By some reports, the word samurai first appeared in the 12th century. For a long time, the samurai provided the main military force used against emishi and other clans. In the 1100s, two powerful clans served the emperor of Japan: the Taira clan, and the Minamoto clan. These two families became bitter rivals, and in 1192, Minamoto Yoritomo led his clan to victory over the Taira.
EEG measures brain activity and must demonstrate regular wave patterns to be considered valid. Therefore, by this rule the onset of life would be the time when fetal brain activity begins to exhibit regular wave patterns, which occurs fairly consistently around week 25. Previous to that time, the EEG only shows small bursts of activity without sustained firing of neurons.
The development of the brain begins in the first few weeks after conception. Most of the structural features of the brain appear during the embryonic period (about the first 8 weeks after fertilization); these structures then continue to grow and develop during the fetal period (the remainder of gestation).ven more importantly, synapses are formed at a faster rate during these years than at any other time. In fact, the brain creates many more of them than it needs: at age two or three, the brain has up to twice as many synapses as it will have in adulthood (Figure 3).