A recent paper (citation below) reports that conscious intent precedes motor preparation activity, and not that motor preparation is well underway before consciousness registers intent. Here is Zschorlich and Köhling conclusion:
“Motor intention (intention in action) describes a process of motor preparation without executing an overt movement. In our study, we explored the link between motor intention in the movement preparatory phase and the motor outcome. The experiments present evidence that the excitability of the agonistic motor system is significantly enhanced when subjects develop an intention to move. The opposite was true for the antagonistic movement direction and muscles. The results presented indicate
that the excitatory cortico-spinal drive is enhanced during directed motor intention. The data shows that movement intention induced during the enhancement of the cortico-spinal pathway was significantly greater than in the no-intention condition, which argues for the movement-specific modulation of cortico-spinal excitability. The results support the hypothesis that conscious intention to move induces the enhancement of target-specific motor circuits prior to overt movement execution. ”
But Neuroskeptic in a recent blog (here) casts doubt on the finding:
“The authors, Zschorlich and Köhling of the University of Rostock, Germany, are weighing into a long-standing debate in philosophy, psychology, and neuroscience, concerning the role of consciousness in controlling our actions. To simplify, one school of thought holds that (at least some of the time), our intentions or plans control our actions. Many people would say that this is what common sense teaches us as well. But there’s an alternative view, in which our consciously-experienced intentions are not causes of our actions but are actually products of them, being generated after the action has already begun. This view is certainly counterintuitive, and many find it disturbing as it seems to undermine ‘free will’. That’s the background. Zschorlich and Köhling say that they’ve demonstrated that conscious intentions do exist, prior to motor actions, and that these intentions are accompanied by particular changes in brain activity. They claim to have done this using transcranial magnetic stimulation (TMS), a way of causing a localized modulation of brain electrical activity….As far as I can see, volunteers could simply have been pressing the TMS button and then moving their wrist of their own accord. Ironically, they might not have consciously intended to do this; they might have really believed that their movements were being externally triggered (by the TMS) even though they themselves were generating them. This can happen: it’s called the ideomotor phenomenon, and is probably the explanation for why people believe in ‘dowsing’ amongst other things.”
Neuroskeptic points out that this possibility could be tested by simply having some of the TMS events be fakes – ie there would be no TMS field on some occasions but the participants would not know this. Either the real and fake TMS events would give the same result (an ideomotor indication) or they would give different results (ideomotor improbable). This was not done.
I had a problem with this paper before I read Neuroskeptic’s useful suggestion. And I have had the same problem with many other papers. In the second paragraph of the introduction they say, “The central question of how the conscious motor intention is connected to complex motor programs still remains unclear. ” I have, always have had, a difficulty with what ‘conscious motor intention’ is supposed to mean. It very obviously does not happen to me. I am conscious, I act, I have intentions – all well and good. But the intentions I am conscious of come fully formed, they ‘pop’ from nowhere (ie they are formed unconsciously). So conscious motor intention can mean one of a number of things: an intention made by some conscious process (never happened to me nor have I found an actual description of how it happened to someone else), an intention that is not made by any sort of process at all and is then rendered conscious (very unbelievable mechanics), or an intention that is made by an unconscious process and is then rendered conscious (a reasonable idea, not a counterintuitive one to me, that the Zschorlich paper purports to disprove). My complaint is that Zschorlich et al have not put forward an alternative that can be believed. Nor have others. It could not be simpler – if I am not conscious of an actual process then it is not a conscious process. This is an old problem for me and one of the reasons I have taken such an interest in consciousness.
Zschorlich VR, & Köhling R (2013). How thoughts give rise to action – conscious motor intention increases the excitability of target-specific motor circuits. PloS one, 8 (12) PMID: 24386291