When I feel the feedback, I become the master of the step - vibration and sense of agency EEG ERP N100 Sense of Agency
When I feel the feedback, I become the master of the step - vibration and sense of agency
EEG ERP N100 Sense of Agency
First-Person Consciousness:
What I call “agency” in my body
I feel a sense of agency when my body says: “I did that.” This happens when what I predicted I would feel matches what I actually felt after my movement. If there is a lack of feedback (or if it feels strange), I make the gesture… but I don't feel the "closure" of the gesture.
What they did to me (the experiment)
I performed a simple stepping task (lifting my dominant leg and placing it back down). The movement was detected by pressure insoles. While I was doing this, I received "artificial" feedback in two ways:
vibration (a vibromotor on the dominant arm)
sound (a tone in the headphones, on the dominant side)
EEG ERP N100 Sense of Agency
And there was an important detail: sometimes the feedback seemed to be the result of my own step (self-generated), and sometimes it seemed like something external. They also manipulated the delay between me placing my foot down and the feedback arriving: 200, 500, or 800 ms.
How they measured whether I “felt that it was me”
They used three methods:
EEG (ERP N100) as an implicit measure (the body "shows" it before I can explain it).
Temporal interval estimation (I said how much time seemed to have passed between the step and the feedback).
Agency questionnaire (I said whether it seemed that I caused and controlled the sound/vibration). What happened in my brain (the main finding)
In the EEG, the N100 changed when the feedback was self-generated versus externally generated. This is the brain distinguishing: "this came from me" vs. "this came from outside."
And there was a subtle and very useful point:
In sound, the classic pattern appeared: attenuated N100 for self-generated stimuli.
In vibration, they saw the opposite: increased N100 for self-generated stimuli.
I interpret this as follows: vibration "pulls" my brain closer to the body and may require more attention (or be "closer" to the movement) — so the signal doesn't need to decrease as in sound; it can increase.
What didn't appear (and why this is important)
They didn't see strong effects on interval estimation (the "perceived time") nor on explicit measures (questionnaire) in the way the N100 showed.
For me, this is a simple lesson:
my body signals "it's me" before my narrative can explain it.
Direct link to "completeness of movement" and anergy
When I move and receive feedback that matches my gesture, I feel a closed loop: intention → action → return. This strengthens agency.
Now imagine someone with sensory loss (neuropathy, amputation, etc.). The body makes the gesture, but the feedback is weak or absent. Then the movement may remain "incomplete" — and this, in our vocabulary, is the kind of thing that turns into anergy (adjustments that start but don't finish). This article suggests that vibrotactile feedback can help restore this closure, because the brain truly differentiates "mine" vs. "external" when the vibration is well coupled to the action. What I would take as a design rule (very practical):
If I'm building a prosthesis, exoskeleton, or sensory replacement, I keep this in mind:
Vibrotactile feedback can generate a neural signal of agency (N100) even when people cannot clearly report it.
So the N100 becomes an objective "meter" to validate whether the feedback is truly closing the movement loop.
BrainLatam questions for the next step:
If I customize the vibration (intensity and location) for each body, does the N100 become more stable and does agency increase? (the text itself mentions individual differences).
Which delay (200/500/800 ms) provides a better "sense of closure" when the movement is more complex (real gait, stairs, exoskeleton)?
If I measure RMSSD + EEG, can I see when the person leaves the optimal state (Zone 2) and loses agency before it turns into a functional error?
