The Forebrain The forebrain is the highest level of the brain and is critical for complex cognitive, emotional, sensory, and motor functions. The forebrain is divided into two parts: the cerebral cortex and the underlying subcortical structures. The cerebral cortex, the outermost layer of the brain, is divided into two hemispheres, connected by the corpus callosum (see Figure 3.18). The subcortical structures include the thalamus, hypothalamus, pituitary gland, amygdala, and hippocampus.