Windows to the goal: Pupillary working memory signatures prospectively adapt to task demands

The pupillary light response was once considered a brainstem reflex, but newer findings indicate that pupil dilation can also reflect remembered luminance of content held "in mind" with working memory (WM). This suggests that WM may recruit even the most primary sensorimotor apparatus for maintenance. Here, we tested two boundaries of this pupillary WM response: whether it generalizes beyond low-level stimuli and whether it adapts to changing behavioral goals. Namely, we tested whether the pupils reflect remembered luminance for real-world scene images, and whether the effect varies when different features dimensions are emphasized for the memory test (i.e., visual detail vs. semantic category). We found a feature-specific pupillary WM effect for remembering natural scenes, but only when the task encouraged a visual maintenance strategy. Rather than a retrospective echo of sensory-evoked stimulus features, the pupillary WM response prospectively adapts to how the memory content will be used.