Neurofeedback using HEG trains the subject to increase blood flow to a targeted area of the brain.
Neurofeedback, as we have known it so far, measures the electrical activity of the brain, EEG, as a feedback signal to be controlled by the patient. Here we have substituted blood oxygenation for the same purpose.
You have probably tried shining a flashlight through your hand and have seen the dark side light up. Our tissues, flesh and bone, are translucent.It's not dark in there.
In the sunlight, if you were in there with your brain, you could read a newspaper by that light. In HEG a light is shone on your brain through the translucent scalp and skull.
A spectrophotometer device is worn on the head. Flashing red and infrared lights are shown in the fi gure as one optode. The light collection amplifier is another type of optode. It responds to the returned light thatis reflected and refracted by the encountered tissue.
These optodes are spaced 3 centimeters apart so as to conduct most of the available light at the depth of cortical tissue. As can be seen the
application is very simple.
Red, 660 nm, and infrared, 850 nm, lights are alternately shown on brain tissue. The graph above shows the large difference in red light attenuation between oxygen rich and oxygen starved hemoglobin whereas the infrared light is minimally changed. (Elwell 1999)
A computer program receives a measure of each light color, calculates their ratio, and graphs the value for the patient to see, hear and alter.
During the summer of 1994 it was discovered that the author could intentionally increase cerebral regional oxygenation. The computer graph responded to thoughts. Brain oxygenation increased merely by intenselywilling it. A neurofeedback system was born.
Neurofeedback using this new technique provides a means to exercise selected brain areas. Exercise increases blood flow to the chosen brain module. Capillaries and dendrites grow with brain exercise (Kaiser 1997, Thompson et al. 1998, Joyce and Seiver 1997, Rossiter 1996, 1996, Kaiser 1997). An audible tone was devised that increased in pitch to signify increased blood oxygenation. To increase oxygenation one would merely attend to the highest note in each trill and will the next higher note to sound. Application of the headband and monitoring patient progress is simple. The treatment process is divided into ten-minute segments. Usually three to four such segments constitute a treatment session.
Marion Diamond (1965) first showed the importance of enhanced environments in 1965. She demonstrated that brain exercise increased the weight of rat brains. Dr. Diamond undertook to determine if old rats could learn new tricks. Rats live to an old age of 900 days. She selected seven hundred-day old rats for her experiment. She divided the rats into three groups: 1. One rat in a cage, 2. Two rats to a cage, and 3. Six rats to a larger cage. All the rats were fed standard laboratory chow. Cages with six rats were provided with new toys; mazes to solve, rotating drums for exercise, etc. almost every day. These rats were held and petted by the lab assistants. (Rats love to be tickled.) After a month the rats were sacrificed and their brains were examined. Those of the high-stimulation group were found to be 8% heavier compared to the solitary group. The additional weight was supported by denser capillary beds. Microscopic examination of enhanced environment cortical slices revealed dendritic trees resembling a dense rain forest. Those of the solitary group resembled a carefully manicured landscape.
What if you could produce the same effects in a different manner? The following SPECT images show
(permanent) changes in blood fl ow after treatment for a manic-depressive patient.
Single Photon Emission Computerized Tomography (SPECT), demonstrating blood flow pre- and post-treatment
Fig. 3: SPECT study of manic depressed patient before treatment
Fig. 4: SPECT study of manic depressed patient after 23 treatment sessions
These SPECT studies are compared to an age related, standardized data. The false color blood fl ow levels are shown by colors ranging from purple (unusually low) through white (unusually high). The scale on the left side of the images shows z-scores (standard deviations) from the mean. The population mean is depicted in yellow. The left margin color scale defi nes standard deviations relative to the population mean.