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

Abstract

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-norepinephrine (LC-NE) system can implement this increased selectivity under arousal and an 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 aging affecting suppression without impacting amplification under arousal. In the fMRI study, arousal increased processing of salient stimuli and decreased processing of non-salient stimuli for younger adults. In 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 decline in LC functional connectivity with frontoparietal networks that coordinate attentional selectivity. Thus, among older adults, arousal increases the potential for distraction from non-salient stimuli.

Noradrenergic responsiveness preserves selective attention across the adult life span

“…On the physiological level, we observed a multimodal response to the arousal 918 manipulation during fear (re)conditioning in younger and older adults. In particular, 919 compared to perceptually matched control stimuli (CS-), conditioned stimuli (CS+) 920 elicited a sustained dilation of the pupil, as previously reported (e.g., Lee et al, 2018). In 921 line with recent animal work linking LC activity to pupil dilation, we thus conclude that 922 our manipulation successfully activated the LC-NE system in younger and older adults 923 (Rasmussen and Jacobs, 1986;Szabadi, 2012;Uematsu et al, 2017;Deitcher et al, 2019).…”

“…The inter-218 trial-interval (ITI; white fixation cross) was set to 6 s to allow sufficient time for the 219 pupil to return to baseline in CS+ trials (cf. Lee et al, 2018). The conditioning phase 220 consisted of 20 CS+ and 20 CS-trials that were presented in pseudorandomized order.…”

Noradrenergic-dependent functions are associated with age-related locus coeruleus signal intensity differences

“…The LC-NA system plays an integral role in several autonomic, cognitive, and behavioral functions via connections with widespread areas of the brain and spinal cord 1,2 , including wakefulness, pupillary control, anxiogenesis, attention, decision-making, and memory 3 . In vivo T1-or MT-weighted magnetic resonance imaging (MRI) studies have previously associated LC signal intensity (a measure of LC structural integrity) or functional activation with measures of emotional memory 4 , emotional regulation/reactivity 5 , inhibitory control 6,7 , executive function 8,9 , sleep quality 10,11 , episodic memory 12 , heart rate variability (HRV) 13 , oddball processing 14 , and attentional selectivity 15,16 .…”

MatherArousalAgingChapter2019

“…Phasic pupil responses are associated with LC activity (Joshi, Li, Kalwani, & Gold, 2015), and interestingly, in middle-aged men, reduced phasic pupil responses during working memory were associated with greater tonic low frequency BOLD variance during a restingstate fMRI scan in key nodes of the ventral attention network (Elman et al, 2017). Greater tonic activity in ventral attention network in older adults may also help explain why arousing circumstances such as expecting an electric shock are less effective at increasing ventral attention network activity and less likely to increase coordination with LC activity than seen in younger adults (Lee et al, 2018).…”