Perhaps you should try some spelling variations:
musical activities » medical activities, physical activities, fiscal activities
general activity » neural activity, gene activity, genetic activity
central activity » mental activity, cultural activity, neural activity

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((musical activities) OR (((general activity) OR (central activity)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((musical activities) or (((general activity) OR (central activity))))".
• Adding a wildcard symbol may retrieve word variants: ((musical activities) or (((general activity) OR (central activity))))*.