Expectancy modulates pupil size during endogenous orienting of spatial attention

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Psychophysiology

Background:

• fMRI studies show right temporal-parietal junction (TPJ) deactivation correlates with cue predictiveness during spatial attention.
• The right TPJ receives noradrenergic (NE) innervation, suggesting TPJ activity changes may reflect NE system fluctuations.
• Previous findings imply different NE activity levels during orienting with predictive versus non-predictive cues.

Purpose of the Study:

• To investigate if cue predictiveness during voluntary spatial attention orienting modulates noradrenergic (NE) activity.
• To test the hypothesis that varying levels of cue predictiveness correspond to distinct NE activity levels.

Main Methods:

• Measured pupil dilation, an indirect index of NE activity, in healthy humans.
• Participants performed voluntary spatial attention tasks using highly predictive (80%) or non-predictive (50%) cues.
• Analyzed pupil dilation changes during baseline-fixation and cue periods across blocks of trials.

Main Results:

• A progressive decrement in baseline pupil dilation was observed across trial blocks, consistent with LC-NE system tonic activity.
• Predictive cues elicited significantly greater pupil dilation compared to non-predictive cues.
• Non-predictive cues showed a duration-dependent increase in pupil size reduction.

Conclusions:

• Changes in cue predictiveness during spatial attention orienting are paralleled by changes in pupil dilation.
• These findings support the hypothesis that pupil dilation reflects, and is modulated by, the activity of the Locus Coeruleus-Norepinephrinic system (LC-NE).
• Cue predictiveness influences NE activity, impacting attentional orienting mechanisms.