| Abstract/Results: | ABSTRACT:
Noradrenaline is a neuromodulator that acts by changing how the neurons respond to incoming input. It is produced in the locus coeruleus, a small brainstem nucleus, and is released throughout the brain1. Yet, it is not clear if the impact of noradrenaline release on the different brain areas is relatively constant, for example enhancing cortical excitability2, and functional connectivity3, or if its impact is modulated by the demands of the task at hand. In this study, we addressed this question by probing noradrenergic function using pupil diameter as a proxy for noradrenergic activity levels, in a group of young adults (n=32; age=23±3 years). Simultaneously, we acquired the electroencephalogram (EEG) to investigate how noradrenergic activity relates to cortical processes. We used two warned auditory tasks, a simple reaction time (RT) task requiring fast responses, and a go/no-go task requiring inhibitory control. In both tasks, a warning stimulus preceded the imperative stimuli. Baseline pupil dilation did not show a significant effect of task, yet phasic pupil dilation responses elicited by the warning stimulus were higher during the go/no-go task than the simple RT task. Notably, response speed was related to the amplitude of the pupil dilation in the simple reaction time task but not in the go/no-go task, suggesting a facilitation of motor processing in one task but not in the other. Accordingly, the contingent negative variation (CNV), a slow negative event-related potential, elicited by the warning stimulus, and related to the readiness to respond, correlated with pupil dilation only during the simple RT task. In summary, our results suggest that the relationship between pupil dilation responses, behaviour, and cortical function are task dependent. These observations indicate that the effect of noradrenaline in the brain is modulated by context, and highlight the complexity underlying the effect of neuromodulation on brain function.
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Reference:
| Ribeiro, M., & Castelo-Branco, M. (2017, August). The noradrenergic system and its relationship with cortical processing. Poster presented at the International Conference for Cognitive Neuroscience (ICON), Amsterdam, The Netherlands. Abstract retrieved at http://www.icon2017.org/program.html
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