The Effect of Long Photoperiod on The Visuospatial Working Memory in Wistar Rats (Rattus norvegicus)

Abstract

Nowadays, the boundary between day and night cannot be distinguished clearly because of artificial lighting at night. Artificial light exposure at night effects the circadian rhythm of the organism body. Light is the primary stimulus in determining the circadian rhythm of an organism. Circadian rhythms play an important role in determining the sleep patterns of an organism. Circadian rhythm disruptions can cause negative effects on health, including cognitive function deficits, such as a working memory. The aim of this study was to determine the effect of long photoperiod on the ability of visuospatial working memory of Wistar rats (Rattus norvegicus). Total of 16 rats comprising two groups were used. The first group was treated with a normal photoperiod, 12 hours light and 12 hours dark, while the second group was treated with a long photoperiod, 21 hours light and 3 hours dark. In this study two different object recognition methods were used to investigate the visuospatial working memory in rat, namely Novel Object Recognition (NOR) to test the visual working memory and Object Location Recognition (OLR) to test the spatial working memory. The results showed that long photoperiod exposure significantly decreased the ability of the spatial working memory, but did not show any effect the visual working memory of the studied rats.