contact the National Aphasia Association. They do have a web site.
Please read my comment to Amber212, comment #3. My mother had a stroke similar to your mother's. My mother also has global
aphasia. Speech therapy has not helped. My mother's cognition is also gone, she cannot tell yes from no. We are just doing our best to communicate. It is very difficult. I believe it is the hardest part of the stroke. It is vertually impossible to communicate with her, she cannot read,write and often does not even understand what we are saying. I can give you some hope. It has been 4 years since my mothers stroke. I do believe she is understanding us a little better...still no speech. About all she can do is smile, say hello, goodnight, yes and no. As I told Amber212, accupunture helped a little, but not much..it fades after a day or two..a little speech and then nothing. If there is anything I can do to help, please let me know.
There has been some experimental evidence that the sleep drug Ambien can cause a momentary regaining of consciousness. There wasn't a good patient sample in the study. The mechanism of action is unclear, because in a normal person ambien induces sleep. In any event this is a prescription drug, and requires a physician, however it is a relatively benign drug, with few contraindications, and experimentally, it will either work within an hour or it won't, so you'll know right away. Consult your M.D.
Don't assume that the loss of cognitive ability and comprehension will last forever. Touch, feel and caress your loved one. There is nothing that bothered me more when working in a hospital than to see relatives visit and stand by the bedside and never touch the patient. The healing power of the human touch cannot be overestimated. And don't assume that because you are not getting verbal or other feedback that your loved one does not understand when you speak to them. Be very careful about what you say in front of them. Always assume they can understand, but not respond.