Romulan mind probes, also referred to as a memory scanner, were a device developed by the Romulan Tal Shiar as an alternate means of interrogating prisoners. The device had the ability to record thoughts and provide that data to be read by the interrogators, thus making it possible to bypass normal interrogation techniques.
In 2375, Chairman Koval ordered that his agents use mind probes on Doctor Julian Bashir in order to ascertain the truth of his claim that an agent from Section 31 was attempting to assassinate Koval. However, the devices did not work on Bashir because of the neural alterations caused by his genetically-engineered nature. (DS9: "Inter Arma Enim Silent Leges")
Later that year, Bashir managed to obtain a pair of mind probes on Deep Space 9, despite the fact that they were illegal in the Federation. Bashir attempted to use them on Sloan to extract information related to a cure for the morphogenic virus. Sloan attempted to commit suicide to prevent Bashir from recovering the information. However, Bashir managed to prolong Sloan's life enough to find the cure in his mind, and he died shortly afterwards. (DS9: "Extreme Measures")