Recording infraslow brain signals (<0.1 Hz) with microelectrodes is severely hampered by current microelectrode materials, primarily due to limitations resulting from voltage drift and high electrode impedance. Hence, most recording systems include high-pass filters that solve saturation issues but come hand in hand with loss of physiological and pathological information. Flexible epicortical and intracortical arrays of graphene solution-gated field-effect transistors (gSGFETs) have recently been demonstrated able to map cortical spreading depression in rats with high fidelity. Importantly, gSGFETs can record infraslow signals together with signals in the typical local field potential bandwidth. The wide recording bandwidth results from the direct field-effect coupling of the active transistor, in contrast to standard passive electrodes, as well as from the electrochemical inertness of graphene. Because of this, gSGFETs are envisioned to have broad applications for monitoring brain activity.