Impact of high sucrose diets on the discrimination of spatial and object memories with overlapping features

High sucrose diets (HSDs) have been shown to have detrimental effects on hippocampal dependent memory in rats, including the performance of spatial tasks reliant on pattern separation, a cognitive process involved in minimising interference during memory encoding. As such we sought to investigate the impact of HSDs on object and spatial recognition tasks that varied the cognitive load placed on pattern separation processes. Young male and female rats were 4 weeks old at the start of diet manipulations. Rats in the HSD condition were provided with daily access to 10% sucrose solution for 2 h per day across a 28 d period, during which they were assessed on their performance of memory tasks that varied the similarity of spatial arrangements (Spontaneous Location Recognition, SLR) and object features (Novel Object Recognition, NOR) to determine the effect of HSD on memory encoding processes. Both female and male rats that consumed HSDs were impaired at NOR when objects shared multiple features (s-NOR), however when objects were distinct, novel object recognition was not impacted by HSD consumption. Male rats in the control condition generally outperformed female rats in the SLR task when there were small spatial separations (s-SLR) but not when there were large spatial separations (d-SLR). HSD consumption disrupted performance of d-SLR in female rats, but not male rats. Specific HSD deficits were observed in HSD consuming male rats in the s-SLR task. However, the volume of sucrose consumed differed between sexes, and may have impacted memory differentially. These findings indicate that HSD-induced memory deficits may extend to pattern separation dependent recognition memory mechanisms when objects share overlapping features, and impairments in spatial tasks may be more pronounced in female rats.