Leta i den här bloggen

torsdag 8 november 2012

ADHD ja aivo , valkoisen aivoaineksen merkitys .

Häiriö konnektiviteetissä.
 (1)
PLoS One. 2012;7(9):e45671. doi: 10.1371/journal.pone.0045671. Epub 2012 Sep 26. Abnormal Brain Connectivity Patterns in Adults with ADHD: A Coherence Study.

Abstract

Studies based on functional magnetic resonance imaging (fMRI) during the resting state have shown decreased functional connectivity between the dorsal anterior cingulate cortex (dACC) and regions of the Default Mode Network (DMN) in adult patients with Attention-Deficit/Hyperactivity Disorder (ADHD) relative to subjects with typical development (TD). Most studies used Pearson correlation coefficients among the BOLD signals from different brain regions to quantify functional connectivity. Since the Pearson correlation analysis only provides a limited description of functional connectivity, we investigated functional connectivity between the dACC and the posterior cingulate cortex (PCC) in three groups (adult patients with ADHD, n = 21; TD age-matched subjects, n = 21; young TD subjects, n = 21) using a more comprehensive analytical approach - unsupervised machine learning using a one-class support vector machine (OC-SVM) that quantifies an abnormality index for each individual. The median abnormality index for patients with ADHD was greater than for TD age-matched subjects (p = 0.014); the ADHD and young TD indices did not differ significantly (p = 0.480); the median abnormality index of young TD was greater than that of TD age-matched subjects (p = 0.016). Low frequencies below 0.05 Hz and around 0.20 Hz were the most relevant for discriminating between ADHD patients and TD age-matched controls and between the older and younger TD subjects. In addition, we validated our approach using the fMRI data of children publicly released by the ADHD-200 Competition, obtaining similar results. Our findings suggest that the abnormal coherence patterns observed in patients with ADHD in this study resemble the patterns observed in young typically developing subjects, which reinforces the hypothesis that ADHD is associated with brain maturation deficits.

(2)

Hum Brain Mapp. 2010 Jun;31(6):904-16.  Is the ADHD brain wired differently? A review on structural and functional connectivity in attention deficit hyperactivity disorder.
Child Neuropsychology Section, Department of Child and Adolescent Psychiatry and Psychotherapy, University Hospital of the RWTH Aachen, Germany. kkonrad@ukaachen.de

Abstract

In recent years, a change in perspective in etiological models of attention deficit hyperactivity disorder (ADHD) has occurred in concordance with emerging concepts in other neuropsychiatric disorders such as schizophrenia and autism. These models shift the focus of the assumed pathology from regional brain abnormalities to dysfunction in distributed network organization. In the current contribution, we report findings from functional connectivity studies during resting and task states, as well as from studies on structural connectivity using diffusion tensor imaging, in subjects with ADHD. Although major methodological limitations in analyzing connectivity measures derived from noninvasive in vivo neuroimaging still exist, there is convergent evidence for white matter pathology and disrupted anatomical connectivity in ADHD. In addition, dysfunctional connectivity during rest and during cognitive tasks has been demonstrated. However, the causality between disturbed white matter architecture and cortical dysfunction remains to be evaluated. Both genetic and environmental factors might contribute to disruptions in interactions between different brain regions. Stimulant medication not only modulates regionally specific activation strength but also normalizes dysfunctional connectivity, pointing to a predominant network dysfunction in ADHD. By combining a longitudinal approach with a systems perspective in ADHD in the future, it might be possible to identify at which stage during development disruptions in neural networks emerge and to delineate possible new endophenotypes of ADHD.

(3) 

 Aivojen funktionaalinen konnektiviteetti ja sen fysiologinen tausta

LÄHDE: 
Proc Natl Acad Sci U S A. 2010 Nov 2;107(44):19067-72. Epub 2010 Oct 18. White matter maturation reshapes structural connectivity in the late developing human brain.
Department of Radiology, University Hospital Center and University of Lausanne, 1011 Lausanne, Switzerland. patric.hagmann@epfl.ch

Abstract

From toddler to late teenager, the macroscopic pattern of axonal projections in the human brain remains largely unchanged while undergoing dramatic functional modifications that lead to network refinement. These functional modifications are mediated by increasing myelination and changes in axonal diameter and synaptic density, as well as changes in neurochemical mediators. Here we explore the contribution of white matter maturation to the development of connectivity between ages 2 and 18 y using high b-value diffusion MRI tractography and connectivity analysis. We measured changes in connection efficacy as the inverse of the average diffusivity along a fiber tract. We observed significant refinement in specific metrics of network topology, including a significant increase in node strength and efficiency along with a decrease in clustering. Major structural modules and hubs were in place by 2 y of age, and they continued to strengthen their profile during subsequent development. Recording resting-state functional MRI from a subset of subjects, we confirmed a positive correlation between structural and functional connectivity, and in addition observed that this relationship strengthened with age. Continuously increasing integration and decreasing segregation of structural connectivity with age suggests that network refinement mediated by white matter maturation promotes increased global efficiency. In addition, the strengthening of the correlation between structural and functional connectivity with age suggests that white matter connectivity in combination with other factors, such as differential modulation of axonal diameter and myelin thickness, that are partially captured by inverse average diffusivity, play an increasingly important role in creating brain-wide coherence and synchrony.

Oma kommentti: Mitä tulee valkoiseen aivoainekseen ja sen osuuteen aivojen integraation kehittymisessä, siihen voi vaikuttaa myös itse. Esim  lasten ravitsemus merkitsee. 
Myeliinin kehittymiseen tarvitaan  mm päivittäistä K-vitamiinia joka päivä aina, Tuskin monikaan lapsi syö vihreitä vihanneksia kasvisöljysalaattikastikkeessa  montaakaan kertaa kuukaudessa, vaikka sellaista pitäisi syödä joka päivä. Toisekseen aivojen kehittymiseen ja konnektiviteetin kehittymiseen on eduksi rauhallinen kouluaika, jossa joka päivä oppii jotakin uutta ja kertaa opittua, ja oppii hallitsemaan kehoaan, käytöstään ja kehittämään lahjakkuuksiaan, ei sitten viime hädässä  joskus  aikuisena ja vikoilemalla huonoja olosuhteita , huonoja vanhempia huonoja kouluja jne.
Koululaitos on luotu kehittämään  lapsissa aivojen  parhaat kyvyt esiin heidän kapasiteettinsa mukaisessa tahdissa. Gaussin käyrän takia tietysti osa  lapsista  selviytyy keskimääräistä heikommin ja sitten on  luotava  luokkia joissa on  suojatusti hieman rauhallisempi tahti, mutta  samat päämäärät.  Aliravitsemus on banaali tekijä , samoin neurotoksiinit, mitkä tulisi eliminoida.
Aivot vaihtavat rasva-aineitaan aivan jatkuvasti, joten hyvästä ravitsemuksesta ei  pitäisi säästää kun on kyse kasvavista  lapsista ja kouluikäisistä.  Asiaan vaikuttavat taudit pitää diagnosoida ja eliminoida.On tekijöitä, esim perheriidat, pahoinpitelyt, diskriminaatiot, huumeet, tupakka,    TV ym  ärsyttävän  aineksen  syöttö, tietokonepelit,  ym   jotka  ylikiihdyttävät lapsia käyttäytymään ADHD tavoin, ilman että he rauhallisissa  olosuhteissa olisivat mitään ADHD diagnoosia ansaitsevia  Voivat olla tavallisia pikku nörttejä, jotka toisessa  miljöössä olisivat aivan ok. Nuoretkin voivat kyllä hankkia pysyviä vaurioita perusterveisiin  aivoihinsa esim imppauksesta ja  huumeista.


Inga kommentarer:

Skicka en kommentar