Mapping and modulating brain dynamics in aging and neurodegeneration with electroencephalography and integrated neurotechnologies in primates.

Non-human primates (NHPs) provide an essential translational platform for investigating neural mechanisms underlying brain aging and neurodegenerative diseases. Their neuroanatomical organization, cortical complexity, and cognitive capacities share close parallels with those of humans, enabling a degree of experimental precision that rodent models cannot achieve. Electroencephalography (EEG) offers a non-invasive method for monitoring neuronal population activity with high temporal resolution, capturing oscillatory patterns and connectivity changes that emerge over the course of aging and in pathological states. In humans, such measures have revealed alterations in dominant frequency bands, network synchrony, and event-related potentials that serve as candidate biomarkers for cognitive decline. Extending EEG to NHP models permits the direct examination of mechanistic hypotheses and assessment of therapeutic interventions in a brain closely resembling that of humans. We emphasize study-level examples and quantitative anchors, including frequency-band ranges and the direction of EEG changes across aging and neurodegenerative disease models. Recent work has expanded EEG applications in NHPs to longitudinal studies, invasive/non-invasive signal comparisons, and integration with other modalities, including magnetoencephalography (MEG), functional magnetic resonance imaging (fMRI), functional near-infrared spectroscopy (fNIRS), and invasive electrophysiology. Furthermore, pairing EEG with neuromodulation techniques such as transcranial magnetic stimulation (TMS), transcranial direct and alternating current stimulation (tDCS, tACS), temporal interference (TI) stimulation, and transcranial focused ultrasound (tFUS) offers a framework for causally probing and modifying network function. This review synthesizes EEG methodologies in NHPs, examines their applications to models of normative aging, Alzheimer's disease, and Parkinson's disease, and discusses multimodal integration, neuromodulation strategies, ethical considerations, and translational relevance for human neuroscience. Sections are organized around five linked goals: establishing EEG measurement validity in primates, summarizing aging and disease-associated EEG signatures, integrating EEG with imaging and invasive recordings, using stimulation to test causality, and translating biomarkers and interventions to human studies.