Review by JongWook Hong, 2008
Newberg, A. B.; Iversen, J. The neural basis of the complex mental task of meditation: neurotransmitter and neurochemical considerations. Medical Hypotheses 61/2 (2003).
How does meditation work in our body, specifically in our brain? How does meditation influence and effect on human body function through working on brain? What neurological effects does meditation generate? These are questions that this article attempts to answer. Human consciousness is a complicated state of the human brain that involves chemical and electrical processes, and meditation provides distinctive access to human consciousness.
In this study, several functional neuroimaging techniques were used, including positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI). These methods have advantages and disadvantages. PET provides better resolution using radioactive tracers having short half life while SPECT has lower resolution but its associated tracers last longer. The strength of both PET and SPECT is the possible evaluation of neurotransmitter systems through tracers that attach to neurotransmitters. fMRI provides better and faster images but it makes noise and meditating can be easily distracted by the noise.
Newberg and Iversen develop a neurological model for the type of meditation they study, as follows. In the beginning of meditation, activity increases in the prefrontal cortex (PFC), which is in the right hemisphere and is related to willful acts. This excites thalamic activation, which governs the flow of sensory information, and results in the increase of a chemical (GABA) that cuts off sensory information to the posterior superior parietal lobule (PSPL). The PSPL analyzes and integrates the sensory information, and thus is important for distinguishing the self from the world. The deafferentation of PSPL—or even partial deafferentation of the right PSPL—could cause stimulation of the right hippocampus, which is deeply interconnected with the prefrontal cortex (PFC), amygdala, and the hypothalamus. These interactions have to do with attention, emotion, and imagination. The stimulation of the amygdala results in the stimulation of the hypothalamus, and this engages the parasympathetic system, which is associated with “the subjective sensation first of relaxation and eventually, of a more profound quiescence” (286). This activity also reduces heart and respiratory rate.
Autonomic nervous system (ANS) activity can be also found during meditation. This results in the stimulation of the lateral hypothalamus and median forebrain bundle, which releases beta-endorphins that produce “both ecstatic and blissful feelings when directly stimulated” (288).
There are many neurotransmitters and neurochemicals involved with meditation such as the endogenous opioid, GABA, norepinephrine, and serotonin. It is difficult and complex to explain what each of them does and how they interact with one another. However, Newberg and Iversen observe that the various neurotransmitters contribute to the outcome of meditation in an integrated manner.
The examination of meditation helps scientists gain access to the structure and features of human consciousness, but in order for such experiments to be relevant to religiosity a few questions should be answered. First, what is the relationship between meditation and religiosity? Since meditation has been performed without religious connotations, this should be addressed. If the relationship is based on religious feelings or ideas, what are criteria for religious feelings and ideas? What makes those feelings and ideas religiously authentic? Second, is the result of brain activity during meditation a unique activity happening only during meditation? If not, what other human activities display the same or similar brain activity? it is difficult to interpret the neurology of meditation experiences without answers to these questions.
This is a fabulous article for investigating human consciousness because of its rich descriptions of human brain function. Although this article would be difficult to read for by those who do not have much knowledge brain anatomy and function, it has the potential to open up the door to the neurology of religious experience for patient readers.
Definitions from The Free Dictionary
electroencephalograph (EEG): An instrument that measures electrical potentials on the scalp and generates a record of the electrical activity of the brain. Also called encephalograph.
positron emission tomography (PET): Tomography in which a computer-generated image of metabolic or physiologic activity within the body is produced through the detection of gamma rays that are emitted when introduced radio-nucleotides decay and release positrons. The images are used in the evaluation of coronary artery disease, epilepsy, and other medical disorders.
single photon emission computer tomography (SPECT): the recording of internal body images at a fixed plane with radiographic equipment to observe physiologic and biochemical processes and the volume and size of target organs.
fluorodeoxyglucose: a glucose analog. Its full chemical name is 2-fluoro-2-deoxy-D-glucose, commonly abbreviated to FDG. FDG is most commonly used in the medical imaging modality of positron emission tomography (PET): the fluorine in the FDG molecule is chosen to be the positron-emitting radioactive isotope fluorine-18, to produce 18F-FDG. After FDG is injected into a patient, a PET scanner can form images of the distribution of FDG around the body. The images can be assessed by a nuclear medicine physician or radiologist to provide diagnoses of various medical conditions.
Ventromedial: both ventral and medial; extending toward the ventral surface and the median line.