Today we learn how that substance — cerebrospinal fluid or CSF — washes in and out of our brain tissues in waves, helping to remove waste products. The cerebrospinal spinal fluid also bathes our brain with proteins or growth factors, facilitating normal development.

Decay theory of memory fading

When we learn something new, we create a neurochemical memory trace. The decay theory posits that our memory fades secondary to the passage of time, with information becoming less available for later retrieval as time goes by; the memory strength simply wears away.

Columbia University (USA) psychologist Edward Thorndike first coined the descriptor “decay theory” in The Psychology of Learning in 1914. Active rehearsal of the information can counteract the memory fading.

Memories fade like old photographs

Why do our memories, like old photographs, fade in quality over time? Not only do our recollections become less accurate over time, but we also experience decreases vibrancy and other visual qualities.

Are you like me? I sometimes have a memory that feels like I am reliving the moment. On other occasions, the details are remarkably fuzzy. An example of the former? After I had an emotionally significant event, getting engaged at New York’s Rainbow Room at Rockefeller Center, I have a good recall of the event, but everything has faded in my mind.

As events are forgotten or stored in memory, Boston College researchers wondered how their visual features evolve? Study participants reported changes in their memories akin to using a filter to edit a photograph on Instagram.

The researchers went a step further, inquiring if forgetting is similar to applying a filter to our experiences and whether the emotional significance of the event would change which filter we apply.

Here are the findings, as detailed by study author Rose Cooper:

“Memories seem to fade literally: people consistently remembered visual scenes as being less vibrant than originally experienced.” She continues, adding, “we had expected that memories would get less accurate after a delay, but we did not expect that there would be this qualitative shift in the way that they remembered them.”

Furthermore, negative emotions study participants experienced when viewing images raised the chances that they would accurately recall the images but did not influence memory fading.

In summary, the researchers discovered that the vibrancy of low-level details — colors and shapes, for example — fades in memory while we keep the general gist of the experience.

The fading appeared less for memories subjectively rated as more robust. Emotional memories did not influence the fading amount but did impact the likelihood with which the subjects remembered an exposure. My Rainbow is recalled, but not vividly.

What drives the memory fading? Do we forget over time, or is new material interfering with new information?

Cerebrospinal fluid basics

Researchers recently reversed memory loss in mice by injecting them with a brain fluid from younger peers. First, let’s take a quick look at that fluid, or cerebrospinal fluid (CSF).

The CSF is a body fluid surrounding the brain and cushion in the skull. Maiken Nedergaard and colleagues discovered that cerebrospinal fluid also acts as a lymph system in the brain.

Via a series of elegant experiments analyzing mice brains, the researchers visualized cerebrospinal fluid entering and flowing through the brain, ultimately draining into the same ducts used by the lymphatic system of the rest of the body.

The cerebrospinal fluid clears harmful amyloid-beta from the brain. The substance is associated with Alzheimer’s disease and other neurological conditions. While Nedergaard and co-investigators honed in on this protein, other leftover proteins are likely also removed.

In summary, cerebrospinal (spinal) fluid washes in and out of the crevices of our brains in waves. The process is central to waste removal.

Reversing memory loss in mice

Researchers reversed memory loss by injecting cerebrospinal fluid from younger mice peers.

Using a tiny tube and pump, the scientists infused cerebrospinal fluid from young adult mice into the brains of 18-month-old animals — the equivalent to about 60 years for humans — over seven days.

Imaging revealed higher levels of myelin, a fatty sheath that covers and protects nerve cells from damage. The injections led to practical changes, too: The elderly mice improved at a fear-conditioning task. The refreshed mice remembered a tone, and a flashing light meant a small electric shock was coming.

Growth factors and memory rejuvenation

Growth factors that can restore nerve cell function are the likely agents of memory improvement. Stimulated cells — oligodendrocytes — made more myelin, creating stronger connections between the nerve cells.

Genes normally expressed in oligodendrocytes appeared revved up or upregulated in the old mice who had received cerebrospinal fluid from young mice.

The researchers also found changes in gene expression in a structure important for memory, the hippocampus. The gene Fgf17 decreases activity with age; the CSF infusion restored function.

This research is stunning. With all of the troubles in the world, it is heartening to see brilliant scientists opening doors to a future where we may be able to improve memory. It is also disturbing. I hope we someday don’t go down this road; gene editing sounds much more appealing to me, especially for those with dementia.

Until we get a drug targeting memory in humans, I will continue to focus on a healthy diet, adequate sleep, regular physical activity, limiting alcohol consumption, and challenging my brain with activities such as my new Haydn Piano Sonatas.

The post Can We Reverse Memory Loss with Brain Liquid From Younger Folks? appeared first on Medika Life.

Chiari malformations may develop when part of the skull is smaller than normal or misshapen, which forces the cerebellum to be pushed down into the foramen magnum and spinal canal.  This causes pressure on the cerebellum and brain stem that may affect functions controlled by these areas and block the flow of cerebrospinal fluid (CSF)—the clear liquid that surrounds and cushions the brain and spinal cord.  The CSF also circulates nutrients and chemicals filtered from the blood and removes waste products from the brain.

What causes Chiari malformations?

CM has several different causes.  Most often it is caused by structural defects in the brain and spinal cord that occur during fetal development.  This can be the result of genetic mutations or a maternal diet that lacked certain vitamins or nutrients.  This is called primary or congenital Chiari malformation.  It can also be caused later in life if spinal fluid is drained excessively from the lumbar or thoracic areas of the spine either due to traumatic injury, disease, or infection.  This is called acquired or secondary Chiari malformation.  Primary Chiari malformation is much more common than secondary Chiari malformation. 

What are the symptoms of a Chiari malformation?

Headache is the hallmark sign of Chiari malformation, especially after sudden coughing, sneezing, or straining.  Other symptoms may vary among individuals and may include:

• neck pain
• hearing or balance problems
• muscle weakness or numbness
• dizziness
• difficulty swallowing or speaking
• vomiting
• ringing or buzzing in the ears (tinnitus)
• curvature of the spine (scoliosis)
• insomnia
• depression
• problems with hand coordination and fine motor skills. 

Some individuals with CM may not show any symptoms.  Symptoms may change for some individuals, depending on the compression of the tissue and nerves and on the buildup of CSF pressure. 

Infants with a Chiari malformation may have difficulty swallowing, irritability when being fed, excessive drooling, a weak cry, gagging or vomiting, arm weakness, a stiff neck, breathing problems, developmental delays, and an inability to gain weight.

How are CMs classified?

Chiari malformations are classified by the severity of the disorder and the parts of the brain that protrude into the spinal canal.

Chiari malformation Type I
Type 1 happens when the lower part of the cerebellum (called the cerebellar tonsils) extends into the foramen magnum.  Normally, only the spinal cord passes through this opening.  Type 1—which may not cause symptoms—is the most common form of CM.  It is usually first noticed in adolescence or adulthood, often by accident during an examination for another condition.  Adolescents and adults who have CM but no symptoms initially may develop signs of the disorder later in life.

Chiari malformation Type II
Individuals with Type II have symptoms that are generally more severe than in Type 1 and usually appear during childhood.  This disorder can cause life-threatening complications during infancy or early childhood, and treating it requires surgery.

In Type II, also called classic CM, both the cerebellum and brain stem tissue protrude into the foramen magnum.  Also the nerve tissue that connects the two halves of the cerebellum may be missing or only partially formed.  Type II is usually accompanied by a myelomeningocele—a form of spina bifida that occurs when the spinal canal and backbone do not close before birth.  (Spina bifida is a disorder characterized by the incomplete development of the brain, spinal cord, and/or their protective covering.)  A myelomeningocele usually results in partial or complete paralysis of the area below the spinal opening.  The term Arnold-Chiari malformation (named after two pioneering researchers) is specific to Type II malformations. 

Chiari malformation Type III

Type III is very rare and the most serious form of Chiari malformation.  In Type III, some of the cerebellum and the brain stem stick out, or herniate, through an abnormal opening in the back of the skull.  This can also include the membranes surrounding the brain or spinal cord. 

The symptoms of Type III appear in infancy and can cause debilitating and life-threatening complications.  Babies with Type III can have many of the same symptoms as those with Type II but can also have additional severe neurological defects such as mental and physical delays, and seizures. 

Chiari malformation Type IV

Type IV involves an incomplete or underdeveloped cerebellum (a condition known as cerebellar hypoplasia).  In this rare form of CM, the cerebellum is located in its normal position but parts of it are missing, and portions of the skull and spinal cord may be visible. 

What other conditions are associated with Chiari malformations?

• Hydrocephalus is an excessive buildup of CSF in the brain.  A CM can block the normal flow of this fluid and cause pressure within the head that can result in mental defects and/or an enlarged or misshapen skull.  Severe hydrocephalus, if left untreated, can be fatal.  The disorder can occur with any type of Chiari malformation, but is most commonly associated with Type II. Spina bifida is the incomplete closing of the backbone and membranes around the spinal cord.  In babies with spina bifida, the bones around the spinal cord do not form properly, causing defects in the lower spine.  While most children with this birth defect have such a mild form that they have no neurological problems, individuals with Type II Chiari malformation usually have myelomeningocele, and a baby’s spinal cord remains open in one area of the back and lower spine.  The membranes and spinal cord protrude through the opening in the spine, creating a sac on the baby’s back.  This can cause a number of neurological impairments such as muscle weakness, paralysis, and scoliosis. 
• Syringomyelia is a disorder in which a CSF-filled tubular cyst, or syrinx, forms within the spinal cord’s central canal.  The growing syrinx destroys the center of the spinal cord, resulting in pain, weakness, and stiffness in the back, shoulders, arms, or legs.  Other symptoms may include a loss of the ability to feel extremes of hot or cold, especially in the hands.  Some individuals also have severe arm and neck pain. 
• Tethered cord syndrome occurs when a child’s spinal cord abnormally attaches to the tissues around the bottom of the spine. This means the spinal cord cannot move freely within the spinal canal. As a child grows, the disorder worsens, and can result in permanent damage to the nerves that control the muscles in the lower body and legs.  Children who have a myelomeningocele have an increased risk of developing a tethered cord later in life.
• Spinal curvature is common among individuals with syringomyelia or CM Type I.  The spine either may bend to the left or right (scoliosis) or may bend forward (kyphosis).

How common are Chiari malformations?

In the past, it was estimated that the condition occurs in about one in every 1,000 births.  However, the increased use of diagnostic imaging has shown that Chiari malformation may be much more common.  Complicating this estimation is the fact that some children who are born with this condition may never develop symptoms or show symptoms only in adolescence or adulthood.  Chiari malformations occur more often in women than in men and Type II malformations are more prevalent in certain groups, including people of Celtic descent. 

How are Chiari malformations diagnosed?

Currently, no test is available to determine if a baby will be born with a Chiari malformation.  Since Chiari malformations are associated with certain birth defects like spina bifida, children born with those defects are often tested for malformations.  However, some malformations can be seen on ultrasound images before birth.

Many people with Chiari malformations have no symptoms and their malformations are discovered only during the course of diagnosis or treatment for another disorder.  The doctor will perform a physical exam and check the person’s memory, cognition, balance (functions controlled by the cerebellum), touch, reflexes, sensation, and motor skills (functions controlled by the spinal cord).  The physician may also order one of the following diagnostic tests:

• Magnetic resonance imaging (MRI) is the imaging procedure most often used to diagnose a Chiari malformation.  It uses radio waves and a powerful magnetic field to painlessly produce either a detailed three-dimensional picture or a two-dimensional “slice” of body structures, including tissues, organs, bones, and nerves. 
• X-rays use electromagnetic energy to produce images of bones and certain tissues on film.  An X-ray of the head and neck cannot reveal a CM but can identify bone abnormalities that are often associated with the disorder.
• Computed tomography (CT) uses X-rays and a computer to produce two-dimensional pictures of bone and blood vessels.  CT can identify hydrocephalus and bone abnormalities associated with Chiari malformation. 

How are Chiari malformations treated?

Some CMs do not show symptoms and do not interfere with a person’s activities of daily living.  In these cases, doctors may only recommend regular monitoring with MRI.  When individuals experience pain or headaches, doctors may prescribe medications to help ease symptoms. 

Surgery

In many cases, surgery is the only treatment available to ease symptoms or halt the progression of damage to the central nervous system.  Surgery can improve or stabilize symptoms in most individuals.  More than one surgery may be needed to treat the condition.

The most common surgery to treat Chiari malformation is posterior fossa decompression. It creates more space for the cerebellum and relieves pressure on the spinal cord.  The surgery involves making an incision at the back of the head and removing a small portion of the bone at the bottom of the skull (craniectomy).  In some cases the arched, bony roof of the spinal canal, called the lamina, may also be removed (spinal laminectomy). The surgery should help restore the normal flow of CSF, and in some cases it may be enough to relieve symptoms.

Next, the surgeon may make an incision in the dura, the protective covering of the brain and spinal cord.  Some surgeons perform a Doppler ultrasound test during surgery to determine if opening the dura is even necessary.  If the brain and spinal cord area is still crowded, the surgeon may use a procedure called electrocautery to remove the cerebellar tonsils, allowing for more free space.  These tonsils do not have a recognized function and can be removed without causing any known neurological problems.

The final step is to sew a dura patch to expand the space around the tonsils, similar to letting out the waistband on a pair of pants.  This patch can be made of artificial material or tissue harvested from another part of an individual’s body.

Infants and children with myelomeningocele may require surgery to reposition the spinal cord and close the opening in the back.  Findings from the National Institutes of Health (NIH) show that this surgery is most effective when it is done prenatally (while the baby is still in the womb) instead of after birth. The prenatal surgery reduces the occurrence of hydrocephalus and restores the cerebellum and brain stem to a more normal alignment.

Hydrocephalus may be treated with a shunt (tube) system that drains excess fluid and relieves pressure inside the head.  A sturdy tube, surgically inserted into the head, is connected to a flexible tube placed under the skin.  These tubes drain the excess fluid into either the chest cavity or the abdomen so it can be absorbed by the body. 

]An alternative surgical treatment in some individuals with hydrocephalus is third ventriculostomy, a procedure that improves the flow of CSF out of the brain.  A small hole is made at the bottom of the third ventricle (brain cavity) and the CSF is diverted there to relieve pressure.  Similarly, in cases where surgery was not effective, doctors may open the spinal cord and insert a shunt to drain a syringomyelia or hydromyelia (increased fluid in the central canal of the spinal cord).

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