) and simultaneously volume conducted to the cortex where it can be objectively measured as a frequency-following response (Oster 1973; Smith, Marsh, & Brown 1975; Marsh, Brown & Smith 1975; Smith et al. 1978; Hink et al. 1980). The objectively measured frequency-following response provides proof that the sensation of binaural beating has neurological efficacy. (Source: Monroe Institute)
