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Why is the order of white/grey matter different in the brain and spinal cord?

Why is the order of white/grey matter different in the brain and spinal cord?


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In the brain proper, grey matter forms the outer layer of the brain, and white matter forms the inner layer. In the spine, this is reversed: white matter forms the outer layer of the spine, and grey matter the inner layer. Is there a developmental or functional reason for this?


I'll tackle this question from a functional point of view.

Gray matter are cell bodies, white matter are myelinated fiber tracts.

In the brain, the gray matter is basically the cortex, the white matter lies mainly underneath it. The Cortex is the place where all the higher mental processing takes place (Fig. 1).


Fig. 1. Cortical functions. Source: Penn Medicine

The white matter in the brain connects the various parts of the cortex so that information can be transported for further processing and integrated.


Fig. 2. Central white matter. Source: NIH Medline

Since the cortex is the 'processor', it makes sense to connect the parts subcortically (more efficient as it leads to shorter connections). However, the cortex has been expanding very late in evolution, so this 'endpoint reasoning' can be contested, because from an evolutionary perspective, more cortex was needed and hence it was expanded right where it happened to be, namely in the outer part of the brain.

In the spinal chord things are pretty much reversed; grey matter within, white matter around it (Fig. 3).


Fig. 3. Section through spinal chord with central grey matter and surrounding white matter. Source: University of Michigan

The white matter, again, is formed by various tracts (Fig. 4) and the grey matter with parts that are processing information (fig. 5).


Fig. 4. Section through spinal chord showing the spinal tracts forming the white matter. Source: Biology.SE


Fig. 5. Section through spinal chord showing the spinal reflex arches forming the gray matter. Source: APSU Biology

The white matter in the spinal chord constitutes the various sensory and motor pathways to and from the brain, respectively. The gray matter constitutes basic processing nuclei that form the reflex arches in the spinal chord. These reflex arches process incoming sensory information (e.g. pain) and govern motor output (e.g., pulling the hand away from the fire).

Again, the structure makes sense in terms of efficiency, as the reflex arches combine the sensory and motor tracts to govern reflexes, and therefore processing them from within saves space.


This is a simple logic to understand. In the brain the grey matter is on the cotex.Grey matter is a tissue made of the cytons due to which the cotex is pinkish Grey in colour. The White matter,the tissue made of axons is inside to the brain. Cortex is the processing centre which has cytons. In the spine the processing is to be done internally. So the cytons concentrate inside the spine which we call the Grey matter.Similarly the axons are to be around the Grey matter to transfer messages from and to other organs.They form the White matter outside the spine.


White matter hyperintensities is a term used to describe spots in the brain that show up on magnetic resonance imaging (MRIs) as bright white areas.  

According to Charles DeCarli, the director of UC Davis Alzheimer's Disease Center, these areas may indicate some type of injury to the brain, perhaps due to decreased blood flow in that area.

The presence of white matter hyperintensities has been correlated with a higher risk of stroke, which can lead to vascular dementia.

White matter hyperintensities are often referred to as white matter disease.

Initially, white matter disease was thought to simply be related to aging. However, we now know there are other specific risk factors for white matter disease, which include:

  • High blood pressure
  • Smoking
  • Cardiovascular disease
  • High cholesterol.

While white matter disease has been associated with strokes, cognitive loss, and dementia, it also has some physical and emotional symptoms such as balance problems, falls, depression, and difficulty multitasking (e.g., walking and talking.)


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Summary

Ascending tracts

Just to recap the ascending spinal tracts:

  • Lateral spinothalamic carries pain and thermal stimuli.
  • Ventral spinothalamic is responsible for pressure and crudetouch sensations.
  • Dorsal column is the area of vibration sensation, proprioception, and two-point discrimination.
  • Spinocerebellar tracts (anterior and posterior divisions) conduct unconscious stimuli for proprioception in joints and muscles.
  • Cuneocerebellar carries the same information as the spinocerebellar tracts.
  • Other ascending tracts in the spinal cord that are discussed in more detail in other articles include:
    • Spinotectal serves an accessory pathway for tactile, painful, and thermal stimuli to reach the midbrain.
    • Spinoreticular integrates the stimuli from the muscles and joints into the reticular formation.
    • Spino-olivary is an accessory pathway that carries additional information to the cerebellum.

    Descending tracts

    In summary, the descending tracts of the spinal cord are:

    • Lateral and ventral (anterior) corticospinal tracts deal with voluntary, discrete, skilledmotoractivities.
    • Lateral and ventral (anterior) reticulospinal tracts provide excitatory or inhibitory regulation of voluntary movements and reflexes
    • Rubrospinaltract promotes flexor and inhibit extensor muscle activity
    • Vestibulospinal tract promotes extensor and inhibit flexor muscle activity. It also supports balance and posture.
    • Tectospinal tracts facilitate posturalmovements arising from visual stimuli.
    • Although the corticobulbartract is a descending pathway, it terminates on the cranial nerve nuclei, which are located in the midbrain and brainstem.

    Ascending and descending tracts of the spinal cord: want to learn more about it?

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    What Is the Function of White Matter in the Brain?

    White matter is the commonly used term for the myelinated axons that provide connections between neurons, or grey matter. The main function of white matter in the brain is to regulate the electrical signals in axons. These signals are a form of communication, and work to pass along information that is translated into chemical signals between neurons. Without white matter, electrical signals would weaken as they traveled along the axon.

    Understanding the structure of white matter is necessary to understand its function. Support cells in the brain, known as glial cells, produce the fatty tissue known as myelin, which wraps around axons like a sheath. Essentially, these sheaths seal the axon and prevent the ions that propagate electrical signals from diffusing out. The result is that these signals can travel more quickly over longer distances than they could without insulation.

    Traveling electrical signals are known as action potentials. To maintain the ionic difference that allows action potentials to take place, there are gaps between myelinated cells, which allow ions to transfer in and out of the axon. This allows the charge in the axon to maintain its strength, even over long distances. The importance of white matter increases for signals that must travel great distances. Nerve cells that transmit sensory signals to the brain, or neurons that regulate breathing or heart rate, would be unable to perform their tasks without the white matter in the brain and spinal cord.

    Inside the brain, white matter is found in many structures, but it is particularly concentrated in areas where many signals must be sent long distance. These areas include the thalamus and hypothalamus, which govern processes like blood pressure and other essential life support functions that do not require conscious attention to execute. The area beneath the cortex of the brain, known as the subcortex, also contains a large amount of white matter.

    Within the subcortex, myelinated axons pass signals between the two hemispheres of the brain, and between different areas in the same hemisphere. These connections are necessary for proper functioning. In diseases and conditions like Alzheimer's, the myelin cells die off, and the axons are no longer able to send signals. When axons cannot propagate their electrical information, they atrophy, and communication between regions suffers. The loss of white matter in Alzheimer's is believed to be directly responsible for the problems with memory and functioning that result.


    White matter helps you problem-solve and focus. It also plays an important role in mood, walking, and balance. So when something’s wrong with it, you might notice:

    • Trouble learning or remembering new things
    • A hard time with problem solving
    • Slowed thinking
    • Leaking urine
    • Depression
    • Problems walking
    • Balance issues and more falls

    White matter disease is different from Alzheimer's, which affects the brain’s gray matter. If you're having memory problems or a loved one is, a doctor will need to run tests to make a diagnosis.


    What Lies Between Grey and White in the Brain

    Traditionally, neuroscience regards the brain as being made up of two basic tissue types. Billions of neurons make up the grey matter, forming a thin layer on the brain’s surface. These neuronal cells are interlinked in a mindboggling network by hundreds of millions of white matter connections, running in bundles, deeper in the brain.

    Until very recently, not much was known about the interface between the white and grey matter – the so-called superficial white matter – because methods were lacking to study it in living human brains. Yet, previous investigations had suggested the region to be implicated in devastating conditions such as Alzheimer’s disease and autism.

    Now a multidisciplinary team led by Nikolaus Weiskopf from the Max Planck Institute for Human Cognitive and Brain Sciences has succeeded in making the superficial white matter visible in the living human brain.

    “We demonstrated that the superficial white matter contains a lot of iron. It is known that iron is necessary for the process of myelination,” explains Evgeniya Kirilina, first author of the study published in Science Advances.

    Myelin is what makes the white matter white. It’s the fatty coating of nerve cell axons that speeds up transmission of information through the brain. The myelination process can occur throughout the lifespan but is predominant during development. In fact, the largest concentration of iron the researchers found was in the superficial white matter in regions of the frontal cortex, which happens to be the slowest developing structure in the human brain. Incredibly, the human frontal cortex is not fully myelinated until the forth decade of life.

    The key to the new method is MRI (Magnetic Resonance Imaging) but at very high field strength. While typical clinical MRI scanners work at 1.5 or 3 Tesla, in terms of the strength of the magnetic field, the Max Planck Institute for Human Cognitive and Brain Sciences houses a powerful 7 Tesla scanner.

    The team created very high resolution maps of the white-grey matter border across the entire living brain. Credit: MPI CBS.

    This, in combination with advanced biophysical model, allowed the team to create very high resolution maps of the white-grey matter border across the entire living brain. The accuracy of their submillimetre maps was assessed against classic and advanced histological methods involving physical dissection and analysis of post mortem brains.

    The new method promises many further insights into the organisation of the interface between white and grey matter. Evgeniya Kirilina adds, “We hope the method can be used to increase our understanding of brain development as well as pathological conditions involving the superficial white matter.”

    About this neuroscience research news

    Source: Max Planck Institute
    Contact: Bettina Hennebach – Max Planck Institute
    Image: Image is credited to Max Planck Institute

    Original Research: Open access.
    “Superficial white matter imaging: Contrast mechanisms and whole-brain in vivo mapping ” by Evgeniya Kirilina, Saskia Helbling, Markus Morawski, Kerrin Pine, Katja Reimann, Steffen Jankuhn, Juliane Dinse, Andreas Deistung, Jürgen R. Reichenbach, Robert Trampel, Stefan Geyer, Larissa Müller, Norbert Jakubowski, Thomas Arendt, Pierre-Louis Bazin, Nikolaus Weiskopf . Science Advances


    Difference Between Grey and White Matter

    Grey Matter vs White Matter

    The nervous system is divided into two parts the central nervous system and the peripheral nervous system. The central nervous system is composed of the brain and the spinal cord. The brain, which has multi-level organized neurons, and connections of indefinite neurons, is divided wholly into grey and white matter. Grey matter, also known as substantia grisea, is the part of the brain that is controlled by the nerve cell bodies and the majority of the true dendrites (numerous, short, branching filaments that carry impulses towards the cell body). The cell body is the area of the neuron that is highlighted by the existence of a nucleus. Grey matter has no myelin blanket.

    The real processing is concluded in the grey matter. It was given the name gray because of its appearance. It has a grey color because of the grey nuclei that comprises the cells. It fills about 40 percent of the whole brain in humans, and consumes 94 percent of oxygen. The neurons of the grey matter do not have extending axons, or long, thin projections of neurons, that send electrical signals away from the soma (another name for the cell body of neurons). Neurons create networks, in which nerve signals travel. From the dendrites to the end of its axons, the signals reproduce in the neural membrane by way of electrical modes. Neurons do not make body contact with each other when conveying messages. The neurotransmitters serve as the medium to connect one neuron to another neuron. The senses of the body (speech, hearing, feelings, seeing and memory) and control of the muscles, are part of the grey matter’s function.

    The white matter, also known as substantia alba, is a neuron that is made up of extending, myelinated nerve fibers, or axons. It composes the structures at the center of the brain, like the thalamus and the hypothalamus. It is found between the brainstem and the cerebellum. It is the white matter that allows communication to and from grey matter areas, and between grey matter and the other parts of the body. It functions by transmitting the information from the different parts of the body towards the cerebral cortex. It also controls the functions that the body is unaware of, like temperature, blood pressure and the heart rate. Dispensing of hormones and the control of food, as well as the intake of water and the exposition of emotions, are additional functions of the white matter.

    Axons are protected by the myelin sheath, which provides insulation from the electrical processes, allowing them to perform nerve signals more quickly. It is also the myelin that is responsible for the white appearance of the white matter. 60 percent of the brain is comprised of white matter.

    1. Grey matter is made up of nerve cell bodies, and white matter is made up of fibers.

    2. Unlike the white matter, the neurons of grey matter do not have extended axons.

    3. Grey matter occupies 40 percent of the brain, while white matter fills 60 percent of the brain.

    4. Grey matter has a grey color because of the grey nuclei that comprises the cells. Myelin is responsible for the white appearance of the white matter.

    5. Processing is concluded in the grey matter, while white matter allows communication to and from grey matter areas, and between the grey matter and the other parts of the body.


    Parts of the Brain

    The brain consists of the:

    • cerebrum
    • cerebellum
    • brain stem
    • diencephalon (thalamus and hypothalamus)
    • limbic system
    • reticular activating system

    The brain can be divided into two major parts: the lower brain stem and the higher forebrain.

    The brain stem sits above the spinal cord and has many connections between them. The brain stem, the most primitive part of the brain, is made up of the medulla, pons, cerebellum, midbrain, hypothalamus and thalamus. The cerebral cortex, limbic system and basal ganglia make up the forebrain. The forebrain deals with homeostasis, emotions and conscious actions.

    The brain’s outer layer is only 1/4 inch thick but if flattened out would cover the size of an office desk. It has about 50 billion nerve cells. The cerebrum is the largest part of the brain and is part of the forebrain. It houses the nerve center that controls sensory, motor activities and intelligence. The outer layer, the cerebral cortex, is made of nerve fibers called gray matter. The inner layer is made of a different type of nerve fibers called white matter.

    The basal ganglia is found in the white matter. The cerebrum is divided in to left and right hemispheres. The left half controls the right side of the body and the right half controls the left side of the body. A mass of nerve fibers known as the corpus callosum connects the two hemispheres and allows communication between the two. The surface of the cerebrum is made up of gyri and sulci.

    A cortex is the outer layer of any organ. The cerebral cortex is the outer layer of the brain, called gray matter. It is where our conscious thoughts and actions take place. Many of the signals our brain receives from our senses are registered in the cerebral cortex. The visual cortex is in the lower back part of the brain and is where our brain registers what we see. The somatosensory cortex is a band that runs over the top of the brain is where our brain registers a touch on any part of our body.

    The motor cortex is just in front of the somatosensory cortex and it sends out signals to muscles to make them move. The more nerve endings a part of the body has, the more of the sensory cortex it occupies. A big portion of the sensory cortex is taken up by our lips and face. Our hands take up almost as much as our face and our feet almost as much as our hands. This is because we move our hands and lips all the time and both are very sensitive.

    The cerebellum, “little brain”, is the second largest region of the brain. It is located behind and below the cerebrum and at the back of the brain stem and attached to the midbrain. It has two hemispheres and an outer cortex of gray matter and an inner core of white matter. The cerebellum is involved in movement and coordination, walking, posture, reflexes, eye and head movement. It coordinates subconscious movements such as balance and coordinated movement. The cerebellum is constantly receiving updates about the body’s position and movement. It also sends instructions to our muscles that adjust our posture and keep our body moving smoothly.

    The diencephalon is located between the cerebrum and midbrain. It consists of the thalamus and hypothalamus which lie deep in the cerebral hemispheres. Centers in the hypothalamus regulate our body temperature, blood sugar, hunger and hormones. The thalamus is involved with sensory signals sent to the higher forebrain, in particular the cerebral cortex. The thalamus also participates in motor control and regulating cortex excitement. Several pathways connect the brainstem to the lower motor centers in the spinal cord and the higher ones in the forebrain.

    The brain is the control center of the body and contains billions of nerve cells. The brain stem lies just below the cerebrum and in front of the cerebellum. It continues from the cerebrum above and connects to the spinal cord below. The brain stem is made up of the midbrain, pons and medulla oblongata. It carries out many vital functions of the body for maintenance and survival such as breathing, heartbeat, and blood pressure. It also controls vomiting, coughing, sneezing and swallowing. It is the body’s “autopilot.” It also provides pathways for nerve fibers between the higher and lower neural centers. It is also the origin for 10 of the 12 cranial nerves. The 12 cranial nerves enter the brain directly and are not connected to the spinal cord.

    The midbrain is the reflex center for cranial nerves III and IV and is involved in eye reflexes and movements. The pons helps regular breathing. It connects the cerebellum with the cerebrum and links the midbrain to the medulla oblongata. The pons is the reflex center for cranial nerves V through VIII. The pons is involved in chewing, taste, saliva, hearing and equilibrium. The medulla oblongata joins the spinal cord at the foramen magnum. It influences heart, breathing and circulation. It’s the center for vomiting, coughing and hiccuping.

    The medulla—the most primitive brain structure—controls our digestive, respiratory and circulatory systems. The ponsinteracts with the cerebellum, motor control and respiration. Other structures in the pons control sleep and excitement. The pons also relays information between the brain and the spinal cord.

    The basal ganglia is found in the forebrain and consist of structures involved in motor processes. The basal ganglia works along with the motor areas of the cortex and cerebellum for planning and coordinating certain voluntary movements. The basal ganglia is made of gray matter.

    The limbic system, or limbic lobe, is involved in the expression of intimate behaviors and emotions, hunger, aggression. The limbic system also screens all sensory messages to the cerebral cortex. It is located deep in the temporal lobe. The limbic system includes these structures: cingulate gyrus, corpus callosum, mammillary body, olfactory tract, amygdala, and hippocampus. The hypothalamus affects body temperature, appetite, water balance, pituitary secretions, emotions, and autonomic functions including cycles of waking and sleeping.

    Even though many functions of the brain are very localized to certain areas and parts of the brain, these parts work together as a whole—particularly in learning, memory, and consciousness.

    Ventricles are fluid filled cavities in the brain there are four of them. The ventricles connect with each other and produce cerebrospinal fluid which is a clear, shock-absorbing liquid that is constantly moving. The cerebrospinal fluid cushions the brain, distributes nutrients and collects wastes.


    Grey Matter vs. White Matter the main difference

    A human brain may look like a small place to anyone, but it has a lot of different functions and parts that help in the processing. To make all these functions happen properly, proper understanding and good piece of information is required, and this understanding and information will be provided in this article. We are discussing the main differences between the terms white matter and grey matter. White Matter is commonly defined as the tissue of the brain and spinal cord and is pale in colour white matter mostly consists of nerve fibers that have myelin sheath around. Grey Matter is basically defined as the major component of the human brain which has different nucleon bodies, neuropil, and other parts that help in working on different body parts.

    White Matter

    White matter is usually found in the deeper tissues of the brain and contains those nerve fibers that have extensions of the nerve cell. These nerve cells have a covering around them to protect the axons, and the reason behind white colour is due to the myelin sheath that not only acts as a coating but also gives the uniqueness to such matter. It increases the speed of transmission and helps the brains move stronger whenever a minor or major injury takes place. It also comes with some basic damage precautions mostly it happens in people at a young age and gets known as the white matter disorders. Diagnosing of this issue can be helped by MRI scans which tell about the problem and different tissue levels. The most basic caution of something not going well is that the myelin sheath is not grown properly so it does help to protect the parts of brain. At earlier stages, people thought that it does not have any especial concern in the brain and that is why no research was done to know the exact issue. Among the two matters present in the spinal cord this one is the fastest and help in connecting others parts, so they stay in touch.

    Grey Matter is defined as the major component of the human brain that has different nucleon bodies, neuropil, and some other parts that help in working on different body parts. Grey matter is more important of two matters present in brain and comes with different functions. It has become the focus of advanced research and that is why few new things are coming up. The type of fat that is present within the myelin sheath but for the grey matter, the actual colour produced from the cell structures of neurons and the brain cells that are called as glial cells. These types of cells provide energy and nutrition to the neurons, that’s how grey colour became part of the system. Most of the times it gets known as the neurons and other different cells present in the central nervous system and is part of brain, brainstem, cerebellum and inside the spinal cord.


    What to know about white matter disease

    White matter disease, or leukoaraiosis, involves the degeneration of white matter in the brain. White matter is tissue that includes nerve fibers (axons), which connect nerve cells.

    A fatty tissue called myelin covers the axons. These axons connect the neurons of the brain and spinal cord and signal nerve cells to communicate with one another.

    Degeneration of the white matter — specifically, the myelin sheaths — can affect a person’s mood, focus, muscle strength, vision, and balance.

    White matter disease may develop with conditions associated with aging, such as stroke, but it can also affect young people due to conditions such as cerebral adrenoleukodystrophy and multiple sclerosis (MS).

    Read on to learn more about white matter disease and its symptoms, causes, and prognosis.

    Share on Pinterest A person with white matter disease may struggle with problem-solving, memory, and focus.

    White matter disease includes many different conditions. It can be progressive, and people who develop this form of white matter disease will notice their symptoms become more pronounced as time goes on.

    The life expectancy of a person with white matter disease depends on many factors, including the specific type, the rate at which it progresses, and the complications it causes.

    Research has suggested a link between white matter disease of an unknown cause and the risk of stroke and dementia. According to a review of six large prospective studies, people with white matter damage have a higher risk of stoke than those without the condition.

    White matter plays an essential role in communication within the brain and between the brain and spinal cord. As a result, damage to this tissue can lead to issues with:

    In the beginning stages of progressive white matter disease, the symptoms may be mild. As time passes, however, the symptoms may get worse.

    Research suggests that the risk of white matter disease increases with age and the presence of cardiovascular disease. Medical, lifestyle, and other risk factors that play a role in white matter disease include:

    • chronic hypertension
    • diabetes
    • genetics
    • high cholesterol
    • history of stroke
    • inflammation of the blood vessels
    • Parkinson’s disease
    • smoking

    One 2014 study suggests that unexplained white matter disease may be the result of damage due to small silent strokes.

    A silent stroke is so small that it occurs without any symptoms. This means that the person does not usually know that they have had a stroke.

    This study suggests that repeated silent strokes could lead to white matter disease.

    There are several conditions that healthcare professionals consider to be white matter diseases. The common factors are impairment of normal myelination or damage to already myelinated nerves. Myelin is a layer of insulation that protects nerves in the brain and spinal cord, and myelination is the formation of this insulation layer.

    Conditions affecting myelin can result from either destruction of existing myelin (demyelinating diseases) or from abnormalities in the formation of myelin (dysmyelinating diseases).

    Processes that cause these types of damage include genetic conditions, autoimmune conditions, and infections.

    Some examples of conditions that affect white matter include:

    • MS
    • Balo concentric sclerosis
    • tumefactive demyelinating lesions
    • Marburg and Schilder variants
    • neuromyelitis optica, or Devic’s disease
    • acute disseminated encephalomyelitis
    • acute hemorrhagic leukoencephalopathy, or Hurst disease
    • progressive multifocal leukoencephalopathy
    • cerebral adrenoleukodystrophy

    Different types of white matter disease may have different stages. For example, there are a few types of MS, and each differs in how it progresses.

    At present, there is no universal staging system for the various forms of white matter disease.

    That said, some researchers have proposed a staging procedure for white matter lesions, which they suggest would help healthcare professionals classify people into stages of white matter disease.

    Doctors try to treat the underlying cause of the myelin condition in order to slow down or stop disease progression.

    For many people with white matter disease due to small strokes, treatment options can include improving their cardiovascular health by eating a healthful diet, avoiding tobacco use, and taking medications for hypertension or high cholesterol.

    Specific forms of white matter disease, such as MS or progressive multifocal leukoencephalopathy, may require other treatments.

    Those who have issues with balance and walking as a result of white matter disease may need physical therapy.

    A physical therapist can provide exercises and other techniques to improve balance and gait. They may also recommend using walking aids and other tools to prevent falls.

    Some forms of white matter disease, such as dysmyelinating diseases, can begin during childhood.

    Dysmyelinating diseases, wherein myelin does not form correctly, can result from problems such as an inherited enzyme deficiency.

    Some examples in children include:

    Late infantile metachromatic leukodystrophy

    This condition occurs between 12 and 18 months of age and causes deterioration in thinking skills, speech, and coordination.

    Within 2 years, children can develop gait and posture problems, as well as blindness and paralysis. It is not possible to stop disease progression, and it is typically fatal within 6 months to 4 years of symptom onset.

    People with the juvenile form of metachromatic leukodystrophy, which develops between the age of 4 and adolescence, may live for many years after diagnosis.

    Krabbe disease

    Also known as globoid cell leukodystrophy, Krabbe disease can develop at any age. However, the most common form is infantile Krabbe disease, which begins before the age of 1.

    In infants, it causes extreme irritability, increased muscle tone, fever, and developmental regression. The condition progresses rapidly and is fatal, usually by the age of 2.

    Zellweger syndrome

    This syndrome is characterized by liver dysfunction, jaundice, intellectual difficulties, and low muscle tone.

    The severity of this condition varies. It can lead to early childhood death.

    Leigh disease

    Infants and children with Leigh disease typically have low muscle tone and noticeably slow speech, physical reactions, and emotional reactions.

    It also causes ataxia, or a loss of coordination of muscle movements, and problems swallowing.

    Vanishing white matter disease

    This is a rare inherited condition that can develop during childhood. It is characterized by early childhood onset of chronic neurological deterioration.

    There are several forms of white matter disease. Each involves problems related to myelin, a fat that covers nerve fibers in the brain.

    The most common forms of white matter disease relate to aging. It may result from small silent strokes, often with the presence of cardiovascular disease.

    Less commonly, other forms of white matter disease affect children and younger adults.


    Difference Between Grey and White Matter

    Grey Matter vs White Matter

    The nervous system is divided into two parts the central nervous system and the peripheral nervous system. The central nervous system is composed of the brain and the spinal cord. The brain, which has multi-level organized neurons, and connections of indefinite neurons, is divided wholly into grey and white matter. Grey matter, also known as substantia grisea, is the part of the brain that is controlled by the nerve cell bodies and the majority of the true dendrites (numerous, short, branching filaments that carry impulses towards the cell body). The cell body is the area of the neuron that is highlighted by the existence of a nucleus. Grey matter has no myelin blanket.

    The real processing is concluded in the grey matter. It was given the name gray because of its appearance. It has a grey color because of the grey nuclei that comprises the cells. It fills about 40 percent of the whole brain in humans, and consumes 94 percent of oxygen. The neurons of the grey matter do not have extending axons, or long, thin projections of neurons, that send electrical signals away from the soma (another name for the cell body of neurons). Neurons create networks, in which nerve signals travel. From the dendrites to the end of its axons, the signals reproduce in the neural membrane by way of electrical modes. Neurons do not make body contact with each other when conveying messages. The neurotransmitters serve as the medium to connect one neuron to another neuron. The senses of the body (speech, hearing, feelings, seeing and memory) and control of the muscles, are part of the grey matter’s function.

    The white matter, also known as substantia alba, is a neuron that is made up of extending, myelinated nerve fibers, or axons. It composes the structures at the center of the brain, like the thalamus and the hypothalamus. It is found between the brainstem and the cerebellum. It is the white matter that allows communication to and from grey matter areas, and between grey matter and the other parts of the body. It functions by transmitting the information from the different parts of the body towards the cerebral cortex. It also controls the functions that the body is unaware of, like temperature, blood pressure and the heart rate. Dispensing of hormones and the control of food, as well as the intake of water and the exposition of emotions, are additional functions of the white matter.

    Axons are protected by the myelin sheath, which provides insulation from the electrical processes, allowing them to perform nerve signals more quickly. It is also the myelin that is responsible for the white appearance of the white matter. 60 percent of the brain is comprised of white matter.

    1. Grey matter is made up of nerve cell bodies, and white matter is made up of fibers.

    2. Unlike the white matter, the neurons of grey matter do not have extended axons.

    3. Grey matter occupies 40 percent of the brain, while white matter fills 60 percent of the brain.

    4. Grey matter has a grey color because of the grey nuclei that comprises the cells. Myelin is responsible for the white appearance of the white matter.

    5. Processing is concluded in the grey matter, while white matter allows communication to and from grey matter areas, and between the grey matter and the other parts of the body.


    Parts of the Brain

    The brain consists of the:

    • cerebrum
    • cerebellum
    • brain stem
    • diencephalon (thalamus and hypothalamus)
    • limbic system
    • reticular activating system

    The brain can be divided into two major parts: the lower brain stem and the higher forebrain.

    The brain stem sits above the spinal cord and has many connections between them. The brain stem, the most primitive part of the brain, is made up of the medulla, pons, cerebellum, midbrain, hypothalamus and thalamus. The cerebral cortex, limbic system and basal ganglia make up the forebrain. The forebrain deals with homeostasis, emotions and conscious actions.

    The brain’s outer layer is only 1/4 inch thick but if flattened out would cover the size of an office desk. It has about 50 billion nerve cells. The cerebrum is the largest part of the brain and is part of the forebrain. It houses the nerve center that controls sensory, motor activities and intelligence. The outer layer, the cerebral cortex, is made of nerve fibers called gray matter. The inner layer is made of a different type of nerve fibers called white matter.

    The basal ganglia is found in the white matter. The cerebrum is divided in to left and right hemispheres. The left half controls the right side of the body and the right half controls the left side of the body. A mass of nerve fibers known as the corpus callosum connects the two hemispheres and allows communication between the two. The surface of the cerebrum is made up of gyri and sulci.

    A cortex is the outer layer of any organ. The cerebral cortex is the outer layer of the brain, called gray matter. It is where our conscious thoughts and actions take place. Many of the signals our brain receives from our senses are registered in the cerebral cortex. The visual cortex is in the lower back part of the brain and is where our brain registers what we see. The somatosensory cortex is a band that runs over the top of the brain is where our brain registers a touch on any part of our body.

    The motor cortex is just in front of the somatosensory cortex and it sends out signals to muscles to make them move. The more nerve endings a part of the body has, the more of the sensory cortex it occupies. A big portion of the sensory cortex is taken up by our lips and face. Our hands take up almost as much as our face and our feet almost as much as our hands. This is because we move our hands and lips all the time and both are very sensitive.

    The cerebellum, “little brain”, is the second largest region of the brain. It is located behind and below the cerebrum and at the back of the brain stem and attached to the midbrain. It has two hemispheres and an outer cortex of gray matter and an inner core of white matter. The cerebellum is involved in movement and coordination, walking, posture, reflexes, eye and head movement. It coordinates subconscious movements such as balance and coordinated movement. The cerebellum is constantly receiving updates about the body’s position and movement. It also sends instructions to our muscles that adjust our posture and keep our body moving smoothly.

    The diencephalon is located between the cerebrum and midbrain. It consists of the thalamus and hypothalamus which lie deep in the cerebral hemispheres. Centers in the hypothalamus regulate our body temperature, blood sugar, hunger and hormones. The thalamus is involved with sensory signals sent to the higher forebrain, in particular the cerebral cortex. The thalamus also participates in motor control and regulating cortex excitement. Several pathways connect the brainstem to the lower motor centers in the spinal cord and the higher ones in the forebrain.

    The brain is the control center of the body and contains billions of nerve cells. The brain stem lies just below the cerebrum and in front of the cerebellum. It continues from the cerebrum above and connects to the spinal cord below. The brain stem is made up of the midbrain, pons and medulla oblongata. It carries out many vital functions of the body for maintenance and survival such as breathing, heartbeat, and blood pressure. It also controls vomiting, coughing, sneezing and swallowing. It is the body’s “autopilot.” It also provides pathways for nerve fibers between the higher and lower neural centers. It is also the origin for 10 of the 12 cranial nerves. The 12 cranial nerves enter the brain directly and are not connected to the spinal cord.

    The midbrain is the reflex center for cranial nerves III and IV and is involved in eye reflexes and movements. The pons helps regular breathing. It connects the cerebellum with the cerebrum and links the midbrain to the medulla oblongata. The pons is the reflex center for cranial nerves V through VIII. The pons is involved in chewing, taste, saliva, hearing and equilibrium. The medulla oblongata joins the spinal cord at the foramen magnum. It influences heart, breathing and circulation. It’s the center for vomiting, coughing and hiccuping.

    The medulla—the most primitive brain structure—controls our digestive, respiratory and circulatory systems. The ponsinteracts with the cerebellum, motor control and respiration. Other structures in the pons control sleep and excitement. The pons also relays information between the brain and the spinal cord.

    The basal ganglia is found in the forebrain and consist of structures involved in motor processes. The basal ganglia works along with the motor areas of the cortex and cerebellum for planning and coordinating certain voluntary movements. The basal ganglia is made of gray matter.

    The limbic system, or limbic lobe, is involved in the expression of intimate behaviors and emotions, hunger, aggression. The limbic system also screens all sensory messages to the cerebral cortex. It is located deep in the temporal lobe. The limbic system includes these structures: cingulate gyrus, corpus callosum, mammillary body, olfactory tract, amygdala, and hippocampus. The hypothalamus affects body temperature, appetite, water balance, pituitary secretions, emotions, and autonomic functions including cycles of waking and sleeping.

    Even though many functions of the brain are very localized to certain areas and parts of the brain, these parts work together as a whole—particularly in learning, memory, and consciousness.

    Ventricles are fluid filled cavities in the brain there are four of them. The ventricles connect with each other and produce cerebrospinal fluid which is a clear, shock-absorbing liquid that is constantly moving. The cerebrospinal fluid cushions the brain, distributes nutrients and collects wastes.


    What Lies Between Grey and White in the Brain

    Traditionally, neuroscience regards the brain as being made up of two basic tissue types. Billions of neurons make up the grey matter, forming a thin layer on the brain’s surface. These neuronal cells are interlinked in a mindboggling network by hundreds of millions of white matter connections, running in bundles, deeper in the brain.

    Until very recently, not much was known about the interface between the white and grey matter – the so-called superficial white matter – because methods were lacking to study it in living human brains. Yet, previous investigations had suggested the region to be implicated in devastating conditions such as Alzheimer’s disease and autism.

    Now a multidisciplinary team led by Nikolaus Weiskopf from the Max Planck Institute for Human Cognitive and Brain Sciences has succeeded in making the superficial white matter visible in the living human brain.

    “We demonstrated that the superficial white matter contains a lot of iron. It is known that iron is necessary for the process of myelination,” explains Evgeniya Kirilina, first author of the study published in Science Advances.

    Myelin is what makes the white matter white. It’s the fatty coating of nerve cell axons that speeds up transmission of information through the brain. The myelination process can occur throughout the lifespan but is predominant during development. In fact, the largest concentration of iron the researchers found was in the superficial white matter in regions of the frontal cortex, which happens to be the slowest developing structure in the human brain. Incredibly, the human frontal cortex is not fully myelinated until the forth decade of life.

    The key to the new method is MRI (Magnetic Resonance Imaging) but at very high field strength. While typical clinical MRI scanners work at 1.5 or 3 Tesla, in terms of the strength of the magnetic field, the Max Planck Institute for Human Cognitive and Brain Sciences houses a powerful 7 Tesla scanner.

    The team created very high resolution maps of the white-grey matter border across the entire living brain. Credit: MPI CBS.

    This, in combination with advanced biophysical model, allowed the team to create very high resolution maps of the white-grey matter border across the entire living brain. The accuracy of their submillimetre maps was assessed against classic and advanced histological methods involving physical dissection and analysis of post mortem brains.

    The new method promises many further insights into the organisation of the interface between white and grey matter. Evgeniya Kirilina adds, “We hope the method can be used to increase our understanding of brain development as well as pathological conditions involving the superficial white matter.”

    About this neuroscience research news

    Source: Max Planck Institute
    Contact: Bettina Hennebach – Max Planck Institute
    Image: Image is credited to Max Planck Institute

    Original Research: Open access.
    “Superficial white matter imaging: Contrast mechanisms and whole-brain in vivo mapping ” by Evgeniya Kirilina, Saskia Helbling, Markus Morawski, Kerrin Pine, Katja Reimann, Steffen Jankuhn, Juliane Dinse, Andreas Deistung, Jürgen R. Reichenbach, Robert Trampel, Stefan Geyer, Larissa Müller, Norbert Jakubowski, Thomas Arendt, Pierre-Louis Bazin, Nikolaus Weiskopf . Science Advances


    White matter helps you problem-solve and focus. It also plays an important role in mood, walking, and balance. So when something’s wrong with it, you might notice:

    • Trouble learning or remembering new things
    • A hard time with problem solving
    • Slowed thinking
    • Leaking urine
    • Depression
    • Problems walking
    • Balance issues and more falls

    White matter disease is different from Alzheimer's, which affects the brain’s gray matter. If you're having memory problems or a loved one is, a doctor will need to run tests to make a diagnosis.


    What Is the Function of White Matter in the Brain?

    White matter is the commonly used term for the myelinated axons that provide connections between neurons, or grey matter. The main function of white matter in the brain is to regulate the electrical signals in axons. These signals are a form of communication, and work to pass along information that is translated into chemical signals between neurons. Without white matter, electrical signals would weaken as they traveled along the axon.

    Understanding the structure of white matter is necessary to understand its function. Support cells in the brain, known as glial cells, produce the fatty tissue known as myelin, which wraps around axons like a sheath. Essentially, these sheaths seal the axon and prevent the ions that propagate electrical signals from diffusing out. The result is that these signals can travel more quickly over longer distances than they could without insulation.

    Traveling electrical signals are known as action potentials. To maintain the ionic difference that allows action potentials to take place, there are gaps between myelinated cells, which allow ions to transfer in and out of the axon. This allows the charge in the axon to maintain its strength, even over long distances. The importance of white matter increases for signals that must travel great distances. Nerve cells that transmit sensory signals to the brain, or neurons that regulate breathing or heart rate, would be unable to perform their tasks without the white matter in the brain and spinal cord.

    Inside the brain, white matter is found in many structures, but it is particularly concentrated in areas where many signals must be sent long distance. These areas include the thalamus and hypothalamus, which govern processes like blood pressure and other essential life support functions that do not require conscious attention to execute. The area beneath the cortex of the brain, known as the subcortex, also contains a large amount of white matter.

    Within the subcortex, myelinated axons pass signals between the two hemispheres of the brain, and between different areas in the same hemisphere. These connections are necessary for proper functioning. In diseases and conditions like Alzheimer's, the myelin cells die off, and the axons are no longer able to send signals. When axons cannot propagate their electrical information, they atrophy, and communication between regions suffers. The loss of white matter in Alzheimer's is believed to be directly responsible for the problems with memory and functioning that result.


    Grey Matter vs. White Matter the main difference

    A human brain may look like a small place to anyone, but it has a lot of different functions and parts that help in the processing. To make all these functions happen properly, proper understanding and good piece of information is required, and this understanding and information will be provided in this article. We are discussing the main differences between the terms white matter and grey matter. White Matter is commonly defined as the tissue of the brain and spinal cord and is pale in colour white matter mostly consists of nerve fibers that have myelin sheath around. Grey Matter is basically defined as the major component of the human brain which has different nucleon bodies, neuropil, and other parts that help in working on different body parts.

    White Matter

    White matter is usually found in the deeper tissues of the brain and contains those nerve fibers that have extensions of the nerve cell. These nerve cells have a covering around them to protect the axons, and the reason behind white colour is due to the myelin sheath that not only acts as a coating but also gives the uniqueness to such matter. It increases the speed of transmission and helps the brains move stronger whenever a minor or major injury takes place. It also comes with some basic damage precautions mostly it happens in people at a young age and gets known as the white matter disorders. Diagnosing of this issue can be helped by MRI scans which tell about the problem and different tissue levels. The most basic caution of something not going well is that the myelin sheath is not grown properly so it does help to protect the parts of brain. At earlier stages, people thought that it does not have any especial concern in the brain and that is why no research was done to know the exact issue. Among the two matters present in the spinal cord this one is the fastest and help in connecting others parts, so they stay in touch.

    Grey Matter is defined as the major component of the human brain that has different nucleon bodies, neuropil, and some other parts that help in working on different body parts. Grey matter is more important of two matters present in brain and comes with different functions. It has become the focus of advanced research and that is why few new things are coming up. The type of fat that is present within the myelin sheath but for the grey matter, the actual colour produced from the cell structures of neurons and the brain cells that are called as glial cells. These types of cells provide energy and nutrition to the neurons, that’s how grey colour became part of the system. Most of the times it gets known as the neurons and other different cells present in the central nervous system and is part of brain, brainstem, cerebellum and inside the spinal cord.


    What to know about white matter disease

    White matter disease, or leukoaraiosis, involves the degeneration of white matter in the brain. White matter is tissue that includes nerve fibers (axons), which connect nerve cells.

    A fatty tissue called myelin covers the axons. These axons connect the neurons of the brain and spinal cord and signal nerve cells to communicate with one another.

    Degeneration of the white matter — specifically, the myelin sheaths — can affect a person’s mood, focus, muscle strength, vision, and balance.

    White matter disease may develop with conditions associated with aging, such as stroke, but it can also affect young people due to conditions such as cerebral adrenoleukodystrophy and multiple sclerosis (MS).

    Read on to learn more about white matter disease and its symptoms, causes, and prognosis.

    Share on Pinterest A person with white matter disease may struggle with problem-solving, memory, and focus.

    White matter disease includes many different conditions. It can be progressive, and people who develop this form of white matter disease will notice their symptoms become more pronounced as time goes on.

    The life expectancy of a person with white matter disease depends on many factors, including the specific type, the rate at which it progresses, and the complications it causes.

    Research has suggested a link between white matter disease of an unknown cause and the risk of stroke and dementia. According to a review of six large prospective studies, people with white matter damage have a higher risk of stoke than those without the condition.

    White matter plays an essential role in communication within the brain and between the brain and spinal cord. As a result, damage to this tissue can lead to issues with:

    In the beginning stages of progressive white matter disease, the symptoms may be mild. As time passes, however, the symptoms may get worse.

    Research suggests that the risk of white matter disease increases with age and the presence of cardiovascular disease. Medical, lifestyle, and other risk factors that play a role in white matter disease include:

    • chronic hypertension
    • diabetes
    • genetics
    • high cholesterol
    • history of stroke
    • inflammation of the blood vessels
    • Parkinson’s disease
    • smoking

    One 2014 study suggests that unexplained white matter disease may be the result of damage due to small silent strokes.

    A silent stroke is so small that it occurs without any symptoms. This means that the person does not usually know that they have had a stroke.

    This study suggests that repeated silent strokes could lead to white matter disease.

    There are several conditions that healthcare professionals consider to be white matter diseases. The common factors are impairment of normal myelination or damage to already myelinated nerves. Myelin is a layer of insulation that protects nerves in the brain and spinal cord, and myelination is the formation of this insulation layer.

    Conditions affecting myelin can result from either destruction of existing myelin (demyelinating diseases) or from abnormalities in the formation of myelin (dysmyelinating diseases).

    Processes that cause these types of damage include genetic conditions, autoimmune conditions, and infections.

    Some examples of conditions that affect white matter include:

    • MS
    • Balo concentric sclerosis
    • tumefactive demyelinating lesions
    • Marburg and Schilder variants
    • neuromyelitis optica, or Devic’s disease
    • acute disseminated encephalomyelitis
    • acute hemorrhagic leukoencephalopathy, or Hurst disease
    • progressive multifocal leukoencephalopathy
    • cerebral adrenoleukodystrophy

    Different types of white matter disease may have different stages. For example, there are a few types of MS, and each differs in how it progresses.

    At present, there is no universal staging system for the various forms of white matter disease.

    That said, some researchers have proposed a staging procedure for white matter lesions, which they suggest would help healthcare professionals classify people into stages of white matter disease.

    Doctors try to treat the underlying cause of the myelin condition in order to slow down or stop disease progression.

    For many people with white matter disease due to small strokes, treatment options can include improving their cardiovascular health by eating a healthful diet, avoiding tobacco use, and taking medications for hypertension or high cholesterol.

    Specific forms of white matter disease, such as MS or progressive multifocal leukoencephalopathy, may require other treatments.

    Those who have issues with balance and walking as a result of white matter disease may need physical therapy.

    A physical therapist can provide exercises and other techniques to improve balance and gait. They may also recommend using walking aids and other tools to prevent falls.

    Some forms of white matter disease, such as dysmyelinating diseases, can begin during childhood.

    Dysmyelinating diseases, wherein myelin does not form correctly, can result from problems such as an inherited enzyme deficiency.

    Some examples in children include:

    Late infantile metachromatic leukodystrophy

    This condition occurs between 12 and 18 months of age and causes deterioration in thinking skills, speech, and coordination.

    Within 2 years, children can develop gait and posture problems, as well as blindness and paralysis. It is not possible to stop disease progression, and it is typically fatal within 6 months to 4 years of symptom onset.

    People with the juvenile form of metachromatic leukodystrophy, which develops between the age of 4 and adolescence, may live for many years after diagnosis.

    Krabbe disease

    Also known as globoid cell leukodystrophy, Krabbe disease can develop at any age. However, the most common form is infantile Krabbe disease, which begins before the age of 1.

    In infants, it causes extreme irritability, increased muscle tone, fever, and developmental regression. The condition progresses rapidly and is fatal, usually by the age of 2.

    Zellweger syndrome

    This syndrome is characterized by liver dysfunction, jaundice, intellectual difficulties, and low muscle tone.

    The severity of this condition varies. It can lead to early childhood death.

    Leigh disease

    Infants and children with Leigh disease typically have low muscle tone and noticeably slow speech, physical reactions, and emotional reactions.

    It also causes ataxia, or a loss of coordination of muscle movements, and problems swallowing.

    Vanishing white matter disease

    This is a rare inherited condition that can develop during childhood. It is characterized by early childhood onset of chronic neurological deterioration.

    There are several forms of white matter disease. Each involves problems related to myelin, a fat that covers nerve fibers in the brain.

    The most common forms of white matter disease relate to aging. It may result from small silent strokes, often with the presence of cardiovascular disease.

    Less commonly, other forms of white matter disease affect children and younger adults.


    White matter hyperintensities is a term used to describe spots in the brain that show up on magnetic resonance imaging (MRIs) as bright white areas.  

    According to Charles DeCarli, the director of UC Davis Alzheimer's Disease Center, these areas may indicate some type of injury to the brain, perhaps due to decreased blood flow in that area.

    The presence of white matter hyperintensities has been correlated with a higher risk of stroke, which can lead to vascular dementia.

    White matter hyperintensities are often referred to as white matter disease.

    Initially, white matter disease was thought to simply be related to aging. However, we now know there are other specific risk factors for white matter disease, which include:

    • High blood pressure
    • Smoking
    • Cardiovascular disease
    • High cholesterol.

    While white matter disease has been associated with strokes, cognitive loss, and dementia, it also has some physical and emotional symptoms such as balance problems, falls, depression, and difficulty multitasking (e.g., walking and talking.)


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    Summary

    Ascending tracts

    Just to recap the ascending spinal tracts:

    • Lateral spinothalamic carries pain and thermal stimuli.
    • Ventral spinothalamic is responsible for pressure and crudetouch sensations.
    • Dorsal column is the area of vibration sensation, proprioception, and two-point discrimination.
    • Spinocerebellar tracts (anterior and posterior divisions) conduct unconscious stimuli for proprioception in joints and muscles.
    • Cuneocerebellar carries the same information as the spinocerebellar tracts.
    • Other ascending tracts in the spinal cord that are discussed in more detail in other articles include:
      • Spinotectal serves an accessory pathway for tactile, painful, and thermal stimuli to reach the midbrain.
      • Spinoreticular integrates the stimuli from the muscles and joints into the reticular formation.
      • Spino-olivary is an accessory pathway that carries additional information to the cerebellum.

      Descending tracts

      In summary, the descending tracts of the spinal cord are:

      • Lateral and ventral (anterior) corticospinal tracts deal with voluntary, discrete, skilledmotoractivities.
      • Lateral and ventral (anterior) reticulospinal tracts provide excitatory or inhibitory regulation of voluntary movements and reflexes
      • Rubrospinaltract promotes flexor and inhibit extensor muscle activity
      • Vestibulospinal tract promotes extensor and inhibit flexor muscle activity. It also supports balance and posture.
      • Tectospinal tracts facilitate posturalmovements arising from visual stimuli.
      • Although the corticobulbartract is a descending pathway, it terminates on the cranial nerve nuclei, which are located in the midbrain and brainstem.

      Ascending and descending tracts of the spinal cord: want to learn more about it?

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