The human brain includes a forebrain, made of two hemispheres almost symmetrical, left and right. 人类大脑包括一个前脑，它由 左右对称的两个半球组成。
And a diencephalon, a medial and single part that includes the thalamus and the hypothalamus. 还有一个间脑，是大脑中央区的独立部分， 其包括丘脑和下丘脑。
The two cerebral hemispheres are connected by commissural pathways, 两个大脑半球通过连合通路相连，
the largest is the corpus callosum. 最大的连合纤维是胼胝体。
It contains more than 200 million nerve fibers crossing from one side to the other. 它包含超过2亿条 从一侧到另一侧的神经纤维。
Each cerebral hemisphere is divided into two distinct regions, 每个大脑半球分为两个不同的区域，
a peripheral part: the cortex "gray matter" that contains the bodies of nerve cells, 周边部分：包含神经细胞体的皮层“灰质”，
and a central part, made of white matter 以及中央部分，由白质所构成
that contains the axonal extensions of neurons and their myelin sheath. 包含神经元延伸的轴突及其髓鞘。
Each hemisphere is cut by deep fissures that define lobes. 每个大脑半球被深的沟裂所分割划分为诸多脑叶。
The first is the lateral sulcus or Sylvian fissure 第一个是外侧沟或称Sylvian裂（外侧裂）
where lies the middle cerebral artery, 大脑中动脉位居于此，
it separates the frontal lobe of the temporal lobe. 它将额叶和颞叶分开。
The second is the central sulcus or fissure of Rolando, 第二个是中央沟或称Rolando裂，
between the frontal lobe and the parietal lobe. 在额叶和顶叶之间。
The third sulcus is the parieto-occipital sulcus 第三个沟是顶枕沟
separating the occipital lobe from the temporal and parietal lobes. 将枕叶与颞叶和顶叶分开。
Not to mention a fifth lobe, non visible on the surface, 更不用说表面看不到的第五脑叶，
the lobe of the insula, found by removing the Sylvian fissure. 岛叶，打开外侧裂才可看到。
In each lobe, there are less deep sulci delimiting the ridges on the cerebral cortex surface, 在每一个脑叶，大脑皮层表面被较深的 脑沟界定形成很多隆起，
each of these is called a gyrus. 每一个称之为脑回。