Some weeks ago an event happened while I was practising biofeedback (on myself) that I found very interesting and revelatory. I got a glimpse of how spontaneous emotions affect the brain, and I wanted to share what I learned with others.

I was working with HEG neurofeedback. This involves having a sensor mounted over the forehead, in this case an infra-red temperature sensor. I discussed this form of biofeedback in a recent blog post. To summarise, the sensor detects changes in heat radiation from the forehead, which are presumed to come from changes in activity in the prefrontal cortex (which is behind the forehead). When I focus intently, with a bright and vivid awareness, the signal increases. When I drift into day-dreaming or dullness, the signal falls.

On this occasion I was working alone in my office on a Saturday afternoon. A group of kids appeared outside. They were playing on skateboards in the car park. Since I was sitting by a ground-floor window, one of them noticed me, with a prominent sensor strapped to my forehead. He invited his mates to ‘come and have a look at this’. Although I’m sure there was no malice on their part – they just wanted to know what I was up to – I decided my best response would be to ignore them. So I kept looking at the screen, didn’t even move (which was useful in that I know that the data I recorded was not caused by movement artefact).

What was so fascinating was what happened to the signal in light of my emotional responses. At first I was embarassed, and quite quickly got annoyed, especially when the kid started to tap on the window.

The figure below shows what happened to the infra-red temperature signal.

You can see there are three quite marked falls, the first beginning at about 2 minutes. The first two are relatively close together, and are really part of the original incident. By the time of the third drop, the kids had moved on, but what happened was that my mind went back to the event. I imagined going out there and giving them a piece of my mind. As I indulged in my anger I got another fall.

I didn’t lose control completely, as is evidenced by this simultaneous recording of my breathing rate:

What’s the interpretation? The negative emotions (principally anger) that the event precipitated, caused my prefrontal cortex to deactivate. The prefrontal cortex acts as the brain’s executive control centre, heavily involved in attention, purposeful behaviour, decision making, and (crucially in this case) emotional regulation. Of course this was quite involuntary, but on reflection it fits with my subjective experience, which was a narrowing, and a sort of fogging out of my awareness, or presence of mind. I’m sure it’s what happens in others too – people commonly report losing control and later regretting what they did or said during the emotional “hijacking” caused by anger (or anxiety for that matter). (Dan Goleman describes the process quite well in his best-selling book ‘Emotional Intelligence’.)

The drops are quite precipitous. The signal dropped much faster than I was able to raise it (either before or after).

Although it was only a one-off event, and therefore does not constitute scientific research, I would say that my experience of HEG biofeedback is consistent with this event – that even passing thoughts that are charged with negative emotion can affect the prefrontal cortex in this way. It was an instance of genuine and clear-cut emotion that would be very hard to reproduce on demand in a controlled scientific experiment. For me it was a hands-on demonstration of how the neurobiology of emotion plays out in real life, in a very tangible way. More convincing and memorable than reading about it!