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fMRI for mapping the plastic somatotopy of primary somatosensory cortex - Development and clinical applications

Weibull, Andreas LU (2009) In Lund University, Faculty of Medicine Doctoral Dissertation Series 2009:119.
Abstract
Functional magnetic resonance imaging (fMRI) is a widely used tool for

studying brain function in vivo. The technique is based on acquiring brain

images sensitive to the physiological response following neural activation,

and hence, allows brain activity to be examined and documented.

In this thesis, methods for fMRI mapping of the primary somatosensory

cortex (S1) are optimised and subsequently applied in studies where a

plastic reorganisation of S1 is hypothesised.

Initially, the impact of spatial resolution and smoothing on fMRI data of

detailed S1 activation was investigated using a theoretical model of fMRI

performance. The impact of these... (More)
Functional magnetic resonance imaging (fMRI) is a widely used tool for

studying brain function in vivo. The technique is based on acquiring brain

images sensitive to the physiological response following neural activation,

and hence, allows brain activity to be examined and documented.

In this thesis, methods for fMRI mapping of the primary somatosensory

cortex (S1) are optimised and subsequently applied in studies where a

plastic reorganisation of S1 is hypothesised.

Initially, the impact of spatial resolution and smoothing on fMRI data of

detailed S1 activation was investigated using a theoretical model of fMRI

performance. The impact of these parameters was also examined in healthy

volunteers where different fingers were mapped in S1. This was

accomplished using computer controlled and reproducible tactile

stimulation. It was found that both the optimal spatial resolution and

preferred level of smoothing were intimately coupled to the experiment’s

contrast-to-noise.

These results were utilised for monitoring sensory activation of S1 in three

cohorts where cortical reorganisation was anticipated: (i) In healthy

volunteers where the volar part of the forearm was anaesthetised, (ii) in

hand amputees and (iii) in subjects suffering from long-term exposure to

vibrating tools. In all these groups, evidence of plastic changes in the

sensorimotor system were found. This suggests that plastic processes could

be an underlying mechanism for the symptoms experienced in patients

following nerve injury and neuropathy.

Finally, alternative methods for mapping functional networks of the

sensorimotor cortex during rest were explored. We found that the resulting

networks were comparable to activation maps during a finger-tapping task,

although only partly overlapping. Such network maps could potentially add

to our understanding of brain plasticity in this region of the brain.

In conclusion, this work has improved the feasibility of monitoring plastic

reorganisation in S1. This may contribute to the process of rehabilitation in

patients suffering from sensory disorders following nerve injury and

neuropathy. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Lundberg, Peter, Avd. för Radiofysik, Inst. för Medicin och Hälsa, Universitetssjukhuset i Linköping
organization
publishing date
type
Thesis
publication status
published
subject
keywords
smoothing, physiological noise, spatial resolution, primary somatosensory cortex, cortical reorganisation, brain plasticity, fMRI, partial volume effects
in
Lund University, Faculty of Medicine Doctoral Dissertation Series
volume
2009:119
pages
160 pages
publisher
Medical Radiation Physics, Lund University
defense location
Universitetssjukhuset MAS, Diagnistiskt Centrum, Ing 44, plan 2, rum 2005
defense date
2009-12-11 09:15
ISSN
1652-8220
ISBN
978-91-86443-08-5
language
English
LU publication?
yes
id
6ba0e870-766c-4ac1-aab5-ce672a71ac87 (old id 1509449)
date added to LUP
2010-01-05 16:11:33
date last changed
2016-09-19 08:44:50
@phdthesis{6ba0e870-766c-4ac1-aab5-ce672a71ac87,
  abstract     = {Functional magnetic resonance imaging (fMRI) is a widely used tool for<br/><br>
studying brain function in vivo. The technique is based on acquiring brain <br/><br>
images sensitive to the physiological response following neural activation, <br/><br>
and hence, allows brain activity to be examined and documented. <br/><br>
In this thesis, methods for fMRI mapping of the primary somatosensory <br/><br>
cortex (S1) are optimised and subsequently applied in studies where a <br/><br>
plastic reorganisation of S1 is hypothesised. <br/><br>
Initially, the impact of spatial resolution and smoothing on fMRI data of <br/><br>
detailed S1 activation was investigated using a theoretical model of fMRI <br/><br>
performance. The impact of these parameters was also examined in healthy <br/><br>
volunteers where different fingers were mapped in S1. This was <br/><br>
accomplished using computer controlled and reproducible tactile <br/><br>
stimulation. It was found that both the optimal spatial resolution and <br/><br>
preferred level of smoothing were intimately coupled to the experiment’s <br/><br>
contrast-to-noise. <br/><br>
These results were utilised for monitoring sensory activation of S1 in three <br/><br>
cohorts where cortical reorganisation was anticipated: (i) In healthy <br/><br>
volunteers where the volar part of the forearm was anaesthetised, (ii) in <br/><br>
hand amputees and (iii) in subjects suffering from long-term exposure to <br/><br>
vibrating tools. In all these groups, evidence of plastic changes in the <br/><br>
sensorimotor system were found. This suggests that plastic processes could <br/><br>
be an underlying mechanism for the symptoms experienced in patients <br/><br>
following nerve injury and neuropathy. <br/><br>
Finally, alternative methods for mapping functional networks of the <br/><br>
sensorimotor cortex during rest were explored. We found that the resulting <br/><br>
networks were comparable to activation maps during a finger-tapping task, <br/><br>
although only partly overlapping. Such network maps could potentially add <br/><br>
to our understanding of brain plasticity in this region of the brain. <br/><br>
In conclusion, this work has improved the feasibility of monitoring plastic <br/><br>
reorganisation in S1. This may contribute to the process of rehabilitation in <br/><br>
patients suffering from sensory disorders following nerve injury and <br/><br>
neuropathy.},
  author       = {Weibull, Andreas},
  isbn         = {978-91-86443-08-5},
  issn         = {1652-8220},
  keyword      = {smoothing,physiological noise,spatial resolution,primary somatosensory cortex,cortical reorganisation,brain plasticity,fMRI,partial volume effects},
  language     = {eng},
  pages        = {160},
  publisher    = {Medical Radiation Physics, Lund University},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctoral Dissertation Series},
  title        = {fMRI for mapping the plastic somatotopy of primary somatosensory cortex - Development and clinical applications},
  volume       = {2009:119},
  year         = {2009},
}