Faculty Collaboration Database

Long days enhance recognition memory and increase insulin-like growth factor 2 in the hippocampus. Sci Rep 2017 Jun 20;7(1):3925

Date

06/22/2017

Pubmed ID

28634329

Pubmed Central ID

PMC5478617

DOI

10.1038/s41598-017-03896-2

Scopus ID

2-s2.0-85021140787 (requires institutional sign-in at Scopus site)   12 Citations

Abstract

Light improves cognitive function in humans; however, the neurobiological mechanisms underlying positive effects of light remain unclear. One obstacle is that most rodent models have employed lighting conditions that cause cognitive deficits rather than improvements. Here we have developed a mouse model where light improves cognitive function, which provides insight into mechanisms underlying positive effects of light. To increase light exposure without eliminating daily rhythms, we exposed mice to either a standard photoperiod or a long day photoperiod. Long days enhanced long-term recognition memory, and this effect was abolished by loss of the photopigment melanopsin. Further, long days markedly altered hippocampal clock function and elevated transcription of Insulin-like Growth Factor2 (Igf2). Up-regulation of Igf2 occurred in tandem with suppression of its transcriptional repressor Wilm's tumor1. Consistent with molecular de-repression of Igf2, IGF2 expression was increased in the hippocampus before and after memory training. Lastly, long days occluded IGF2-induced improvements in recognition memory. Collectively, these results suggest that light changes hippocampal clock function to alter memory, highlighting novel mechanisms that may contribute to the positive effects of light. Furthermore, this study provides insight into how the circadian clock can regulate hippocampus-dependent learning by controlling molecular processes required for memory consolidation.

Author List

Dellapolla A, Kloehn I, Pancholi H, Callif B, Wertz D, Rohr KE, Hurley MM, Baker KM, Hattar S, Gilmartin MR, Evans JA

Author

Jennifer A. Evans PhD Assistant Professor in the Biomedical Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Animals
Circadian Clocks
Hippocampus
Insulin-Like Growth Factor II
Male
Memory Consolidation
Mice
Models, Animal
Photoperiod
Rod Opsins
Time Factors
Up-Regulation
Wnt1 Protein