Marcel Brass’ group has published a very wide ranging and interesting article on volition (citation below). They look at what fMRI results have shown (and not shown) on a number of questions regarding how volition works in the brain. Near the end of the paper they outline their own model of the progression of stages from goals to actions.
Here is their figure 1: Brain regions in the medial frontal cortex that have been implicated in human volition. SMA supplementary motor area, preSMA pre-supplementary motor area, RCZ rostral cingulate zone, dmPFC dorsomedial prefrontal cortex, vmPFC ventromedial prefrontal cortex
And here is their section on the funnel model:
Based on the research outlined above, we propose an extension of the WWW model (whether, what, when) of intentional action. This extension assumes that intentional action follows a kind of funnel-like organization that is related to an anterior-posterior gradient within the medial frontal cortex. It is, however, crucial to note that while this model focuses on the role of the mPFC (medial prefrontal cortex) in intentional action, we assume that areas in the lateral pre-frontal cortex, subcortical regions, and parietal regions are involved in intentional control of action as well.
Our model assumes that early stages of intentional action are related to anterior prefrontal brain regions. These brain regions process complex and heterogeneous information that is only broadly determined by specific task instructions or goals. Processing in these brain regions provide a sort of
informational background, or intuition, and has a biasing function towards later processing stages. This complex set of information is funnelled when information travels more posteriorly and enters later stages of intentional action. Regions in the RCZ (rostral cingulate zone) are related to choices between different response options. Such choices are biased by bottom-up information but also by concrete instructions that operate as a top-down influence and thus are a result of the interplay between top-down and bottom-up processing. Furthermore, the RCZ determines the level of effort that is invested in pursuing a specific behaviour and thus regulates the ‘willpower’ that is invested in a specific choice. When a specific response option is selected, this information is transferred to brain areas more closely related to the motor system, namely SMA/PreSMA (supplementary motor area/pre-supplementary area). Here, the impulse to initiate a specific response is generated. At this point in the processing stream, it is still possible to disengage from the intention to act or to change the intended behaviour. Intentional inhibition is achieved by a signal from the dorso-medial prefrontal cortex that down-regulates activation in the SMA/preSMA. As a working hypothesis, we assume that the subjective experience of volition results from supra-threshold activation in brain circuits that are involved in the control of intentional action. Such subjective experiences are phenomenologically rich because they can be related to any level of the processing stream, ranging from intuitive feelings to concrete urges to act.
The funnel-like organization of human volition guarantees that choices are based on a broad scope of information. At the same time, it also ensures that we can choose very quickly and efficiently when necessary. Whether our choices are primarily determined by intuitions and introspective thoughts, or by explicit deliberation and task instructions, strongly depends on the specific task context and the time
frame of our choices.
Brass M, Lynn MT, Demanet J, & Rigoni D (2013). Imaging volition: what the brain can tell us about the will. Experimental brain research. Experimentelle Hirnforschung. Experimentation cerebrale, 229 (3), 301-12 PMID: 23515626