Deanna Troi was a half-Betazoid, half-Human Starfleet officer. Under the command of Captain Jean-Luc Picard, she served as ship's counselor aboard the USS Enterprise-D and the USS Enterprise-E. In 2451 N.E, Troi transferred to the USS Titan and later the first councilor to represent the United Federation of Planets within the Allied Council. As a half-Betazoid, Troi was capable of extra-sensory empathy, but was incapable of reading aliens with brain structures dissimilar to Humans and other Betazoids, such as the Scarran and the Geonosians. Like most Betazoids, Troi had telepathic abilities; due to her half-Human heritage, however, the range of her telepathic abilities were limited compared to full-blooded Betazoids, and could usually only read the thoughts of other Betazoids, most notably her mother.