Neural Correlates for Intrinsic Motivational Deficits of Schizophrenia; Implications for Therapeutics of Cognitive Impairment

Abstract

The ultimate goal of the treatment of schizophrenia is recovery, a notion related to improvement of cognitive and social functioning. Cognitive remediation therapies (CRT), one of the most effective cognition enhancing methods, have been shown to moderately improve social functioning. For this purpose, intrinsic motivation, related to internal values such as interest and enjoyment, has been shown to play a key role. Although the impairment of intrinsic motivation is one of the characteristics of schizophrenia, its neural mechanisms remain unclear. This is related to the lack of feasible measures of intrinsic motivation, and its response to treatment. According to the self-determination theory (SDT), not only intrinsic motivation, but extrinsic motivation has been reported to enhance learning and memory in healthy subjects to some extent. This finding suggests the contribution of different types of motivation to potentiate the ability of the CRT to treat cognitive impairment of schizophrenia. In this paper, we provide a review of psychological characteristics, assessment methods, and neural correlates of intrinsic motivation in healthy subjects and patients with schizophrenia. Particularly, we focus on neuroimaging studies of intrinsic motivation, including our own. These considerations are relevant to enhancement of functional outcomes of schizophrenia.

Keywords: cognitive remediation therapy; intrinsic motivation; lateral prefrontal cortex; neuroimaging; schizophrenia; self-determination theory; social functioning; striatum.

Figure 1

(A) Representation of motivation in self-determination theory (SDT). This figure modified from Ryan and Deci (22). (B) Representation of motivation based on SDT in patients with SCZ. This shows data from Gard et al. (38) applied to the continuum in SDT.

Figure 2

(A) The stopwatch (SW) task. (B) The differences in IMI-SR between SW and WS tasks showed a significant between-group difference. (Mann–Whitney U-test, error bar: SEM, ^*p < 0.05). (C) In HC, the neural activity in LPFC was positively and significantly correlated with the index of intrinsic motivation, whereas not in SCZ. (Pearson, ^*p < 0.0125, n.s.: not significant). (D) Comparison of the performance level following the Overshoot between SCZ and HC. There was a significant main effect of Post-Overshoot (Success vs. Undershoot vs. Overshoot) (p < 0.001), and a significant interaction between Post-Overshoot and Group (SCZ vs. HC) (p = 0.01). The secondary analysis for each Post-Overshoot trial revealed a significant main effect of group for Success (p = 0.01) and Undershoot (p = 0.01). These figures modified from Takeda et al. (54).