What is Hemoencephalography (nIR & pIR)
Is a relatively new neurofeedback technique in the neurotherapy field based on the idea that human beings can consciously alter their brain function by utilizing some neurological feedback mechanism. By training their brain, participants learn to increase their cerebral blood flow to a specified region of the brain, thus increasing brain activity and performance on tasks involving the targeted brain region.
Both near infrared and passive infrared approaches to hemoencephalography (nIR and pIR) indirectly measure neural activity based on neurovascular coupling. This coupling represents the mechanism by which cerebral blood flow is matched to metabolic activity. It is known that neuronal activity increases when a region of the cortex is involved in a specific cognitive task, consequently, there is an increase it the local metabolic rate. To maintain the nutritional and waste removal demands of a higher metabolic rate, an increase of cerebral blood flow to the cortical area is proportionally needed. In addition, increasing blood flow increases the hemoglobin molecules in the blood. These molecules are responsible for the transport and transference of oxygen to tissue throughout the body and the oxygen delivered to the region of the cortex that has been activated, resulting in a higher blood and oxygenation level for that region. This phenomenon is referred to as the haemodynamic response.
Near Infrared (nIR) was developed by Dr. Hershel Toomim. nIR hemoencephalography measures changes in the local oxygenation level of the blood. Like functional magnetic resonance imaging, which uses changes in the magnetic properties of blood resulting from oxygenation to form an image of brain activity, nIR utilizes the changes in blood translucence resulting from oxygenation to generate a signal that can be consciously manipulated in neurofeedback sessions. In nIR hemoencephalography I light is shined red light (660 nm) and near infra-red (850 nm) are shinned on the frontal area of the brain. While the skull is largely translucent to these light wavelengths, blood is not. The red light emitted from the headband is used as a probe, while the infrared light provides a relatively stable baseline for comparison. To achieve this, a photoelectric cells in a spectrophotometer device measure the amount of each wavelength of light reflected by cerebral blood flow in the activated cortical tissue sending the data to a computer, which is responsible for calculating the ratio of red to infrared light. The result is translated into a visual signal which corresponds to an oxygenation level on a graphic or a game like representation that the patient can see. The key nutrient monitored by NIR is oxygen. Therefore, as the ratio of oxygenated hemoglobin (HbO2) to deoxygenated hemoglobin (Hb) increases the blood translucency decreases, scattering more the red light instead of absorbing it. When this happens, the amount of infrared light scattered by the blood is largely impermeable to changes in the oxygenation level of hemoglobin.
Passive Infrared (pIR) was developed by Dr. Jeffrey Carmen, a privately practicing psychologist in New York Passive infrared HEG is based on Dr. Tommin’s hemoencephalography principles and a technique known as thermoscopy. pIR ustilize a sensor similar to the one used in nIR. This sensor detects light from a narrow band of the infrared spectrum related to the amount of heat being generated by an active brain region and the local blood oxygenation level. The heat detected is proportional to the amount of sugar being burned to maintain the increased metabolic rate necessary to fuel elevated neuronal activity. pIR focuses on more global increases in cerebral blood flow in the frontal area and it has been argued that its resolution is lower compared to that of the nIR.
The first true instance of neurofeedback occurred in 1963, when University of Chicago professor Joseph Kamiya trained a volunteer to recognize and alter alpha brain wave activity. Just five years later, Barry Sterman conducted a revolutionary study on cats at the behest of NASA that proved that cats trained to consciously alter their sensorimotor rhythm were resistant to doses of hydrazine that typically induce seizures. This finding was applied to humans in 1971 when Sterman trained an epileptic to control her seizures through a combination of sensorimotor rhythm and EEG neurotherapy to the extent that she obtained a driver's license after only three months of treatment. Around the same time Hershel Toomim was founding Toomim Biofeedback Laboratories and Biocomp Research Institute on the basis of a device known as the Alpha Pacer that measured brain waves. After decades of work with various biofeedback mechanisms, Toomim accidentally stumbled upon conscious control of cerebral blood flow in 1994. He developed a device specific to this measure that he called a Near Infrared Spectrophotometry Hemencephalography system, coining the term "hemoencephalography", in 1997. A clinician user of NIR HEG, Jeffrey Carmen, adapted Toomim's system for migraines in 2002 by integrating peripheral thermal biofeedback into the design. Since then, both techniques have been applied to numerous disorders of frontal and prefrontal lobe function. Sherrill, R. (2004).
Prior to training with the HEG device, patients are given a standardized pre test, most often the Test of Variables of Attention (TOVA), to assess baseline cognitive functioning. Patient progress will be tracked using the same measure at the beginning and end of every neurotherapy session. Single photon emission computed tomography (SPECT) assessments may also be conducted pre and post treatment, depending on the patient's disorder. Training sessions are typically 45 minutes to an hour in length, with intermittent breaks. At the outset, all sessions are performed at a certified neurotherapy provider's clinic (though some at-home options are now available) and begin 2-3 times weekly in frequency. Depending on the patient, training may last from a couple of months to a couple of years. High variability in red light activity (large range from low to high output) is typically characteristic of people with problems of the prefrontal cortex. Low variability is associated with more normal functioning. The ratio of red/infrared light refraction is displayed as a visual signal on a computer monitor and may also be translated into an auditory signal in which higher pitch corresponds to greater oxygenation. During a HEG training session patients attempt to increase the signal generated by the HEG sensor. Progress is measured by reduced variability.
Most research in HEG has focused on disorders of the prefrontal cortex (PFC), the cortical region directly behind the forehead that controls high level executive functions such as planning, judgment, emotional regulation, inhibition, organization, and cause and effect determination. The prefrontal cortex is thought essential for all goal-directed and socially-mediated behavior. The PFC is an ideal target for HEG due to both its location on the scalp (behind the forehead, where there is no hair to disrupt the scattering of the red and infrared light) and the susceptibility of its primary functions to learning.
Research with PIR has focused almost exclusively on alleviating tension headaches and migraines. A four year study of 100 chronic migraine sufferers found that after as few as six 30-minute training sessions, 90% of patients reported significant improvements with their migraines. Another study conducted combined the biofeedback measures of EEG, hemoencephalography and thermal handwarming during thrice weekly sessions for 14 months. 70% of sufferers saw a 50% or more reduction in their migraines following combined neurotherapy and drug treatment, as opposed to 50% undergoing only traditional drug therapy.
The term autism encompasses a wide range of syndromes, such as Rett disorder, pervasive developmental disorder (PDD) and Asperger's syndrome, that are collectively referred to as autism spectrum disorders (ASD). All ASD sufferers exhibit impaired understanding and performance of social and communicative skills, impulsivity, difficulties with attention and some mode of obsessive behavior. Many patients with ASD have normal to above normal intelligence, but exhibit wildly abnormal EEG readings, which combined with symptoms synonymous with impaired executive control make them prime candidates for pre-frontal centric neurotherapy. The myriad of studies exploring the potency of neurotherapy as a treatment for ASD have primarily involved EEG and QEEG, but one recent study investigated the efficacy of both NIR and PIR training against a QEEG only control group and found that, according to parental reports, those in both HEG groups experienced a more than 50% decrease in symptoms. These reports were supported by decreased EEG variability and improvements on measures of neurobiological and neuropsychological functioning. Interestingly, NIR was found to have a greater impact on attention, while PIR had greater efficacy in the realms of emotional regulation and social interactions.
Attention Deficit Hyperactivity Disorder
With many symptoms reminiscent of ASD, Attention Deficit Hyperactivity Disorder (ADHD) has also been a focus of HEG research. In one typical case study, an adolescent with ADHD presented with highly abnormal QEEG readings and attentional scores on neuropsychological tests. After only ten biweekly HEG training sessions, he rendered a completely normal QEEG reading and significantly improved scores on attentional measures. Notable about this research is that the improvements persisted eighteen months post-treatment, allowing the patient to greatly reduce the drug therapy necessary for him to function successfully in school and offering a quick and relatively cheap treatment alternative for school systems and parents of children with ADD/ADHD.
A large group of researchers headed up by Dr. Hershel Toomim and his wife Marjorie have repeatedly found that NIR HEG training can consciously enhance regional cerebral oxygenation to specific areas of the brain and result in increased performance on cognitiive tasks. It is widely known that regular cardiovascular exercise results in increased cerebral blood flow due to increased vascularization of the capillaries feeding neuronal tissue. Toomim, Mize, Kwong et al. found that after only ten 30-minute sessions of HEG brain exercise training, participants with various neurological disorders showed increases in attention and decreases in impulsivity to within normal levels. A subset of participants also experienced increases in cerebral vascularization similar to those witnessed upon increasing physical activity. More importantly, degree of improvement was found to be reliably related to the initial TOVA score of each participant, with the lowest initial TOVA scores exhibiting the greatest improvement. In addition, HEG has shown promise at alleviating depression, stress and chronic anxiety. (http://en.wikipedia.org/wiki/Hemoencephalography)
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