The Influence of Noradrenergic Activity on Attentional Control in Younger and Older Adults
Conditions: Aging
Sponsor: University of Southern California

 
 
 
 
Title of Study: The Influence of Noradrenergic Activity on Attentional Control in Younger and 
Older Adults 
NCT number: 05120713 
Date: September 3rd, 2024 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Study Protocol 
Increased distractibility is a hallmark of aging and dysregulated processing in the 
brain (Li et al., 2001; Weeks & Hasher, 2014). The noradrenergic system plays important 
roles in modulating attention, memory, and decision processes and recent neuroimaging 
findings suggests that older adults have abnormal tonic noradrenergic discharge (Elman et 
al., 2017; Zhang et al., 2016). Importantly, elevated tonic noradrenergic activity reduces 
phasic noradrenergic discharge to task-related information (Aston-Jones & Cohen, 2005), 
which together may stimulate progression of neurodegenerative diseases (Janitzky, 2020). 
Thus, understanding the mechanisms by which noradrenergic activity and dysregulation 
modulates age-related distractibility is a critical need in preventing cognitive decline. For 
example, it is yet unclear whether noradrenergic hyperactivity or hypoactivity mediates 
cognitive behavioral impairments such as attentional control. We will increase or decrease 
tonic noradrenergic activity and investigate the behavioral and neural effects on attentional 
control. The threat-of-shock paradigm has previously been utilized to investigate the 
effects of induced negative arousal on attention (Kim & Anderson, 2020a, 2020b; Kim et al., 
2021a) and importantly has demonstrated neural evidence of high tonic noradrenergic 
activity (Balderston et al., 2017). Thus, we will utilize the threat-of-shock paradigm to 
investigate the consequences of elevating tonic noradrenergic discharge. We will utilize 
two different types of visual search tasks. The first visual search task will be adapted from 
Gaspelin et al. (2017). Participants will be asked to search for a specific shape (e.g., 
diamond) among different shapes (e.g., square, circle, hexagon). The second visual search 
task will be adapted from Kim & Anderson (2020b). Participants will be asked to search for 
a unique shape (e.g., circle among diamonds or diamond among circles) among the visual 
search array. Both visual search tasks are designed to have the participant search for a 
target while trying to ignore other non-target stimuli. On some trials, a distractor stimulus 
may be included that can be physically salient (e.g., different color or shape) or associated 
with a valent outcome (e.g., reward). Participants will be informed of the presence of 
feedback (if included in the task), but will not be informed of the specific stimulus-
outcome pairings, which must be learned in the task. The consequence of this learning on 
distraction will then be examined when previously outcome-predicting stimuli are 
presented as task-irrelevant stimuli that participants try to ignore. If stimuli are not 
associated with any outcome, there will be no feedback provided on that trial (e.g., 
physically salient distractor stimuli).  
Statistical Analysis Plan 
Mixed ANOVA (MANOVA) analyses were conducted with age as a between-subjects factor 
and all other measures as a within-subjects measure. To determine if the threat of shock 

differentially modulated the oculomotor suppression effect by, we conducted a 2x2 
MANOVA over factors age (young vs. older) and intervention (no shock vs. shock).