RT Journal Article
A1 Naber, Marnix
A1 Frässle, Stefan
A1 Rutishauser, Ueli
A1 Einhäuser, Wolfgang
T1 Pupil size signals novelty and predicts later retrieval success for declarative memories of natural scenes
JF Journal of Vision
JO JOV
YR 2013
DO 10.1167/13.2.11
JF Journal of Vision
VO 13
IS 2
SP 11
OP 11
SN 1534-7362
AB   Declarative memories of personal experiences are a key factor in defining oneself as an individual, which becomes particularly evident when this capability is impaired. Assessing the physiological mechanisms of human declarative memory is typically restricted to patients with specific lesions and requires invasive brain access or functional imaging. We investigated whether the pupil, an accessible physiological measure, can be utilized to probe memories for complex natural visual scenes. During memory encoding, scenes that were later remembered elicited a stronger pupil constriction compared to scenes that were later forgotten. Thus, pupil size predicts success or failure of memory formation. In contrast, novel scenes elicited stronger pupil constriction than familiar scenes during retrieval. When viewing previously memorized scenes, those that were forgotten (misjudged as novel) still elicited stronger pupil constrictions than those correctly judged as familiar. Furthermore, pupil constriction was influenced more strongly if images were judged with high confidence. Thus, we propose that pupil constriction can serve as a marker of novelty. Since stimulus novelty modulates the efficacy of memory formation, our pupil measurements during learning indicate that the later forgotten images were perceived as less novel than the later remembered pictures. Taken together, our data provide evidence that pupil constriction is a physiological correlate of a neural novelty signal during formation and retrieval of declarative memories for complex, natural scenes. 
RD 12/14/2019
UL https://doi.org/10.1167/13.2.11