Hello! As i suppose your mother suffers from dementia (you are not clear if the memory loss was acute, from a trauma, stroke, or any other condition) Behaviour disorders and psychotic manifestations are common as teh disease progresses. In most cases they become more troubling for the caregivers than the cognitive loos itself. These manifestations are also more challenging for the health proffesionals who deal with these patients. Agitation, agression, insomnia are bahavioural disorders, hallucinations and delusions are psychotic. These symptoms are treated mos frequently with atypical antipsychotics, which are the most studied class of drugs in demntia. Some antypsychotics that may be more effective for your mother, who in my opinion has behavioural disorders more than psychotic, are quetiapine or olanzapine. The drug the psychiatrist suggested is an antidepressant (miratzapine) which is commonly and successfully used in insomnia. It may be used along with the antipsychotic drug. I hope i have been of help.