Leonard's mother. She is unemotional and logical to the point of being cold. She criticizes Leonard mercilessly, without seeming to realize that she's hurting him. She is a neuroscientist (and also a psychiatrist) who analyses everyone she meets, in the process reducing Penny to tears, and provoking Howard and Raj into bickering like a married couple, especially after her comment that they are in an "ersatz homosexual marriage". She has an affinity for Sheldon, based on the fact that she is very much like him: logical, analytical, and disdainful of social conventions. Leonard calls her "mother" (0215).
She is played by Christine Baranski
See also Hofstadter family