diffusion tensor imaging

The Curious Case of the Woman with No Cerebellum

Not sure how many of you have read about this by now, but it is such an amazing finding I decided to write about it (even though I retweeted this yesterday). 

This study is a clinical case report of a living patient with cerebellar   agenesis, an extremely rare condition characterized by the absence of the cerebellum. The cause is currently unknown, there are limited reported cases of complete cerebellar  agenesis, and most of what we know about the condition comes from autopsy reports instead of living patients. Moreover, the condition is difficult to study because most individuals with complete primary cerebellar agenesis are infants or children with severe mental impairment, epilepsy, hydrocephaly and other gross lesions of the CNS. The fact that this woman is alive and has a somewhat “normal” life is ground-breaking and presents a unique opportunity to study the condition.

The patient described in the study is 24 years old. She has mild mental impairment and moderate motor deficits. For example, she is unable to walk steadily and commonly experiences dizziness/nausea. She also has speech problems and cannot run or jump. However, she has no history of neurological disorders and even gave birth without any complications. 

Importantly, as shown above, CT  and MRI scans revealed no presence of recognizable cerebellar structures. Just look at that dark sport towards the back of the brain! In addition to these findings, magnetic resonance angiography also demonstrated vascular characteristics of this patient consistent with complete cerebellar agenesis- meaning that the arteries that normally supply this area were also absent bilaterally. How crazy is that? Futhermore, diffusion tensor imaging  indicated a complete lack of the efferent and afferent limbs of the cerebellum. 

Given that the cerebellum is responsible for both motor and non-motor functions, these results are pretty amazing. How can the brain compensate for such a heavy blow to its architecture and connectivity? According to the authors of the study: 

This surprising phenomenon supports the concept of extracerebellar motor system plasticity, especially cerebellum loss, occurring early in life. We conclude that the cerebellum is necessary for normal motor, language functional and mental development even in the presence of the functional compensation phenomenon.

Source:

Yu, F., Jiang, Q., Sun, X., and Zhang, R. (2014). A new case of complete primary cerebellar a genesis: clinical and imaging findings in a living patient. Brain. doi: 10.1093/brain/awu239

Networks of the brain reflect the individual gender identity

Our sense of belonging to the male or female gender is an inherent component of the human identity perception. As a general rule, gender identity and physical sex coincide. If this is not the case, one refers to trans-identity or transsexuality. In a current study, brain researcher Georg S. Kanz of the University Clinic for Psychiatry and Psychotherapy of the MedUni Vienna was able to demonstrate that the very personal gender identity of every human being is reflected and verifiable in the cross-links between brain regions.

While the biological gender is usually manifested in the physical appearance, the individual gender identity is not immediately discernible and primarily established in the psyche of a human being. As the brain is responsible for our thoughts, feelings and actions, several research institutions worldwide are searching for the neural representation of gender identity.

In a study under the guidance of Rupert Lanzenberger (http://www.meduniwien.ac.at/neuroimaging/) of the University Clinic for Psychiatry and Psychotherapy of the MedUni Vienna published in the renowned magazine “Journal of Neuroscience" it was now possible to demonstrate neural correlates (analogies) of the identity perception in the network of the brain.

Trans-gender persons as well as female and male control subjects were examined by way of diffusion-based magnetic resonance tomography (MRT). The examination revealed significant differences in the microstructure of the brain connections between male and female control subjects. Transgender persons took up a middle position between both genders.

It was furthermore possible to detect a strong relationship between the microstructure connections among these networks and the testosterone level measured in the blood. Lanzenberger: “These results suggest that the gender identity is reflected in the structure of brain networks which form under the modulating influence of sex hormones in the course of the development of the nervous system.”

Flying Through Inner Space

It’s hard to truly see the brain. I don’t mean to simply see a three-pound hunk of tissue. I mean to see it in a way that offers a deep feel for how it works. That’s not surprising, given that the human brain is made up of over 80 billion neurons, each branching out to form thousands of connections to other neurons. A drawing of those connections may just look like a tangle of yarn.

As I wrote in the February issue of National Geographic, a number of neuroscientists are charting the brain now in ways that were impossible just a few years ago. And out of these surveys, an interesting new way to look at the brain is emerging. Call it the brain fly-through. The brain fly-through only became feasible once scientists started making large-scale maps of actual neurons in actual brains. Once they had those co-ordinates in three-dimensional space, they could program a computer to glide through it. The results are strangely hypnotic.

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31 May 2013

Connection Spectrum

Our brain is an über-processing hub comprising 100 billion neurons, each with around 10,000 connections. Scanning techniques such as magnetic resonance imaging can highlight active areas, but tell us little about how the brain is wired. Scientists working together on the Human Connectome Project are mapping the brain’s wiring system to help identify glitches. Here, a technique called diffusion tensor imaging measures water diffusing in different directions through the brain. In this side-on view, each colour traces the route of one of the brain’s ‘wires’ – white matter tracts consisting of nerve fibre bundles ‘insulated’ with fatty myelin. The more tightly packed the bundles of white matter, the less water can diffuse. This translates into a spectrum of colours when the data are processed and visualised on a map. A colour-coded wiring map of the brain will direct doctors to damaged connections, and help them locate and treat brain disorders.

Written by Caroline Cross

Las diferencias entre hombres y mujeres están en las conexiones cerebrales

Los hombres se casan con las mujeres con la esperanza de que ellas nunca cambien, mientras que las mujeres se casan con los hombres con la esperanza de que ellos sí lo hagan. Esta frase de Albert Einstein sirve para ejemplificar cómo los hombres y las mujeres somos diferentes en muchos aspectos. Y si nos metiéramos a los cerebros de ambos géneros, podríamos observar que hay diferencias notables en las conexiones neuronales entre ambos, mismas que dan sustento a las diferencias a nivel cognitivo y conductual.

Trabajos anteriores han mostrado que existen diferencias entre sexos a nivel cerebral, pero nunca se había hecho un estudio con tantos participantes para observar las conexiones neuronales a lo largo de todo el cerebro. En este trabajo, realizado por diferentes instituciones de investigación estadounidenses, se analizaron los cerebros de 949 personas de entre 8 y 22 años con el objetivo de observar las diferencias entre ambos géneros. Para esto, utilizaron una técnica llamada diffusion tensor imaging (DFI), la cual se basa en la formación de imágenes cerebrales en tercera dimensión que captan el movimiento de agua dentro del cerebro. Así, los investigadores pueden conocer las conexiones estructurales en el cerebro.

Los resultados mostraron que los cerebros de los hombres tienen una buena conexión intrahemisférica, esto es, dentro del mismo hemisferio, mientras que los de las mujeres tienen una buena comunicación interhemisférica, es decir, entre los dos hemisferios, al nivel donde se localiza el telencéfalo, la parte más grande del cerebro. Por otro lado, los hombres tienen mejor conexión entre hemisferios a nivel del cerebelo, región importante para el control motor, mientras que las mujeres tienen buena conexión intrahemisférica a este nivel.

Esto sugiere que los cerebros de los hombres tienen una estructura que facilita la conexión entre la percepción y la acción coordinada, mientras que el las mujeres facilita la comunicación entre los modos de procesamiento analítico e intuitivo. Dichos resultados son consistentes con otras investigaciones donde las mujeres han demostrado ser mejores para poner atención y memorizar caras y palabras, mientras que los hombres sobresalen por realizar mejores actividades que involucran procesamiento espacial y velocidad sensomotora.

Este trabajo da más argumentos para explicar por qué los hombres son buenos para ciertas tareas y las mujeres para otras. Por ejemplo, ellos son mejores para aprender y desempeñar una tarea en cuestión como andar en bicicleta o navegar en direcciones, mientras que ellas tienen mayor habilidad para la memoria superior y para las tareas de cognición social, por lo que son mejores para desempeñar muchas actividades a la vez y generar soluciones que funcionan para los grupos.

Además, este trabajo demuestra que las trayectorias del desarrollo de hombres y mujeres se separa a los 13 años, pues antes de esa edad no se ven muchas diferencias a nivel de conexiones cerebrales, pero entre los 14 y 17, las diferencias comienzan a pronunciarse mucho.

Trabajos como estos no son realizados sólo para satisfacer el morbo colectivo, sino también para generar terapias neurocognitivas propias para cada género, por ejemplo. 

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Fuentes:

Nota fuente de SciencedailyArtículo original.

Imagen que muestra las conexiones dentro del mismo hemisferio en hombres (arriba) y entre hemisferio en mujeres (abajo). Tomada de la nota de Sciencedaily.

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Diffusion tensor imaging

Diffusion tensor imaging (DTI) is a magnetic resonance imaging technique that enables the measurement of the restricted diffusion of water in tissue in order to produce neural tract images instead of using this data solely for the purpose of assigning contrast or colors to pixels in a cross sectional image. It also provides useful structural information about muscle—including heart muscle—as well as other tissues such as the prostate.

The principal application is in the imaging of white matter where the location, orientation, and anisotropy of the tracts can be measured. The architecture of the axons in parallel bundles, and their myelin sheaths, facilitate the diffusion of the water molecules preferentially along their main direction. The imaging of this property is an extension of diffusion MRI.

Fiber tracking algorithms can be used to track a fiber along its whole length (e.g. the corticospinal tract, through which the motor information transit from the motor cortex to thespinal cord and the peripheral nerves). Tractography is a useful tool for measuring deficits in white matter, such as in aging. 

Some clinical applications of DTI are in the tract-specific localization of white matter lesions such as trauma and in defining the severity of diffuse traumatic brain injury. The localization of tumors in relation to the white matter tracts (infiltration, deflection), has been one of the most important initial applications. In surgical planning for some types of brain tumors, surgery is aided by knowing the proximity and relative position of thecorticospinal tract and a tumor.

The use of DTI for the assessment of white matter in development, pathology and degeneration has been the focus of over 2,500 research publications since 2005. It promises to be very helpful in distinguishing Alzheimer’s disease from other types of dementia.

Your Brain Is Fine-Tuning Its Wiring Throughout Your Life

The white matter microstructure, the communication pathways of the brain, continues to develop/mature as one ages. Studies link age-related differences in white matter microstructure to specific cognitive abilities in childhood and adulthood.

Most prior studies, however, did not include individuals from the entire life span or evaluated a limited section of white matter tracts. This knowledge gap prompted a new study published this week in Biological Psychiatry.

Dr. Bart Peters, of the Zucker Hillside Hospital, and his colleagues investigated the relationship of age and neurocognitive performance to nine white matter tracts from childhood to late adulthood.

To accomplish this, they recruited 296 healthy volunteers who ranged from 8 to 68 years of age. The participants completed a comprehensive battery of tests designed to measure their cognitive functioning, including speed, attention, memory, and learning. They also underwent a non-invasive diffusion tensor imaging scan, a technology that allowed the researchers to create maps of the 9 major white matter tracts under investigation.

The combination of this data allowed them to identify the neurocognitive correlates of each white matter tract in relation to its unique aging pattern.

They found that, from childhood into early adulthood, differences in fractional anisotropy – a measure of connectivity – of the cingulum were associated with executive functioning, whereas fractional anisotropy of the inferior fronto-occipital fasciculus was associated with visual learning and global cognitive performance via speed of processing.

"Our study identified key brain circuits that develop during adolescence and young adulthood that are associated with the growth of learning, memory and planning abilities. These findings suggest that young people may not have full capacity of these functions until these connections have completed their normal trajectory of maturation beyond adolescence," explained Peters.

"Our brain is changing throughout our lives. These changes underlie the capacities that emerge and are refined through adulthood," commented Dr. John Krystal, Editor of Biological Psychiatry. “There are clues that the steps that we take to preserve our medical health and stimulate our minds also serve to further refine and maintain these connections. For good reasons, attending to brain health is increasingly a focus of healthy aging.”

In addition, many individuals diagnosed with psychiatric disorders suffer with neurocognitive dysfunction as part of their illness, which is particularly difficult to alleviate with currently available treatments. Studies such as this may help to identify specific brain circuits/pathways that could serve as potential targets for treatment interventions.

Male and female brains wired differently, scans reveal

Neural map of a typical man’s brain. Photograph: National Academy of Sciences/PA

Scientists have drawn on nearly 1,000 brain scans to confirm what many had surely concluded long ago: that stark differences exist in the wiring of male and female brains.

Maps of neural circuitry showed that on average women’s brains were highly connected across the left and right hemispheres, in contrast to men’s brains, where the connections were typically stronger between the front and back regions.

Ragini Verma, a researcher at the University of Pennsylvania, said the greatest surprise was how much the findings supported old stereotypes, with men’s brains apparently wired more for perception and co-ordinated actions, and women’s for social skills and memory, making them better equipped for multitasking.

"If you look at functional studies, the left of the brain is more for logical thinking, the right of the brain is for more intuitive thinking. So if there’s a task that involves doing both of those things, it would seem that women are hardwired to do those better," Verma said. "Women are better at intuitive thinking. Women are better at remembering things. When you talk, women are more emotionally involved – they will listen more."

She added: “I was surprised that it matched a lot of the stereotypes that we think we have in our heads. If I wanted to go to a chef or a hairstylist, they are mainly men.”

Neural map of a typical woman’s brain. Photograph: National Academy of Sciences/PA

The findings come from one of the largest studies to look at how brains are wired in healthy males and females. The maps give scientists a more complete picture of what counts as normal for each sex at various ages. Armed with the maps, they hope to learn more about whether abnormalities in brain connectivity affect brain disorders such as schizophrenia and depression.

Verma’s team used a technique called diffusion tensor imaging to map neural connections in the brains of 428 males and 521 females aged eight to 22. The neural connections are much like a road system over which the brain’s traffic travels.

The scans showed greater connectivity between the left and right sides of the brain in women, while the connections in men were mostly confined to individual hemispheres. The only region where men had more connections between the left and right sides of the brain was in the cerebellum, which plays a vital role in motor control. “If you want to learn how to ski, it’s the cerebellum that has to be strong,” Verma said. Details of the study are published in the journal Proceedings of the National Academy of Sciences.

Male and female brains showed few differences in connectivity up to the age of 13, but became more differentiated in 14- to 17-year-olds.

"It’s quite striking how complementary the brains of women and men really are," Ruben Gur, a co-author on the study, said in a statement. "Detailed connectome maps of the brain will not only help us better understand the differences between how men and women think, but it will also give us more insight into the roots of neurological disorders, which are often sex-related."

Brain damage caused by severe sleep apnea is reversible

A neuroimaging study is the first to show that white matter damage caused by severe obstructive sleep apnea can be reversed by continuous positive airway pressure therapy. The results underscore the importance of the “Stop the Snore” campaign of the National Healthy Sleep Awareness Project, a collaboration between the Centers for Disease Control and Prevention, American Academy of Sleep Medicine, Sleep Research Society and other partners.

Results show that participants with severe, untreated sleep apnea had a significant reduction in white matter fiber integrity in multiple brain areas. This brain damage was accompanied by impairments to cognition, mood and daytime alertness. Although three months of CPAP therapy produced only limited improvements to damaged brain structures, 12 months of CPAP therapy led to an almost complete reversal of white matter abnormalities. Treatment also produced significant improvements in nearly all cognitive tests, mood, alertness and quality of life.

“Structural neural injury of the brain of obstructive sleep apnea patients is reversible with effective treatment,” said principal investigator and lead author Vincenza Castronovo, PhD, clinical psychologist at the Sleep Disorders Center at San Raffaele Hospital and Vita-Salute San Raffaele University in Milano, Italy. “Treatment with CPAP, if patients are adherent to therapy, is effective for normalizing the brain structure.”

The study results are published in the September issue of the journal Sleep.

“Obstructive sleep apnea is a destructive disease that can ruin your health and increase your risk of death,” said American Academy of Sleep Medicine President Dr. Timothy Morgenthaler, a national spokesperson for the Healthy Sleep Project. “Treatment of sleep apnea can be life-changing and potentially life-saving.”

The “Stop the Snore” campaign was launched recently to encourage people to talk to a doctor about the warning signs for sleep apnea, which afflicts at least 25 million adults in the U.S. Sleep apnea warning signs include snoring and choking, gasping or silent breathing pauses during sleep. Pledge to stop the snore at www.stopsnoringpledge.org.

The study involved 17 men with severe, untreated obstructive sleep apnea who had an average age of 43 years. They were evaluated at baseline and after both three months and 12 months of treatment with CPAP therapy. At each time point they underwent a neuropsychological evaluation and a diffusion tensor imaging examination. DTI is a form of magnetic resonance imaging that measures the flow of water through brain tissue. Participants were compared with 15 age-matched, healthy controls who were evaluated only at baseline.

A previous study by Castronovo’s research team found similar damage to gray matter volume in multiple brain regions of people with severe sleep apnea. Improvements in gray matter volume appeared after three months of CPAP therapy. According to the authors, the two studies suggest that the white matter of the brain takes longer to respond to treatment than the gray matter.

“We are seeing a consistent message that the brain can improve with treatment,” said co-principal investigator Mark Aloia, PhD, Associate Professor of Medicine at National Jewish Health in Denver, Colorado, and Senior Director of Global Clinical Research for Philips Respironics, Inc. “We know that PAP therapy keeps people breathing at night; but demonstrating effects on secondary outcomes is critical, and brain function and structure are strong secondary outcomes.”

Modulation of the Cerebello-Thalamo-Cortical Network in Thalamic Deep Brain Stimulation for Tremor

Neurosurgery 75:657–670, 2014 Deep brain stimulation alleviates tremor of various origins. Several regions like the ventralis intermediate nucleus of thalamus, the caudal zona incerta, and the posterior subthalamic region are generally targeted.

[WEB SITE] Stanford study finds brain abnormalities in chronic fatigue patients

[WEB SITE] Stanford study finds brain abnormalities in chronic fatigue patients

An imaging study by Stanford University School of Medicine investigators has found distinct differences between the brains of patients with chronic fatigue syndrome and those of healthy people.

The findings could lead to more definitive diagnoses of the syndrome and may also point to an underlying mechanism in the disease process.

It’s not uncommon for CFS patients to face several…

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