Major Brain Structures and Their Functions

Looking at the brain from above, you can see a deep fissure called the longitudinal fissure, which divides the brain into two cerebral hemispheres. The surface of these cerebral hemispheres is riddled with many smaller fissures called sulci. The ridges around those sulci are called gyri. Sulci and gyri are formed from the folding of the outermost layer of the brain: the cerebral cortex. The cerebral cortex contains important areas devoted to processing sensory information,

important areas for movement, and what are known as association areas, which are regions where information from other brain areas is integrated to support higher-level cognitive functions. The cerebral cortex is often divided into lobes, with the most common division being into four lobes: frontal, parietal, occipital, and temporal. While each lobe contains numerous individual regions, we can identify some important areas for specific functions in each lobe. The frontal lobe,

for example, contains the motor cortex, an area of the brain that’s critically important for voluntary movement. The primary motor cortex makes up a large portion of the motor cortex. Neurons in the primary motor cortex cause movement in the head and body. The portion of the frontal lobe that’s in front of the motor cortex is called the prefrontal cortex. The prefrontal cortex is particularly involved in higher-level cognitive functions, including

decision-making, planning, impulse control, and the ability to act in pursuit of long-term goals. Although there are a number of areas of the frontal lobe that are involved in language, one well-known language area is Broca’s area, which is found in the left cerebral hemisphere in most people. The precise role of Broca’s area in language is still being debated, but it’s thought to be important for language production, because

damage to the region often disrupts the ability to produce language. A sulcus called the central sulcus separates the frontal lobe from the parietal lobe. The parietal lobe is involved with a number of functions, including language, spatial orientation, and attention, and it also contains the primary somatosensory cortex—an area of the brain that’s responsible for processing sensations from the body such as touch,

pain, temperature, and proprioception, or awareness of the body’s position in space. The occipital lobe is found at the very back of the brain; it’s primarily associated with visual processing. The primary visual cortex, the main area for visual processing, is found here, along with several other visual areas. The temporal lobe is involved in a number of functions, including higher order processing

of visual information, learning and memory, and hearing. It contains the primary auditory cortex, which plays a critical role in our ability to perceive sound. Near the junction between the temporal and parietal lobes is another important language area known as Wernicke’s area. Wernicke’s area is typically associated with language comprehension, although its contribution to language processing is still being explored.

Extending from the very back and bottom of the brain is the cerebellum. The cerebellum is best known for its roles in movement, which include motor coordination and control, balance and posture, fine-tuning of voluntary movements, and movement-related learning. When we look at a medial view of the brain, we can see a number of other structures that were obscured with a lateral view. We can, for example, clearly see the brainstem, which connects the

brain to the spinal cord. The brainstem contains a number of important pathways that run between the brain and spinal cord, but it also has many important areas of its own. The brainstem is divided into three regions: the midbrain, pons, and medulla. The medulla, or medulla oblongata, is the lowest part of the brainstem, found just above the spinal cord. One of the important roles linked to the medulla is the regulation of vital functions such as cardiovascular and respiratory

activity. The pons contains important pathways that carry information to and from the cerebellum, and is home to a number of nuclei—or clusters of neurons–associated with the cranial nerves, a group of nerves that are involved with sensory and motor functions of the head and face. The midbrain is the uppermost portion of the brainstem. The midbrain contains the two largest dopamine-producing areas in the brain. One is

activity. The pons contains important pathways that carry information to and from the cerebellum, and is home to a number of nuclei—or clusters of neurons–associated with the cranial nerves, a group of nerves that are involved with sensory and motor functions of the head and face. The midbrain is the uppermost portion of the brainstem. The midbrain contains the two largest dopamine-producing areas in the brain. One is

the substantia nigra; dopamine neurons here play important roles in movement among other things. Large numbers of dopamine neurons in the substantia nigra die in Parkinson’s disease, leading to problems with movement. The other major dopamine producing area in the midbrain is called the ventral tegmental area, or VTA. Dopamine neurons in the VTA extend to various parts of the brain, one of them being

a region called the nucleus accumbens. This pathway between the VTA and nucleus accumbens seems to be critically important for rewarding experiences, such as the use of addictive drugs. The substantia nigra and nucleus accumbens are also part of a larger group of structures called the basal ganglia. The basal ganglia include several other regions as well, and are involved in movement, habit formation, and reward processing, among other things.

Above the brainstem is a structure called the thalamus.The thalamus is often described as a relay station because a great deal of the information that proceeds to the cortex first stops in the thalamus before being sent on to its destination. For example, all sensory information except olfaction travels from sensory receptors to a nucleus in the thalamus specialized for dealing with that type of sensory data. Then, the information is

sent from the thalamus to the appropriate area of the cortex where it is further processed. Posterior to the thalamus is the pineal gland, whose main function is to secrete the hormone melatonin. Melatonin plays an important role in regulating circadian rhythms, and is primarily secreted during darkness. The hypothalamus is found just below the thalamus. The hypothalamus is involved in a long list of processes, many of which are critically important to

maintaining homeostasis across various bodily systems. Some of the major functions generally attributed to the hypothalamus include the regulation of: thirst and drinking behavior, hunger and feeding, body temperature, stress responses, circadian rhythms, and more. One of the ways the hypothalamus helps to regulate all of these functions is through its connections to the pituitary gland, a hormone-secreting gland that sits just

below the hypothalamus. The pituitary gland produces a number of hormones, such as growth hormone, thyroid-stimulating hormone, follicle stimulating hormone, and luteinizing hormone, which it releases in response to signals from the hypothalamus. The pituitary gland also secretes two hormones, oxytocin and vasopressin, which are made in the hypothalamus and sent down to the pituitary gland to be released into the bloodstream.

The hippocampus is found in the temporal lobe, but was not visible with the lateral view of the brain we used earlier when discussing the temporal lobe. Typically, the hippocampus would be surrounded by brain tissue, but in this image its approximate location is highlighted. The hippocampus has many functions, but is best known for its role in memory. It seems to be especially important for turning short-term memories into long-term memories.

Adjacent to the hippocampus is the amygdala, an almond-shaped structure known for its role in emotion. The amygdala is most well-known for processing fear and responding to threats in the environment, but it is also involved in other emotions, including positive emotions such as pleasure. This c-shaped area is called the corpus callosum. The corpus callosum is the largest bundle of axons in the brain, and it connects the left

and right cerebral hemispheres, enabling communication between them to occur. There is a system of cavities found throughout the brain; these hollow spaces are called ventricles. Specialized membranes in the ventricles produce cerebrospinal fluid, or CSF. CSF performs a number of important functions for the brain. For example, it surrounds the brain, forming a protective layer, and suspending the brain in fluid,

which reduces the strain forces like gravity would have on the brain. It also removes waste products from the brain and helps to regulate the extracellular environment of neurons.