How does Lady Macbeth explain Macbeth's behavior?

Lady Macbeth accounts for Macbeth's behavior in William Shakespeare's "Macbeth," by saying that he has had this kind of behavior since he was child, and even has seizures during these moments. She essentially tries to explain his behavior away as a mental illness. This occurs during Act 3, Scene 4, when they attend a feast and Macbeth alone sees the ghost of Banquo.

When Macbeth appears unwell at the inexplicable sight of Banquo's ghost, Lady Macbeth publicly brushes it off, but privately calls him a coward. In spite of this, Macbeth continues to see the ghost, and even berates it. His behavior ultimately disrupts the feast.