Why don’t you make an effort? Computational dissection of motivation disorders and treatments

Apathy can be defined as a reduction of
goal-directed behavior. It is frequently observed in
psychiatric and neurological diseases, and presently
assessed using clinical questionnaires. To
understand the neural dysfunction underlying
apathy, it is necessary to decompose this syndrome
into elementary computational processes. A key
motivational process is the arbitrage between costs
and benefits: apathy can result either from
hyposensitivity to potential rewards or from
hypersensitivity to potential efforts. In this talk, I
will present behavioral paradigms that implement
the conflict between effort and reward in humans,
the crucial feature being that payoff is proportional
to the energy expended. As suggested by
model-based analyses of neuroimaging and patient
studies, such a paradigm might provide some
insights into the brain mechanisms underlying
normal and deficient motivation, as well as
treatment effects. For instance, dopamine agonists
appeared to enhance reward attractiveness,
whereas serotonin reuptake inhibitors seemed to
alleviate effort cost.