We have developed a novel type of graphene-based transistors capable of delivering high-resolution brain mapping, implementing multiplexing strategies, and monitoring activity across a wide range of frequencies, including low frequencies. We circumvented the bottlenecks faced by other approaches thanks to the unique properties of graphene. Graphene is an outstanding conductor and provides the perfect platform for multiplexing. Thus, our system requires much fewer wires than current alternatives. Further, graphene is just one atom thick, flexible and can be integrated into ultra-soft flexible substrates, providing excellent contact with brain tissue. Our graphene transistor technology has been developed as part of the FET-Graphene Flagship and FET-proactive BrainCom projects. We have assessed the technology in rodents and demonstrated that our devices allow monitoring brain activity with very high spatial resolution and over a wide bandwidth frequency range. This project will pave the way for the clinical translation of brain-mapping neural interfaces based on graphene-transistor arrays for brain-computer interfaces.