Discrepancies in the Morris water maze versus the IntelliCage in the APP/PS1 mouse model of Alzheimer’s disease; a sex-based examination

Dementia is a collective term used to describe symptoms of cognitive impairment in learning and memory. The most prevalent form of dementia is Alzheimer’s disease (AD). In order to understand the pathological mechanisms associated with AD, animal models have been created. These various mouse models replicate the pathology found in humans with AD. As a consequence of the fact that this disease impairs cognitive abilities in humans, testing apparatuses have been developed to measure impaired cognition in animal models. One of the most common behavioral apparatuses that has been in use for nearly 40 years is the Morris water maze (MWM). In the MWM, animals are tasked to find a hidden platform in a pool of water and thereby are subjected to stress that can unpredictably influence cognitive performance. In an attempt to circumvent such issues, the IntelliCage was designed to remove the external stress of the human experimenter and provide a social environment during task assessment which is fully automated and programable. Additionally, the motivation is water consumption, which is less stressful than escaping a pool. This study examined the difference in performance of male and female cohorts of APP/PS1 and non-transgenic (NonTg) mice in both the MWM and the IntelliCage. Initially, 12-month-old male and female APP/PS1 and NonTg mice were tested in the hippocampal-dependent MWM maze for five days. Next, animals were moved to the IntelliCage and underwent 39 days of testing to assess prefrontal cortical and hippocampal function. The results of this experiment showed significant sex differences in task performance, but inconsistency between the two testing paradigms. Notably, males performed significantly better in the MWM, which is consistent with prior research. Interestingly however, APP/PS1 females showed higher Amyloid-β plaque load and performed significantly better in the more complex tasks of the IntelliCage. This suggests that Aβ plaque load may not directly contribute to cognitive deficits, which is consistent with recent reports in humans with AD. Collectively, these results should inform scientists about the caveats of behavioral paradigms and will aid in determining translation to the human condition.