Getting a glass of water when you’re thirsty or having a snack when you’re hungry is called goal-directed behaviour. However, when you repeat that behaviour many times the sight of water or a snack may be sufficient to eat and drink. Behaviour is then no longer driven by the goal to alleviate the hunger and/or thirst, but by the stimulus (snack, water). This is called habitual behaviour. It has been shown that in a stressful situation you no longer consume snacks because you are hungry, but because they just make you feel like eating them; behaviour shifts from goal-directed to habitual. The underlying neural processes are highly complicated but we know that there is a role for the neurotransitters noradrenaline and dopamine. However, the exact role isn’t clear.
In our recent paper, we hypothesised that higher levels of these transmitters may prevent the effects of stress. We administered methylphenidate to increase both transmitters in the brain, induced acute stress, and determined if their behaviour was predominantly goal-directed or habitual. We also assessed brain activation during behavioural performance. We have shown that stress renders behaviour slightly more habitual, but increasing levels of noradrenaline and dopamine in the brain did not reverse this effect as expected. However, activation in relevant brain areas did change following stress and was reversed to baseline after giving methylphenidate. Taken together, our experiment showed that despite the small effects, increasing noradrenaline and dopamine may prevent stress-induced changes in behaviour. This may be beneficial in situations where habitual behaviour is not favourable, like addiction.
