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.