Structure of the Human Brain: the Forebrain
In general, the human brain can be divided in three large parts:
- The forebrain with the telencephalon, consisting out of the neocortex, the basal ganglia and the limbic system as most important structures, and the diencephalon, with the thalamus and hypothalamus as noteworthy structures.
- The midbrain, or mesencephalon
- The hindbrain with the metencephalon, which is made up out of the cerebellum and the pons, and the myelencephalon or medulla.
Figure 1: Divisions of the Brain
The telencephalon (also known as the cerebrum) is the largest part of our brain and controls voluntary movements and cognitive and emotional processes. It is divided in a left and right hemisphere, which are connected through a large bundle of nerve fibers called the corpus callosum.
It can be divided in:
- The neocortex,
- The basal ganglia, and
- The limbic system
The two halves of the brain are quite distinct in function:
- The left hemisphere: language and analytic thinking.
- The right hemisphere: spatial interpretation and visual/musical memories.
The neocortex is characterized by two distinct furrows, the lateral and central furrow. This divides the neocortex in four lobes:
- Occipital lobe: visual cortex
- Temporal lobe: understanding of language, area of Wernicke
- Parietal lobe: spatial insight
- Frontal lobe: motor movements, speech (area of Broca)
Figure 2: Brain Lobes
The basal ganglia
These form a kind of ring around the thalamus and control the position of the body and the sense of direction and distance. They can be divided in four parts:
- Nucleus caudatus
- Globus Pallidus
- Nucleus accumbens
The limbic system
This also forms a ring, but this time around the brainstem. The system controls emotion, memory and learning processes and is composed out of six parts:
- Hippocampus: long-term memory
- Gyrus cinguli: feeling of reward/punishment
- Hypothalamus (sometimes classified within the diencephalon): homeostasis and behavior
- Amygdala: aggression and fear
- Orbitofrontal cortex: decision making
- Septum: Impulse reactions
This part of the brain is located in between the telencephalon and the mesencephalon and is composed out of:
- The thalamus, which has two functions; firstly it acts as a ‘switch station’ between the senses and the brain; secondly, it regulates emotion, attention and consciousness.
- (The hypothalamus: sometimes included in the telencephalon, see above)
- Hypophysis or pituitary gland, which regulates several homeostatic processes, such as blood pressure, water balance in the body and the function of the sexual organs.
- Epiphysis or pineal gland (also referred to as the ‘third eye’), which regulates the secretion of a chemical called melatonin, which is largely responsible for our diurnal rhythm.
- Figure 1: Carlson, N.R. (2001) Physiology of Behavior, 7th edition, Boston: Allyn & Bacon
- Figure 2: http://en.wikipedia.org/wiki/File:BrainLobesLabelled.jpg