Agents strapped wires ot his head, telling him that the device was an electroencephalograph, a made-up device which could read his brain waves, in order to help persuade him to "tell the truth".
Agents strapped wires ot his head, telling him falsely that the device was an electroencephalograph which, while a real device to read brainwave patterns, would allow them to read his mind. This was a form of psychological intimidation in order to help persuade him to "tell the truth".