TOEFL - Test of English as a Foreign Language TOEFL Practice Test #6

Read the following paragraph and answer the question at the bottom1.
The leading causes of amnesia are either physical or psychological.
In2. antergrade amnesia, the subject is unable to recall the events that occur after3. a shock or an injury to the brain; however, past memories will not be lost.
In4. retrograde amnesia, the patient is capable of recalling events that occurs after the5. trauma; interestingly enough, information stored before the shock, is lost and6. cannot be retrieved.
In paraamnesisa, established memories are contorted.
In7. psychogenic fugue, the subject may venture into a new lifestyle, trying to8. repress memories which lead to trepidation.
The events happening during9. psychogenic fugue are non-retrievable.
Nonetheless, the experiences that10. happened before the onset can be recovered.
Among the most popular11. treatments for psychologically related amnesia are psychotherapy, the use of12. drugs, and hypnosis.What is the main topic of the passage?