Pupillometry and Declarative Long-Term Memory

Long-term memory (LTM) encompasses a broad range of learning and memory abilities supported by diverse brain regions. According to the Multiple Memory Systems framework (Squire, 2004), declarative LTM is supported by medial temporal and frontal lobe structures, including the diencephalon. Although declarative LTM is typically divided into episodic and semantic memories, with no further divisions within those categories, both memories are themselves quite diverse, capable of producing memorial experiences ranging from strong to weak and vivid to vague. This chapter reviews evidence about the diversity of LTM phenomena and argues that this diversity is due to reciprocal connections between neural systems supporting these memory types and the locus coeruleus–norepinephrine (LC–NE) system. Specifically, because the LC–NE plays a role in neural gain modulation, it may be a key structure involved in producing the diverse memories that characterize declarative LTM. Key findings from memory studies using pupil size as an indirect index of LC–NE activity are reviewed.