There are a number of herbs that can be beneficial to brain function. Have a look at the Nervous System lessons.
St. John’s wort can cause some photosensitivity in some folks with long term use. Take a day off every couple of weeks. Wear a hat and long sleeves in the bright sun or try won of the other plants if it becomes miserable.
Don't use herbs or combine herbs with medications or use them during lactation or pregnancy without talking with your healthcare provider.