On a recent Monday night livestream I walked through one of the tools people ask me about most and one I have been slow to cover: hemoencephalography, or HEG. It is a form of vascular dynamics biofeedback, which means you train cerebral blood flow rather than electrical activity. This piece pulls together what I taught that night, including the hardware, the two main HEG variants, the targets I use it for, and a live demonstration of what a session looks like.
What is hemoencephalography (HEG)?
HEG trains the blood supply to your prefrontal cortex. Standard neurofeedback rewards changes in EEG signals, the electrical rhythms your cortex produces. HEG works on a different signal entirely: the metabolic and vascular activity feeding the frontal lobe. When a brain region works harder, it pulls in more oxygenated blood and produces more local heat. HEG measures that change and feeds it back to you in real time so your brain can learn to drive more energy to the front.
The frontal lobe handles executive function, attention, and self-regulation. Driving more perfusion and metabolic activity there is what makes HEG useful across the targets I describe below.
What is the difference between nirHEG and pirHEG?
Two clinicians developed HEG in two forms.
Hershel Toomim built the near-infrared version, nirHEG. The headset has a red light emitter and a receiver sitting against the skin. Oxygenated and deoxygenated blood absorb near-infrared light differently, so the amount of light reflected back gives you a proxy for local oxygenation. Because nirHEG sends light in and reads a focal signal, you can move the sensor around to train different frontal locations. The consumer Mendi device works on the same near-infrared principle and runs a few hundred dollars.
I use passive infrared, pirHEG, developed by Jeff Carmen. The headset holds unfocused infrared cameras a small distance off the skin. Instead of a sharp, spatially specific reading, you get a summed global signal of frontal heat. You train one site, the midline, a finger's width above the eyebrows. You do not move it left or right the way you can with nirHEG.
I prefer pirHEG for two practical reasons. It works better for the things I use it for, and it is insensitive to movement. Small kids who are wiggling, rocking, and shifting can still produce a clean signal. The placement takes seconds.
What does pirHEG help with?
These are clinical observations from my own practice, supported by Carmen's pre/post infrared photography showing more stable frontal blood flow patterns after a handful of sessions.
Migraine. This is the most reliable target I have. pirHEG can reduce the general tendency toward migraine, stop one cold when it is threatening to show up, and break up a long-running low-grade one. I had a low-key migraine going during the stream, and a round of blood flow training cleared the fog I walked in with.
Brain fog from concussion and post-viral states. Residual fog from concussion or long COVID often responds. The mechanism appears to involve re-recruiting frontal perfusion that has been allocated away.
Autism and social function. pirHEG sometimes produces strong changes in eye contact, sense of humor, and language timing. I do not have a clean mechanism for why frontal blood flow training shifts social processing, so I file this as clinical observation. I bring it in when there is a developmental complaint. If social and sensory processing interests you, I have written more on biohacking sensory and social processing.
Peak performance. With healthy high performers, pirHEG can sharpen executive function and reaction time. I have watched baseball players hit better and fencers get faster. Fencing rewards staying calm under intense exertion for up to five minutes; the people who fatigue slow down, and faster recovery of frontal control keeps them quick. If performance is your interest, see biohacking flow state.
Can pirHEG cause headaches or fatigue?
One viewer asked about this directly. He tried passive HEG and got extreme headaches and mental fatigue for two to three days afterward, and wanted to know the mechanism and whether to push through.
My read is that this was an acute overtraining effect. HEG raises the metabolic load on frontal tissue. When someone has active inflammation, the system may not have the metabolic headroom to handle that load. I see this with active POTS, dysautonomia, chronic fatigue, mold, Lyme, or inflammation following chemotherapy or COVID. A severe active Lyme flare, for example, would not tolerate HEG without further exhausting the person. Some of the fatigue may also be a healing-phase response, the result of moving energy and resources in a way they have not moved in a long time.
Pushing through is the wrong call. My rule of thumb: once you can tolerate a sauna or some exercise without exercise-induced fatigue, you have the metabolic headroom HEG requires, and it becomes worth doing.
Is pirHEG safe for healthy people?
Yes. I see no real risk for healthy brains, and healthy people derive benefits. The caution is for fragile vasculature: very elderly clients with a history of multiple strokes, bleeds, or aneurysms. The device is passive and measures surface heat from the outside, but biofeedback on blood flow still warrants a clearance conversation with the neurologist before proceeding when vascular history is in the picture. They have always cleared it in my experience. When there is a medical condition in play, the treating physician makes that call, not me.
How a pirHEG session actually works
I set one up live so people could see it. The PIR headset goes on the midline, a finger's width above the brow. It plugged into a Neurobit amplifier, and I ran the signal through software called BioExplorer.
The display gave me a ball that rises and falls, a pink trace, and an audio pitch that climbs as frontal energy increases. When my frontal blood flow surged, the pitch went up, the ball rose, and the trace climbed. It is mostly involuntary, but it responds to voluntary effort. When I focused or held a positive emotional state, I could drive the signal up and the whole frontal lobe ran hotter.
One detail worth watching for: when I first tried to push the signal up, it dropped first. My brain attempted to marshal energy, could not quite do it, then a couple of seconds later the perfusion kicked in and the trace climbed. That dip-then-surge is the system learning to recruit energy on demand.
I tie the energy level to the audio pitch so the brain gets a clean stream of information about what it is doing. My approach is semi-voluntary, closer to peripheral biofeedback. Carmen, who invented this style, tends to use longer sessions with formal thresholding. Both work.
How long and how often should you train pirHEG?
For dosing, I start adults at five or six minutes and kids at about four. I add one minute per session and cap a full session around ten minutes. Up to five days a week is reasonable.
I often place HEG before a beta-based EEG session. If someone is doing neurofeedback that rewards beta or inhibits theta, a short HEG round first primes the tissue. HEG is activating; it wakes up the cortex and supports beta. For that reason it is contraindicated alongside relaxation-oriented training. Stacking it with alpha training or alpha-theta work pulls the activating effect and the relaxation goal in opposite directions.
What does a pirHEG setup cost?
Rough numbers as of the stream:
- PIR headset (Carmen): roughly $750 to $800, sold directly.
- BioExplorer software: around $350 from resale channels.
- A Neurobit Optima 2 Plus amplifier with the auxiliary port: around $800.
With a low-cost mini computer, you are looking at about two grand all in. For a tool that reliably trains away migraines, I think that is worth it.
Can neurofeedback help with weight loss?
A viewer asked whether neurofeedback helps people lose weight. It can, and it works indirectly. Carrying extra weight has many drivers: chronic stress, poor sleep, anxiety, impulsivity, depression, occasionally OCD, and sometimes the sensory hyperfocus you see in autism, where food becomes the primary focus.
You usually train the whole person rather than the weight directly. When sleep improves and end-of-day anxiety settles, late-night impulsive eating tends to drop. Some of the benefit is also behavioral, leaning into better habits like not eating in the two hours before bed.
There is one more direct option I use, a protocol I call the snacker's protocol: FP1 referenced to M2 (the mastoid behind the right ear), inhibiting theta and rewarding a narrow 12 to 14 Hz beta band. I do not have a clean mechanism for it, but it seems to reduce the taste for sugar and the urge to snack at the end of the day. If habit change is your focus, see biohacking bad habits and the neuroscience of making habits stick.
One more personal data point
When I moved from Boston to UCLA in 2005, I rode a motorcycle over the Rockies on a bike that was, in hindsight, a little small for the job. As I climbed in altitude I started feeling altitude sickness. I stopped, hydrated, ate, and still felt off. I had a neurofeedback system with me, strapped on the HEG, and trained for about fifteen minutes. The altitude sickness lifted, and I crossed the range that day. Migraine and altitude sickness are both vascular events, which is likely why blood flow training touched both.
Bottom line
pirHEG trains prefrontal blood flow through passive infrared biofeedback. In my practice it is the most reliable migraine tool I have, it helps brain fog from concussion and post-viral states, it can shift social function in developmental cases, and it sharpens executive function and reaction time in healthy performers. The one real caution is metabolic load: if active inflammation is in the picture, start small and build tolerance through gentler stressors like sauna or exercise first.
If you want to see what your own frontal patterns look like before training anything, start with a QEEG brain map. Know your own brain first, then decide what is worth training.