Elsevier

NeuroImage

Volume 210, 15 April 2020, 116560
NeuroImage

Isometric exercise facilitates attention to salient events in women via the noradrenergic system

https://doi.org/10.1016/j.neuroimage.2020.116560Get rights and content
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Highlights

  • We examined how handgrip affects subsequent arousal-attention dynamics.

  • Tonic pupil size decreased for a brief period after handgrip.

  • Salient oddball stimuli enhanced pupil dilation and were detected faster post-handgrip.

  • MRI-assessed LC structural contrast was related to oddball detection and pupil dilation.

  • LC contrast also associated with LC-frontoparietal network functional connectivity.

Abstract

The locus coeruleus (LC) regulates attention via the release of norepinephrine (NE), with levels of tonic LC activity constraining the intensity of phasic LC responses. In the current fMRI study, we used isometric handgrip to modulate tonic LC-NE activity in older women and in young women with different hormone statuses during the time period immediately after the handgrip. During this post-handgrip time, an oddball detection task was used to probe how changes in tonic arousal influenced functional coordination between the LC and a right frontoparietal network that supports attentional selectivity. As expected, the frontoparietal network responded more to infrequent target and novel sounds than to frequent sounds. Across participants, greater LC-frontoparietal functional connectivity, pupil dilation, and faster oddball detection were all positively associated with LC MRI structural contrast from a neuromelanin-sensitive scan. Thus, LC structure was related to LC functional dynamics and attentional performance during the oddball task. We also found that handgrip influenced pupil and attentional processing during a subsequent oddball task. Handgrip decreased subsequent tonic pupil size, increased phasic pupil responses to oddball sounds, speeded oddball detection speed, and increased frontoparietal network activation, suggesting that inducing strong LC activity benefits attentional performance in the next few minutes, potentially due to reduced tonic LC activity. In addition, older women showed a similar benefit of handgrip on frontoparietal network activation as younger women, despite showing lower frontoparietal network activation overall. Together these findings suggest that a simple exercise may improve selective attention in healthy aging, at least for several minutes afterwards.

Keywords

Arousal
Locus coeruleus
Neuromelanin
Oddball task
Frontoparietal attention network
Functional connectivity

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