Background and Aim: In healthy aging, there is a decline of cognitive functions such as episodic memory, i.e., long-term memories of events in one’s life. This process is exacerbated in neurodegenerative diseases such as Alzheimer’s disease. Therefore, developing interventions to maintain memory functions in old age is essential, but requires the identification of the underlying neuronal processes of this decline. However, the neuronal processes underlying age-related memory decline have been inconclusively investigated, particularly regarding the temporal dynamics of memory content integration within brain networks. Here, electroencephalography (EEG) and transcranial alternating current stimulation (tACS) provide methods for investigating and modulating brain oscillations and their association with memory. However, methodological advancements are still required for more practicable and better-tolerated assessments of the neuronal mechanisms of memory impairments and their effective neuromodulation, e.g., in clinical populations. Therefore, this dissertation aims to provide a comprehensive picture of oscillatory processes during memory performance, their age-related changes, and new methods for investigation and potential intervention in healthy older adults and patients. Methods: To this end, I investigated and compared the neuronal correlates of episodic memory in young and older adults using EEG in paper 1. Paper 2 is a Stage 1 Registered Report aiming to investigate the effect of tACS on memory performance and oscillatory activity in healthy older adults. Here, I used EEG, functional magnetic resonance imaging (fMRI) and computational modeling of electric fields of older adults to determine the appropriate stimulation frequency, the exact stimulation sites, and the appropriate electrode set-up to target the identified regions. Paper 2 also includes a pilot study with young adults to ensure the feasibility of the stimulation protocol and involvement of subcortical activity in stimulation effects. In paper 3, I compared memory-relevant measures between conventional and newer dry electrodes (dry EEG) to test whether dry EEG provides a reliable method for investigations in groups or environments where conventional EEG would not be possible, e.g., patient populations in their home. Results: Analyses showed disturbed oscillatory processes in healthy older adults, compared to younger adults, related to age-related memory impairments (paper 1). To target the disturbed memory network in older adults, I developed a multimodal, data-driven approach analyzing EEG, fMRI and electric field modeling pilot data of healthy older adults to identify suitable tACS parameters for modulation of memory and network functioning. An additional pilot study showed the feasibility of the protocol. It also showed that despite the lack of effect on memory performance in a small, high-performing sample of young adults, the stimulation changed this group’s oscillatory processes in cortical and subcortical regions of the memory network (paper 2). The memory-relevant processes investigated in papers 1 and 2 could also be detected with dry EEG, especially using global network measures (paper 3). Conclusion: Together, this dissertation presents a comprehensive account of oscillatory processes during memory performance and the changes they undergo in healthy aging. It introduces novel methods for investigation and possible intervention in healthy older adults and patients. In future work, these findings could be extended to investigate memory- relevant EEG signatures and their modulation in patient groups to develop effective interventions in memory-impaired populations in a home-based setting.