
==== Front
Schizophr Res Cogn
Schizophr Res Cogn
Schizophrenia Research: Cognition
2215-0013
Elsevier

S2215-0013(24)00026-X
10.1016/j.scog.2024.100325
100325
Article
Abnormal hedonic process in patients with stable schizophrenia: Relationships to negative symptoms and social functioning
Zhou Qi a1
Zheng Yue b1
Guo Xiaodong b
Wang Yi cd
Pu Chengcheng b
Shi Chuan shichuan@bjmu.edu.cn
b⁎
Yu Xin yuxin@bjmu.edu.cn
b⁎
a The Affiliated Brain Hospital of Nanjing Medical University, Nanjing, China
b Peking University Sixth Hospital, Peking University Institute of Mental Health, NHC Key Laboratory of Mental Health (Peking University), National Clinical Research Center for Mental Disorders (Peking University Sixth Hospital), Beijing, China
c Neuropsychology and Applied Cognitive Neuroscience Laboratory, CAS Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
d Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
⁎ Corresponding authors at: Peking University, Institute of Mental Health, Huayuanbeilu 51, Haidian District, Beijing, China. shichuan@bjmu.edu.cnyuxin@bjmu.edu.cn
1 These authors have contributed equally to this work.

24 8 2024
12 2024
24 8 2024
38 10032516 4 2024
13 8 2024
19 8 2024
© 2024 The Authors. Published by Elsevier Inc.
2024

https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Background

Anhedonia is a deficit of dynamic reward process, and a large proportion of schizophrenia patients continue to experience anhedonia even during the stable phase. However, few studies have examined the multiple aspects of performance in reward processing in patients with stable schizophrenia and evidence suggests that physical and cognitive effort may involve different neural mechanisms.

Methods

Parallel measures of effort-based expenditure for reward tasks (EEfRT) and self-report questionnaires of pleasure were applied in 61 patients with stable schizophrenia (SSZ) and 46 healthy controls (HCs), and percentages of hard task choices (HTC%) were used to assess motivation in reward processing. Negative symptoms, neurocognitive and social function were evaluated in SSZ patients, and associations with performance in reward tasks were explored.

Results

SSZ patients reported more severe consummatory and anticipatory anhedonia and social anhedonia. HTC% in reward tasks of SSZ patients were significantly lower than that of HCs, especially in cognitive-effort tasks. HTC% in cognitive tasks were correlated with motivation and pleasure dimension of negative symptoms, whereas HTC% in physical tasks were associated with expression dimension. Anticipatory anhedonia and negative symptoms were correlated with Personal and Social Performance Scale (PSP) scores.

Conclusion

Patients with stable schizophrenia have social anhedonia, physically consummatory and anticipatory anhedonia and reduced reward motivation. They are less willing to make cognitive effort than physical effort for reward. The different associations of physical and cognitive effort with negative symptoms indicate physical and cognitive effort may represent disparate neuropsychological processes. Anticipatory anhedonia is closely related to social functioning.

Keywords

Schizophrenia
Anhedonia
Negative symptoms
Cognition
==== Body
pmc1 Introduction

Schizophrenia is a severe mental disorder and brings a significant burden on society (Marder and Cannon, 2019). Negative symptoms are major characteristics and greatly influence the functional outcomes (An der Heiden et al., 2016; Correll and Schooler, 2020). Anhedonia is defined as a loss of interest and traditionally recognized as a part of negative symptoms in schizophrenia. Yang et al. (2021b) reported that anhedonia influences social function and predicts occupational outcome. However, the problem seems to be more complicated than previously thought. Clinical studies have revealed that hedonic processes have different correlations with negative symptoms (Chan et al., 2010).

The understanding of anhedonia has been continuously enriched. Kring and Barch (2014) summarized the reward processing model, depicting it as a dynamic process associated with stimulus-reward. The reward process consists of interest, anticipation, motivation, effort, hedonic response and feedback integration. It is closely correlated with cognitive function (Wang et al., 2019) and the destruction of any process may lead to anhedonia.

Multiple behavioral tasks have been devised based on effort-cost decision-making (ECDM), which refers to mental process of deciding whether to make an effort to obtain rewards. Abnormal ECDM is considered an important cause of motivational deficit, which is an intermediate process of anhedonia (Culbreth et al., 2018). In recent years, at least two effort types (physical and cognitive effort) have been identified, and animal studies suggest that neural mechanisms of reward motivation and decision-making may differ across effort (Hosking et al., 2015).

A recent meta-analysis revealed that schizophrenia patients commonly exhibit anhedonia (Krzyzanowski et al., 2022). Regarding various domains of anhedonia, most studies suggest that anhedonia in schizophrenia is related to anticipatory deficits (Kring and Barch, 2014; Gard et al., 2006; Gard et al., 2007). However, studies have shown that both consummatory and anticipatory anhedonia exist (Li et al., 2015). Hence, it has been proposed that anhedonia in schizophrenia patients is better defined as apathy or amotivation rather than a mere decline in the ability to experience pleasure. Several behavioral studies have demonstrated that schizophrenia patients exhibit an impaired ability to learn reward information (Saperia et al., 2019; Fervaha et al., 2013). Therefore, schizophrenia patients may have problems in parts of the reward system, and anticipatory anhedonia may be a stable manifestation.

According to a recent meta-analysis of ECDM (Blouzard et al., 2023), schizophrenia patients are likely to make fewer hard task choices across conditions, and the magnitude of motivation deficit is significantly greater for high-reward and high-probability trials. However, it does not distinguish effort types. Although a generalized deficit across effort modalities has been found in schizophrenia (Culbreth et al., 2023), only a moderate correlation was observed. To date, Effort-Expenditure for Rewards Task (EEfRT) paradigms involve physical effort requiring key pressing (Treadway et al., 2015; Whitton et al., 2020; Treadway et al., 2009), while cognitive effort is mostly used in progressive ratio tasks or discounting tasks (Wolf et al., 2014; Culbreth et al., 2020; Chang et al., 2020), indicating that they are not completely parallel. Furthermore, contradictory results concerning correlation between reward motivation and negative symptoms have been found (Huang et al., 2016; Wolf et al., 2014; Yang et al., 2021a; Chang et al., 2019). Therefore, negative symptoms are related to anhedonia, but different dimensions of negative symptoms may play different roles. The correlation between dimensions of negative symptoms and ECDM performance has not been further explored and may explain the discrepancy.

In this study, we evaluated dimensions of anhedonia in patients with stable schizophrenia (SSZs) from perspectives of self-reports and behavioral experiments. We hypothesized that SSZs would exhibit more severe anticipatory anhedonia and reduced reward motivation, while still experience intact consummatory pleasure. The effort tasks in this study needed participants to make a series of choices between completing a low-effort/low-reward (“easy”) or high-effort/high-reward (“hard”) task. The physical and cognitive effort tasks were designed relatively parallelly and we compared the performance between SSZs and healthy controls (HCs) under different effort types. For the SSZs, we compared performance of cognitive and physical effort tasks and explored the correlation between negative symptoms, social function and task performance.

2 Methods and materials

2.1 Participants

The participants consisted of 61 SSZs and 46 HCs. All the participants were 18–45 years old, with an estimated Intelligence Quotient (IQ) >70. Individuals with current major medical conditions were excluded. All patients were recruited from outpatient clinic of Peking University Sixth Hospital. The inclusion criteria also included: 1) a diagnosis of schizophrenia based on Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5); 2) currently in stable condition according to Positive and Negative Syndrome Scale (PANSS) (Kay et al., 1987) score of <60 with no change in treatment for at least 4 weeks; and 3) no obvious extrapyramidal or depressive symptoms (Rating Scale for Extrapyramidal Side Effects (RSESE) score < 3 and Calgary Depression Scale for Schizophrenia (CDSS) score < 6). Patients with diagnoses of other mental disorders; a history of drug or substance abuse in the past 6 months; presence of a history of brain trauma, epilepsy or other central nervous system disorders; or who received modified electric convulsive therapy within 6 months were excluded. HCs were excluded if they met any criteria for mental disorders, were taking psychotropic medications, or had a family history of mental disorders in first-degree relatives. Written informed consent was obtained. The trial complied with the Declaration of Helsinki and was approved by the ethics committees of Peking University Sixth Hospital.

2.2 Materials and measurements

All participants were screened by Mini International Neuropsychiatric Interview (MINI, Version 7.0) (Sheehan et al., 1998).The severity of clinical symptoms was assessed by PANSS. Negative symptoms were measured by CAINS, and Motivation and Pleasure (MAP) and Expression (EXP) scores were derived from the subscales. The CDSS (Addington et al., 1993) and RSESE (Morosini et al., 2000) were used to measure depressive and extrapyramidal symptoms. The self-administered measures consisted of Temporal Experience of Pleasure Scale (TEPS) (Gard et al., 2006) and Chapman Social Anhedonia Scale (CSAS) (Chapman et al., 1976; Chan et al., 2012). The TEPS consists of two subscales measuring consummatory (TEPS-CON) and anticipatory (TEPS-ANT) pleasure physically, while CSAS was used to evaluate social pleasure. Cognitive function and social function were measured by Chinese Brief Cognitive Test (C-BCT) (Ye et al., 2022) and Personal and Social Performance Scale (PSP) (Morosini et al., 2000), respectively.

2.3 EEfRT task

All participants performed a modified version of physical- and cognitive-EEfRT, requiring subjects to choose between a low-effort, low-reward (easy) and a high-effort, high-reward (hard) task. Both tasks consisted of 18 trials, and each trial proceeded in the same order (Fig. 1). The easy trial offered ¥0.5, and the hard trial offered ¥0.8 or ¥5 for successful completion. Whether to get the reward depended on three probability levels (20 %, 50 % or 80 %) based on the successful completion. Each reward magnitude and probability were presented three times for each type of EEfRT.Fig. 1 Schematic representation for a single trial of “EEfRT”.

A. See a 1s fixation cue; B. choice period in which participants are presented with information rewarding the reward magnitude of the task for the trial, and the probability of receiving the reward with no time limit; C. 1s “ready” screen; D. participants make rapid key presses in 4 s with their right index fingers or left little fingers (or judge the easy 1-back task or the difficult 2-back task where each number appears for 500 ms and followed by a 1500 ms reaction window); E. participants receive feedback on whether they have completed the trial; F. participants receive reward feedback as to whether they received reward for the trial.

Fig. 1

Calibration trials were conducted to confirm the success criterion individually. In physical task, participants were encouraged to press a key with the dominant index finger or nondominant little finger as fast as possible within 4 s three times. In cognitive task, we applied a number variant N-back working memory task. The N-back task needed participants to view an item pre-randomized list of numbers, and respond “yes” or “no” to indicate whether the number presented was the same as the N items earlier in the sequence. The one- and two-back difficulty levels were used for the easy and hard trials, respectively. Participants were encouraged to perform the best accuracy and ignorant of the purpose of calibration.

In formal trials, 50 % and 80 % of the key presses or accuracy of n-back achieved in the calibration trials were considered successful for the easy and hard tasks, respectively. It took approximately 20 min. The percentage of hard task choices (HTC%) in physical tasks (pHTC%) and cognitive tasks (cHTC%) represented the motivation to expend effort.

2.4 Data analysis

Data analyses were conducted in SPSS version 24.0. All antipsychotic drugs were converted to chlorpromazine equivalents (CPZs). Independent sample t-tests, Mann-Whitney U tests, analyses of variance and Fisher's exact tests were used to compare demographic, cognitive and hedonic data between SSZs and HCs. Repeated measures analysis of variance was used to explore factors affecting motivation between groups under different reward conditions in EEfRT tasks. Correlation analysis was used to explore associations of components of anhedonia with clinical characteristics. Regression analyses were further used to analyze factors influencing reward motivation and social functioning. All the statistical tests were 2-tailed, and a p value <0.05 was used to indicate statistical significance.

3 Results

3.1 Characteristics of participants

The socio-demographics, neurocognitive function and hedonic function of SSZs and HCs are summarized in Table 1. There were no group differences in age, sex, education levels, smoking or drinking status, while SSZs had a lower proportion of employment, lower C-BCT scores, lower subscale scores of TEPS and higher scores of CSAS. Among the patients, mean onset age was 21.44 ± 5.40 years, mean duration of disease was 7.71 ± 5.06 years, and mean PANSS score was 44.69 ± 7.70. The means and standard deviations of CAINS and PSP were 22.97 (9.30) and 73.20 (9.73), respectively (Supplementary Table S1).Table 1 Sociodemographic, neurocognitive and hedonic characteristics between schizophrenia patients and healthy controls.

Table 1	SSZ
(n = 61)	HC
(n = 46)	χ2/t/Z	p	
Age, years	29.10 ± 6.00	28.24 ± 6.81	0.692	0.491	
Sex (male, n, %)	23(37.7 %)	19(41.3 %)	0.142	0.706	
Education, years	16.00(14.50–16.00)	16.00(14.75–16.00)	−0.264	0.792	
Employment (unemployed, n, %)	32(52.5 %)	4(8.7 %)	22.497	<0.001	
BMI, kg/m2	26.08 ± 4.54	22.67 ± 3.37	4.276	<0.001	
TEPS	80.92 ± 15.56	91.37 ± 11.62	−3.821	<0.001	
TEPS-CON	41.62 ± 8.69	48.26 ± 6.81	−4.281	<0.001	
TEPS-ANT	35.07 ± 8.17	38.57 ± 5.47	−2.648	0.009	
CSAS total	12.83 ± 6.76	7.04 ± 3.51	5.742	<0.001	
C-BCT total	47.07 ± 4.50	51.68 ± 3.52	−5.729	<0.001	
- TMT-A	47.15 ± 3.38	49.57 ± 2.73	−3.970	<0.001	
- Symbol coding	44.48 ± 6.80	52.67 ± 9.80	−5.108	<0.001	
- CPT	47.84 ± 6.20	52.24 ± 3.33	−4.720	<0.001	
- Digit span	48.80 ± 8.15	52.15 ± 6.20	−2.324	0.022	
Abbreviations: SSZ, patient with stable schizophrenia; HC, healthy control; BMI, body mass index; TEPS, The Temporal Experience of Pleasure Scale; TEPS-CON, consummatory anhedonia subscale of TEPS; TEPS-ANT, anticipatory anhedonia subscale of TEPS; CSAS, Chapman Social Anhedonia Scale; C-BCT, The Chinese Brief Cognitive Test; TMT-A, Trail Making Test, Part A; CPT, Continuous Performance Test.

3.2 Performance in the EEfRT tasks

3.2.1 Calibration performance and completion rates

In calibration section, SSZs performed worse than HCs in both easy and hard tasks. Both SSZs and HCs performed better in easy tasks (Supplementary Table S2 and Table S3). In physical tasks, there was no difference in completion rates between groups (easy task: Z = -0.883, p = 0.377; hard task: Z = -1.237, p = 0.216). In cognitive tasks, SSZs had lower completion rates in easy tasks (Z = -2.109, p = 0.035), but there was no difference in hard tasks (Z = -1.842, p = 0.065) (Supplementary Table S4).

3.2.2 Group difference in motivation to expand effort

The repeated-measures ANOVA was used to examine effects of different types and groups on hard task choice. Box's test of equal within-group covariance was significant (Box's M = 167.96, p < 0.001); as a result, Pillai's trace criterion was used to describe within-subjects effects. Results showed that the main effect of effort type was significant (p < 0.001), whereby participants chose more hard tasks in physical tasks than in cognitive tasks. The main effect of group was significant (p < 0.001), in which HCs chose more difficult tasks than SSZs. The main effects of reward magnitude and probability were also significant (p < 0.001), and participants preferred hard tasks with increasing reward magnitude and probability. There was a significant interaction effect between effort type and group (p = 0.003), indicating that difference in hard task choices between physical and cognitive tasks was more pronounced in SSZs. There was also a significant interaction effect between reward magnitude and group (p = 0.025), suggesting that HCs chose more hard tasks as reward magnitude increased compared to SSZs (Fig. 2).Fig. 2 Group differences of motivation to expand effort. (a) Percentage of hard task choice across effort types; (b) percentage of hard task choice across reward magnitudes; (c) percentage of hard task choice across reward probabilities. Abbreviations: SSZ, patients with stable schizophrenia; HC, healthy control; HTC%: percentage of hard task choice. Values were expressed as mean ± standard error; ⁎⁎p < 0.01; ⁎⁎⁎p < 0.001.

Fig. 2

3.3 Correlations between reward motivation and clinical characteristics of SSZs

In physical tasks, HTC% was correlated with onset age, MAP, EXP, TEPS-ANT and CPT performance (Supplementary Table S5). However, no similar correlations were found in HCs (Supplementary Table S6). Logistic regression analysis showed that a higher EXP score was an unfavorable factor for hard task selection (Table 2). In cognitive tasks, HTC% was associated with onset age, duration, MAP, EXP, TEPS-ANT and CPT performance (Supplementary Table S5). Logistic regression analysis revealed that older onset age and a higher MAP score were unfavorable factors for hard task selection in cognitive tasks (Table 2).Table 2 Linear regression analyses of the factors influencing reward motivation of patients with schizophrenia.

Table 2Reward motivation	Clinical factors	B(95 % CI)	SE	β	t	p	
p-HTC%	EXP	−3.995(−6.698–1.291)	1.315	−0.359	−2.957	0.004	
c-HTC%	Age of onset	−2.233(−3.417–1.049)	0.592	−0.420	−3.417	<0.001	
	MAP	−1.155(−2.005–0.306)	0.424	−0.303	−2.722	0.009	
Abbreviations: p-HTC%, percentage of hard task choice in physical tasks; c-HTC%, percentage of hard task choice in cognitive tasks; MAP, Motivation and Pleasure; EXP, Expression.

3.4 Predictors of social functioning

Correlation analysis revealed that PSP scores were mildly to moderately associated with education level (r = 0.435, p < 0.05), MAP (r = −0.731, p < 0.05), EXP (r = −0.635, p < 0.05), global cognitive function (r = 0.346, p < 0.05), CPZs (r = 0.324, p < 0.05) and hedonic process (TEPS-CON: r = 0.363, p < 0.05; TEPS-ANT: r = 0.500, p < 0.05; CSAS: r = −0.335, p < 0.05; pHTC%: r = 0.263, p < 0.05; cHTC%: r = 0.254, p < 0.05). Furthermore, regression analysis showed that anticipatory anhedonia (B = 0.270, 95 % confidence interval [CI] 0.088 to 0.453, p = 0.004) was an independent predictor of social function, and both MAP and EXP dimensions (MAP: B = -0.564, 95 % CI -0.792 to −0.336, p < 0.001; EXP: B = -1.104, 95 % CI -1.742 to −0.465, p = 0.001) were involved in social function outcomes (Table 3).Table 3 Linear regression analyses of predicted factors on social function of patients with schizophrenia.

Table 3Variables	B(95 % CI)	β	t	p	Adjusted R2	
MAP	−0.564(−0.792–0.336)	−0.436	−4.960	<0.001	0.697	
EXP	−1.104(−1.742–0.465)	−0.297	−3.463	0.001		
Educational level	0.785(0.255–1.316)	0.222	2.966	0.004		
TEPS-ANT	0.270(0.088–0.453)	0.227	2.964	0.004		
Abbreviations: TEPS-ANT, anticipatory anhedonia subscale of the Temporal Experience of Pleasure Scale; MAP, Motivation and Pleasure; EXP, Expression. Included variables: educational level, MAP score, EXP score, global cognitive function, CPZ equivalent, TEPS-CON, TEPS-ANT, CSAS, pHTC%, cHTC%.

4 Discussion

We evaluated self-reported anhedonia and motivation to expand physical and cognitive effort in clinically stable patients with schizophrenia and explored the associations between performance in ECDM and negative symptoms, as well as social function. Three major findings emerged from our analysis. First, SSZs exhibited social anhedonia, physically consummatory and anticipatory anhedonia and decreased motivation. Second, reduction in effort expenditure for reward was more pronounced in cognitive tasks. Third, motivation to exert physical effort for reward was related to diminished expression, while motivation to exert cognitive effort was associated with motivation and pleasure. Anticipatory anhedonia and negative symptoms were found to be independent predictors of social function.

4.1 Reward processing in SSZs

A recent meta-analysis indicated that schizophrenia patients have anhedonic symptoms. However, findings regarding specific dimensions have been inconsistent. Yu et al. (2020) found both consummatory and anticipatory pleasure were impaired, aligning with our results. However, Strauss et al. (2011) proposed that patients with stable medication use retain intact anticipatory pleasure but experience reduced consummatory pleasure. The clinical stage and specific psychiatric symptoms may influence self-rated anhedonia. We recruited clinically stable patients with mild to moderate positive symptoms and thought disorders, ensuring reliable self-assessment results. The use of antipsychotic drugs may have a certain effect on patients' pleasant experience (Scheggi et al., 2015; Scheggi et al., 2018). Under regular treatment, the patients in this study still had consummatory and anticipatory anhedonia. However, further follow-up studies are needed to confirm whether anhedonia is partly caused by antipsychotics.

Current research has consistently proposed the existence of an “anhedonia paradox”(Strauss and Cohen, 2018) in schizophrenia, which means that there is consummatory anhedonia in young patients with a schizoid personality and prodromal schizophrenia, but schizophrenia patients retain an intact capacity for pleasure (Gruber et al., 2018; Cohen et al., 2012). Contrary to our hypothesis, consummatory anhedonia was also observed. One possible explanation is that SSZs face greater realistic pressure when they recover from the disease. Self-reports of pleasure may be more grounded in actual experience, as studies have confirmed lack of goal-directed behavior (Barch et al., 2016). This defect may result in a lack of pleasant situations in real life, leading to a lower level of consummatory pleasure.

This study reveals decreased reward motivation in SSZs. Similar to the previous study (Barch et al., 2014), patients were less willing to put forth effort, and it indicated that as reward increased, reward motivation of patients did not increase correspondingly, and they did not make optimal choices. Overall, these findings highlight deficits in reward motivation and decision-making among schizophrenia patients.

The difference in performance between patients and HCs suggests that motivational deficit in SSZs is more prominent concerning cognitive effort. However, this has not been observed in patients with other mental disorders (Tran et al., 2021). In addition, the discrepancy in correlation between reward motivation in different tasks and clinical symptoms, further suggests that neurobiological basis for different effort types may be at least partially separated, as supported by the results of previous animal experiments (Hosking et al., 2015; Schmidt et al., 2012).

Results suggested that motivation to exert effort for reward was related to anticipatory anhedonia and attention, while this was not observed in HCs, which contradicted the results of Barch et al. (2014). Distinguishing between reward processes related to anhedonia is likely to contribute to the difference. The absence of this association in HCs could be attributed to their minimal experience of anhedonia and cognitive deficits. Cooper et al. (2019) employed the paradigm of effort-based decision-making and discovered that motivation to exert effort was linked to cognition but limited to reasoning. Conversely, McCarthy et al. (2016) did not find a similar correlation. The inconsistency of cognitive assessments and variations in patient populations may contribute to this inconsistency. Attention scores may reflect motivation to some extent. Consequently, patients with higher motivation tend to pay more attention during the test, resulting in better performance on attention task.

4.2 Influencing factors of reward motivation in SSZs

Notably, influencing factors of reward motivation in different effort types were not consistent. Evidence has demonstrated that physical effort-based reward motivation is closely related to negative symptoms (Barch et al., 2014; Treadway et al., 2015); furthermore, McCarthy et al. (2016) found that motivation to expend effort was only associated with expression dimension. Consistent with above results, our results indicated the relevance of physical effort-based motivation and expression dimension. Moreover, correlations between cognitive effort-based motivation and motivation and pleasure dimension were found in our study, enriching the existing results. Physical effort may require additional physical activity, and expression dimension mainly manifests as decreased speech and activity. Therefore, physical effort seems to cover the symptoms of communication and expression, while cognitive effort simply reflects the performance of motivation and pleasure. Interestingly, early onset age may be a protective factor against cognitive effort-based motivation. A 10-year follow-up study revealed that the functional outcome of early-onset schizophrenia patients was more optimistic than commonly thought (Xu et al., 2020). And early-onset schizophrenia patients may have to bear financial burden of chronic disease treatment at an early stage, leading to considerable loss of social income (Hakulinen et al., 2019). It is plausible that these patients would attach greater significance to same monetary reward, thereby displaying a greater willingness to obtain more financial compensation.

4.3 Predictors of social function

Previous studies (Hu et al., 2022; Yang et al., 2021b; Best et al., 2020) highlighted the significance of negative symptoms for social function, with some related research (Hu et al., 2022) emphasizing the importance of the motivation and pleasure, which is consistent with our results. Moreover, our study showed contribution of expression dimension to social function. A previous study (Buck and Lysaker, 2013) found that anticipatory pleasure could predict interpersonal function. This finding suggested that multiple components of hedonic process were associated with social function, although only anticipatory anhedonia emerged as a predictive factor. Driven by anticipatory pleasure, patients may have greater motivation to engage in social activities, including person-to-person interactions, ultimately leading to improved social functioning.

Several limitations should be acknowledged. First, experiment-based reward tasks in this study involved only monetary reward tasks. The motivation for receiving financial rewards may be affected by the economic and social status, which was not collected in this study. Moreover, there are other kinds of rewards, such as social rewards and the measurement is limited to laboratory, which is not completely consistent with real situation. Therefore, further research is warranted to clarify the cofounding factors involved. Second, although our analyses revealed no significant correlations between antipsychotic dose and effort task performance, as previous studies have reported that antipsychotics may influence motivation (Kirschner et al., 2017; Mosolov and Yaltonskaya, 2021), we cannot rule out the effect of a dopamine D2-receptor antagonist on the reward process. Prospective studies of the reward process in drug-naïve patients following antipsychotic treatment are needed to clarify the influence of medication and changes in the course of illness.

In conclusion, clinically stable patients with schizophrenia exhibit multiple aspects of anhedonia, including social anhedonia, physically consummatory anhedonia, physically anticipatory anhedonia and reward motivation. The EEfRT behavioral task effectively captures the reward motivation defect in schizophrenia patients, highlighting patients' reduced willingness to invest cognitive effort compared to physical effort. These effort types appear to have distinct neural mechanisms and impact patients differently. Anticipatory anhedonia may serve as a predictor of social function.

Funding

This study was financially supported by 10.13039/501100001809 National Natural Science Foundation of China (grant Nos. 82171500 , 82071509 ).

CRediT authorship contribution statement

Qi Zhou: Writing – original draft, Methodology, Formal analysis, Data curation, Conceptualization. Yue Zheng: Writing – original draft, Investigation, Conceptualization. Xiaodong Guo: Investigation, Data curation. Yi Wang: Methodology, Conceptualization. Chengcheng Pu: Data curation, Conceptualization. Chuan Shi: Writing – review & editing, Funding acquisition. Xin Yu: Writing – review & editing, Supervision, Project administration, Funding acquisition.

Declaration of competing interest

The authors declare that the research was conducted in the absence of any conflict of interest.

Appendix A Supplementary data

Supplementary tables

Image 1

Appendix A Supplementary data to this article can be found online at https://doi.org/10.1016/j.scog.2024.100325.
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