1. A method comprising: receiving, from a sensing module, a bioelectrical brain signal indicative of electrical activity in a first portion of a brain of a patient; determining, with a processor, that the brain of the patient is in a first arousal state based on at least one characteristic of the bioelectrical brain signal; and controlling, with the processor, a stimulation module to deliver electrical stimulation to a second portion of the brain of the patient that is different than the first portion in response to determining that the first portion of the brain of the patient is in the first arousal state, wherein the electrical stimulation is configured to activate an arousal neural network in the first portion of the brain of the patient to induce a second arousal state in the brain of the patient, and wherein the electrical stimulation is configured to treat a cognitive disorder of the patient.