Deciphering decision making: exploring the interactions between neural and neurochemical systems underlying the evaluation versus employment of cognitive effort in rats

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Most of the key decisions that determine our economic success involve the choice between something easy that provides lower returns, or something difficult that, should we succeed, provides great reward. Understanding how our brains make such decisions is one of the primary goals of the academic disciplines of cognitive and behavioural neuroscience. A lot of useful information is obtained from studying the decision making of healthy volunteers in laboratory-based games, but it is often hard to determine whether relationships observed between, say, brain activity and choice patterns indicate that a brain region is causing someone to act a certain way, or simply correlates with behavior. By translating these games into behavioral tasks for non-human animals, such as laboratory rats, it is possible to directly test the strength of causal relationships between brain regions and decision making, as it is possible to temporarily shut down neural activity in a particular brain region with incredible precision and control. Furthermore, it is possible to determine what kinds of brain chemicals are involved in decision making by giving rats different drugs, such as purified forms of cannabis, and evaluating whether such compounds really do alter cognition, and over what kind of timescale. Are the effects present right away, and how do they change if the drugs are given repeatedly? ******To try and answer such questions, we have developed the rat cognitive effort task (rCET). In this task, rats choose whether to perform an attentionally demanding task, in which they have to correctly spot a very brief light stimulus, or an easier task, in which the light is turned on for longer and is therefore easier to locate. Correct performance of a more difficult option leads to a greater amount of reward. Interestingly, there are marked individual differences in the degree to which animals select the harder trials, leading to the classification of animals as either “workers” or “slackers”. This classification is independent of animals' ability to perform the hard or easy trials i.e. both workers and slackers are just as good at detecting the visual target, regardless of how difficult that is. Therefore, it would appear that willingness to exert cognitive effort is distinct from, and can vary regardless of, the ability to perform a more effortful task. We now want to use this behavioral game for rats to figure out which brain regions and brain chemicals regulate decision making, and what drugs that alter willingness to work actually do to the neurons inside the brain to produce their behavioral effects (do they activate certain brain areas, or reduce cell-to-cell communication?) In the long term, we want to find out if we can tell what makes some rats naturally more likely to choose harder, but more rewarding options, and some to want to “slack off”. These are the goals of this research program.