Basics of HEG Neurofeedback

By Dr Ernesto Sholomo Korenman, December 2005

Introduction

HEG (Hemo-Encephalo-Graphy ) biofeedback is an effective and drugless treatment

for many neuropsychological conditions which involves the self-regulation of cortical

activation.

HEG represents a simple and non-intrusive way for both: monitoring and training

cerebral function without the inconvenience of electrode preparation which other

neurofeedback methods generally require.

HEG has high compliance by clients and patients and the training can be delivered

with a help of entertaining and attractive feedback suitable for children and adults.

Physiological Basis

HEG devices measure and feed back changes correlated with blood flow dynamics

and cellular metabolism in localized parts of the brain cortex. These measurements

are closely correlated with brain activation due to a phenomenon called

“neurovascular coupling”. Briefly, blood carries all the nutrients and oxygen needed

to fuel neuronal activation and the localized delivery of blood supply to each part of

the cortex is closely linked to the particular metabolic requirements and the level of

neuronal activity in that region at every single moment.

The logic behind this biofeedback intervention is that repeatedly engaging in HEG

biofeedback, "exercises" the brain in a unique way which confers very promising and

long lasting neuro-behavioural benefits for the trainee. Special pre/post SPECT

(Single Positron Emission Computerized Tomography) imaging techniques has been

already used to verify that HEG biofeedback treatment promotes conspicuous blood

flow increases, (activation), below the treated areas.

History

State of the art HEG methodology is originally based on brain monitoring

technologies like nIR Spectrophotometry and Thermoscopy developed in the last 10-

15 years.

In 1994 Dr. Hershel Toomim developed his own nIR Spectrophotometer

methodology and subsequently was the first to show that that the monitored activity

can be self-regulated by biofeedback means. His early work on the application of nIR

HEG biofeedback in the treatment of ADD and ADHD and other neurobehavioral

conditions followed soon after that.

Slightly afterwards, Dr. Jeff Carmen started experimenting to build and test a device

to measure cerebrovascular activation using passive infrared technology in an attempt

to both monitor migraine activity and to train control over the associated abnormal

cerebrovascular behavior. In 1998 Dr Carmen formally reported success in the

treatment of migraine through pIR HEG biofeedback.

In the last five years other researchers and clinicians have joined this exciting area of

neurofeedback, (mainly in the USA). However, this technology is still considered to

be the newest modality addition to the central biofeedback practice and a therapeutic

tool with extremely promising future.

Methodology

There are two types of HEG measurement in current use:

1. nIR HEG: Active near infrared HEG measures changes in the relative

absorption of red and infrared light passed into the tissue below the nIR

sensor. The light traverses scalp and skull and reaches brain tissue and the

ratio of red to infrared light received back by the sensor is dependent on

localized blood perfusion and oxygenation in the underlying tissue. This

method is used by Hershel Tommim in his instruments.

2. pIR HEG: Passive infrared HEG measures the heat (IR emission) radiated by

the tissue below the pIR HEG sensor, which is dependent on the localized

blood perfusion and metabolic activity in that region. This method is used by

Jeff Carmen in his instruments.

With both modalities of HEG, there are no electrodes to be applied to the skin, no

electrode gels to be used to improve skin contact and no impedance criteria to insure

reliable recordings. HEG does not measure electrical activity; therefore, there are no

big problems with eye blinking, eye movements, ECG cardiac signals or other muscle

source of artifact.

Nevertheless, some care should be exercise when applying HEG biofeedback in order

to avoid artifactual readings. Possible known sources of data contamination are:

a) Positional changes of the subject. This changes cranial blood pressure and

affects perfusion. It can be controlled by observing the subject.

b) Direct flow of cold air from an air conditioner or extremely high temperatures

in the clinic that lead to forehead sweating.

c) Effects of small skin blemishes, inflammation or hair under the HEG sensors.

The actual details of the monitored display used to feedback HEG data can vary

slightly depending on the instrument and software application used. However, HEG

biofeedback practice is always straightforward for the trainee:

If the user maintains a relaxed but focused state of active concentration, the displayed

graph keeps moving upwards, the digital display of data keeps increasing and, (when

shown), a movie display keeps playing on. If there is a reduction in active focus by

relaxing too much, trying too hard, or becoming tense, frustrated, excited or stressed,

the graph reading and digital display drop and by reaching a pre-determined threshold

value the movie goes into pause mode and returns to play mode only when the trainee

regains active focus and raise the reading above the threshold value. Of course, the

threshold difficulty variable is controlled by the neurofeedback therapist and can be

made easier or more challenging, depending on the skill level of the trainee.

Figure 1. Display of nIR HEG during biofeedback training

HEG and Frontal Lobe activation

HEG cannot be easily measured through human hair and is particularly suited to be

applied over the forehead, (Fp1, Fpz and Fp2), in order to entrain the prefrontal

ortex. c

While the pre-frontal cortex represents only 29% of neocortex they mediate some of

the most advanced forms of thinking and cognitive activity by human beings. The prefrontal

lobes host the "executive attention networks" and their engagement is required

in order to sustain complex thinking, focused concentration, emotional tone and

eneral arousal. g

Frontal activation appears to be necessary to succeed in the treatment of many

neurobehavioral conditions such as ADD and ADHD. QEEG topographic brain maps

and functional MRI images of ADHD patients identify the prefrontal lobes as

dysfunctional or even "disconnected" from the rest of the brain through the presence

f excessive slow wave activity instead of desirable fast wave activity. o

Since the prefrontal lobes mediate so many complex, auto-regulatory brain functions,

they would seem to be the best choice of all brain lobes to be the target for HEG

raining. t

Clinical applications

Although HEG instruments are relatively new devices, increases in brain blood flow

via HEG neurofeedback have already shown significant clinical benefits, especially in

the areas of migraine, depression and ADHD.

Figure 2. TOVA gains after EEG and HEG biofeedback treatment

With permission from H Toomim et.al. 2005

In addition, HEG biofeedback has promising clinical potential for many types of

learning, perceptual, cognitive, neurological and neurobehavioral disorders, such as

ODD, OCD, Tourette's, Asperger's and mild Autism, as well as mild to severe head

rauma, closed head injuries and seizure disorders. t

It is important to note that HEG does not replace EEG; some therapists claim they

work best when both methods are used together. However, HEG appears to often be

superior to EEG when the QEEG brain map and/or other clinical indicators suggest a

eed for prefrontal lobe training. n

Example of temporary frontal activation through HEG biofeedback

I have recently developed a method for mapping forehead IR emissions. The

technique is only in his early experimental stage and its clinical significance is

currently under discussion. However, these maps may provide useful information

about the topographical activation of frontal lobes in general and the effect of HEG

raining in particular. t

Here follows a pre/post IR forehead mapping of a girl (12 years old) diagnosed with

dyslexia + ADHD taken before and after 10 minutes over the centre of the forehead

(Fpz).

Figure 3. Forehead IR emission maps before and after 10 mins of nIR HEG on Fpz

The whole left side of the picture seems to be less active than the right one in the pretreatment

map. There is a clear “colder” (less active) spot centrally over the left eye

that remains in IR maps before and after treatment. However, after just 10 minutes of

Fpz HEG training the whole of the frontal lobe appears to be clearly activated.