Neuroimaging Techniques in the
Investigation of Auditory
Processing Disorders
Rola Farah and Robert W. Keith
University of Cincinnati/CCHMC
[email protected]
Disclosure
We have no relevant financial or nonfinancial
relationship(s) within the products or services described,
reviewed, evaluated or compared in this presentation.
Neuroimaging
Neuroimaging techniques are used to image the structure
and/or function of the brain either directly or indirectly
E.g. CT, fMRI, PET, MEG, DTI, SPECT
Each technique is used based on the information needed
and has its advantages and disadvantages
Source: http://www.psych.nyu.edu/pylkkanen/LOT_2005/DAY1/Funct_neuroimaging.pdf
Brain Connectivity
Source:http://www.fmri4newbies.com
Functional Connectivity
• Temporal correlations between different neurophysiological
events (Friston, 1994)
• Examines which brain areas are active when we perform a
task
• Observed correlations not how these correlations are
mediated
Functional Magnetic Resonance
Imaging (fMRI)
Task
Neural
activity
O2
Blood flow
Hemodynamics
End Result
• Activation map
• Correlation with behavioral task performance
fMRI
Image source:http://sitemaker.umich.edu/fmri.training.course/home
Effective Connectivity
• “Defined”: The influence one neuronal system exerts
over another” (Friston, 1994)
• Provides information about the communication
between different brain regions during a cognitive task
• Describes influences among brain regions using
structural equation modeling (SEM) to determine how
regions of the brain influence each other during a
specific task
STG
PFC
ACC
Structural Connectivity
Diffusion Tensor Imaging (DTI)
• An MRI-based neuroimaging
technique used to measure
white matter microstructure
• Provides visualization of the
location and orientation of the
brain's white matter tracts
(Le Bihan et al., 2001)
Source: http://www.neurofmri.bme.wisc.edu/research/dti.html
White Matter
White matter tracts are the pathways communicating
neural interactions between different brain areas
Mapping these pathways; the white matter tracts is the
main aim of DTI
DTI
• Diffusion tensor imaging measures the displacement of
water molecules and provides information about white
matter fibers that pass within a pixel
• Water molecules are used as a probe that can reveal
microscopic details about the architecture of the tissue
Isotropy and Anisotropy
• Isotropic diffusion:
When water molecules moves
equally in all directions
(gray matter)
• Anisotropic diffusion
Movement along one axis but
not others (white matter)
Water movement reveals information
about fiber structure
Source: http://white.stanford.edu/~brian/papers/mri/2006-Wandell-NIPS-Tutorial.pdf
DTI Measures
• Fractional anisotropy (FA) common parameter used to
estimate white matter structural integrity and connectivity
• FA: ranges from “0” – complete isotropy to “1”
complete anisotropy
• In white matter regions, diffusion anisotropy is expected
because water diffusion is faster in a direction parallel to
the axon than perpendicular to it.
• Increased FA may represent:
- Increased myelination
- Increased fiber organization
- Increased axonal diameter
- FA correlated with reading ability, intelligence in normal
children and other cognitive tasks
DTI Measures
• DTI tractography:
Fiber tracking procedure, in
color-coded map, used to track a
fiber along its whole length
(Nucifora et al., 2007)
•
•
•
Red = left-right
Green = anterior-posterior
Blue = superior-inferior
Source: http://en.wikipedia.org/wiki/Tractography
How can fMRI and DTI Assist in
Auditory Processing Research?
• Once we increase our understanding of how the typical
brain processes auditory stimuli, we may be able to
answer the question
• What is different about the brains of individuals with
auditory processing disorders (APD)?
fMRI
(Bartel-Friedrich et al., 2010)
Aim:
Develop fMRI tests for children with APD
Methods:
11 healthy children (7 to 10 years)
11 healthy adults (23 to 31 years)
the Hannover phoneme discrimination test (HPDT);
the auditory memory span test (MST) and the dichotic
listening test (DLT).
BOLD fMRI
Results:
HPDT : Bilateral superior temporal gyrus (STG),
Broca area and left middle temporal gyrus
MST: Bilateral STG, typical for processing of pseudowords, bilateral hippocampus, no clear activity in the
left supramarginal gyrus, where the phonological
store is thought to be located.
DLT: bilateral STG and left inferior frontal gyrus
DTI
(Schmithorst et al., 2011)
Aim:
Investigate the correlation of white matter
microstructure with auditory processing tasks used
to diagnose APD
Methods:
17 typically developing children (9-11 years)
Bamford-Kowal-Bench Speech-in-Noise test, SCAN-C
Filtered Words, Time-Compressed Sentences
DTI
Results:
Positive correlations were found between white
matter FA and speech-in noise in white matter
adjoining prefrontal areas
Positive correlations between FA and filtered words in
the corpus callosum
Correlations with time-compressed sentences
varied depending on the degree of compression
correlations of FA with
performance on a speech-innoise test
Orange
Negative correlations with task
Performance: Centrum semiovale
Blue
Positive correlations with task
Performance: left and right
prefrontal cortices
Conclusions
• Independent white matter regions for different tasks
correlated with task performance
• Controversy: do these tests measure dependent or
independent constructs?
• Results supported the claim that the neurological bases
for each of these tasks are at least partially independent”
Future Directions
Multimodal approach is the way
forward!!!
Segregation and integration in brain
networks
References
•
American Speech Language Hearing Association, A. (2005). (Central) Auditory Processing
Disorders ([ Technical Report ] Available at www.asha.org/policy
•
Bartel-Friedrich, S., Y. Broecker, et al. (2010). "Development of fMRI Tests for Children with
Central Auditory Processing Disorders." In vivo (Athens) 24(2): 201-209.
•
Guimaraes, A. R., J. R. Melcher, et al. (1998). "Imaging subcortical auditory activity in humans."
Hum Brain Mapp 6(1): 33-41.
•
Huettel, S. A., A. W. Song, et al. (2008). Functional Magnetic Resonance Imaging, Sinauer
Associates.
•
Le Bihan, D., Mangin, J.-F., Poupon, C., Clark, C. A., Pappata, S., Molko, N., et al. (2001).
Diffusion tensor imaging: Concepts and applications. Journal of Magnetic Resonance Imaging,
13(4), 534-546.
•
Nucifora, P. G. P., Verma, R., Lee, S.-K., & Melhem, E. R. (2007). Diffusion-Tensor MR Imaging
and Tractography: Exploring Brain Microstructure and Connectivity1. Radiology, 245(2), 367-384.
•
Price, D. L., J. P. De Wilde, et al. (2001). "Investigation of acoustic noise on 15 MRI scanners
from 0.2 T to 3 T." J Magn Reson Imaging 13(2): 288-293.
•
Schmithorst, V. J., Holland, S. K., & Plante, E. (2011). Diffusion Tensor Imaging Reveals White
Matter Microstructure Correlations With Auditory Processing Ability. Ear and hearing, 32(2), 156167.
•
Schmithorst, V. J., & Holland, S. K. (2004). Event-related fMRI technique for auditory processing
with hemodynamics unrelated to acoustic gradient noise. Magn Reson Med, 51(2), 399-402.