The exact mechanisms as to how the dominating reward effects of CIs emerge and

The exact mechanisms as to how the dominating reward

This preview shows page 9 - 10 out of 12 pages.

The exact mechanisms as to how the dominating reward effects of CIs emerge and interfere with the re- ward value of social engagement in ASD are, however, yet unclear. When CIs are indeed rewarding, their pur- suit may be strengthened through self-reinforcement that turns them into rigid habits [ 45 ]. The self- reinforcing character of RRBIs, like CIs, may hijack the normal developmental trajectories of entire repertoires of behaviors, including social ones. We suggest that the caudate nucleus in concert with other frontolimbic structures [ 46 ] may dominate the formation and main- tenance of RRBIs. On a daily basis, RRBIs hinder social development and functioning because they absorb resources typically dedicated to social learning oppor- tunities [ 4 ]. This view converges with recent evidence demonstrating the role of the caudate nucleus, as part of a cortico-striatal-thalamo-cortical loop [ 47 ], in CIs as well as compulsive and ritualistic behaviors in individ- uals with ASD across different age groups [ 42 , 48 51 ]. While we could demonstrate robust neural activation differences between ASD and TDC for CI rewards ver- sus social rewards in dorsal striatum, other brain regions that have previously been related to CIs did not emerge in our study (i.e., ventral striatum/Nacc and vmPFC [ 15 ] as well as ACC and insula [ 14 ]). Despite our specific finding of an imbalance of caudate nucleus responsive- ness in ASD, we acknowledge that CIs are not limited to a single anatomical correlate, but are mediated by vari- ous distinct yet interacting subcortical and cortical systems [ 1 , 47 ]. Follow-up studies are warranted to bet- ter define how different subcomponents of reward processing and their neural correlates contribute to the emergence of and adherence to CIs. Incentive delay tasks, such as the one applied here, can principally be used to test reward learning, reward anticipation and re- ward valuation as three crucial reward components to consider with regard to CIs and the responsiveness to other conventional rewards in ASD [ 2 ]. While each re- ward component has been associated with some distinct (and some interrelated) neural correlates [ 52 ], recent hu- man research highlights, however, the difficulty to effect- ively decompose the neural signals of the various components within a single experimental paradigm (see for a discussion on this issue, [ 53 ]). Thus, we foresee that refined inventories of specifically tailored reward measures preferably grounded in preclinical studies and adequately validated in humans will benefit this line of research. Importantly, future fMRI investigations need to con- trol more strictly for multiple comparisons at the whole- brain level. This will help avoiding high degrees of false positive findings and, thus, will ensure that neuroimag- ing results particularly between-group findings are more reliably reproduced. In the present study, we implemented most recent recommendations from the literature using whole-brain cluster thresholding that rigorously controls type I errors [ 32 ]; this could also
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