Actions and habits: The relation between cognitive control and behavioural autonomy

When one comes to a difficult task, such as learning to drive a car, for the first time, each action you perform seems to require tremendous mental effort, and sequencing appropriate actions together (mirror, signal, manoeuvre) even more so, especially whilst you are performing some other task, such as changing gear. However, over time and with practice, you become able to perform each of these tasks seemingly effortlessly, with little apparent interference between them; now you can change gear, change lanes and hold a conversation with your passenger. Tasks that were once almost impossible, and that took all your attention to perform, become simple, and are performed without much conscious thought or dedicated attention. This project examines the different brain systems that underpin this transition between the mentally challenging, effortful production of responses that each require your full attention, and the fluid, reflexive production of habits that comes with experience. There is good reason for these two systems to exist / if we were all required to devote our full attention to all the tasks we perform, we would have little time or attention left to think about anything else / it is only because we can learn to perform tasks habitually and without effort that we free up our mental resources for learning about new events and concentrating on things that are important to us. At the same time, we need to have a way of concentrating our mind to allow us to override habits / just because we usually drive one route to work, and traverse that route almost without thinking, doesn't mean we should be incapable of varying that route if we know there are going to be roadworks. Recent evidence from non-human animals and humans suggests that we do indeed possess two systems of this sort. The proposed research will examine in detail the way in which different parts of the brain participate in the two systems. In particular, we will examine the involvement of two regions of the brain that seem to be involved. One, known as the prefrontal cortex, is the part of the brain that is most well developed in humans relative to other animals, and is often thought to be the region that allows us to control and plan our actions, and make decisions about what we want to do. The second is an evolutionarily more ancient region of the brain known as the striatum, and this is thought to be involved in basic response learning processes that then need control and direction, perhaps from the prefrontal cortex. What we want to know is how are different areas of these two regions involved in tasks when they are mentally-demanding and when they subsequently become habitual. At the same time, we also want to know if there is competition between these systems, and if this competition is the same sort of competition one experiences when trying to do two things at once (such as patting one's head and rubbing one's stomach). Finally, we want to find out what features of a task, and our experience with it, allow us to make the transition from effortful to habitual control (and back) / despite what is commonly thought, recent evidence suggests that it is not simple repetition of an action that leads to habit formation. Rather, the transition to habits seems to depend on the relationship between an action and the consistency with which that action produces a certain outcome. This work will not only inform us about the mental and brain processes that allow us to function normally, but is also important in relation to a variety of mental disorders in which processes governing our voluntary and habitual responses are disrupted. These include obsessive-compulsive disorder, Tourette syndrome, and, of course, habitual processes known to be important in drug-addiction.

The ability to learn to perform purposive, goal-directed actions endows animals with a highly beneficial degree of behavioural flexibility in the face of ever-changing environmental conditions. However, this voluntary control of performance comes with a price in terms of effortful control and monitoring of the response, frequently reducing the capacity for alternative cognitive processing. One way in which animals can come to balance the twin desire for simplicity and flexibility is through the development of habits. A venerable research history documents the notion that an initially effortful and cognitively-demanding response comes, with practice, to be produced fluidly and without difficulty. This view is reflected in the development of two-process theories of behavioural responding that depends on both mechanistic, reflexive stimulus-response (S-R) habits (either acquired or innate) and on actions that are voluntary and goal-directed. The project proposed will use rats to examine the neural substrates of goal-directed and habitual responding, contrasting a goal-directed circuit involving the prelimbic prefrontal cortex, (posterior) dorsomedial striatum and basolateral amygdala, with a habitual circuit comprising infralimbic prefrontal cortex, dorsolateral striatum, and potentially the central nucleus of the amygdala. Further experiments will examine the involvement of these circuits in another situation where there is competition between alternative response systems using a recently developed response conflict task that pitches alternative instrumental responses against one another. Finally, we will use a novel virtual maze environment to examine the role of habitual and goal-directed systems in the control of proximal and distal instrumental responses, to examine the role of uncertainty in the transition between these systems, and to examine the exploration vs. exploitation trade-off in the development of novel instrumental response sequences.