As for brain exercise, it usually happens when our colleague or friends asked any questions regarding academic matters or things that need brain storming. Our brain will work hard to find the answer and if we knew the answer, automatically we can recalled it thus, made we remember those particular answer.
About mind therapy, okay this is a little bit fuzzy and kinda hard to explain. It is more in spiritual and feeling towards oneself. Honestly, if we helped someone and they appreciate it, we will feel happy and our mood will be lifted up. But it is only applicable to those who are sincere when helping others without expecting any reward.
The reason why I'm making this entry is because I'm quite 'allergic' towards people who being so petty about sharing their knowledge with others. It is like they want to keep it by themselves and make others look like loser. It is nothing wrong to share your knowledge as insyaAllah you'll be rewarded in the hereafter. People will respect you more if you're willing to share you knowledge and help those in need.