How Meditation Alters Consciousness
Consciousness arises from the bottom up, from the most primitive regions of the brain to the most sophisticated. It is those more sophisticated brain regions (such as the cerebral hemispheres) that give us higher functions, such as thoughts, emotions, reasoning and intelligence. But given their tendency to “overthink,” they can also get us into trouble!
Meditation alters consciousness in such a way that these higher brain regions (e.g., the frontal cortex) can inhibit or exert control over incoming sensory impulses, allowing us, for example, to ignore pain or noises in our environment.
This capacity to inhibit trickles all the way down to the level of the reticular activating system (RAS) in the brain stem. The RAS controls arousal; that is, brain states such as our ability to wake up every morning or our ability to ignore stimuli and inhibit impulses during meditation. The ability to awaken, sleep, dream, or meditate is dependent on the reticular activating system.
The RAS or reticular formation is a primitive intricate network of interlacing neurons and nerve fibers that receives input from multiple sensory pathways and transmits them to higher order brain centers. The RAS extends from the spinal cord to the lower brain stem, upward through the midbrain and thalamus, then distributively throughout the cerebral cortex. The RAS is involved in most central nervous system activity, including regulation of states of consciousness, such as wakefulness and sleep. During meditation, the RAS influences our ability to direct attention toward specific areas of our conscious minds.
The RAS consists of chemically-specific clusters of neurons that generate specific neurotransmitters, such as acetylcholine, norepinephrine, dopamine, serotonin, histamine, glutamate, GABA, and orexin. These neurotransmitters either activate or inhibit the spinal cord and various regions of the cerebral cortex. For more information see: Evidence of Meditation’s Impact on Neurotransmitters & Neurohormones.)
The RAS integrates the regulation of cardiovascular, respiratory and motor response to external stimuli. The medulla oblongata, the lowermost portion of the brain that is continuous with the spinal cord, is responsible for the control of respiration, circulation, and other autonomic bodily functions.
The hypothalamus, a substation of the limbic system, integrates complex mind-body responses throughout our autonomic (involuntary) and somatic (motor and sensory) nervous system. Meditation partially inhibits the hypothalamus as it is regulating the RAS, which may help explain common physiological meditation effects, such as decreases in blood pressure, blood lactate and urinary vanillylmandelic acid (Newberg, A., Iverson, J., 2003). Through it’s connection to the RAS, the hypothalamus influences the flow of incoming sensory stimuli. During meditation, the RAS is partially inhibited, which stops the flow of irrelevant and distracting sensory information and allows cell nuclei to emit the alpha waves that are commonly observed during most all forms of meditation and are associated with a relaxed state of mind.
Newberg, A.B. and Iversen, J. (2003) The neural basis of the complex mental task of meditation: neurotransmitter and neurochemical considerations. Med. Hypotheses 61(2), 282–291.