In addition to playing matriarch Nora Holden on "Brothers & Sisters", she has played Abby's mom on "ER"
... the mother 
of doctor Abby (Maura Tierney) who suffers from bipolar disorder, in ER earned ... 
Brothers & Sistersa late addition, as her character, family matriarch Nora 
Walker,... [DOC] [TLE] Brothers & Sisters (season 4) - Wikipedia [PAR] The fourth season of Brothers & Sisters was picked up for a fourth season on 
April 23, 2009.