Hippocampal function during an associative memory task is influenced by early bilateral salpingo‐oophorectomy

Abstract

AbstractBackgroundWomen with mid‐life 17β‐estradiol loss due to early bilateral salpingo‐oophorectomy (BSO; removal of ovaries and fallopian tubes) have heightened Alzheimer’s disease (AD) risk (Rocca et al., 2007). 17β‐estradiol loss is related to AD risk factors, including associative memory decrements and decreased functional magnetic resonance imaging (fMRI)‐measured hippocampal activation during encoding (Jacobs et al., 2016; Rentz et al., 2017). Our objective was to investigate the effects of early BSO and 17β‐estradiol replacement therapy (ERT) on associative memory and hippocampal function.MethodWomen with BSO either taking ERT (BSO+ERT; M±SEage= 45±1.03, n = 23) or not taking ERT (BSO; M±SEage= 45.7±1.01, n = 23) were compared to age‐matched premenopausal control women (AMC; M±SEage= 43.7±0.48, n = 37) on fMRI‐measured brain activation during encoding and retrieval trials of a face‐name associative memory task. We compared groups on activation from anterior and posterior anatomical hippocampal regions‐of‐interest during retrieval and encoding (retrieval‐encoding contrast) trials between groups. We also compared hippocampal activation during novel and repeat face‐name pair encoding trials (novel‐repeat encoding contrast). Face‐name pair recognition accuracy between groups was also assessed.ResultCompared to BSO+ERT, BSO exhibited significantly lower activation during novel compared to repeat encoding trials (Fig.1A) in the right anterior hippocampal region‐of‐interest (Fig.1B). There were no significant group differences in hippocampal activation during retrieval compared to encoding trials, and no group differences in recognition accuracy.ConclusionYounger women with BSO either taking ERT or not showed comparable hippocampal activation to age‐matched premenopausal women during retrieval of face‐name pairs. However, during encoding of face‐name pairs, BSO showed significantly lower right anterior hippocampal activation compared to BSO+ERT. ERT may influence associative encoding processes dependent on hippocampal novelty detection, rather than retrieval processes. Expanding on work from others (Phillips & Sherwin, 1992), these results suggest ERT may ameliorate the negative influence of oophorectomy on hippocampal‐dependent memory processes.