Haemoencephalography (HEG)

Haemoencephalography (HEG) is a recently developed non-invasive technology that is used to improved bloodflow in the brain. While neurofeedback involves the self-regulation of the brain's electrical signal, or EEG, haemoencephalography is all about the self-regulation of  cerebral bloodflow.

HEG is only a recently discovered biofeedback technique. Within a similar timeframe in the mid-1990s, Hershel Toomim invented near infrared haemoencephalography (nir HEG) while Jeff Carmen came up with passive infrared haemoencephalography (pir HEG). Nir HEG utilises a headband with sensors that measure reflected red and infrared light from brain tissue in order to calculate the degree of oxygenation. Trainees are basically rewarded for increasing red colouration. Carmen's device employs an infrared thermometer to measure the temperature immediately below the sensor, with trainees being rewarded for increasing core brain temperature. Rewards are the same as those used for neurofeedback with, for example, a video that plays as bloodflow increases and pauses when it decreases. Over time, the brain learns that if it wants to achieve the reward of seeing the video it needs to produce more bloodflow in the area below the headband sensor.

Both HEG methods have been shown to improve metabolism of hypoperfused (underactive) brain regions. While nir HEG can be used at multiple cortical sites, pir HEG is only used at the prefrontal cortex, which is the area immediately behind the forehead. The prefrontal cortex is the brain's "central executive" that is involved in decision-making about how the brain will allocate it's resources at any given moment. It is, therefore, involved in actions such as attention, concentration, working memory, impulse control and emotional regulation. Increasing bloodflow at the prefrontal cortex results in increased oxygenation and, therefore, a healthier brain that is better able to cope with the demands of life.

Because HEG is such a recent discovery, research is still in its infancy. In research conducted in Thailand, however, a series of 181 students with Autism Spectrum Disorder were given 20 sessions of nir HEG in which they were rewarded for increasing cerebral blood flow to the prefrontal cortex of the brain. The result was a Grade Point Average increase of 0.94 on a 4-point scale, as well as a 53% increase in prefrontal blood oxygenation readings (Limsila et al, 2004).

Dr Robert Coben from the Brain Labs in New York has also recently published a study involving 32 autistic subjects identified as having frontal system dysfunction based on QEEG, infrared imaging, neurobehavioural and neuropsychological testing. The children in the experimental group each received 20 sessions or either nir or pir HEG. A wait list control group of 12 subjects matched for gender, age, race, handedness, IQ and previous treatment was used.

Following treatment, 90% of subjects showed improvement, with an average 42% reduction in autistic symptoms on the Autism Treatment Evaluation Checklist. There were also statistically significant improvements on tests of neurobehavioural and neuropsychological functioning, brain thermal imaging and QEEG data. While both forms of HEG provided statistically significant improvements, pir HEG proved more successful than nir HEG on some key measures of functioning.

Dr Coben's study was part of a larger research project that involved 40 neurofeedback sessions along with the 20 HEG sessions for a group of children with autism. When taken together, the result was an average 80% reduction in autistic symptoms across the entire group for those who completed the 60 sessions.

At Neuro Development Services we utilise both forms of HEG. We find HEG to be a helpful intervention when the individual has problems that impact upon frontal lobe function.