Alzheimer's disease (AD) is a complex and multi-factorial disorder, leading to progressive cognitive impairment. Hippocampal dysfunction plays a crucial role in spatial memory deficits in AD. However, the precise alterations in hippocampal neuronal activity in AD during memory-guided behaviour remain unclear. To study this, we introduced a novel behavioural paradigm for assessing spatial memory in head-fixed mice during a continuous alternation task, which can be used in conjunction with two-photon calcium imaging to investigate changes in hippocampal network activity, including spatial and trajectory-dependent representations. 5xFAD mice displayed age-related performance decline in the alternation task (performance dropping from 79.2±4.3% in young control(N=10) to 65.4±8.2% in young 5xFAD(N=8), 71.7±7.9% in old control(N=6), and 47.2±13.4% in old 5xFAD(N=7)). Additionally, speed tuning of CA1 neurons was disrupted in 5xFAD mice during the alternation task. 5xFAD hippocampal neurons demonstrated increased hyperactivity during rest periods, particularly during correct trials, with young 5xFAD showing 14.5±3.2% hyperactivity versus 9.9±1.1% in young controls, and old 5xFAD at 22.7±3.9% compared to 15.6±3.4% in old controls. Spatial tuning information and stability were also compromised significantly from young 5xFAD and continued to decline with age. Finally, our results suggest that the quality and dynamics of trajectory-dependent neural activity are linked to performance deficits in 5xFAD mice. Taken together, our research provides a novel behavioural paradigm for assessing spatial memory deficits in a mouse model of AD, demonstrating putative mechanisms of hippocampal circuit deficits and providing new perspectives for potential AD therapies.