Effects of Night Illumination on Behavior, Body Mass and Learning in Male Zebra Finches

Abstract

An increase in artificial night lighting has blurred the boundaries of day and night and transformed the natural day-night environment with alteration in the temporal niche of the animals. Male zebra finches were exposed to a dim light at night (dLAN) protocol (Light: dLAN, 12L = 200 lux: 12dLAN = 5 lux) with controls on darkness at night (Light: dark, 12L = 200 lux: 12D = 0 lux) for six weeks. We assayed sleep-wake, daily behaviors, mood, and cognition, as well as changes in physiological parameters. Dim light at night increased sleep frequency, delayed sleep onset, advanced awakening latency, and caused a reduction in total sleep duration. dLAN birds did not associate (physical association) with novel object and birds spent significantly lesser time on perch with novel object as compared to LD. In colour learning task, night illuminated birds took more time to learn and made more error, compared to LD. dLAN significantly altered the 24-h daily behavioral rhythm (amplitude and acrophase) of feeding, drinking, preening, and perch-hopping behavior. In particular, birds extended their feeding hours in the nighttime under dLAN, with no difference in total food intake. Birds under dLAN increased fattening and hence significantly increased body mass. Our results show that dim light at night altered feeding rhythm, caused decrease in sleep behavior, and negatively affected learning and memory performance in male zebra finches.

Artificial Light at Night, Higher Brain Functions and Associated Neuronal Changes: An Avian Perspective

“…In addition, LL induced a decline in advanced brain functions such as learning and personality traits in Zebra Finches (Taeniopygia guttata) in adults, and in future generations as well [19]. Similarly, recent study also suggested dLAN negatively affects cognitive performance (novel object exploration and learning and memory) in Zebra Finches [37].…”

“…Another study demonstrated that House Crows exposed to dLAN showed depressivelike responses, such as reduced eating and grooming and increased feather-picking and selfmutilation associated with sleep deprivation [18]. Feather-picking and self-mutilation in birds can be considered analogous to trichotillomania (hair-pulling behaviour) in humans and is associated with a depression-like negative state [37,38]. In these crows, dLAN induces changes in hippocampal bdnf, il-1β, tnfr1, and nr4a2 expression, and importantly, dLAN affected the histone H3 acetylation at the brain-derived neurotrophic factor (bdnf ) gene and repressed bdnf mRNA expression.…”