Brain

The amygdala - This part of the limbic system regulates behaviour. The hippocampus - This area is responsible for the formation, storing and organizing of memories. The midbrain and the limbic system also form part of the reticular activating system (RAS). It is this area that regulates wakefulness and sleep. The fore-brain This region contains the cerebral cortex and surrounds the brain stem and midbrain. In humans, it is highly developed and has a very complicated structure. The forebrain is involved in thought and problem solving. The cerebral cortex has two cerebral hemispheres and a folded, wrinkled surface. The folds in the layer are called the sulci. The top layer of the cortex is about two millimeters thick and has a total surface area of about 1.5 square meters. The two hemispheres work in co-ordination, although one side is dominant. For example, right handed people have a dominant left cerebral hemisphere.

The cortex is made up of four lobes which include:

The frontal lobe - This region of the brain occupies the front part of the skull and lies behind the forehead. The frontal lobe is associated with planning, decision making, voluntary muscle movement, processing speech, smell, and emotions. The parietal lobe - This area of the brain processes sensory information and is responsible for determining spatial awareness, navigation and positioning. It is also involved in processing information related to taste; temperature and touch. The temporal lobe - The temporal lobe is involved in processing visual and auditory information and controls some aspects of language perception, memory and emotion. The occipital lobe - This is the visual processing Centre of the brain and contains the largest proportion of the visual cortex region. Language and the Human Brain The human brain is divided into two hemispheres. The left hemisphere is the "logical brain" and is involved in language and analysis and the right hemisphere is the "creative brain," involved in daydreaming and imagination. The left hemisphere controls the right side of the body while the right hemisphere controls the left side. The earliest research on speech and language centers of the brain dates back to the early nineteenth century. Physicians noted that brain-injured patients with damage to the left hemisphere would lose power of speech and language abilities, while those with injuries to the right hemisphere did not lose this ability. Recent studies have shown that in around 97% of people, language is represented in the left hemisphere. However, in about 19% of left-handed people, the areas responsible for language are in the right hemisphere and as many as 68% of them have some language abilities in both the left and the right hemispheres. The central part of the brain includes the brain stem and the midbrain. The function of the midbrain and has been largely preserved over years of evolution. The functions of the forebrain, however, have changed somewhat. The cortex is highly developed with a high capacity for complex thinking and prof em solving. The brain stem This part of the human brain is similar to animals of lower order and has not changed much with evolution. The brain stem contains vital structures including the medulla oblongata which controls breathing, heart rate, and digestion and the cerebellum which coordinates sensory input and maintains muscle movement and balance. The mid-brain This region of the brain is responsible for vision, hearing, temperature control, motor control and alertness. The midbrain also connects the brain stem to the thalamus, allowing for information to be relayed from the senses to the brain and back to the muscles. The midbrain also includes a limbic system which lies above the brain stem and under the cortex. It consists of a number of interrelated structures that regulate temperature control, hormones, and emotions. The limbic system also deals with long term memory.

The limbic system includes:

The hypothalamus - The hypothalamus regulates emergency responses such as the "fight or flight" response, as well as non-emergency vital processes such as feeding and reproduction. The hypothalamus also controls the release of hormones. Neurons affecting heart rate and respiration are concentrated in the hypothalamus. Determination of language areas A procedure called cortical stimulation mapping Is a technique that is used to analyze regions of the brain that are related to speech. On performing brain surgery to treat epilepsy or remove tumors for example, electrical stimulation of speech-related areas in the cortex prevents the patient from being able to name things that are shown to them and may also prevent their ability to produce grammatically coherent sentences. When such a site is identified, it is spared, since damaging these areas could cause a temporary or permanent loss of speech. Neural networks are established over time as an individual learns and experiences things. Language and speech skills are therefore acquired after birth. The human genome codes for the speech ability that will evolve as the brain is trained. Speech and language brain regions The visual cortex is the part of the cerebral cortex that is responsible for processing visual information. The auditory cortex in the cerebral cortex processes auditory information and as part of the sensory system for hearing performs both basic and higher hearing functions. Wernicke's area is an area in the cerebral cortex related to speech and is involved in both spoken and written language. This area was named after Carl Wernicke, a German neurologist who discovered that the area is related to how words and syllables are pronounced. Broca's area is an area in the frontal lobe of the brain that is related to the production of speech. The area is named after Pierre Paul Broca who noticed an impaired ability to produce speech in two patients who had sustained injury to the region.