Yes it does happen jeza, more prone to lose their temper, also less able to understand how to work things out. Perhaps it's frustration, not being able to act or understand things as quickly as they used to.
I remember a lovely lady who was always very polite, attached to the church and never missed a service. After her stroke she used such vile language, we wondered where she could have heard it unless it was from her past. Her husband only brought her out to get her hair done (that's where i used to see her) as he was so shocked. Very sad really.