Toward an objective characterization of an anhedonic phenotype: a signal-detection approach.
BACKGROUND
Difficulties in defining and characterizing phenotypes has hindered progress in psychiatric genetics and clinical neuroscience. Decreased approach-related behavior and anhedonia (lack of responsiveness to pleasure) are considered cardinal features of depression, but few studies have used laboratory-based measures to objectively characterize these constructs.


METHODS
To assess hedonic capacity in relation to depressive, particularly anhedonic, symptoms, 62 participants completed a signal-detection task based on a differential reinforcement schedule. Anhedonia was operationalized as decreased reward responsiveness.


RESULTS
Unequal frequency of reward between two correct responses produced a response bias (i.e., a systematic preference to identify the stimulus paired with the more frequent reward). Subjects with elevated depressive symptoms (Beck Depression Inventory scores >/= 16) failed to show a response bias. Impaired reward responsiveness predicted higher anhedonic symptoms 1 month later, after controlling for general negative affectivity.


CONCLUSIONS
Impaired tendency to modulate behavior as a function of prior reinforcement might underline diminished hedonic capacity in depression. When applied to a clinical population, objective assessments of participants' propensity to modulate behavior as a function of reward might provide a powerful tool for improving the phenotypic definition of depression and thus offer a reliable behavioral screening approach for neuroscience studies of depression.
Pizzagalli
Diego A
DA
Department of Psychology, Harvard University, Cambridge, Massachusetts, USA.
Jahn
Allison L
AL
O'Shea
James P
JP
D000293:Adolescent; D000328:Adult; D000342:Affective Symptoms / Q000175:diagnosis / Q000523:psychology*; D000704:Analysis of Variance; D015982:Bias; D002605:Character; D003866:Depressive Disorder / Q000175:diagnosis / Q000523:psychology*; D019260:Expressed Emotion / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009042:Motivation; D010555:Personality Inventory; D010641:Phenotype; D011336:Probability; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D013223:Statistics as Topic