Arousal increases neural gain via the locus coeruleus–noradrenaline system in younger adults but not in older adults

In younger adults, arousal amplifies attentional focus to the most salient or goal-relevant information while suppressing other information. A computational model of how the locus coeruleus–noradrenaline system can implement this increased selectivity under arousal and a functional magnetic resonance imaging (fMRI) study comparing how arousal affects younger and older adults’ processing indicate that the amplification of salient stimuli and the suppression of non-salient stimuli are separate processes, with ageing affecting suppression without affecting amplification under arousal. In the fMRI study, arousal increased processing of salient stimuli and decreased processing of non-salient stimuli for younger adults. By contrast, for older adults, arousal increased processing of both low- and high-salience stimuli, generally increasing excitatory responses to visual stimuli. Older adults also showed a decline in locus coeruleus functional connectivity with frontoparietal networks that coordinate attentional selectivity. Thus, among older adults, arousal increases the potential for distraction from non-salient stimuli.