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Masking level differences--a diffusion tensor imaging and functional MRI study.

Wack DS, Polak P, Furuyama J, Burkard RF - PLoS ONE (2014)

Bottom Line: The current study revealed regions of increased and decreased activity within the auditory cortex when comparing the combined noise and signal of the dichotic MLD stimuli (N0Sπ and NπS0) with N0S0.Furthermore, we found evidence of inferior colliculus involvement.Patterns of correlation when the signal was presented only to the right ear showed an extensive network in the left hemisphere; however, the opposite was not true for the signal presented only to the left ear.

View Article: PubMed Central - PubMed

Affiliation: Department of Nuclear Medicine, State University of New York at Buffalo, Buffalo, New York, United States of America.

ABSTRACT
In our previous study we investigated Masking Level Differences (MLD) using functional Magnetic Resonance Imaging (fMRI), but were unable to confirm neural correlations for the MLD within the auditory cortex and inferior colliculus. Here we have duplicated conditions from our previous study, but have included more participants and changed the study site to a new location with a newer scanner and presentation system. Additionally, Diffusion Tensor Imaging (DTI) is included to allow investigation of fiber tracts that may be involved with MLDs. Twenty participants were included and underwent audiometric testing and MRI scanning. The current study revealed regions of increased and decreased activity within the auditory cortex when comparing the combined noise and signal of the dichotic MLD stimuli (N0Sπ and NπS0) with N0S0. Furthermore, we found evidence of inferior colliculus involvement. Our DTI findings show strong correlations between DTI measures within the brainstem and signal detection threshold levels. Patterns of correlation when the signal was presented only to the right ear showed an extensive network in the left hemisphere; however, the opposite was not true for the signal presented only to the left ear. Our current study was able to confirm what we had previously hypothesized using fMRI, while extending our investigation of MLDs to include the characteristics of connecting neural pathways.

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Related in: MedlinePlus

Red color indicates increased activity for dichotic condition versus N0S0.Blue indicates increased activity for N0S0 versus the dichotic condition. The overall patterns for N0Sπ vs. N0S0 (left image) and NπS0 vs. N0S0 (right image) are similar within the left auditory cortex. Regions are threshold at p<.01, uncorrected. Images are spatially normalized to SPM MNI template, but have been rotated (pitch) by .38 radians, to enable the view of the three regions of activation within the axial view. Orthogonal slices were selected to pass through the region of activation for N0Sπ – N0S0 (MNI coordinates: −52, −30, 1 mm) and NπS0 – N0S0 (MNI coordinates: −47, −27, −2 mm).
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pone-0088466-g004: Red color indicates increased activity for dichotic condition versus N0S0.Blue indicates increased activity for N0S0 versus the dichotic condition. The overall patterns for N0Sπ vs. N0S0 (left image) and NπS0 vs. N0S0 (right image) are similar within the left auditory cortex. Regions are threshold at p<.01, uncorrected. Images are spatially normalized to SPM MNI template, but have been rotated (pitch) by .38 radians, to enable the view of the three regions of activation within the axial view. Orthogonal slices were selected to pass through the region of activation for N0Sπ – N0S0 (MNI coordinates: −52, −30, 1 mm) and NπS0 – N0S0 (MNI coordinates: −47, −27, −2 mm).

Mentions: There is a strong similarity in the fMRI activation pattern for N0Sπ vs. N0S0 and NπS0 vs. N0S0. Both showed increased and decreased activation within auditory cortex regions (Table 3, Rows 1, 2, 5, 6, 8, 9, 11–14), with stronger activations seen in the left hemisphere (Figure 4). The contrast N0Sπ – N0S0 additionally showed a weak activation within the corpus callosum (Table 3, rows 3 and 4), and the contrast NπS0 – N0S0 additionally showed activation in the left pulvinar thalamus (Table 3, row 10). Negative correlations of signal detection threshold for both N0Sπ and NπS0, and FA, MD and AD DTI measures (Table 4, rows 8, 12, 14, 15, 17) were found in the lateral lemniscus (Figure 5). The contrast NπS0 – N0Sπ had a small activation in the left pulvinar thalamus (Table 3, row 29). The contrast N0Sπ – NπS0 had activation in the left auditory cortex and corpus callosum (Table 3, rows 30–32).


Masking level differences--a diffusion tensor imaging and functional MRI study.

Wack DS, Polak P, Furuyama J, Burkard RF - PLoS ONE (2014)

Red color indicates increased activity for dichotic condition versus N0S0.Blue indicates increased activity for N0S0 versus the dichotic condition. The overall patterns for N0Sπ vs. N0S0 (left image) and NπS0 vs. N0S0 (right image) are similar within the left auditory cortex. Regions are threshold at p<.01, uncorrected. Images are spatially normalized to SPM MNI template, but have been rotated (pitch) by .38 radians, to enable the view of the three regions of activation within the axial view. Orthogonal slices were selected to pass through the region of activation for N0Sπ – N0S0 (MNI coordinates: −52, −30, 1 mm) and NπS0 – N0S0 (MNI coordinates: −47, −27, −2 mm).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3928251&req=5

pone-0088466-g004: Red color indicates increased activity for dichotic condition versus N0S0.Blue indicates increased activity for N0S0 versus the dichotic condition. The overall patterns for N0Sπ vs. N0S0 (left image) and NπS0 vs. N0S0 (right image) are similar within the left auditory cortex. Regions are threshold at p<.01, uncorrected. Images are spatially normalized to SPM MNI template, but have been rotated (pitch) by .38 radians, to enable the view of the three regions of activation within the axial view. Orthogonal slices were selected to pass through the region of activation for N0Sπ – N0S0 (MNI coordinates: −52, −30, 1 mm) and NπS0 – N0S0 (MNI coordinates: −47, −27, −2 mm).
Mentions: There is a strong similarity in the fMRI activation pattern for N0Sπ vs. N0S0 and NπS0 vs. N0S0. Both showed increased and decreased activation within auditory cortex regions (Table 3, Rows 1, 2, 5, 6, 8, 9, 11–14), with stronger activations seen in the left hemisphere (Figure 4). The contrast N0Sπ – N0S0 additionally showed a weak activation within the corpus callosum (Table 3, rows 3 and 4), and the contrast NπS0 – N0S0 additionally showed activation in the left pulvinar thalamus (Table 3, row 10). Negative correlations of signal detection threshold for both N0Sπ and NπS0, and FA, MD and AD DTI measures (Table 4, rows 8, 12, 14, 15, 17) were found in the lateral lemniscus (Figure 5). The contrast NπS0 – N0Sπ had a small activation in the left pulvinar thalamus (Table 3, row 29). The contrast N0Sπ – NπS0 had activation in the left auditory cortex and corpus callosum (Table 3, rows 30–32).

Bottom Line: The current study revealed regions of increased and decreased activity within the auditory cortex when comparing the combined noise and signal of the dichotic MLD stimuli (N0Sπ and NπS0) with N0S0.Furthermore, we found evidence of inferior colliculus involvement.Patterns of correlation when the signal was presented only to the right ear showed an extensive network in the left hemisphere; however, the opposite was not true for the signal presented only to the left ear.

View Article: PubMed Central - PubMed

Affiliation: Department of Nuclear Medicine, State University of New York at Buffalo, Buffalo, New York, United States of America.

ABSTRACT
In our previous study we investigated Masking Level Differences (MLD) using functional Magnetic Resonance Imaging (fMRI), but were unable to confirm neural correlations for the MLD within the auditory cortex and inferior colliculus. Here we have duplicated conditions from our previous study, but have included more participants and changed the study site to a new location with a newer scanner and presentation system. Additionally, Diffusion Tensor Imaging (DTI) is included to allow investigation of fiber tracts that may be involved with MLDs. Twenty participants were included and underwent audiometric testing and MRI scanning. The current study revealed regions of increased and decreased activity within the auditory cortex when comparing the combined noise and signal of the dichotic MLD stimuli (N0Sπ and NπS0) with N0S0. Furthermore, we found evidence of inferior colliculus involvement. Our DTI findings show strong correlations between DTI measures within the brainstem and signal detection threshold levels. Patterns of correlation when the signal was presented only to the right ear showed an extensive network in the left hemisphere; however, the opposite was not true for the signal presented only to the left ear. Our current study was able to confirm what we had previously hypothesized using fMRI, while extending our investigation of MLDs to include the characteristics of connecting neural pathways.

Show MeSH
Related in: MedlinePlus