title: Apathy but not diminished expression in schizophrenia is associated with discounting of monetary rewards by physical effort.
abstract: Negative symptoms in schizophrenia have been grouped into the 2 factors of apathy and diminished expression, which might be caused by separable pathophysiological mechanisms. Recently, it has been proposed that apathy could be due to dysfunctional integration of reward and effort during decision making. We asked whether apathy in particular is associated with stronger devaluation ("discounting") of monetary rewards that require physical effort. Thirty-one patients with schizophrenia and 20 healthy control participants performed a computerized effort discounting task in which they could choose to exert physical effort on a handgrip to obtain monetary rewards. This procedure yields an individual measure for the strength of effort discounting. The degree of effort discounting was strongly correlated with apathy, but not with diminished expression. Importantly, the association between apathy and effort discounting was not driven by cognitive ability, antipsychotic medication, or other clinical and demographic variables. This study provides the first evidence for a highly specific association of apathy with effort-based decision making in patients with schizophrenia. Within a translational framework, the present effort discounting task could provide a bridge between apathy as a psychopathological phenomenon and established behavioral tasks to address similar states in animals.
authors: Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland; Laboratory for Social and Neural Systems Research, Department of Economics, University of Zurich, Zurich, Switzerland matthias.hartmann@uzh.ch.
authors: Matthias N
authors: MN
authors: Hartmann
authors: Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland; Laboratory for Social and Neural Systems Research, Department of Economics, University of Zurich, Zurich, Switzerland.
authors: Oliver M
authors: OM
authors: Hager
authors: Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland;
authors: Anna V
authors: AV
authors: Reimann
authors: Laboratory for Social and Neural Systems Research, Department of Economics, University of Zurich, Zurich, Switzerland.
authors: Justin R
authors: JR
authors: Chumbley
authors: Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland;
authors: Matthias
authors: M
authors: Kirschner
authors: Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland;
authors: Erich
authors: E
authors: Seifritz
authors: Laboratory for Social and Neural Systems Research, Department of Economics, University of Zurich, Zurich, Switzerland.
authors: Philippe N
authors: PN
authors: Tobler
authors: Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland;
authors: Stefan
authors: S
authors: Kaiser
mesh_terms: D000328:Adult; D057565:Apathy / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D011618:Psychotic Disorders / Q000503:physiopathology*; D012201:Reward; D012559:Schizophrenia / Q000503:physiopathology*
keywords: cost-benefit calculation; effort-based decision making; negative symptoms