Manipulating the ionic-electronic coupling in organic electrochemical transistors (OECTs) offers opportunities for interesting phenomena and advanced applications but has not been systematically exploited. Here, we develop monolithically integrated solid-state vertical OECTs to fully explore polyelectrolyte's strengths, enabling the OECTs to switch between neuromorphic and logic functions. This transition capability is achieved by mastering the complex transport of large-size polycations within the channel through well-designed drain electrodes. Frame drains positioned atop the organic channel act as ion barriers, regulating the penetration and relaxation of polycations. This regulation allows our multilevel synaptic OECTs to transform from short-term depression (STD) to STD-based long-term memory, and eventually to long-term depression (LTD). Conversely, placing frame drains beneath the channel exposes the polyelectrolyte fully, hence yielding high-density logic OECTs, which have been successfully used to construct unipolar integrated circuits such as NOT, NAND, and NOR gates. These achievements represent a substantial advancement in manipulating polyelectrolyte-based ionic-electronic interactions, introducing more possibilities beyond small ion-based OECTs.