The sign for brain (clawed hand at temple) is generally represents knowledge and ideas that are going in or coming out of your brain when blended with different movements; like remember where hand closes (to represent holding the thought), or forget where the thought exits the head sideways. To teach is to take ideas from your head and send them to someone else so the bunch hand goes from your brain towards someone else.
The think sign (pointer touching temple) gets used to represent thoughts and concerns of the mind. Confused starts with thoughts that are all mixed up. Expect blends thought with hope.
Generally the hook finger modification tends to express a negative or emotive thought like concern and worry.