The telencephalon contains the most advanced parts of the brain. Although present in all vertebrates, it is most developed in birds and mammals. In humans the telencephalon develops into the cerebral cortex, the limbic system, the basal ganglia, and important white matter regions. The cerebral cortex includes the four lobes of the neocortex as well as those areas on the inside surface of the cortex that directly contact the subcortical regions. These include the cingulate gyrus, hippocampal and parahippocampal regions, as well as the insula, which is sandwiched between the temporal, frontal, and parietal cortices. The basal ganglia, amygdala, and septum also develop out of the telencephalon. Finally, cerebral white matter is made up of bundles of axons that travel across large sections of the brain. Important cerebral white matter structures that develop out of the telencephalon include the anterior commissure, the internal capsule, and the corpus callosum.
Given the extraordinary journey that brain cells must travel during fetal development it is amazing that so many babies are born without brain damage (iStock).