Pilot study: Stress‐induced noradrenergic activity as potential indicator for practice effects — Association between acute stress, noradrenaline response and practice effects

Abstract

AbstractBackgroundStress has both enhancing and impairing influences on memory performance. Interestingly, aging has been associated with changes in the stress system as well as a decline in memory performance. Reductions in memory practice effects have gained interest as a risk factor for future cognitive decline, yet research on how stress influences practice effects in older individuals is scarce. Considering the age‐related changes in the stress systems, it is conceivable that exposure to stressors may facilitate the identification of individuals with an absence or attenuation of practice effects.MethodA total of thirty healthy individuals aged 40‐70 years old were subjected to a pattern separation memory task with and without an acute cognitive stressor before encoding. Several salivary alpha amylase (SAA) samples were obtained at different time points as a proxy of noradrenaline activity. Using the change scores on the memory task, we divided participants in learners (exhibiting practice effects) and non‐learners (Figure 1A). Spearman correlation coefficients were calculated to examine the relation between practice effects and SAA levels. Subsequently, an age by SAA interaction on practice scores was explored with a linear model for SAA levels at all time points.ResultIn the entire group, higher baseline SAA levels correlated to worse practice effects (r s= ‐0.46, p=0.02) while controlling for age. The non‐learners showed significantly higher SAA scores at all time points compared to learners (table 1). The learners demonstrated a significant interaction between age and SAA levels after encoding (b=0.02, t=4.35,p=0.0019) on pattern separation difference scores controlled for SAA baseline levels (Figure 1B). No such interaction was observed for non‐learners (b=0.0009, t=0.56, p=0.6; Figure 1C).ConclusionThese results show that elevated baseline noradrenaline activation is associated with the absence of practice effects. Additionally, in learners practice effects were observed in middle‐aged individuals with relatively lower levels of noradrenergic activity. These findings suggest that noradrenergic system activation may be a promising indicator of imminent cognitive decline. Future research is needed to understand variability in noradrenaline activation and practice effects over the adult age span.