​We measured pupil dilation (PD) in younger and older adults in an emotional memory task. Increased pupil dilation can point to a stronger engagement of the noradrenergic system (heightened arousal). Participants were shown old and new, negative and neutral pictures. A) PD was increased for negative pictures (red). The effect of negative emotionality on PD was particularly pronounced  in younger adults, as well as for new stimuli (thin line, e.g. upper right plot). B) Pupil diameter was also increased for old stimuli (thick line). Memory certainty (dark blue) modulated PD further, but only for old stimuli (thick line, e.g. upper left plot). A) and B) Older adults showed an overall reduced responsiveness in PD. Shaded error bars represent standard error (across individuals within age groups).

This suggests weaker emotional arousal responses in older adults (A), in line with their assumed weaker noradrenergic modulation. However, top-down modulated arousal responses related to memory certainty (B) were comparable between age groups. Maybe older adults can boost their weaker noradrenergic responses via a stronger top-down modulation.