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fMRI in Glasgow

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Intra-subject variation in language laterality. ... Age Related Macular Degeneration. fMRI in ARMD with Eccentric Viewing Learning ... – PowerPoint PPT presentation

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Title: fMRI in Glasgow


1
fMRI in Glasgow
  • Jennifer Chisholm
  • Institute of Neurological Sciences
  • Glasgow

2
Outline
  • Scanner stability in EPI scanning.
  • Intra-subject variation in language laterality.
  • Effect of learning Eccentric Viewing Techniques
    on fMRI in ARMD subjects.

3
Project 1
4
Temporal Stability of 3T
Materials Methods
  • 30 minute EPI, phantom acquisition
  • 600 volumes, TR 3s, TE 30ms, matrix 64x64, 25
    slices.
  • Analysis
  • FSLs motion correction McFLIRT
  • MIPAV ROI tools

5
Temporal stability of 3T
Results
  • Levitation of 2.5mm in y-dir.
  • Significant heating.
  • Non-significant signal drift.
  • GE INTERVENTION - Bore Lining Installation.

6
Temporal Stability of 3T
Results
  • Eliminated levitation
  • Introduced Signal error
  • Vacuum switch
  • Vacuum off
  • Drift remained, no sawtooth.
  • ? Vacuum pressure changes
  • Vacuum off for several days
  • Sawtooth drift resolved to within acceptable
    limits
  • Small positional shift (0.35mm).

7
Temporal Stability of 3T
Results
  • Vacuum pump modification
  • Electrical switch replaced by mechanical valve.
  • Positional stability.
  • Signal stability - 1.2 variation over 30 mins.

8
Project 2
9
Language Laterality Reproducibility
Introduction
  • Epilepsy cannot always be treated with drugs
  • In severe, intractable cases, surgical removal of
    the seizure focus (often frontal lobe) is used as
    treatment.
  • Area can be close to areas that provide language
    and memory function
  • need to determine likelihood of post-surgical
    deficit

10
Language Laterality Reproducibility
Introduction
  • WADA test.
  • Injection of barbiturate (anaesthetic) into right
    or left internal carotid artery.
  • Send half of brain to sleep.
  • Perform memory language tasks.
  • lt1 risk of inducing a stroke.

11
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12
WADA Test

Delivery of amytal
Receptors (BZR/GABA)




intra-arterial injection of HMPAO with amytal
intra-venous injection of iomazenil

Effect on function




intra-venous injection of HMPAO
13
WADA Test

Delivery of amytal
Receptors (BZR/GABA)




intra-arterial injection of HMPAO with amytal
intra-venous injection of iomazenil

Effect on function




intra-venous injection of HMPAO
14
Language Laterality Reproducibility
Materials Methods
  • fMRI language tasks
  • Word generation
  • Verb generation
  • Block design

0
30
60
90
120
15
Language Laterality Reproducibility
Materials Methods
  • Laterality indices based on
  • No. of activated voxels, NV
  • Average value of Z-statistic in activated voxels,
    ZAV
  • Repeated at a 2 week interval on each of 15
    normal, healthy volunteers.

16
Language Laterality Reproducibility
Results
  • NV
  • Different laterality outcome in 2/15 subjects
    between two time points
  • Mixed at both time points using ZAV.
  • ZAV
  • Different laterality outcome in a different 1/15
    subjects
  • Left at both time points using NV .
  • In all 3 subjects, change from Left to Mixed or
    vice versa

17
Language Laterality Reproducibility
Conclusion
  • Two language paradigm approach is reproducible
    over 2 week period in healthy volunteers.
  • Calculation of both laterality indices is useful.
  • Repetition of protocol with epileptic patients
    and comparison with WADA test data under way.

18
Project 3
19
fMRI Learning
  • Neuron. 2004 Oct 2844(3)411-22 Neural changes
    following remediation in adult developmental
    dyslexia. Eden GF et al
  • Cogn Affect Behav Neurosci. 2004 Mar4(1)67-88
  • The neurobiology of adaptive learning in reading
    a contrast of different training conditions.
  • Sandak R et al.

20
fMRI in ARMD with Eccentric Viewing Learning
Age Related Macular Degeneration
21
fMRI in ARMD with Eccentric Viewing Learning
Eccentric Viewing
  • Peripheral retina employed for fixation tasks.
  • Training
  • 1 hours sessions 4 - 12 weeks.

22
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23
fMRI in ARMD with Eccentric Viewing Learning
Hypothesis
  • MD subjects have been shown to recruit visual
    cortex usually receiving foveal input to receive
    input from the new preferred retinal locus
  • Baker C et al
  • Eccentric viewing may increase the significance
    and/or extent of activation seen in previous
    foveal cortical locations.

24
fMRI in ARMD with Eccentric Viewing Learning
Study Protocol
  • 8 ARMD subjects
  • 8 age and gender matched controls
  • Ophthalmic investigations
  • Standard
  • Electrophysiology mfERG
  • Retinotopic mapping via fMRI

25
fMRI in ARMD with Eccentric Viewing Learning
Multifocal Electroretinogram (mfERG)
26
fMRI in ARMD with Eccentric Viewing Learning
Multifocal Electroretinogram (mfERG)
Normal
ARMD
27
fMRI in ARMD with Eccentric Viewing Learning
fMRI
  • Simulator
  • Eyetracker
  • Reversing checkerboard pattern
  • Expanding annulus
  • Dilating contracting
  • (to remove and examine between-area phase
    delays).
  • Rotating hemi-field
  • Clockwise anti-clockwise
  • E-prime

28
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