title: Fatigue modulates dopamine availability and promotes flexible choice reversals during decision making.
abstract: During decisions, animals balance goal achievement and effort management. Despite physical exercise and fatigue significantly affecting the levels of effort that an animal exerts to obtain a reward, their role in effort-based choice and the underlying neurochemistry are incompletely known. In particular, it is unclear whether fatigue influences decision (cost-benefit) strategies flexibly or only post-decision action execution and learning. To answer this question, we trained mice on a T-maze task in which they chose between a high-cost, high-reward arm (HR), which included a barrier, and a low-cost, low-reward arm (LR), with no barrier. The animals were parametrically fatigued immediately before the behavioural tasks by running on a treadmill. We report a sharp choice reversal, from the HR to LR arm, at 80% of their peak workload (PW), which was temporary and specific, as the mice returned to choose the HC when the animals were successively tested at 60% PW or in a two-barrier task. These rapid reversals are signatures of flexible choice. We also observed increased subcortical dopamine levels in fatigued mice: a marker of individual bias to use model-based control in humans. Our results indicate that fatigue levels can be incorporated in flexible cost-benefits computations that improve foraging efficiency.
authors.affiliation: Institute of Cognitive Sciences and Technologies, National Research Council, Via San Martino della Battaglia 44, 00185, Rome, Italy.
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Iodice
authors.affiliation: Department of Pharmacy, University G. d'Annunzio of Chieti, via dei Vestini 31, 66013, Chieti, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Ferrante
authors.affiliation: Department of Pharmacy, University G. d'Annunzio of Chieti, via dei Vestini 31, 66013, Chieti, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Brunetti
authors.affiliation: University Sapienza, Dept. Psychology, Centro D. Bovet, 00185, Rome, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Cabib
authors.affiliation: CeSI-Met - Center for Research on Ageing and Translational Medicine & DNICS - Department of Neuroscience, Imaging and Clinical Sciences, University G. d' Annunzio of Chieti, Chieti, 66100, Italy.
authors.forename: Feliciano
authors.initials: F
authors.lastname: Protasi
authors.affiliation: Department of Experimental Psychology, University of Oxford, Oxford, UK.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Walton
authors.affiliation: Institute of Cognitive Sciences and Technologies, National Research Council, Via San Martino della Battaglia 44, 00185, Rome, Italy. giovanni.pezzulo@istc.cnr.it.
authors.forename: Giovanni
authors.identifier: http://orcid.org/0000-0001-6813-8282
authors.initials: G
authors.lastname: Pezzulo
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002755:Choice Behavior; D003216:Conditioning, Operant; D003657:Decision Making; D004298:Dopamine / Q000378:metabolism*; D005221:Fatigue / Q000378:metabolism* / Q000523:psychology*; D005260:Female; D018782:Maze Learning; D051379:Mice; D012701:Serotonin / Q000378:metabolism
chemical_list: D012701:Serotonin; D004298:Dopamine