An experiment separates the threads of consciousness and action
One of the deepest sources of supernaturalism is the mystery of consciousness- the sense that our soul/spirit is so unmaterial, shiny, and pure that it could not possibly be sullied with evolutionary origins, messy neurological mechanisms, and eventual death. There is an undeniable and to some an unbridgeable tension between this remarkable experience and its rather obvious dependence on our brains.
One expression of this tension is the doctrine of "free will", which has two senses. One theological dilemma is, if god is so good and powerful, why are we not His obedient automata? Because He gave us free will, with which to be bad and yet also with which to worship Him, if we are smart, because he likes to be freely loved, not slavishly obeyed. Related to this theodicy is the second sense of free will- that our inmost soul yet still partakes somehow in the divine to the extent that it is immaterial, has a smidgen of moral knowledge (often ignored), and is eternal, even if, looking backward, it has its origin in a mysterious and divine implantation process concomitant with sperm and egg intromission.
At any rate, we feel free in our actions, while at the very same time physics tells us that no action happens without causes- causes that would obviate the felt authorship of our actions. The answer in scientific terms is to posit an "illusion of free will", where our actions, when not obvious responses to conscious exigencies, are caused by unconscious promptings which simultaneously arise in consciousness as 1: the idea which "pops" into one's head to move one's arm, and 2: the action itself, activated in parallel. In this scheme, our actions all have causes, just not always causes we are aware of. And the sense of authorship is a fiction conjured simultaneously as the actual causes activate planning and action.
The motor areas of the brain are known to form a crescent across the top midline from ear to ear, where past experiments have generated a "homunculus", or map of body parts moved by stimulating brain locations in this region. A completely separate sensory homunculus maps bodily sensations to brain locations, and is not involved in this work.
A group in France experimented on seven patients getting brain surgery for other reasons, stimulating the surfaces of their brains to figure out how actions arise and how they are perceived. Stimulation in the areas shaded purple below, which are in the motor area, caused body parts to move, but without any cognition that the person had caused the action, that they had wanted to cause the action, or indeed that the action had taken place at all.
Conversely, stimulation in the areas shaded yellow and orange below (the volitional field) caused patients to experience urges to begin an action, and at higher levels of stimulation, even the sensation they had carried out an action, though none had actually taken place. One patient, stimulated with 5 mA at site a in the figure, said "I felt a desire to lick my lips", while at 8 mA at the same location was quoted "I moved my mouth and talked, what did I say?" (Doubtless these quotes are translations from the French!) No action took place, however, and electrical EMG recording of the corresponding muscles gave no trace of any activity, confirming that the feeling the patients had was not connected to their bodies.
Locations of experimental stimulation, in the motor area (purple) and volitional area (orange, yellow), also called Broca areas 39 and 40. The SMA lies slightly forward of the motor area.
Of these two fields, the motor field is easier to understand. The output end of the process could be followed down the spinal chord and even to the muscles with electrical stimulation, creating actions authored by the experimenter rather than by the patient, who would have no sense of volition. The paper mentions that lesions in this area of the brain are sometimes associated with "patients who obstinately claim that they can move their paralyzed limbs." This paralysis is not physical but due to a disconnect between volition, which is intact, and motor execution, which is not. Additionally, the paralysis is not apparent to the patient, indicating that, as the paper hypothesizes, perception of action is more dependent on the internal sense of volition, which assumes as a matter of course that an action has taken place as planned, than on feedback from the body, surprisingly enough.
Tracking down the sense of will and authorship is more interesting. A consistent model is that a normal action engages a more extensive network of brain activity, of which only tiny portions were activated in these experiments. One terminus of a consciously or unconsciously generated action is the motor areas that actually control their fulfillment (purple), but another terminus elsewhere (yellow, orange) creates the consciousness first of wanting to do the action, and if intense enough, of having performed it. This second area may later integrate sensory feedback to enhance the sense of authorship and allow learning, but based on these experiments, this feedback is not critical to a sense of authorship, matching the conclusion of Wegner. The volitional area maps closely to the mid-brain regions that were pointed out in a recent blog to be the best guess for those responsible for consciousness.
There is another area adjacent to the motor field, called the supplemental motor area (SMA), where others have done experiments of this type. Here, electrical stimulation generates both what is sensed as an urge to perform an action contrary to one's will, and also, at higher currents, the action itself. The key distinction is that here, the urge is recognized to be contrary to the patient's will (as happens in various tic and involuntary movement syndromes), while stimulating the volitional area creates such will directly, without generating the action. The SMA may be a preparatory area for motor action, placed after the unconscious originating signal has separated between paths to the motor area and to the volition/will/feedback area, but still having partial input to non-volitional consciousness.
The bottom line is that the sense of authorship is conjured in an area of the brain that doesn't actually cause the action, but is a post-processing epiphenomenon. This sense is essential to learning, to a coherent sense of self, and to moral responsibility, but it is not causally essential. Given that the causes of action are often "reflex", or "spontaneous", or otherwise unconscious, it would require impossible circular logic to have our sense of authorship be mechanistically equivalent to actual authorship.
- Philosophy bites podcast does neuroscience- the senses, blindsight, mirror neurons, alienation, anarchic hand, bodily coherence, etc.
- New Yorker profiles neuroscientist Vilayanur Ramachandran, who deals with paralysis and other neurological oddities.
- Science mag review of above paper.
- Feminist atheist activist ... Taslima Nasreen
- Supernaturalism explained, and podcast.