4.2. Stress-induced modulation of SAM activation on creativity
The present study also examined the role of SAM activation in how acute stress affects creativity performance. The activation of the dopaminergic system and central noradrenergic system are the markers of SAM activation (Allen et al., 2014; Bremner et al., 1996). The mediation of SAM activation was examined via two serial modulation models, with Model 2 focusing on DA and Model 3 on NE. In such a way, we investigated how stress impairs creativity by affecting SAM activation and cognitive flexibility.
As a reliable measure of assessing DA function, we found the EBR of participants significantly increased after acute stress induction, thereby implying increased DA release. The serial mediation model indicated that stress conditions enhanced EBR, which was related to decreased cognitive flexibility and ultimately resulted in worse creative performance. The enhancement in DA levels facilitates or impairs creativity and is influenced by the concurrent effects of the increased striatal and prefrontal DA (Boot et al., 2017). The striatal DA of the nigrostriatal pathway is associated with flexible processing, while prefrontal DA and the integrity of the mesocortical dopaminergic pathway are associated with persistent processing (Boot et al., 2017). According to a recent model, the fronto-striatal network biases towards flexibility when striatal DA exceeds prefrontal DA, and the fronto-striatal network biases towards persistence when prefrontal DA exceeds striatal DA (Dodds et al., 2008). When dopaminergic activity in either the PFC or striatum is too high or low, the balance between flexibility and stability is disturbed. This is indicated by the inverted U-shaped relationship between DA levels and flexibility in divergent thinking (Chermahini & Hommel, 2010). An excessive release of DA under stress is associated with attenuated striatal activity (Kellendonk et al., 2006), which leads to the enhancement of perseverative errors and a decrease in creativity, consistent with our findings.
As we expected, the ocular results showed that participants in the stress group had significantly higher pupil dilation during acute stress induction, reflecting higher NE levels. The results also indicated that the NE levels of the participants significantly increased after the MIST task. The serial mediation model showed that the stress condition was associated with higher pupil dilation, which reduced cognitive flexibility, leading to inferior creative performance. Previous evidence suggests that NE improves the transmission of dominant neural signals while inhibiting noise to enhance vigilance and alter cognitive processing under threatening conditions (Hermans et al., 2014). According to Adaptive Gain Theory, the activity of the LC neurons can be distinguished into two modes: phasic and tonic (Usher et al., 1999). The activity of the LC neurons shifts from tonic to phasic to optimize behavior in a changing environment, which is modulated by the NE level (Guedj et al., 2017; Usher et al., 1999). This account is also consistent with findings that the effects of stress on cognitive flexibility are adjusted by antagonists of β-adrenergic receptors (Alexander et al., 2007). Evidence has shown that only a narrow range of 1–3 Hz tonic firing of LC-NE neurons would facilitate phasic firing of the LC-NE neurons, leading to optimal performance (Howells et al., 2012). This is consistent with the inverted U-shaped curve relationship between stress and creativity. When the stress-induced tonic activity of LC neurons is too high, then an individual’s attention span becomes narrow, which is detrimental to flexible switching and impairs creative thinking, otherwise the opposite is the case. By such means, stress-related NE elevation would impair cognitive flexibility, and thus reduce creativity, which is in line with our data.