The research looks sketchie and variable. Some see improvement. Others do not. In one study, there was some improvement and some degrading of function.

http://www.ncbi.nlm.nih.gov/pubmed/11094401

I have very poor memory and find it is most important for me to not casually rely on my memory. It takes a concerted effort. Some suggest it is a focus issue. I struggle to focus on the task/information at hand due to easy distractability.

Does he know what types of memory he is struggling with, auditory, visual ?