I agree that it has to do with muscle tension, and thus plugs into (weirdely) Reichian muscle-armor/orgone/'subtle-energy'.
The quick notes follow(I have many tabs open). I will attempt to synthesize this information later today or tomorrow, or sometime.
Mirror Neurons (the trigger of watching others focusing intently on a task, awareness is drawn to the muscle cortex because the mirror neurons queue up the signals necessary to do the same)
Pranayama / Breath Control (placing your awareness on your muscle cortex by following your breath while using meditative techniques to clear other sense data from your mind relatively quickly)
Most other triggers on the ASMR sites pull awareness (where we focus our attention) from where it normally rests, our sight/center-of-vision-focal-area, sometimes it seems, through the above secondary triggers.
Having practiced a few Zanshin techniques, I can say that this pull away from the center-of-visual-field changes the way visual information is sent to the brain, placing focus on spatial relationships over form/detail (by tracking multiple points in the focal and peripheral visions). This seems to queue up spatial relationship information in the body via the kinesthetic sense (Proprioception+Balance, look it up).
The word "Prana" in pranayama comes from the "Upper vortex" or
Prana-Vayu – located in the head and centred at the point of the ajna chakra (third eye) this is known as the inward moving wind as it governs all receptive activities including inhalation, sensory stimulation and mental recognition. This energy also pervades the thoracic region and is the fundamental force feeding the other vayus.
Which is roughly analogous to the "Upper Dan Tien" in WingChun/Qigong. Both systems say that the human body habitually falls "out of balance", and when this happens the 'subtle energy' from the upper energy point cannot fully enter the lower before getting cycled back out. In these systems, these feelings always have "flow-directions" (something Richard Bandler took advantage of with some of his NLP tricks, more on that later on when I collect my thought on all of this). Also, many of these systems claim that moving the focus of attention from our forehead/visual field to lower in the body is supposed to have noticeable results in the rest of our day-to-day lives.
In these systems, we find descriptors like this:
When the prana is concentrated in the anahata chakra (the "green" heart/lung chakra), the seat of the gaseous or "air element," a variety of changes can happen: spontaneous rapid breathing or trembling, called kampa; or blocking of the voice so that one cannot speak and only hoarse sounds come out (svarbanga); or pulaka, when the hairs on the scalp prickle or stand up, goosebumps arise on the skin, and there is a feeling of joy in the heart.
The practive of "moving the attention willfully" is calles
Sati in
Thai Theravada Buddhism.
Use a posture that will keep your back straight without strain. A simple upright chair may be helpful, or you may be able to use the lotus posture. These postures may look awkward at first, but in time they can provide a unique balance of gentle firmness that gladdens the mind without tiring the body.
If the chin is tilted very slightly down this will help but do not allow the head to loll forward as this encourages drowsiness. Place the hands on your lap, palm upwards, one gently resting on the other with the thumb-tips touching. Take your time and get the right balance.
Now, collect your attention, and begin to move it slowly down your body. Notice the sensations in each part of your body. Relax any tensions, particularly in the face, neck and hands. Allow the eyelids to close or half close.
Investigate how you are feeling. Are you expectant or tense? Then relax your attention a little. With this, the mind will probably calm down and you may find some thoughts drifting in - reflections, daydreams, memories, or doubts about whether you are doing it right! Instead of following or contending with these thought patterns, bring more attention to the body, which is a useful anchor for a wandering mind.
Cultivate a spirit of inquiry in your meditation attitude. Take your time. Move your attention, for example, systematically from the crown of the head down over the whole body. Notice the different sensations - such as warmth, pulsing, numbness, and sensitivity - in the joints of each finger, the moisture of the palms, and the pulse in the wrist. Even areas that may have no particular sensation, such as the forearms or the earlobes can be "swept over" in an attentive way. Notice how even the lack of sensation is something the mind can be aware of. This constant and sustained investigation is called mindfulness (sati) and is one of the primary tools of Insight Meditation.
I lost a lot of my meditation bookmarks when an online bookmarking site I used went under, so I'm still finding stuff. Oh, I have PDFs on my computer from an old hard-drive where I found some, too. I'll look those up.
More later.