ADHD brain study finds slower development of key connections

13 10 2014

Slow to mature, quick to distract: ADHD brain study finds slower development of key connections.

Brain networks to handle internal & external tasks mature more slowly in ADHD.

A peek inside the brains of more than 750 children and teens reveals a key difference in brain architecture between those with attention deficit hyperactivity disorder and those without.

 

The new research may help lead to the development of a ‘neuromarker’ — a way to use brain imaging to improve diagnosis and treatment of ADHD.

Kids and teens with ADHD, a new study finds, lag behind others of the same age in how quickly their brains form connections within, and between, key brain networks.

The result: less-mature connections between a brain network that controls internally-directed thought (such as daydreaming) and networks that allow a person to focus on externally-directed tasks. That lag in connection development may help explain why people with ADHD get easily distracted or struggle to stay focused.

What’s more, the new findings, and the methods used to make them, may one day allow doctors to use brain scans to diagnose ADHD — and track how well someone responds to treatment. This kind of neuroimaging “biomarker” doesn’t yet exist for ADHD, or any psychiatric condition for that matter.

The new findings come from a team in the University of Michigan Medical School’s Department of Psychiatry. They used highly advanced computing techniques to analyze a large pool of detailed brain scans that were publicly shared for scientists to study. Their results are published in the Proceedings of the National Academy of Sciences.

Lead author Chandra Sripada, M.D., Ph.D., and colleagues looked at the brain scans of 275 kids and teens with ADHD, and 481others without it, using “connectomic” methods that can map interconnectivity between networks in the brain.

The scans, made using function magnetic resonance imaging (fMRI) scanners, show brain activity during a resting state. This allows researchers to see how a number of different brain networks, each specialized for certain types of functions, were “talking” within and amongst themselves.

The researchers found lags in development of connection within the internally-focused network, called the default mode network or DMN, and in development of connections between DMN and two networks that process externally-focused tasks, often called task-positive networks, or TPNs. They could even see that the lags in connection development with the two task-related networks — the frontoparietal and ventral attention networks –  were located primarily in two specific areas of the brain.

 

The new findings mesh well with what other researchers have found by examining the physical structure of the brains of people with and without ADHD in other ways.

Such research has already shown alterations in regions within DMN and TPNs. So, the new findings build on that understanding and add to it.

The findings are also relevant to thinking about the longitudinal course of ADHD from childhood to adulthood. For instance, some children and teens “grow out” of the disorder, while for others the disorder persists throughout adulthood. Future studies of brain network maturation in ADHD could shed light into the neural basis for this difference.

“We and others are interested in understanding the neural mechanisms of ADHD in hopes that we can contribute to better diagnosis and treatment,” says Sripada, an assistant professor and psychiatrist who holds a joint appointment in the U-M Philosophy department and is a member of the U-M Center for Computational Medicine and Bioinformatics. “But without the database of fMRI images, and the spirit of collaboration that allowed them to be compiled and shared, we would never have reached this point.”

Sripada explains that in the last decade, functional medical imaging has revealed that the human brain is functionally organized into large-scale connectivity networks. These networks, and the connections between them, mature throughout early childhood all the way to young adulthood. “It is particularly noteworthy that the networks we found to have lagging maturation in ADHD are linked to the very behaviors that are the symptoms of ADHD,” he says.

Studying the vast array of connections in the brain, a field called connectomics, requires scientists to be able to parse through not just the one-to-one communications between two specific brain regions, but the patterns of communication among thousands of nodes within the brain. This requires major computing power and access to massive amounts of data – which makes the open sharing of fMRI images so important.

“The results of this study set the stage for the next phase of this research, which is to examine individual components of the networks that have the maturational lag,” he says. “This study provides a coarse-grained understanding, and now we want to examine this phenomenon in a more fine-grained way that might lead us to a true biological marker, or neuromarker, for ADHD.”

Sripada also notes that connectomics could be used to examine other disorders with roots in brain connectivity – including autism, which some evidence has suggested stems from over-maturation of some brain networks, and schizophrenia, which may arise from abnormal connections. Pooling more fMRI data from people with these conditions, and depression, anxiety, bipolar disorder and more could boost connectomics studies in those fields.

 

Volunteers needed for research:

To develop such a neuromarker, Sripada has embarked on follow-up research. One study is enrolling children between the ages of 7 and 17 who have ADHD and a comparison group of those without it; information is at http://umhealth.me/adhdchild. Another study is enrolling adults between the ages of 18 and 35 who have ADHD and a comparison group of those without it; information is at http://umhealth.me/adhdadult. Of note, fMRI scans do not expose a person to radiation. Anyone interested in these studies can email Psych-study@med.umich.edu or call (734) 232-0353; for the study of children, parents should make the contact and consent to research on behalf of their children.

Besides Sripada, the study’s authors are Psychiatry computer specialists Daniel Kessler and Mike Angstadt. Kessler, a graduate of U-M with a degree in neuroscience and statistics, helped develop the key connectomic methods used in the study and plans to pursue this research further in a graduate program starting in 2015. The research was funded by a National Institutes of Health grant (AA020297), a UMCCMB pilot grant, and the John Templeton Foundation. It used fMRI scans from the ADHD-200 and ABIDE projects.

Reference: www.pnas.org/cgi/doi/10.1073/pnas.1407787111

 

By ANN ARBOR

 

 

Uofmhealth.org [en línea] Ann Arbor, MI (USA): uofmhealth.org, 13 de octubre de 2014 [ref. 15 de septiembre de 2014] Disponible en Internet: http://www.uofmhealth.org/news/archive/201409/slow-mature-quick-distract-adhd-brain-study-finds-slower



Los adultos con trastornos alimentarios tienen peor pronóstico si sufren hiperactividad

1 08 2013

Un estudio realizado con 191 pacientes revela que los síntomas de hiperactividad del trastorno de déficit de atención e hiperactividad (TDAH) van asociados a una mayor impulsividad y severidad y probablemente a un peor pronóstico en pacientes con trastornos alimentarios.

El investigador Fernando Fernández-Aranda

El investigador Fernando Fernández-Aranda

El TDAH está poco estudiado en adultos y, aunque varios trabajos han descrito asociaciones entre este trastorno y conductas alimentarias anómalas, hasta ahora no se habían descrito asociaciones entre TDAH y trastornos alimentarios en adultos.

Los resultados del estudio realizado por investigadores del grupo de Psiquiatría y Salud Mental del Instituto de Investigación Biomédica de Bellvitge (IDIBELL) en la Unidad de Trastornos de la Conducta Alimentaria del Hospital Universitario de Bellvitge, y del Servicio de Psiquiatría del Hospital Universitario Vall d’Hebron se han publicado en la edición electrónica de la revista BMC Psychiatry.

 

 

Impulsividad y trastornos alimentarios

Los síntomas relacionados con la hiperactividad del TDAH como la impulsividad están muy presentes en las pacientes con trastornos alimentarios que han participado en el estudio, pero no en todas, según ha explicado Fernando Fernández-Aranda, jefe de la Unidad de Trastornos de la Conducta Alimentaria del Hospital Universitario de Bellvitge e investigador del IDIBELL. Estos trastornos “los encontramos sobre todo en las pacientes con rasgos de personalidad más impulsivos: las pacientes con bulimia, trastornos por atracón y también en pacientes con trastornos alimentarios sin especificar. En cambio, las pacientes anoréxicas más restrictivas y con más control no tienen asociados estos síntomas”.

Esta investigación ha permitido desarrollar un modelo que podría ser útil en la clínica para detectar de forma precoz factores de riesgo que podrían llevar a un trastorno alimentario.

Los síntomas de TDAH se asocian positivamente a rasgos de personalidad más impulsiva y la edad. Es decir cuanta más impulsividad y más edad, mayor riesgo de desarrollar un trastorno alimentario. También se asocian a una mayor severidad del trastorno.

Por otra parte, estos síntomas de TDAH de impulsividad están asociados a una baja autodirección, un rasgo del carácter que implica ser capaces de planificar y alcanzar objetivos a medio y largo plazo. “De modo que las pacientes con síntomas de TDAH también tienen peor pronóstico porque les es más difícil ser capaces de seguir un tratamiento”, ha explicado Fernández-Aranda.

Sistema de recompensa

Según Fernández-Aranda, este modelo será útil no sólo en la clínica sino también para la investigación de los circuitos cerebrales que regulan el sistema de recompensa y que son similares en varios trastornos de conducta como los trastornos alimentarios, el juego patológico o otras adicciones conductuales.

Más información

Bulimia. Trastorno de la conducta alimentaria que afecta sobre todo a mujeres de entre 18 y 30 años preocupadas por su imagen. Suelen comenzar una dieta para bajar de peso pero pierden el control al poco tiempo e inician episodios de atracones (comer de forma compulsiva) varias veces al día. Una vez han sufrido esta pérdida de control, buscan la manera de compensarlo: el 80% vomita y otras realizan ejercicio de manera desmesurada o restringen la comida durante un tiempo. El proceso se repite hasta llegar a siete u ocho episodios de atracón-vómito al día.

Trastorno por atracón. El 90-95% de los pacientes que sufren este trastorno alimentario son obesos que utilizan la comida como válvula de escape. Ante problemas emocionales, pierden el control y comen de forma compulsiva. No disfrutan de la comida como otros obesos.

Anorexia. Trastorno de la conducta alimentaria que aparece especialmente en mujeres de entre 14 y 30 años caracterizado por una preocupación excesiva por la imagen y una distorsión de la propia imagen personal. Las afectadas siguen una dieta estricta para adelgazar hasta llegar a perder el 15% de su peso normal y tienen miedo a engordar. El 40% son de tipo restrictivo y el resto combina atracones y vómitos.

 

Idibell.cat [en línea] Barcelona (ESP): idibell.cat, 01 de agosto de 2013 [ref. 10 de julio de 2013] Disponible en Internet: http://www.idibell.cat/modul/noticias/es/588/los-adultos-con-trastornos-alimentarios-tienen-peor-pronostico-si-sufren-hiperactividad