Abstract
Shifting between motor plans is often necessary for adaptive behavior. When faced with changing consequences of one’s actions, it is often imperative to switch from automatic actions to deliberative and controlled actions. The pre-supplementary motor area (pre-SMA) in primates, akin to the premotor cortex (M2) in mice, has been implicated in motor learning and planning, and action switching. We hypothesized that M2 would be differentially involved in goal-directed actions, which are controlled by their consequences vs. habits, which are more dependent on their past reinforcement history and less on their consequences. To investigate this, we performed M2 lesions in mice and then concurrently trained them to press the same lever for the same food reward using two different schedules of reinforcement that differentially bias towards the use of goal-directed versus habitual action strategies. We then probed whether actions were dependent on their expected consequence through outcome revaluation testing. We uncovered that M2 lesions did not affect the acquisition of lever-pressing. However, in mice with M2 lesions, lever-pressing was insensitive to changes in expected outcome value following goal-directed training. However, habitual actions were intact. We confirmed a role for M2 in goal-directed but not habitual actions in separate groups of mice trained on the individual schedules biasing towards goal-directed versus habitual actions. These data indicate that M2 is critical for actions to be updated based on their consequences, and suggest that habitual action strategies may not require processing by M2 and the updating of motor plans.
Highlights
Adaptive behavior requires the ability to change motor plans depending on the consequence of actions
Mice included in the study showed none or only slight lesion spread into surrounding cortices (Figure 1A)
By training the same mouse to shift between performing a similar action using goal-directed versus habitual action strategies, we were able to investigate the contribution of M2 to the learning and performance of different action strategies in the same animal
Summary
Adaptive behavior requires the ability to change motor plans depending on the consequence of actions. The distinction between goal-directed and habitual actions can be seen in the different control over actions by expected outcome value following random ratio (RR) and random interval (RI) schedule training, respectively (Adams and Dickinson, 1981; Adams, 1982; Dickinson et al, 1983; Colwill and Rescorla, 1985). We investigated whether goal-directed action strategies, which require control based on changes in expected outcome value, depend on premotor cortex function. M2 is necessary for goal-directed actions outcome value We confirmed this in separate groups of M2 lesion mice trained only to make goal-directed or only habitual actions. These findings show that while goal-directed actions depend upon M2, habitual action strategies are executed independently of processing by M2 and suggest the automatic actions do not require updating of motor plans
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