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Left hemispheric dominance during auditory processing in a noisy environment.

Okamoto H, Stracke H, Ross B, Kakigi R, Pantev C - BMC Biol. (2007)

Bottom Line: We observed significant decrements of auditory evoked responses and a significant inter-hemispheric difference for the N1m response during both ipsi- and contra-lateral masking.The decrements of auditory evoked neural activities during simultaneous masking can be explained by neural interactions evoked by masker and test stimulus in peripheral and central auditory systems.The inter-hemispheric differences of N1m decrements during ipsi- and contra-lateral masking reflect a basic hemispheric specialization contributing to the processing of complex auditory stimuli such as speech signals in noisy environments.

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Affiliation: Institute for Biomagnetism and Biosignalanalysis, University of Muenster, Muenster, Germany. okamotoh@uni-muenster.de

ABSTRACT

Background: In daily life, we are exposed to different sound inputs simultaneously. During neural encoding in the auditory pathway, neural activities elicited by these different sounds interact with each other. In the present study, we investigated neural interactions elicited by masker and amplitude-modulated test stimulus in primary and non-primary human auditory cortex during ipsi-lateral and contra-lateral masking by means of magnetoencephalography (MEG).

Results: We observed significant decrements of auditory evoked responses and a significant inter-hemispheric difference for the N1m response during both ipsi- and contra-lateral masking.

Conclusion: The decrements of auditory evoked neural activities during simultaneous masking can be explained by neural interactions evoked by masker and test stimulus in peripheral and central auditory systems. The inter-hemispheric differences of N1m decrements during ipsi- and contra-lateral masking reflect a basic hemispheric specialization contributing to the processing of complex auditory stimuli such as speech signals in noisy environments.

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Normalized source strength decrements for contra-lateral masking. Normalized N1m and ASSR source strength decrements for contra-lateral masking (graphs are assorted according to Figure 5).
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Figure 6: Normalized source strength decrements for contra-lateral masking. Normalized N1m and ASSR source strength decrements for contra-lateral masking (graphs are assorted according to Figure 5).

Mentions: The means of the normalized N1m and ASSR source strength decrements across subjects for the contra-lateral masking condition are presented in Figure 6. A repeated measures ANOVA applied to the normalized N1m source strength decrements during contra-lateral masking resulted in significant main effects for TS-TYPE (F (1, 9) = 7.8, p = 0.021) and HEMISPHERE (F (1, 9) = 6.0, p = 0.036), as well as a significant interaction between TS-TYPE and HEMISPHERE (F (1, 9) = 8.0, p = 0.020). These findings indicated that the N1m decrement pattern observed during contra-lateral masking was identical to the N1m decrement pattern observed during ipsi-lateral masking, even though the masking effects during contra-lateral masking were far smaller than during ipsi-lateral masking. Contra-lateral masking effects were larger for the test sound of similar frequency and for the right hemisphere. This hemispheric difference was independent of stimulation side.


Left hemispheric dominance during auditory processing in a noisy environment.

Okamoto H, Stracke H, Ross B, Kakigi R, Pantev C - BMC Biol. (2007)

Normalized source strength decrements for contra-lateral masking. Normalized N1m and ASSR source strength decrements for contra-lateral masking (graphs are assorted according to Figure 5).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2194668&req=5

Figure 6: Normalized source strength decrements for contra-lateral masking. Normalized N1m and ASSR source strength decrements for contra-lateral masking (graphs are assorted according to Figure 5).
Mentions: The means of the normalized N1m and ASSR source strength decrements across subjects for the contra-lateral masking condition are presented in Figure 6. A repeated measures ANOVA applied to the normalized N1m source strength decrements during contra-lateral masking resulted in significant main effects for TS-TYPE (F (1, 9) = 7.8, p = 0.021) and HEMISPHERE (F (1, 9) = 6.0, p = 0.036), as well as a significant interaction between TS-TYPE and HEMISPHERE (F (1, 9) = 8.0, p = 0.020). These findings indicated that the N1m decrement pattern observed during contra-lateral masking was identical to the N1m decrement pattern observed during ipsi-lateral masking, even though the masking effects during contra-lateral masking were far smaller than during ipsi-lateral masking. Contra-lateral masking effects were larger for the test sound of similar frequency and for the right hemisphere. This hemispheric difference was independent of stimulation side.

Bottom Line: We observed significant decrements of auditory evoked responses and a significant inter-hemispheric difference for the N1m response during both ipsi- and contra-lateral masking.The decrements of auditory evoked neural activities during simultaneous masking can be explained by neural interactions evoked by masker and test stimulus in peripheral and central auditory systems.The inter-hemispheric differences of N1m decrements during ipsi- and contra-lateral masking reflect a basic hemispheric specialization contributing to the processing of complex auditory stimuli such as speech signals in noisy environments.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Biomagnetism and Biosignalanalysis, University of Muenster, Muenster, Germany. okamotoh@uni-muenster.de

ABSTRACT

Background: In daily life, we are exposed to different sound inputs simultaneously. During neural encoding in the auditory pathway, neural activities elicited by these different sounds interact with each other. In the present study, we investigated neural interactions elicited by masker and amplitude-modulated test stimulus in primary and non-primary human auditory cortex during ipsi-lateral and contra-lateral masking by means of magnetoencephalography (MEG).

Results: We observed significant decrements of auditory evoked responses and a significant inter-hemispheric difference for the N1m response during both ipsi- and contra-lateral masking.

Conclusion: The decrements of auditory evoked neural activities during simultaneous masking can be explained by neural interactions evoked by masker and test stimulus in peripheral and central auditory systems. The inter-hemispheric differences of N1m decrements during ipsi- and contra-lateral masking reflect a basic hemispheric specialization contributing to the processing of complex auditory stimuli such as speech signals in noisy environments.

Show MeSH