Amazing stuff! A very clever experiment! Unfortunately, only EEG but not fMRI was used for these experiments.
"Being acutely aware of every single action we take would be overwhelming, which is why our brains can go into “autopilot” during rote or mundane tasks like driving. In a new study, Yale scientists examined what happens in the brain during these moments — and settled a 130-year-old scientific dispute in the process."
"A new ... study ... is the first to examine the brain signals that determine whether we're conscious of our own actions as we perform them and resolves a debate that has persisted for more than 130 years.
A century-old debate: How the brain handles awareness
In the late 19th century, psychologists William James, MD, and Wilhelm Wundt, MD, staked out opposing theories of action awareness. James believed it comes after an action, through sensory feedback. Wundt argued it arises from the brain's act of planning and initiating movement, before any sensation occurs. The debate went unresolved because no one had a method to test it.
But ... more than a century later, had an idea. His solution was to adapt the sliding block puzzle game Rush Hour, in which players move toy cars and trucks around to create a path for one main car to exit the puzzle. ...
For the study, ... had participants play the game while simultaneously watching background videos they were told to memorize. Periodically, the game paused and asked them to identify their last move and rate their confidence. Correct answers with high confidence were deemed "aware." Incorrect answers with low confidence were labeled "unaware." ...
The researchers measured brain activity with electroencephalography (EEG) across 67 participants as they completed the task. They found that brain signals differed between aware and unaware moves both before and after the action.
A motor-planning signal called the pre-movement positivity was stronger in aware trials. A sensory processing signal called the N140, tied to awareness of bodily sensation, was also enhanced. Neither alone was sufficient.
"It turns out James and Wundt were both right," ... "Both the volition- and the perception-related signals are bigger when we're aware of what we do."
The study also found a third factor neither theorist had anticipated: As participants worked deeper into the session, pupil diameter shrank—a proxy for dwindling alertness—and awareness declined in lockstep. ...
The lab's next step is functional magnetic resonance imaging (fMRI), which will offer better spatial resolution to untangle some of the study's remaining puzzles, including how signals deep in the brain not reachable by surface EEG may contribute to awareness. ..."
From the abstract:
"Awareness of action (AoA), or conscious awareness of an action just performed, is an important part of daily experience with major practical and ethical relevance, yet the neural mechanisms of AoA remain largely unknown. The main barrier to studying AoA is a lack of experimental paradigms to directly compare neural activity in aware versus unaware actions.
Borrowing from the field of perceptual awareness, where exciting progress has been made by contrastive analysis of aware versus unaware stimuli, we developed a game where participants repeatedly perform nearly identical moves while engaged in a distractor task, and the participants then report awareness or unawareness of the moves they just performed.
We found that on short timescales, aware actions had larger neurophysiological signals both preceding and following movement. The differences included both volitional and perceptual event-related potentials (premovement positivity, N140, and P300), as well as frontal midline theta, event-related alpha/beta desynchronization, and postmove blink rates.
On longer time scales, we identified a novel positive event-related potential only preceding unaware moves and found behavioral and pupillometric evidence for decreased attention and arousal over minutes concurrent with AoA loss.
Our findings reveal three neural mechanisms that may synergistically contribute to AoA:
(i) long-term increases in arousal/attentional state at time of action;
(ii) increased action-related motor volitional signals; and
(iii) increased action-related sensory perceptual signals.
Deeper understanding of AoA may ultimately elucidate the causes of variable AoA in daily life and lead to better treatments for impaired AoA in neuropsychiatric disorders."
Neural mechanisms of awareness of action (open access)
Figure 1 Experimental design and definition of aware and unaware trials.
Figure 2Larger volitional and perceptual event-related potentials for aware actions. Event-related potentials relative to move confirmation on the Rush Hour game for aware and unaware moves (n = 57 participants). A, B) Premovement positivity (PMP).
