The cerebrum has two hemispheres, accounting for 85% of the brain's weight. The two hemispheres are connected by thick bundles of nerve fibers called the corpus callosum.
Each hemisphere has four lobes. Their functions are closely related, the following is a rough division of their roles.
- Frontal lobe is in charge of the central decision-making, such as thinking, planning, and problem solving.
- Parietal lobe deals with the perception and integration of sensory inputs.
- Temporal lobe is involved in sensory processing and memory storage.
- Occipital lobe, located at the back of the brain, is the visual processing center.
The cerebral cortex refers to the outer layer of the cerebrum, with thickness about 2-4 mm. It can be further divided into six layers. From the surface to the deepest,
they are designated as I, II, III, IV, V, VI (Figure 1-3). The layer V is most relevant to consciousness.
Figure 1-3. The cerebral cortex is divided into six layers. The layer V is most relevant to consciousness.
[Source: Schumacher et al, 2012]
The limbic system is located under the cortex, including:
- Hippocampus: It is buried in the temporal lobe, responsible for the formation of short-term memory and conversion into long-term memory stored in the cortex.
- Thalamus: It is located at the top of the brainstem, receiving and processing information from the sensory system and limbic system and then transmitting to the cerebral cortex.
- Hypothalamus: It is a structure under the thalamus, regulating food intake, body temperature and biological clock.
- Amygdala: It is located in the temporal lobe just in front of the hippocampus, involved in the memory processing of fear and other emotions.