walking during sleep

im a hospital pharmacist and very keen to know about the problem from which my younger brother had to face few years ago.actually when  he was 12 years old he had this habbit of walking during sleep so when in the morning we used to ask about him about last night event really he was completly unaware about it .but now he is 16 years old now he hasn t this habbit but still he mostly talk during his sleep

                                                                              it will be very informative for me if u kindly tell me about the so far research about this real story

                                                                thanks