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How does it come about that specific areas of the brain are associated with specific functions?

How does it come about that specific areas of the brain are associated with specific functions?

During the development of the human brain, specific areas come to perform specific functions. How (and when) does this differentiation come about?

Presumably, some areas of the brain naturally take on a function that is based on their physical proximity - for example, the visual cortex is the brain area directly connected to the optic pathway. Hence from a developmental perspective, it is natural for it to take on the role of processing visual information.

However, the production of language, for example, could potentially take place in any area of the brain adjacent to the auditory cortex. So how does it come about that it typically always gets processed in Wernicke's area?

  • Is it predetermined genetically? And if so, how? (pre-mapped synapses?)
  • Or is it determined later through some kind of learning process? And if so, what is the explanation for the similarity of brain maps between individuals?

Short answer
Neural wiring is governed by nature and nurture.

Background
I'm not a language person, but I will try to address the question on more familiar grounds to me, namely sensory systems.

A bunch of most intriguing studies have addressed your question directly. Among these is the study from Frost & Metin (1985), who severed the optic tracts of newborn hamsters and found that optic axons would project to the somatosensory thalamic (ventrobasal) nucleus instead. The experimentally induced retinal projection to the somatosensory nucleus occurred through the stabilization of an early, normally transient projection. Moreover, visual stimulation reliably evoked neural responses in the primary and secondary somatosensory cortices (SI and SII) in treated hamsters. Not only that - the representations of the visual field in SI and SII showed a partially retinotopic organization. In other words, the animals had effectively converted (part of) their somatosensory cortex into visual cortex.

Later, Sur et al. (1988) showed with a similar procedure that retinal cells could be induced to project to the medial geniculate nucleus (MGN), the principal auditory thalamic nucleus, in newborn ferrets. They showed that many MGN cells were then visually driven and that the auditory cortex became visually responsive. Some visual cells in auditory cortex were direction-selective or orientation-sensitive, resembling the complex cells in primary visual cortex.

Hence, functional visual projections can be routed into nonvisual structures in higher mammals, suggesting that the modality of a sensory thalamic nucleus or cortical area may be specified by its inputs during development. However, there is a short time window where the extent of neural plasticity will allow such gross abnormalities to develop - both studies used newborn animals therefore.

References
- Frost & Metin, Nature (1985); 317(6033): 162-4
- Sur et al. Science (1988); 242(4884): 1437-41


Localization of Function

To investigate the localisation of function in Phineas Gage's case of how his brain damage resulted in a change of behaviour.

→ Phineas Gage was a 25-year-old railroad worker in the 19th century who survived the an iron rod passing through his head/skull.

→ It entered below his left cheek and exited through the top of his skull on the frontal lobe.

→ J.M Harlow nursed Gage to recovery while observing his behaviour.

→ Harlow saw dramatic changes in his personality after the injury which were not apparent before.
Þ For example: rude language, little restraint, tardiness.

→ Gage's left prefrontal region was damaged which accounted for his change in behaviour.

→ To investigate the unusual language ability by studying Tan's brain.

→ Broca studied Tan over a number of years (longitudinal study).

→ He conducted a post-mortem autopsy on this patient and a few others to investigate what caused his and other similar conditions.

→ After the autopsy, he found that the area of the brain responsible for speak was damaged and cause the speech problem in the patient Tan.

→ This area of the brain was known as Broca's area.

→ This damage effect can be seen in stroke victims who exhibit these kind of speech problems.


The Cerebral Cortex Creates Consciousness and Thinking

All animals have adapted to their environments by developing abilities that help them survive. Some animals have hard shells, others run extremely fast, and some have acute hearing. Human beings do not have any of these particular characteristics, but we do have one big advantage over other animals—we are very, very smart.

You might think that we should be able to determine the intelligence of an animal by looking at the ratio of the animal’s brain weight to the weight of its entire body. But this does not really work. The elephant’s brain is one thousandth of its weight, but the whale’s brain is only one ten-thousandth of its body weight. On the other hand, although the human brain is one 60th of its body weight, the mouse’s brain represents one fortieth of its body weight. Despite these comparisons, elephants do not seem 10 times smarter than whales, and humans definitely seem smarter than mice.

The key to the advanced intelligence of humans is not found in the size of our brains. What sets humans apart from other animals is our larger cerebral cortex —the outer bark-like layer of our brain that allows us to so successfully use language, acquire complex skills, create tools, and live in social groups (Gibson, 2002). In humans, the cerebral cortex is wrinkled and folded, rather than smooth as it is in most other animals. This creates a much greater surface area and size, and allows increased capacities for learning, remembering, and thinking. The folding of the cerebral cortex is referred to as corticalization.

Although the cortex is only about one tenth of an inch thick, it makes up more than 80% of the brain’s weight. The cortex contains about 20 billion nerve cells and 300 trillion synaptic connections (de Courten-Myers, 1999). Supporting all these neurons are billions more glial cells (glia) , cells that surround and link to the neurons, protecting them, providing them with nutrients, and absorbing unused neurotransmitters. The glia come in different forms and have different functions. For instance, the myelin sheath surrounding the axon of many neurons is a type of glial cell. The glia are essential partners of neurons, without which the neurons could not survive or function (Miller, 2005).

The cerebral cortex is divided into two hemispheres, and each hemisphere is divided into four lobes, each separated by folds known as fissures. If we look at the cortex starting at the front of the brain and moving over the top (see Figure 3.10 “The Two Hemispheres”), we see first the frontal lobe (behind the forehead), which is responsible primarily for thinking, planning, memory, and judgment. Following the frontal lobe is the parietal lobe , which extends from the middle to the back of the skull and which is responsible primarily for processing information about touch. Then comes the occipital lobe , at the very back of the skull, which processes visual information. Finally, in front of the occipital lobe (pretty much between the ears) is the temporal lobe , responsible primarily for hearing and language.

Figure 3.10 The Two Hemispheres

The brain is divided into two hemispheres (left and right), each of which has four lobes (temporal, frontal, occipital, and parietal). Furthermore, there are specific cortical areas that control different processes.


Other Areas of the Forebrain

Other areas of the forebrain , located beneath the cerebral cortex, include the thalamus and the limbic system. The thalamus is a sensory relay for the brain. All of our senses, with the exception of smell, are routed through the thalamus before being directed to other areas of the brain for processing ([link]).


The limbic system is involved in processing both emotion and memory. Interestingly, the sense of smell projects directly to the limbic system therefore, not surprisingly, smell can evoke emotional responses in ways that other sensory modalities cannot. The limbic system is made up of a number of different structures, but three of the most important are the hippocampus, the amygdala, and the hypothalamus ([link]). The hippocampus is an essential structure for learning and memory. The amygdala is involved in our experience of emotion and in tying emotional meaning to our memories. The hypothalamus regulates a number of homeostatic processes, including the regulation of body temperature, appetite, and blood pressure. The hypothalamus also serves as an interface between the nervous system and the endocrine system and in the regulation of sexual motivation and behavior.



What are neurotransmitters?

Neurotransmitters are chemical messengers in the body. Their job is to transmit signals from nerve cells to target cells. These target cells may be in muscles, glands, or other nerves.

The brain needs neurotransmitters to regulate many necessary functions, including:

  • heart rate
  • breathing
  • sleep cycles
  • digestion
  • mood
  • concentration
  • appetite
  • muscle movement

The nervous system controls the body’s organs, psychological functions, and physical functions. Nerve cells, also known as neurons, and their neurotransmitters play important roles in this system.

Nerve cells fire nerve impulses. They do this by releasing neurotransmitters, which are chemicals that carry signals to other cells.

Neurotransmitters relay their messages by traveling between cells and attaching to specific receptors on target cells.

Each neurotransmitter attaches to a different receptor — for example, dopamine molecules attach to dopamine receptors. When they attach, this triggers action in the target cells.

After neurotransmitters deliver their messages, the body breaks down or recycles them.

Share on Pinterest Many bodily functions need neurotransmitters to help communicate with the brain.

Experts have identified more than 100 neurotransmitters to date.

Neurotransmitters have different types of action:

  • Excitatory neurotransmitters encourage a target cell to take action.
  • Inhibitory neurotransmitters decrease the chances of the target cell taking action. In some cases, these neurotransmitters have a relaxation-like effect.
  • Modulatory neurotransmitters can send messages to many neurons at the same time. They also communicate with other neurotransmitters.

Some neurotransmitters can carry out various functions, depending on the type of receptor that they are connecting to.

The following sections describe some of the best-known neurotransmitters.

Acetylcholine triggers muscle contractions, stimulates some hormones, and controls the heartbeat. It also plays an important role in brain function and memory. It is an excitatory neurotransmitter.

Low levels of acetylcholine are linked with issues with memory and thinking, such as those that affect people with Alzheimer’s disease. Some Alzheimer’s medications help slow the breakdown of acetylcholine in the body, and this can help control some symptoms, such as memory loss.

Having high levels of acetylcholine can cause too much muscle contraction. This can lead to seizures, spasms, and other health issues.

The nutrient choline, which is present in many foods, is a building block of acetylcholine. People must get enough choline from their diets to produce adequate levels of acetylcholine. However, it is not clear whether consuming more choline can help boost levels of this neurotransmitter.

Choline is available as a supplement, and taking high doses can lead to serious side effects, such as liver damage and seizures. Generally, only people with certain health conditions need choline supplements.

Dopamine is important for memory, learning, behavior, and movement coordination. Many people know dopamine as a pleasure or reward neurotransmitter. The brain releases dopamine during pleasurable activities.

Dopamine is also responsible for muscle movement. A dopamine deficiency can cause Parkinson’s disease.

A healthful diet may help balance dopamine levels. The body needs certain amino acids to produce dopamine, and amino acids are found in protein-rich foods.

Meanwhile, eating high amounts of saturated fat can lead to lower dopamine activity, according to research from 2015 . Also, certain studies suggest that a deficiency in vitamin D can lead to low dopamine activity.

While there are no dopamine supplements, exercise may help boost levels naturally. Some research has shown that regular exercise improves dopamine signaling in people who have early stage Parkinson’s disease.

Endorphins inhibit pain signals and create an energized, euphoric feeling. They are also the body’s natural pain relievers.

One of the best-known ways to boost levels of feel-good endorphins is through aerobic exercise. A “runner’s high,” for example, is a release of endorphins. Also, research indicates that laughter releases endorphins.

Endorphins may help fight pain. The National Headache Foundation say that low levels of endorphins may play a role in some headache disorders.

A deficiency in endorphins may also play a role in fibromyalgia. The Arthritis Foundation recommend exercise as a natural treatment for fibromyalgia, due to its ability to boost endorphins.

Also known as adrenaline, epinephrine is involved in the body’s “fight or flight” response. It is both a hormone and a neurotransmitter.

When a person is stressed or scared, their body may release epinephrine. Epinephrine increases heart rate and breathing and gives the muscles a jolt of energy. It also helps the brain make quick decisions in the face of danger.

While epinephrine is useful if a person is threatened, chronic stress can cause the body to release too much of this hormone. Over time, chronic stress can lead to health problems, such as decreased immunity, high blood pressure, diabetes, and heart disease.

People who are dealing with ongoing high levels of stress may wish to try techniques such as meditation, deep breathing, and exercise.

Anyone who thinks that their levels of stress could be dangerously high or that they may have anxiety or depression should speak with a healthcare provider.

Meanwhile, doctors can use epinephrine to treat many life threatening conditions, including:

Epinephrine’s ability to constrict blood vessels can decrease swelling that results from allergic reactions and asthma attacks. In addition, epinephrine helps the heart contract again if it has stopped during cardiac arrest.

Gamma-aminobutyric acid (GABA) is a mood regulator. It has an inhibitory action, which stops neurons from becoming overexcited. This is why low levels of GABA can cause anxiety, irritability, and restlessness.

Benzodiazepines, or “benzos,” are drugs that can treat anxiety. They work by increasing the action of GABA. This has a calming effect that can treat anxiety attacks.

GABA is available in supplement form, but it is unclear whether these supplements help boost GABA levels in the body, according to some research .

Serotonin is an inhibitory neurotransmitter. It helps regulate mood, appetite, blood clotting, sleep, and the body’s circadian rhythm.

Serotonin plays a role in depression and anxiety. Selective serotonin reuptake inhibitors, or SSRIs, can relieve depression by increasing serotonin levels in the brain.

Seasonal affective disorder (SAD) causes symptoms of depression in the fall and winter, when daylight is less abundant. Research indicates that SAD is linked to lower levels of serotonin.

Serotonin-norepinephrine reuptake inhibitors (SNRIs) increase serotonin and norepinephrine, which is another neurotransmitter. People take SNRIs to relieve symptoms of depression, anxiety, chronic pain, and fibromyalgia.

Some evidence indicates that people can increase serotonin naturally through:

A precursor to serotonin, called 5-hydroxytryptophan (5-HTP), is available as a supplement. However, some research has found that 5-HTP is not a safe or effective treatment for depression and can possibly make the condition worse.

Neurotransmitters play a role in nearly every function in the human body.

A balance of neurotransmitters is necessary to prevent certain health conditions, such as depression, anxiety, Alzheimer’s disease, and Parkinson’s disease.

There is no proven way to ensure that neurotransmitters are balanced and working correctly. However, having a healthful lifestyle that includes regular exercise and stress management can help, in some cases.

Before trying a supplement, ask a healthcare provider. Supplements can interact with medications and may be otherwise unsafe, especially for people with certain health conditions.

Health conditions that result from an imbalance of neurotransmitters often require treatment from a professional. See a doctor regularly to discuss physical and mental health concerns.


The Parts of the Brain

Steven Gans, MD is board-certified in psychiatry and is an active supervisor, teacher, and mentor at Massachusetts General Hospital.

The human brain is not only one of the most important organs in the human body it is also the most complex. The brain is made up of billions of neurons and that it also has a number of specialized parts that are each involved in important functions.

While there is still a great deal that researchers do not yet know about the brain, they have learned a great deal about the anatomy and function of the brain. Understanding these parts can help give people a better idea of how disease and damage may affect the brain and its ability to function.


3.4 The Brain & Spinal Cord

The brain is a remarkably complex organ comprised of billions of interconnected neurons and glia. It is a bilateral, or two-sided, structure that can be separated into distinct lobes. Each lobe is associated with certain types of functions, but, ultimately, all of the areas of the brain interact with one another to provide the foundation for our thoughts and behaviors. In this section, we discuss the overall organization of the brain and the functions associated with different brain areas, beginning with what can be seen as an extension of the brain, the spinal cord.

The Spinal Cord

It can be said that the spinal cord is what connects the brain to the outside world. Because of it, the brain can act. The spinal cord is like a relay station, but a very smart one. It not only routes messages to and from the brain, but it also has its own system of automatic processes, called reflexes.

The top of the spinal cord merges with the brain stem, where the basic processes of life are controlled, such as breathing and digestion. In the opposite direction, the spinal cord ends just below the ribs—contrary to what we might expect, it does not extend all the way to the base of the spine.

The spinal cord is functionally organized in 30 segments, corresponding with the vertebrae. Each segment is connected to a specific part of the body through the peripheral nervous system. Nerves branch out from the spine at each vertebra. Sensory nerves bring messages in motor nerves send messages out to the muscles and organs. Messages travel to and from the brain through every segment.

Some sensory messages are immediately acted on by the spinal cord, without any input from the brain. Withdrawal from heat and knee jerk are two examples. When a sensory message meets certain parameters, the spinal cord initiates an automatic reflex. The signal passes from the sensory nerve to a simple processing center, which initiates a motor command. Seconds are saved, because messages don’t have to go the brain, be processed, and get sent back. In matters of survival, the spinal reflexes allow the body to react extraordinarily fast.

The spinal cord is protected by bony vertebrae and cushioned in cerebrospinal fluid, but injuries still occur. When the spinal cord is damaged in a particular segment, all lower segments are cut off from the brain, causing paralysis. Therefore, the lower on the spine damage is, the fewer functions an injured individual loses.

The Two Hemispheres

The surface of the brain, known as the cerebral cortex, is very uneven, characterized by a distinctive pattern of folds or bumps, known as gyri (singular: gyrus), and grooves, known as sulci (singular: sulcus). These gyri and sulci form important landmarks that allow us to separate the brain into functional centers. The most prominent sulcus, known as the longitudinal fissure, is the deep groove that separates the brain into two halves or hemispheres: the left hemisphere and the right hemisphere.

The surface of the brain is covered with gyri and sulci. A deep sulcus is called a fissure, such as the longitudinal fissure that divides the brain into left and right hemispheres. (credit: modification of work by Bruce Blaus)

There is evidence of some specialization of function—referred to as lateralization—in each hemisphere, mainly regarding differences in language ability. Beyond that, however, the differences that have been found have been minor. What we do know is that the left hemisphere controls the right half of the body, and the right hemisphere controls the left half of the body.

The two hemispheres are connected by a thick band of neural fibers known as the corpus callosum, consisting of about 200 million axons. The corpus callosum allows the two hemispheres to communicate with each other and allows for information being processed on one side of the brain to be shared with the other side.

Normally, we are not aware of the different roles that our two hemispheres play in day-to-day functions, but there are people who come to know the capabilities and functions of their two hemispheres quite well. In some cases of severe epilepsy, doctors elect to sever the corpus callosum as a means of controlling the spread of seizures. While this is an effective treatment option, it results in individuals who have split brains. After surgery, these split-brain patients show a variety of interesting behaviors. For instance, a split-brain patient is unable to name a picture that is shown in the patient’s left visual field because the information is only available in the largely nonverbal right hemisphere. However, they are able to recreate the picture with their left hand, which is also controlled by the right hemisphere. When the more verbal left hemisphere sees the picture that the hand drew, the patient is able to name it (assuming the left hemisphere can interpret what was drawn by the left hand).

(a, b) The corpus callosum connects the left and right hemispheres of the brain. (c) A scientist spreads this dissected sheep brain apart to show the corpus callosum between the hemispheres. (credit c: modification of work by Aaron Bornstein)

This interactive animation on the Nobel Prize website walks users through the hemispheres of the brain.

Much of what we know about the functions of different areas of the brain comes from studying changes in the behavior and ability of individuals who have suffered damage to the brain. For example, researchers study the behavioral changes caused by strokes to learn about the functions of specific brain areas. A stroke, caused by an interruption of blood flow to a region in the brain, causes a loss of brain function in the affected region. The damage can be in a small area, and, if it is, this gives researchers the opportunity to link any resulting behavioral changes to a specific area. The types of deficits displayed after a stroke will be largely dependent on where in the brain the damage occurred.

Consider Theona, an intelligent, self-sufficient woman, who is 62 years old. Recently, she suffered a stroke in the front portion of her right hemisphere. As a result, she has great difficulty moving her left leg. (As you learned earlier, the right hemisphere controls the left side of the body also, the brain’s main motor centers are located at the front of the head, in the frontal lobe.) Theona has also experienced behavioral changes. For example, while in the produce section of the grocery store, she sometimes eats grapes, strawberries, and apples directly from their bins before paying for them. This behavior—which would have been very embarrassing to her before the stroke—is consistent with damage in another region in the frontal lobe—the prefrontal cortex, which is associated with judgment, reasoning, and impulse control.

Forebrain Structures

The two hemispheres of the cerebral cortex are part of the forebrain, which is the largest part of the brain. The forebrain contains the cerebral cortex and a number of other structures that lie beneath the cortex (called subcortical structures): thalamus, hypothalamus, pituitary gland, and the limbic system (collection of structures). The cerebral cortex, which is the outer surface of the brain, is associated with higher level processes such as consciousness, thought, emotion, reasoning, language, and memory. Each cerebral hemisphere can be subdivided into four lobes, each associated with different functions.

The brain and its parts can be divided into three main categories: the forebrain, midbrain, and hindbrain.

Lobes of the Brain

The four lobes of the brain are the frontal, parietal, temporal, and occipital lobes. The frontal lobe is located in the forward part of the brain, extending back to a fissure known as the central sulcus. The frontal lobe is involved in reasoning, motor control, emotion, and language. It contains the motor cortex, which is involved in planning and coordinating movement the prefrontal cortex, which is responsible for higher-level cognitive functioning and Broca’s area, which is essential for language production.

The lobes of the brain are shown.

People who suffer damage to Broca’s area have great difficulty producing language of any form. For example, Padma was an electrical engineer who was socially active and a caring, involved mother. About twenty years ago, she was in a car accident and suffered damage to her Broca’s area. She completely lost the ability to speak and form any kind of meaningful language. There is nothing wrong with her mouth or her vocal cords, but she is unable to produce words. She can follow directions but can’t respond verbally, and she can read but no longer write. She can do routine tasks like running to the market to buy milk, but she could not communicate verbally if a situation called for it.

Probably the most famous case of frontal lobe damage is that of a man by the name of Phineas Gage . On September 13, 1848, Gage (age 25) was working as a railroad foreman in Vermont. He and his crew were using an iron rod to tamp explosives down into a blasting hole to remove rock along the railway’s path. Unfortunately, the iron rod created a spark and caused the rod to explode out of the blasting hole, into Gage’s face, and through his skull. Although lying in a pool of his own blood with brain matter emerging from his head, Gage was conscious and able to get up, walk, and speak. But in the months following his accident, people noticed that his personality had changed. Many of his friends described him as no longer being himself. Before the accident, it was said that Gage was a well-mannered, soft-spoken man, but he began to behave in odd and inappropriate ways after the accident. Such changes in personality would be consistent with loss of impulse control—a frontal lobe function.

Beyond the damage to the frontal lobe itself, subsequent investigations into the rod’s path also identified probable damage to pathways between the frontal lobe and other brain structures, including the limbic system. With connections between the planning functions of the frontal lobe and the emotional processes of the limbic system severed, Gage had difficulty controlling his emotional impulses.

However, there is some evidence suggesting that the dramatic changes in Gage’s personality were exaggerated and embellished. Gage’s case occurred in the midst of a 19 th century debate over localization—regarding whether certain areas of the brain are associated with particular functions. On the basis of extremely limited information about Gage, the extent of his injury, and his life before and after the accident, scientists tended to find support for their own views, on whichever side of the debate they fell (Macmillan, 1999).

(a) Phineas Gage holds the iron rod that penetrated his skull in an 1848 railroad construction accident. (b) Gage’s prefrontal cortex was severely damaged in the left hemisphere. The rod entered Gage’s face on the left side, passed behind his eye, and exited through the top of his skull, before landing about 80 feet away. (credit a: modification of work by Jack and Beverly Wilgus)

The brain’s parietal lobe is located immediately behind the frontal lobe, and is involved in processing information from the body’s senses. It contains the somatosensory cortex, which is essential for processing sensory information from across the body, such as touch, temperature, and pain. The somatosensory cortex is organized topographically, which means that spatial relationships that exist in the body are maintained on the surface of the somatosensory cortex. For example, the portion of the cortex that processes sensory information from the hand is adjacent to the portion that processes information from the wrist.

Spatial relationships in the body are mirrored in the organization of the somatosensory cortex.

The temporal lobe is located on the side of the head (temporal means “near the temples”), and is associated with hearing, memory, emotion, and some aspects of language. The auditory cortex, the main area responsible for processing auditory information, is located within the temporal lobe. Wernicke’s area, important for speech comprehension, is also located here. Whereas individuals with damage to Broca’s area have difficulty producing language, those with damage to Wernicke’s area can produce sensible language, but they are unable to understand it.

Damage to either Broca’s area or Wernicke’s area can result in language deficits. The types of deficits are very different, however, depending on which area is affected.

The occipital lobe is located at the very back of the brain, and contains the primary visual cortex, which is responsible for interpreting incoming visual information. The occipital cortex is organized retinotopically, which means there is a close relationship between the position of an object in a person’s visual field and the position of that object’s representation on the cortex. You will learn much more about how visual information is processed in the occipital lobe when you study sensation and perception.

Other Areas of the Forebrain

Other areas of the forebrain , located beneath the cerebral cortex, include the thalamus and the limbic system. The thalamus is a sensory relay for the brain. All of our senses, with the exception of smell, are routed through the thalamus before being directed to other areas of the brain for processing.

The thalamus serves as the relay center of the brain where most senses are routed for processing.

The limbic system is involved in processing both emotion and memory. Interestingly, the sense of smell projects directly to the limbic system therefore, not surprisingly, smell can evoke emotional responses in ways that other sensory modalities cannot. The limbic system is made up of a number of different structures, but three of the most important are the hippocampus, the amygdala, and the hypothalamus. The hippocampus is an essential structure for learning and memory. Alzheimer’s is a disease that affects the hippocampus and impairs an individual’s ability to recall memories. It then progresses to affect the cerebral cortex, which is responsible for language, reasoning, and social behavior, eventually leading to dementia a general term for memory loss and other cognitive abilities serious enough to interfere with daily life. There is a large amount of research being done in the area of Alzheimer’s disease and its effect on the entire brain, including work here at WSU in Dr. Maureen Schmitter-Edgecombe’s Neuropsychology and Aging laboratory The amygdala is involved in our experience of emotion and in tying emotional meaning to our memories. The hypothalamus regulates a number of homeostatic processes, including the regulation of body temperature, appetite, and blood pressure. The hypothalamus also serves as an interface between the nervous system and the endocrine system and in the regulation of sexual motivation and behavior.

The limbic system is involved in mediating emotional response and memory.

The Case of Henry Molaison (H.M.)

In 1953, Henry Gustav Molaison (H. M.) was a 27-year-old man who experienced severe seizures. In an attempt to control his seizures, H. M. underwent brain surgery to remove his hippocampus and amygdala. Following the surgery, H.M’s seizures became much less severe, but he also suffered some unexpected—and devastating—consequences of the surgery: he lost his ability to form many types of new memories. For example, he was unable to learn new facts, such as who was president of the United States. He was able to learn new skills, but afterward he had no recollection of learning them. For example, while he might learn to use a computer, he would have no conscious memory of ever having used one. He could not remember new faces, and he was unable to remember events, even immediately after they occurred. Researchers were fascinated by his experience, and he is considered one of the most studied cases in medical and psychological history (Hardt, Einarsson, & Nader, 2010 Squire, 2009). Indeed, his case has provided tremendous insight into the role that the hippocampus plays in the consolidation of new learning into explicit memory.

Clive Wearing, an accomplished musician, lost the ability to form new memories when his hippocampus was damaged through illness. Check out the first few minutes of this documentary for an introduction to this man and his condition.

Midbrain and Hindbrain Structures

The midbrain is comprised of structures located deep within the brain, between the forebrain and the hindbrain. The reticular formation is centered in the midbrain, but it actually extends up into the forebrain and down into the hindbrain. The reticular formation is important in regulating the sleep/wake cycle, arousal, alertness, and motor activity.

The substantia nigra (Latin for “black substance”) and the ventral tegmental area (VTA) are also located in the midbrain. Both regions contain cell bodies that produce the neurotransmitter dopamine, and both are critical for movement. Degeneration of the substantia nigra and VTA is involved in Parkinson’s disease. In addition, these structures are involved in mood, reward, and addiction (Berridge & Robinson, 1998 Gardner, 2011 George, Le Moal, & Koob, 2012).

The substantia nigra and ventral tegmental area (VTA) are located in the midbrain.

The hindbrain is located at the back of the head and looks like an extension of the spinal cord. It contains the medulla, pons, and cerebellum. The medulla controls the automatic processes of the autonomic nervous system, such as breathing, blood pressure, and heart rate. The word pons literally means “bridge,” and as the name suggests, the pons serves to connect the brain and spinal cord. It also is involved in regulating brain activity during sleep. The medulla, pons, and midbrain together are known as the brainstem.

The pons, medulla, and cerebellum make up the hindbrain.

The cerebellum (Latin for “little brain”) receives messages from muscles, tendons, joints, and structures in our ear to control balance, coordination, movement, and motor skills. The cerebellum is also thought to be an important area for processing some types of memories. In particular, procedural memory, or memory involved in learning and remembering how to perform tasks, is thought to be associated with the cerebellum. Recall that H. M. was unable to form new explicit memories, but he could learn new tasks. This is likely due to the fact that H. M.’s cerebellum remained intact.

Brain Dead and on Life Support

What would you do if your spouse or loved one was declared brain dead but his or her body was being kept alive by medical equipment? Whose decision should it be to remove a feeding tube? Should medical care costs be a factor?

On February 25, 1990, a Florida woman named Terri Schiavo went into cardiac arrest, apparently triggered by a bulimic episode. She was eventually revived, but her brain had been deprived of oxygen for a long time. Brain scans indicated that there was no activity in her cerebral cortex, and she suffered from severe and permanent cerebral atrophy. Basically, Schiavo was in a vegetative state. Medical professionals determined that she would never again be able to move, talk, or respond in any way. To remain alive, she required a feeding tube, and there was no chance that her situation would ever improve.

On occasion, Schiavo’s eyes would move, and sometimes she would groan. Despite the doctors’ insistence to the contrary, her parents believed that these were signs that she was trying to communicate with them.

After 12 years, Schiavo’s husband argued that his wife would not have wanted to be kept alive with no feelings, sensations, or brain activity. Her parents, however, were very much against removing her feeding tube. Eventually, the case made its way to the courts, both in the state of Florida and at the federal level. By 2005, the courts found in favor of Schiavo’s husband, and the feeding tube was removed on March 18, 2005. Schiavo died 13 days later.

Why did Schiavo’s eyes sometimes move, and why did she groan? Although the parts of her brain that control thought, voluntary movement, and feeling were completely damaged, her brainstem was still intact. Her medulla and pons maintained her breathing and caused involuntary movements of her eyes and the occasional groans. Over the 15-year period that she was on a feeding tube, Schiavo’s medical costs may have topped $7 million (Arnst, 2003).

These questions were brought to popular conscience 25 years ago in the case of Terri Schiavo, and they persist today. In 2013, a 13-year-old girl who suffered complications after tonsil surgery was declared brain dead. There was a battle between her family, who wanted her to remain on life support, and the hospital’s policies regarding persons declared brain dead. In another complicated 2013–14 case in Texas, a pregnant EMT professional declared brain dead was kept alive for weeks, despite her spouse’s directives, which were based on her wishes should this situation arise. In this case, state laws designed to protect an unborn fetus came into consideration until doctors determined the fetus unviable.

Decisions surrounding the medical response to patients declared brain dead are complex. What do you think about these issues?

Brain Imaging

You have learned how brain injury can provide information about the functions of different parts of the brain. Increasingly, however, we are able to obtain that information using brain imaging techniques on individuals who have not suffered brain injury. In this section, we take a more in-depth look at some of the techniques that are available for imaging the brain, including techniques that rely on radiation, magnetic fields, or electrical activity within the brain

Techniques Involving Radiation

A computerized tomography (CT) scan involves taking a number of x-rays of a particular section of a person’s body or brain. The x-rays pass through tissues of different densities at different rates, allowing a computer to construct an overall image of the area of the body being scanned. A CT scan is often used to determine whether someone has a tumor, or significant brain atrophy.

A CT scan can be used to show brain tumors. (a) The image on the left shows a healthy brain, whereas (b) the image on the right indicates a brain tumor in the left frontal lobe. (credit a: modification of work by “Aceofhearts1968″/Wikimedia Commons credit b: modification of work by Roland Schmitt et al)

Positron emission tomography (PET) scans create pictures of the living, active brain. An individual receiving a PET scan drinks or is injected with a mildly radioactive substance, called a tracer. Once in the bloodstream, the amount of tracer in any given region of the brain can be monitored. As brain areas become more active, more blood flows to that area. A computer monitors the movement of the tracer and creates a rough map of active and inactive areas of the brain during a given behavior. PET scans show little detail, are unable to pinpoint events precisely in time, and require that the brain be exposed to radiation therefore, this technique has been replaced by the fMRI as an alternative diagnostic tool. However, combined with CT, PET technology is still being used in certain contexts. For example, CT/PET scans allow better imaging of the activity of neurotransmitter receptors and open new avenues in schizophrenia research. In this hybrid CT/PET technology, CT contributes clear images of brain structures, while PET shows the brain’s activity.

A PET scan is helpful for showing activity in different parts of the brain. (credit: Health and Human Services Department, National Institutes of Health)

Techniques Involving Magnetic Fields

In magnetic resonance imaging (MRI), a person is placed inside a machine that generates a strong magnetic field. The magnetic field causes the hydrogen atoms in the body’s cells to move. When the magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their original positions. Tissues of different densities give off different signals, which a computer interprets and displays on a monitor. Functional magnetic resonance imaging (fMRI) operates on the same principles, but it shows changes in brain activity over time by tracking blood flow and oxygen levels. The fMRI provides more detailed images of the brain’s structure, as well as better accuracy in time, than is possible in PET scans. With their high level of detail, MRI and fMRI are often used to compare the brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This comparison helps determine what structural and functional differences exist between these populations.

An fMRI shows activity in the brain over time. This image represents a single frame from an fMRI. (credit: modification of work by Kim J, Matthews NL, Park S.)

Visit this virtual lab to learn more about MRI and fMRI.

Techniques Involving Electrical Activity

In some situations, it is helpful to gain an understanding of the overall activity of a person’s brain, without needing information on the actual location of the activity. Electroencephalography (EEG) serves this purpose by providing a measure of a brain’s electrical activity. An array of electrodes is placed around a person’s head. The signals received by the electrodes result in a printout of the electrical activity of his or her brain, or brainwaves, showing both the frequency (number of waves per second) and amplitude (height) of the recorded brainwaves, with an accuracy within milliseconds. Such information is especially helpful to researchers studying sleep patterns among individuals with sleep disorders.

Using caps with electrodes, modern EEG research can study the precise timing of overall brain activities. (credit: SMI Eye Tracking)

SUMMARY

The brain consists of two hemispheres, each controlling the opposite side of the body. Each hemisphere can be subdivided into different lobes: frontal, parietal, temporal, and occipital. In addition to the lobes of the cerebral cortex, the forebrain includes the thalamus (sensory relay) and limbic system (emotion and memory circuit). The midbrain contains the reticular formation, which is important for sleep and arousal, as well as the substantia nigra and ventral tegmental area. These structures are important for movement, reward, and addictive processes. The hindbrain contains the structures of the brainstem (medulla, pons, and midbrain), which control automatic functions like breathing and blood pressure. The hindbrain also contains the cerebellum, which helps coordinate movement and certain types of memories.

Individuals with brain damage have been studied extensively to provide information about the role of different areas of the brain, and recent advances in technology allow us to glean similar information by imaging brain structure and function. These techniques include CT, PET, MRI, fMRI, and EEG.

Openstax Psychology text by Kathryn Dumper, William Jenkins, Arlene Lacombe, Marilyn Lovett and Marion Perlmutter licensed under CC BY v4.0. https://openstax.org/details/books/psychology

Exercises

Review Questions:

1. The ________ is a sensory relay station where all sensory information, except for smell, goes before being sent to other areas of the brain for further processing.

2. Damage to the ________ disrupts one’s ability to comprehend language, but it leaves one’s ability to produce words intact.

3. A(n) ________ uses magnetic fields to create pictures of a given tissue.

4. Which of the following is not a structure of the forebrain?

Critical Thinking Questions:

1. Before the advent of modern imaging techniques, scientists and clinicians relied on autopsies of people who suffered brain injury with resultant change in behavior to determine how different areas of the brain were affected. What are some of the limitations associated with this kind of approach?

2. Which of the techniques discussed would be viable options for you to determine how activity in the reticular formation is related to sleep and wakefulness? Why?

Personal Application Questions:

1. You read about H. M.’s memory deficits following the bilateral removal of his hippocampus and amygdala. Have you encountered a character in a book, television program, or movie that suffered memory deficits? How was that character similar to and different from H. M.?

amygdala: structure in the limbic system involved in our experience of emotion and tying emotional meaning to our memories

auditory cortex: strip of cortex in the temporal lobe that is responsible for processing auditory information

Broca’s area: region in the left hemisphere that is essential for language production

cerebellum: hindbrain structure that controls our balance, coordination, movement, and motor skills, and it is thought to be important in processing some types of memory

cerebral cortex: surface of the brain that is associated with our highest mental capabilities

computerized tomography (CT) scan: imaging technique in which a computer coordinates and integrates multiple x-rays of a given area

corpus callosum: thick band of neural fibers connecting the brain’s two hemispheres

electroencephalography (EEG): recording the electrical activity of the brain via electrodes on the scalp

forebrain: largest part of the brain, containing the cerebral cortex, the thalamus, and the limbic system, among other structures

frontal lobe: part of the cerebral cortex involved in reasoning, motor control, emotion, and language contains motor cortex

functional magnetic resonance imaging (fMRI): MRI that shows changes in metabolic activity over time

gyrus: (plural: gyri) bump or ridge on the cerebral cortex

hemisphere: left or right half of the brain

hindbrain: division of the brain containing the medulla, pons, and cerebellum

hippocampus: structure in the temporal lobe associated with learning and memory

hypothalamus: forebrain structure that regulates sexual motivation and behavior and a number of homeostatic processes serves as an interface between the nervous system and the endocrine system

lateralization: concept that each hemisphere of the brain is associated with specialized functions

limbic system: collection of structures involved in processing emotion and memory

longitudinal fissure: deep groove in the brain’s cortex

magnetic resonance imaging (MRI): magnetic fields used to produce a picture of the tissue being imaged

medulla: hindbrain structure that controls automated processes like breathing, blood pressure, and heart rate

midbrain: division of the brain located between the forebrain and the hindbrain contains the reticular formation

motor cortex: strip of cortex involved in planning and coordinating movement

occipital lobe: part of the cerebral cortex associated with visual processing contains the primary visual cortex

parietal lobe: part of the cerebral cortex involved in processing various sensory and perceptual information contains the primary somatosensory cortex

pons: hindbrain structure that connects the brain and spinal cord involved in regulating brain activity during sleep

positron emission tomography (PET) scan: involves injecting individuals with a mildly radioactive substance and monitoring changes in blood flow to different regions of the brain

prefrontal cortex: area in the frontal lobe responsible for higher-level cognitive functioning

reticular formation: midbrain structure important in regulating the sleep/wake cycle, arousal, alertness, and motor activity

somatosensory cortex: essential for processing sensory information from across the body, such as touch, temperature, and pain

substantia nigra: midbrain structure where dopamine is produced involved in control of movement

sulcus: (plural: sulci) depressions or grooves in the cerebral cortex

temporal lobe: part of cerebral cortex associated with hearing, memory, emotion, and some aspects of language contains primary auditory cortex

thalamus: sensory relay for the brain

ventral tegmental area (VTA): midbrain structure where dopamine is produced: associated with mood, reward, and addiction

Wernicke’s area: important for speech comprehension

Answers to Exercises

Review Questions:

Critical Thinking Questions:

1. Before the advent of modern imaging techniques, scientists and clinicians relied on autopsies of people who suffered brain injury with resultant change in behavior to determine how different areas of the brain were affected. What are some of the limitations associated with this kind of approach?

2. Which of the techniques discussed would be viable options for you to determine how activity in the reticular formation is related to sleep and wakefulness? Why?

Personal Application Questions:

1. You read about H. M.’s memory deficits following the bilateral removal of his hippocampus and amygdala. Have you encountered a character in a book, television program, or movie that suffered memory deficits? How was that character similar to and different from H. M.?

amygdala: structure in the limbic system involved in our experience of emotion and tying emotional meaning to our memories

auditory cortex: strip of cortex in the temporal lobe that is responsible for processing auditory information

Broca’s area: region in the left hemisphere that is essential for language production

cerebellum: hindbrain structure that controls our balance, coordination, movement, and motor skills, and it is thought to be important in processing some types of memory

cerebral cortex: surface of the brain that is associated with our highest mental capabilities

computerized tomography (CT) scan: imaging technique in which a computer coordinates and integrates multiple x-rays of a given area

corpus callosum: thick band of neural fibers connecting the brain’s two hemispheres

electroencephalography (EEG): recording the electrical activity of the brain via electrodes on the scalp

forebrain: largest part of the brain, containing the cerebral cortex, the thalamus, and the limbic system, among other structures

frontal lobe: part of the cerebral cortex involved in reasoning, motor control, emotion, and language contains motor cortex

functional magnetic resonance imaging (fMRI): MRI that shows changes in metabolic activity over time

gyrus: (plural: gyri) bump or ridge on the cerebral cortex

hemisphere: left or right half of the brain

hindbrain: division of the brain containing the medulla, pons, and cerebellum

hippocampus: structure in the temporal lobe associated with learning and memory

hypothalamus: forebrain structure that regulates sexual motivation and behavior and a number of homeostatic processes serves as an interface between the nervous system and the endocrine system

lateralization: concept that each hemisphere of the brain is associated with specialized functions

limbic system: collection of structures involved in processing emotion and memory

longitudinal fissure: deep groove in the brain’s cortex

magnetic resonance imaging (MRI): magnetic fields used to produce a picture of the tissue being imaged

medulla: hindbrain structure that controls automated processes like breathing, blood pressure, and heart rate

midbrain: division of the brain located between the forebrain and the hindbrain contains the reticular formation

motor cortex: strip of cortex involved in planning and coordinating movement

occipital lobe: part of the cerebral cortex associated with visual processing contains the primary visual cortex

parietal lobe: part of the cerebral cortex involved in processing various sensory and perceptual information contains the primary somatosensory cortex

pons: hindbrain structure that connects the brain and spinal cord involved in regulating brain activity during sleep

positron emission tomography (PET) scan: involves injecting individuals with a mildly radioactive substance and monitoring changes in blood flow to different regions of the brain

prefrontal cortex: area in the frontal lobe responsible for higher-level cognitive functioning

reticular formation: midbrain structure important in regulating the sleep/wake cycle, arousal, alertness, and motor activity

somatosensory cortex: essential for processing sensory information from across the body, such as touch, temperature, and pain

substantia nigra: midbrain structure where dopamine is produced involved in control of movement

sulcus: (plural: sulci) depressions or grooves in the cerebral cortex

temporal lobe: part of cerebral cortex associated with hearing, memory, emotion, and some aspects of language contains primary auditory cortex

thalamus: sensory relay for the brain

ventral tegmental area (VTA): midbrain structure where dopamine is produced: associated with mood, reward, and addiction


The hypothalamus, also a part of the limbic system, feeds information into the amygdala. Shippensburg University states that the hypothalamus acts as a regulator of emotion, controlling levels of sexual desire, pleasure, aggression and anger.

The cingulate gyrus acts as a pathway between the thalamus and the hippocampus, and plays a role in remembering emotional charged events. Shippensburg University notes that the cingulate gyrus focuses the attention on the event, alerting the rest of the brain that it is emotionally significant.


Parts of the Brain: Structures and Their Functions

The brain is made up of 3 essential parts: Cerebrum, Cerebellum, and Brainstem.

1.Cerebrum

The cerebrum is the largest part of the human brain. It has a rough surface (cerebral cortex) with gyri and sulci. It can also be divided into 2 parts: the left hemisphere and the right hemisphere.

Although the hemispheres look identical, the left and right hemispheres have particular functions. While the left hemisphere (logical side) controls language and speech, the right hemisphere (creative side) is responsible for translating visual information.

According to the function, the cerebrum is further divided into 4 different lobes: frontal lobes, parietal lobes, temporal lobes, and occipital lobes. Each lobe has different functions:

Frontal Lobe

The frontal lobe rests just below the forehead and controls our reasoning, organizing, our ability to speak, solve problems, pay attention, and our emotions.

Parietal Lobe

The parietal lobe lies at the upper rear of our brain. This lobe manages our complex behaviors, including the 5 senses: touch, vision, and spatial awareness.

The parietal lobe also relays sensory information from different parts of the body, helps us process and learn a language, and maintains the body’s positioning and movement.

Occipital Lobe

The occipital lobe is located at the rear of our brain. This lobe is responsible for our visual awareness, including visual attention, optical recognition, and spatial awareness.

It also controls our ability to interprets body language like facial expressions, gestures, and body postures.

Temporal Lobe

Your temporal lobe sits close to your ears and is associated with interpreting and translating auditory stimuli. For example, your temporal lobe allows you to focus on one voice at a loud party.

This lobe also helps you understand oral language, general process knowledge and stores your verbal and visual memory.

2. Cerebellum

The cerebellum, also known as the little brain, is located in the back of the brain. It sits just below the occipital lobes and on top of the pons. Just like the cerebrum, the cerebellum has two equal hemispheres and a wrinkly surface.

Although the cerebellum is small, it contains numerous neurons. It can help coordinate the movement of body muscles, especially the fine movement of hands and feet. The function of the cerebellum also includes maintaining posture, equilibrium, body balance, and even speech.

3. Brainstem

The brain stem is the posterior part of the brain that connects the brain with the spinal cord. Brain stem works together to regulate essential life functions, including body temperature, breathing, heartbeat, and blood pressure.

In addition, the brain stem coordinates the fine movement of the face and limbs. Functions of this area include sneezing, vomiting, swallowing, and movement of the eyes and mouth.

The brain stem comprises parts of the midbrain, pons, and medulla, all of which have specific functions.

Midbrain

The midbrain consists of the tegmentum and the tectum, located in the mouth of the brain stem. It plays a key role in controlling voluntary motor function and transferring messages. In addition, it controls eye movement and processes auditory, visual information, and eye movement.

The pons is the largest structure in the brain stem and is found above the medulla and underneath the midbrain, and in front of the cerebellum. It functions as a bridge between several parts of the nervous system, including the cerebrum and cerebellum. The pons also contains many vital nerves, such as

  • The trigeminal nerve – This nerve controls facial muscles involved in chewing, biting, and swallowing.
  • The abducens nerve – The abducens nerve allows the eyes to look from side to side.
  • The vestibulocochlear nerve – This nerve controls hearing and balance.

The pons also helps regulate sleep cycles, breathing patterns, respiration, and reflexes.

Medulla

The medulla is a cone-shaped structure located in front of the cerebellum. The prominent role of the medulla oblongata is regulating involuntary (autonomic) functions, including breathing, digestion, sneezing, swallowing, and heart rate.

4. Limbic System

The limbic system is a complex brain structure that lies deep in the cerebrum. It contains the thalamus, hypothalamus, hippocampus, and amygdala.

Since it plays a significant role in controlling our emotions and forming our memories, it is often called our “emotional brain” or ‘childish brain.’

Thalamus

The thalamus is a small mass of grey matter that relays sensory information from the spinal cord, brainstem, and other parts of the brain to the cerebral cortex.

The thalamus is a relay station for signals received by the human body from the outside to enter the brain. In addition, it is also related to consciousness, memory, and sleep.

Hypothalamus

The hypothalamus is a part of the brain that sits right below the thalamus. Although the hypothalamus is a tiny part of the brain, it has one of the most crucial and busiest roles.

The primary function of the hypothalamus is maintaining homeostasis in the body. It’s also responsible for releasing hormones, regulating body temperature, controlling appetite, and managing sexual behavior.

Amygdala

The amygdala is a small, almond-shaped structure in the limbic system that processes strong emotions like fear, aggression, and anxiety.

The amygdala is located close to the hippocampus. It contains many receptor sites that can also perceive certain emotions and the storing and retrieving of emotional memories.

Hippocampus

The principal role of the hippocampus is forming, organizing, and storing short and long-term memories.

The hippocampus also helps form new memories and links emotions, feelings, and sensations such as specific smell and sound to these memories.

Pituitary Gland

The pituitary gland is a small, pea-shaped gland located at the brain’s base, just behind the bridge of the nose. The pituitary gland produces different hormones that regulate many of the body’s processes, including growth, sexual development, metabolism, and reproduction.

5. Skull

The skull is a fusion of bones that protects the brain, the brainstem and outlines the face. The 8 bones that protect your bones from injury include:

  • 1 frontal bone
  • 2 parietal bones
  • 1 occipital bone
  • 2 temporal bones
  • 1 sphenoid bone
  • 1 Ethmoid bone

Brain Conditions When the Brains Structure is Damaged

Your brain is one of the most complex organs in the human, and if one of the brain’s structures is damaged, it could lead to a brain condition.

For example, if your Broca’s area is damaged, you may have trouble moving your tongue, and your speech may be slow and poorly articulated. Other conditions that could affect the brain include:

Brain aneurysm: When an artery in the brain swells, it could lead to a brain aneurysm. If the aneurysm ruptures, it could cause a stroke.

Brain tumor: When any tissue in your brain starts growing abnormally, it could be symptoms of benign or malignant cancer.

Intracerebral hemorrhage: Bleeding inside the brain can cause difficulty speaking or difficulty walking.

Concussion: When there’s a heavy blow to the head, you may experience a concussion and temporarily lose brain function.

Cerebral edema: Electrolyte imbalance in the brain could lead to swelling of the brain tissue.

Glioblastoma: Glioblastoma is a brain tumor that develops very rapidly and creates pressure on the brain.

Pro tip: Glioblastoma is usually aggressive and could be very difficult to cure.

Meningitis: When the lining around the brain or spinal cord becomes inflamed from an infection, you may have meningitis. Other symptoms associated with meningitis include headache, fever, sleepiness, neck pain, and stiff neck.

Encephalitis: Encephalitis usually arises when tissue in the brain becomes inflamed. It’s usually a result of a viral infection and could cause fever, headache, and confusion.

Traumatic brain injury: A severe head injury could lead to permanent brain damage. Other symptoms include mental impairment and personality and mood changes.

Parkinson’s disease: Degeneration of nerves in the brain could lead to the development of Parkinson’s disease. People with Parkinson’s disease may experience hand tremors and problems with their coordination and movement.

Epilepsy: Although there’s no exact cause for epilepsy, head injuries and several strokes can trigger epilepsy. People with epilepsy may also experience seizures.

Dementia: When a nerve cell in the brain starts malfunctioning or degenerating slowly, it could lead to dementia. Strokes and alcohol abuse could also cause brain dementia.

Alzheimer’s disease: Alzheimer’s disease is known as senile dementia. Here, the nerves in the brain degenerate, causing progressive dementia.

Brain abscess: A brain abscess occurs when there’s a pocket of infection in the brain. Brain abscesses are usually caused by bacteria and may require either antibiotics or surgical removal.

How to maintain a healthy brain

As we age, certain brain areas start to shrink, especially areas that are important to learning and storing memories. The good news is – You can follow some tips to keep your brain in excellent health and slow down mental decline. Here are some tips you can use to maintain a healthy brain.

Doing mental exercises like doing crossword puzzles, reading regularly, or learning a new language helps improve your mental fitness. Doing mental exercises stimulate nerve cells and may even trigger the development of new brain cells.

Injuries to the head can cause brain concussions, other severe brain injuries. You can protect your head by wearing helmets or other protective gear when you’re playing contact sports.

Doing regular physical exercises doesn’t only help your muscles it helps your brain too. Exercising improves blood flow in your body, including your brain.

Moderate exercise also lowers blood pressure, reduces mental stress, and could trigger the development of new nerve cells.

Smoking isn’t only bad for your general health it could also lead to cognitive decline in the brain.


Thalamus And Hypothalamus

Deep in the core area of the brain, just above the top of the brainstem, are structures that have a great deal to do with perception, movement, and the body's vital functions. The thalamus consists of two oval masses, each embedded in a cerebral hemisphere, that are joined by a bridge. The masses contain nerve cell bodies that sort information from four of the senses—sight, hearing, taste, and touch𠅊nd relay it to the cerebral cortex. (Only the sense of smell sends signals directly to the cortex, bypassing the thalamus.) Sensations of pain, temperature, and pressure are also relayed through the thalamus, as are the nerve impulses from the cerebral hemispheres that initiate voluntary movement.

The hypothalamus, despite its relatively small size (roughly that of a thumbnail), controls a number of drives essential for the functioning of a wide-ranging omnivorous social mammal. At the autonomic level, the hypothalamus stimulates smooth muscle (which lines the blood vessels, stomach, and intestines) and receives sensory impulses from these areas. Thus it controls the rate of the heart, the passage of food through the alimentary canal, and contraction of the bladder.

The hypothalamus is the main point of interaction for the body's two physical control systems: the nervous system, which transmits information in the form of minute electrical impulses, and the endocrine system, which brings about changes of state through the release of chemical factors. It is the hypothalamus that first detects crucial changes in the body and responds by stimulating various glands and organs to release hormones.

The hypothalamus is also the brain's intermediary for translating emotion into physical response. When strong feelings (rage, fear, pleasure, excitement) are generated in the mind, whether by external stimuli or by the action of thoughts, the cerebral cortex transmits impulses to the hypothalamus the hypothalamus may then send signals for physiological changes through the autonomic nervous system and through the release of hormones from the pituitary. Physical signs of fear or excitement, such as a racing heartbeat, shallow breathing, and perhaps a clenched "gut feeling," all originate here.

Also in the hypothalamus are neurons that monitor body temperature at the surface through nerve endings in the skin, and other neurons that monitor the blood flowing through this part of the brain itself, as an indicator of core body temperature. The front part of the hypothalamus contains neurons that act to lower body temperature by relaxing smooth muscle in the blood vessels, which causes them to dilate and increases the rate of heat loss from the skin. Through its neurons associated with the sweat glands of the skin, the hypothalamus can also promote heat loss by increasing the rate of perspiration. In opposite conditions, when the body's temperature falls below the (rather narrow) ideal range, a portion of the hypothalamus directs the contraction of blood vessels, slows the rate of heat loss, and causes the onset of shivering (which produces a small amount of heat).

The hypothalamus is the control center for the stimuli that underlie eating and drinking. The sensations that we interpret as hunger arise partly from a degree of emptiness in the stomach and partly from a drop in the level of two substances: glucose circulating in the blood and a hormone that the intestine produces shortly after the intake of food. (Receptors for this hormone gauge how far digestion has proceeded since the last meal.) This system is not a simple "on" switch for hunger, however: another portion of the hypothalamus, when stimulated, actively inhibits eating by promoting a feeling of satiety. In experimental animals, damage to this portion of the brain is associated with continued excessive eating, eventually leading to obesity.

In addition to these numerous functions, there is evidence that the hypothalamus plays a role in the induction of sleep. For one thing, it forms part of the reticular activating system, the physical basis for that hard-to-define state known as consciousness (about which more later) for another, electrical stimulation of a portion of the hypothalamus has been shown to induce sleep in experimental animals, although the mechanism by which this works is not yet known. In all, the hypothalamus is a richly complex cubic centimeter of vital connections, which will continue to reward close study for some time to come. Because of its unique position as a midpost between thought and feeling and between conscious act and autonomic function, a thorough understanding of its workings should tell us much about the earliest history and development of the human animal.


Watch the video: Πώς μπορούμε να αναπτύξουμε νέους νευρώνες στον εγκέφαλο. TED (January 2022).