Sex differences regulate memory capacity during ageing

Memory Capacity (MC) is the number of information maintained in memory. It is known to be regulated by fronto-striatal dopamine circuit and hippocampus. Using the Different and the Identical Object Recognition Task (DOT/IOT), we have showed that adult male mice discriminate 3,4,6 but not 9 different objects after a 1 min or 24 hr delay. Moreover, it has been reported that male mice use the hippocampus to solve the task (Sannino et al 2012, Olivito et al 2014), similar to humans. Although gender differences in humans are reported, less is known about MC in females and about the mechanisms underlying these differences. To study the role of sex differences in influencing MC, we have challenged female and male mice with different number of objects, to remember for different delays. We have found that female mice have a memory load-dependent deficit. Using a combination of ex-vivo brain activation imaging and in vivo brain activity manipulation techniques we are testing the hypothesis that female mice use a different neuronal circuitry to solve the task in condition of high load, which makes their memory more vulnerable to memory decay. These findings might be relevant to understand the higher impact of dementia in women with early mild cognitive impairment as compared to men.