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Posts Tagged ‘Cerebral cortex’

New virus isolated from patients with severe brain infections


Researchers have identified a new virus in patients with severe brain infections in Vietnam. Further research is needed to determine whether the virus is responsible for the symptoms of disease.

The virus was found in a total of 28 out of 644 patients with severe brain infections in the study, corresponding to around 4%, but not in any of the 122 patients with non-infectious brain disorders that were tested.

Infections of the brain and central nervous system are often fatal and patients who do survive, often young children and young adults, are left severely disabled. Brain infections can be caused by a range of bacterial, parasitic, fungal and viral agents, however, doctors fail to find the cause of the infection in more than half of cases despite extensive diagnostic efforts. Not knowing the causes of these brain infections makes public health and treatment interventions impossible.

Researchers at the Oxford University Clinical Research Unit, Wellcome Trust South East Asia Major Overseas Programme and the Academic Medical Center, University of Amsterdam identified the virus, tentatively named CyCV-VN, in the fluid around the brain of two patients with brain infections of unknown cause. The virus was subsequently detected in an additional 26 out of 642 patients with brain infections of known and unknown causes.

Using next-generation gene sequencing techniques, the team sequenced the entire genetic material of the virus, confirming that it represents a new species that has not been isolated before. They found that it belongs to a family of viruses called the Circoviridae, which have previously only been associated with disease in animals, including birds and pigs.

Dr Rogier van Doorn, Head of Emerging Infections at the Wellcome Trust Vietnam Research Programme and Oxford University Clinical Research Unit Hospital for Tropical Diseases in Vietnam, explains: “We don’t yet know whether this virus is responsible for causing the serious brain infections we see in these patients, but finding an infectious agent like this in a normally sterile environment like the fluid around the brain is extremely important. We need to understand the potential threat of this virus to human and animal health.”

The researchers were not able to detect CyCV-VN in blood samples from the patients but it was present in 8 out of 188 fecal samples from healthy children. The virus was also detected in more than half of fecal samples from chickens and pigs taken from the local area of one of the patients from whom the virus was initially isolated, which may suggest an animal source of infection.

Dr Le Van Tan, Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, said: “The evidence so far seems to suggest that CyCV-VN may have crossed into humans from animals, another example of a potential zoonotic infection. However, detecting the virus in human samples is not in itself sufficient evidence to prove that the virus is causing disease, particularly since the virus could also be detected in patients with other known viral or bacterial causes of brain infection. While detection of this virus in the fluid around the brain is certainly remarkable, it could still be that it doesn’t cause any harm. Clearly we need to do more work to understand the role this virus may play in these severe infections.”

The researchers are currently trying to grow the virus in the laboratory using cell culture techniques in order to develop a blood assay to test for antibody responses in patient samples, which would indicate that the patients had mounted an immune response against the virus. Such a test could also be used to study how many people in the population have been exposed to CyCV-VN without showing symptoms of disease.

The team are collaborating with scientists across South East Asia and in the Netherlands to determine whether CyCV-VN can be detected in patient samples from other countries and better understand its geographical distribution.

Professor Menno de Jong, head of the Department of Medical Microbiology of the Academic Medical Centre in Amsterdam said: “Our research shows the importance of continuing efforts to find novel causes of important infectious diseases and the strength of current technology in aid of these efforts.”

Journal reference: L.V. Tan et al . Identification of a new cyclovirus in cerebrospinal fluid of patients with acute central nervous system infections. mBio, June 2013. DOI: 10.1128/mBio.00231-13

The above story is reprinted from materials provided by Wellcome Trust, via MedicalXpress.

Neuronal Connections in the Cerebellum in Short

January 13, 2013 3 comments

Control of movement is largely determined by incoming (afferent) and outgoing (efferent) neural impulses in the cerebellum.

Motor information input travels from the spinal cord, cerebral cortex and vestibular system via mossy fibers.

Feedback regarding movements returns to the cerebellum via the inferior olivary nucleus in the medulla oblongata. This feedback loop allows the brain to coordinate movement.

All outgoing neural impulses from the cerebellum travel via the deep cerebellar and vestibular nuclei. Proper functioning of the neuronal pathway between mossy fibers, granular cells, parallel fibers, climbing fibers and Purkinje cells are thought to be essential for coordinated muscular movement. Glutamate is a neurotransmitter in the excitatory synapses between climbing fibers and Purkinje cells as well as between granular cells and mossy fibers. Disruptions in this system are thought to be involved in a variety of movement disorders.

Cerebellar connections(click on the picture to view full size)

Neural Networks Forget Information Quickly

December 16, 2012 Leave a comment

Researchers have figured out the speed that neural networks in the cerebral cortex can delete sensory information is a bit of information per active neuron per second. The activity patterns of the neural network models are deleted nearly as soon as they are passed on from sensory neurons.

The scientists used neural network models based on real neuronal properties for the first time for these calculations. Neuronal spike properties were figured into the models which also helped show that the cerebral cortex processes were extremely chaotic.

Neural networks and this type of research in general are all helping researchers better understand learning and memory processes. With better knowledge about learning and memory, researchers can work toward treatments for Alzheimer’s disease, dementia, learning disabilities, PTSD related memory loss and many other problems.

More details are provided in the release below. Read more…

Math ability requires crosstalk in the brain

September 9, 2012 Leave a comment

 

Examples of the simple numerical and arithmetic tasks used in the study. Participants were asked to judge whether the numerical operation was correct or not. Credit: Center for Vital Longevity, University of Texas at Dallas. (up)

A new study by researchers at UT Dallas’ Center for Vital Longevity, Duke University, and the University of Michigan has found that the strength of communication between the left and right hemispheres of the brain predicts performance on basic arithmetic problems. The findings shed light on the neural basis of human math abilities and suggest a possible route to aiding those who suffer from dyscalculia— an inability to understand and manipulate numbers.

It has been known for some time that the parietal cortex, the top/middle region of the brain, plays a central role in so-called numerical cognition—our ability to process numerical information. Previous brain imaging studies have shown that the right parietal region is primarily involved in basic quantity processing (like gauging relative amounts of fruit in baskets), while the left parietal region is involved in more precise numerical operations like addition and subtraction. What has not been known is whether the two hemispheres can work together to improve math performance. The new study demonstrates that they can. The findings were recently published online in Cerebral Cortex.

In the study, conducted in Dallas and led by Dr. Joonkoo Park, now a postdoctoral fellow at Duke University, researchers used functional magnetic resonance imaging, or fMRI, to measure the brain activity of 27 healthy young adults while they performed simple numerical and arithmetic tasks. In one task, participants were asked to judge whether two groups of shapes contained the same or different numbers of items. In two other tasks, participants were asked to solve simple addition and subtraction problems.

Consistent with previous studies, the researchers found that the basic number-matching task activated the right parietal cortex, while the addition and subtraction tasks produced additional activity in the left parietal cortex. But they also found something new: During the arithmetic tasks, communication between the left and right hemispheres increased significantly compared with the number-matching task. Moreover, people who exhibited the strongest connection between hemispheres were the fastest at solving the subtraction problems.

“Our results suggest that subtraction performance is optimal when there is high coherence in the neural activity in these two brain regions. Two brain areas working together rather than either region alone appears to be key” said co-author Dr. Denise C. Park, co-director of the UT Dallas Center for Vital Longevity and Distinguished University Chair in the School of Behavioral and Brain Sciences. Park (no relation to the lead author) helped direct the study along with Dr. Thad Polk, professor of psychology at the University of Michigan.

Lead author Dr. Joonkoo Park points out that the findings suggest that disrupted or inefficient neural communication between the hemispheres may contribute to the impaired math abilities seen in dyscalculia, the numerical equivalent of dyslexia. “If such a causal link exists,” he said, “one very interesting avenue of research would be to develop training tasks to enhance parietal connectivity and to test whether they improve numerical competence.”

Such a training program might help develop math ability in children and could also help older adults whose arithmetic skills begin to falter as a normal part of age-related cognitive decline.

 

Reference:

The above story is reprinted from materials provided by University of Texas at Dallas, via MedicalXpress.

Journal: Cerebral Cortex

 

Descending Tracts

February 17, 2012 Leave a comment

Descending tracts have three neurons:

1.   1st order neurons (UMN): cell bodies are in the cerebral cortex and other supra spinal areas

2.   2nd order neurons: short and situated in the anterior grey column of the spinal cord

3.  3rd  order neuron (LMN): situated in the anterior grey column and innervate the skeletal muscles through anterior roots of the spinal nerves

Corticospinal tract: rapid, skilled and voluntary movements

1st order neuron

Axons arise from the pyramidal cells of the cerebral  cortex  (situated  in  the  5th   layer),  2/3 from the pre central gyrus and 1/3 from the post central gyrus:

1. 1/3 of fibers arise from the 1stry motor  cortex (Area 4)

2. 1/3 of fibers arise from the 2ndry motor cortex (Area 6)

3. 1/3 of fibers arise from the parietal lobe

(Area 1, 2 and 3).

Descending fibers converge in the corona radiata and  pass  though  the   posterior  limb  of  the internal capsule; organization of fibers within the internal capsule:

1. close to genu (medial): concerned with the cervical parts of the body

2. away from the genu (lateral): concerned with the lower extremity.

The tract then passes through the middle 3/5 of the basis pedunculi of the midbrain; organization of fibers in the midbrain:

    1. medially: cervical parts of the body
    2. laterally: lower limbs.

When the tract enters the pons, it’s broken into many bundles by the transverse pontocerebellar fibers. In the medulla oblongata, the bundles group together to form the pyramids. At the junction of the MO and the spinal cord, most fibers cross the midline at the decussation of the pyramids and enter the lateral white column of the spinal cord to form the lateral corticospinal tract (LCST). LCST descends length of the spinal cord and terminates in the anterior grey column of all the spinal segments.

The fibers which didn’t cross, descend in the anterior white column of the spinal cord as the anterior corticospinal tract (ACST). Fibers of the ACST eventually cross and terminate in the anterior grey column of the spinal cord segments in the cervical and upper thoracic regions.

2nd order neuron:

It’s an internuncial neuron.

3rd order neuron:

It’s a alpha or gamma motor neuron.

To read more click on this link to the full article: Descending Tracts

Ascending Tracts

February 10, 2012 Leave a comment

Introduction

They are located in the white matter and conduct afferent information (may or may not reach consciousness). There are two types of information:

  1. Exteroceptive : originates from outside the body (pain, temperature and touch
  2. Proprioceptive : originates from inside the body (from muscles and joints)

Normally there are three neurons in an ascending pathway:

  1. 1st order neuron: cell body is in the posterior root ganglion
  2. 2nd  order neuron: decussates (crosses to the opposite side) and ascends to a higher level of the    CNS
  3. 3rd neuron: located in the thalamus and passes to a sensory region of the cortex

Pain and temperature pathway: lateral spinothalmic tract

1st order neuron

Peripheral process extends to skin or other tissues and ends as free nerve endings (receptors). Cell body is situated in the posterior root ganglion. Central process extends into the posterior grey column and synapses with the 2nd order neuron.

2nd order neuron

The axon crosses obliquely to the opposite side in the anterior grey and white commissures within one spinal segment of the cord. It ascends in the contralateral white column as the lateral spinothalamic tract (LSTT).

As the LSTT ascends through the spinal cord new fibers are added to the anteromedial aspect of the tract (sacral fibers are lateral and cervical fibers are medial). The fibers carrying pain are situated anterior to those conducting temperature.

As the LSTT ascends through the medulla oblongata,  it’s  joined  by  the  anterior spinothalamic tract and the spinotectal tract and forms the spinal lemniscus. Spinal lemniscus ascends through the pons and the mid brain.

Fibers of the LSTT end by synapsing with the 3rd order  neurons  in  the  ventral  posterolateral nucleus  of  the  thalamus  (here  crude  pain  and temperature sensations are appreciated).

3rd order neuron

Axons pass through the posterior limb of the internal capsule and corona radiata  to reach the somatosensory  area  in  the  post  central  gyrus  of  the  cerebral  cortex.  From  here  information is transmitted to other regions of the cerebral cortex to be used by motor areas. The role of the cerebral  cortex  is  interpreting  the  quality  of  the  sensory  information  at  the  level  of  the consciousness.

Light (crude) touch and pressure pathway: anterior spinothalamic tract (ASTT)

1st order neuron

It is similar to the pain and temperature pathway.

2nd order neuron

The axon crosses obliquely to the opposite side in the anterior grey and white commissures within several spinal segments. It ascends in the contralateral white column as the anterior spinothalamic tract (ASTT). As the ASTT ascends through the spinal cord new fibers are added to the anteromedial aspect of the tract (sacral fibers are lateral and cervical fibers are medial).

As the ASTT ascends through the medulla oblongata, it’s joined by the lateral spinothalamic tract and the spinotectal tract and forms the spinal lemniscus. Spinal lemniscus ascends through the pons and the midbrain. Fibers of the ASTT end by synapsing with the 3rd order neurons in the ventral posterolateral nucleus of the thalamus (here crude awareness of touch and pressure sensations are appreciated).

3rd order neuron

Axons pass through the posterior limb of the internal capsule and corona radiata to reach the somatosensory area in the post central gyrus of the cerebral cortex. The sensations can be crudely localized. Very little discrimination is possible.

To read more click on this link to the full article: Ascending Tracts (pdf).