The forebrain is the largest section of the brain in humans and most animals. As its name suggests, it sits in the most forward position of any brain section, and is normally separated into two hemispheres known as the diencephalon and the telencephalon. Each serves a unique and important role in information processing and transmission. Sensory processing and emotional response are some of the biggest tasks of these regions. Associative processing, including voluntary and involuntary motor control, emotion, cognition and language are also included. This frontal part of the brain is often seen as one of the most important, and damage or injury can have a serious impact on many different functions, from communication to emotional well-being.
Brain Basics
The brain is one of the most complex organs of the human body. It’s made up of an intensive system of nerves and soft tissues that relay and conduct signals, and the organ as a whole serves as the main processing unit for the entire body. Looking at the brain from the outside it often looks like one uniform mass, but researchers have identified six major areas, each with its own identity that distinguishes it from surrounding regions. The forebrain, also sometimes referred to as the prosencephalon, sits at the front of the brain, usually directly behind a person’s forehead. Behind that is the parietal lobe and the occipital lobe; to the sides are the temporal lobes. All of this sits atop the cerebellum and the brain stem, which connects the organ to the spine.
Diencephalon
In terms of shape, the forebrain looks sort of like a semi-circle or cup turned on its side, and it’s usually quite large. In adults it can take up about half of the total brain space. A lot is going on in the tissues here, and it’s often easiest to identify the exact functions by taking things one hemisphere at a time.
The diencephalon sits on the bottom. This important section includes the pretectum, prethalamus, epithalamus, hypothalamus, thalamus and subthalamus, all of which are important sub-parts of brain anatomy. As a whole, this hemisphere serves as a central sensory processing area and controls the autonomic nervous system. The autonomic nervous system, in turn, regulates things like body temperature and sleep states. It also controls the hormones released to the pituitary gland that regulate metabolism as well as other autonomic functions, such as equilibrium, controlling eye movement, sensing facial movement or sensation, and controlling respiration. Salivating, swallowing, and chewing food also are controlled in this area of the brain, as are hearing and speech processing.
Telecephalon
Central nervous system (CNS) functioning primarily happens in the upper hemisphere, also known as the telencephalon. This portion includes the cerebrum, also known as the cerebral cortex. It mainly controls personality, memory, and cognitive function. Most researchers also think that the cerebral cortex is what affords humans the ability to think abstractly, reason, and concentrate.
The telencephalon also includes the basal ganglia, which is responsible for controlling motor functions. Defects in this area of the brain are closely connected with such conditions as Parkinson's disease and Huntington's disease.
Emotional Controls
The forebrain also includes a number of smaller lobes, divided between the two hemispheres, that control several important intermediary functions. These include the frontal lobe, parietal lobe, temporal lobe, amygdala, and hippocampus. The amygdala and hippocampus form the part of the brain that’s known more broadly as the limbic system. This area is often referred to as the "emotional brain" because it controls such things as the fight-or-flight response, sexual behavior, emotional expression, and long-term memory development. It has sometimes also been linked to depression, but scientists aren't exactly sure about where depression and mood disorders originate; there is a lot of controversy and disagreement on this point.
Associative Processes
There are also a number of associated processes associated with both hemispheres. The frontal brain tissue sends sensory signals throughout the body, for example, and as the information is received, the brain connects the new data with previously acquired memories. This is why the smell of something baking may produce a sudden memory of mom or grandma in the kitchen, for instance, or the smell of flowers might remind someone of a past bee sting.