You wrote:
There is simply no escape: without a supernatural soul, humans are tied down by the laws of physics. We are reduced to automatons, and the implications of this are far-reaching. Showing this to the atheist is a very good way to begin to take the roof off their false worldview.
I see no problem with this. I am an atheist and I don’t think that I have free will.
But where does consciousness originate? Well, most scientists believe that it is an emergent property of the brain. It’s safe to say that there’s more than one “master switch” for consciousness. For example, Blumenfeld (2014) reviewed and described a very interesting experiment conducted by Koubeissi et al. (2014):
During cortical mapping of a patient undergoing intracranial EEG and video monitoring, the authors stimulated a single-electrode contact and produced behavioral unresponsiveness and amnesia. The electrode was located in the region of the left extreme capsule adjacent to the anterior dorsal insula and claustrum. The effect was seen in 10 of 10 stimuli at 14 mA, and stimuli consisted of 3- to 10-s 50-Hz brief square wave pulses, using a medial frontal electrode as reference (stimulation between the medial frontal contact and other electrodes produced no behavioral change). During stimulation, the patient stared blankly and did not respond to commands. After the stimulus, the patient immediately returned to baseline with no recall of events during stimulation and no recall of words presented during stimulation. Stimulation also produced arrest of reading; however, the patient could continue repetitive hand or tongue movements for up to 4 s after stimulus onset.
Blumenfeld concludes that the claustrum may represent “a new potentially critical hub in the network of consciousness.” This does not mean that consciousness originates there. But it is clear that consciousness is governed by the activity of the brain.