The dark side of light exposure: impacts on object recognition memory and spatial associative memory in Wistar rats

May 24, 2026Physiology & behavior

Negative effects of light exposure on object and location memory in rats

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Rats re-exposed to constant light showed impairments in object recognition and spatial associative memory after 3 weeks.

Permanent exposure to constant light may induce arrhythmic behavior and impair spatial memory.
Impairments in memory were observed in rats re-exposed to constant light compared to those maintained in a light-dark cycle.
Rats exhibited a free-running locomotor rhythm with reduced variability after re-exposure to constant light.
No differences in certain brain cell populations were found between the light-exposed and control groups.
The negative effects on learning performance may arise from a sustained effect of light exposure rather than just circadian disruption.

AI simplified

Permanent exposure to constant light (LL) induces arrhythmicity in locomotor activity and impairs spatial memory, an effect that has been associated with reduced hippocampal neurogenesis in rodents. However, it remains unclear whether these memory deficits result from circadian disruption or from a sustained (tonic) effect of light exposure. In this study, rats were exposed to LL during lactation (21 days) to prevent the development of arrhythmicity in adulthood. Subsequently, animals were maintained under a 12:12 light and dark (LD) cycle for 39 days and then re-exposed to LL. Behavior assessments were conducted after 3 (LL) and 7 (LL) weeks after LL re-exposure. Control groups maintained in a 12:12 LD cycle (LDand LD) were tested at the same time points. LL re-exposed rats exhibited a free-running locomotor rhythm with a reduced percentage of variance. Compared to LD rats, LL re-exposed rats showed impairments in object recognition memory and spatial associative memory in the LL, but not in LL. Immunohistochemical analyses of parvalbumin- and neuronal nucleus protein-positive cells in the dorsal hippocampus and prefrontal cortex, performed 7 weeks after LL re-exposure, revealed no differences between groups. These findings suggest that the negative impacts of the LL exposure on learning performance may be due to a tonic effect of the light that emerges after a prolonged LL re-exposure. 3 7 3 7 7 3

Full Text

Full text is available at the source.

View full text (XML) ↗View full text ↗

The dark side of light exposure: impacts on object recognition memory and spatial associative memory in Wistar rats

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief