<p>Photoperiodism and biological sex are factors that may influence cognitive impairments. Scopolamine, a muscarinic acetylcholine receptor antagonist, is a widely used pharmacological tool for modelling cognitive impairments, but its cellular interaction with photoperiodic cycle and sex is poorly understood. This study aimed to evaluate the effects of photoperiodism and sex on neurobehavioural and ionic chnages in scopolamine-induced cognitively-impaired mice. Sixty-four male and female mice (18.5 ± 0.9&#xa0;g) were assigned to eight groups; four tested during the photophase and four during the scotophase, each comprising normal controls and scopolamine-treated animals of both sexes. Memory was assessed using the elevated plus maze and novel object recognition tests. Spinal tissue ionic concentrations of sodium, potassium and chloride were measured. Control mice outperformed scopolamine-treated mice in memory retention across both phases. Novel object recognition scores were paradoxically lower in controls than in impaired mice during the photophase. Scotophase analysis revealed elevated sodium and chloride levels in impaired mice; while potassium concentrations were specifically raised in scopolamine-treated females during the photophase, pointing to sex-specific changes in neuronal excitability. The findings suggest that photophase and female sex potentiated long-term memory consolidation and may modulate neuronal excitability in scopolamine-induced cognitive impairments. In conclusion, the result shows the need to incorporate photoperiodism and sex as important variables in the interpretation of cognitive impairment and in pre-clinical cognitive research. Overlooking the two factors may mask or misrepresent the true neurobiological effects of pharmacological models of impairment.</p>