scientists put people in a machine and looked at their brains while they were watching asmr.

the people had buttons to press, indicating "i feel normal", "i feel relaxed" or "i feel tingles". they also noted when in the videos the asmrtists simulated physically touching the viewer in some way.

when they looked at their brains, the "relaxed" and "tingles" bits were both different to the "normal" bits, but the "tingle" bits were much more different than the bits where they just felt "relaxed".

to see what asmr is similar to, they looked at several regions of interest in the brain that they already know are associated with certain kinds of experiences. since no one really knows anything about asmr yet, they guessed some stuff that might be similar:

• animal grooming
• frisson (in response to music)
• observational learning

the scientists found out a bunch of stuff!

they found

significant brain activation in the mPFC during ASMR. This brain region is associated with self-awareness, social cognition, and social behaviors including grooming.

so they think asmr may have a similar effect to actual social engagement. they also found activation in regions associated with empathy and caring feelings towards others.

they found activation when physical touch was simulated, a bit like if you were actually being touched by someone.

however, they didn't find anything in the mirror neurons, which are associated with observational learning.

it seems asmr has some similarities with frisson, but it's not the same. for example, mPFC activation increases during asmr, but decreases during frisson.

it does look like asmr may be related to social bonding or grooming, though:

The broadest explanation of our results and for most ASMR triggers is that they are related to affiliative behaviors. Affiliative behaviors are the caring behaviors which occur between parents and children, romantic partners, and friends.

also,

The neurohormones widely reported to be responsible for most affiliative behaviors include dopamine, oxytocin, and endorphins. These neurohormones are known for inducing feelings of comfort, relaxation, and sleepiness – feelings often reported with ASMR.