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Plasticity in neuromagnetic cortical responses suggests enhanced auditory object representation.

Ross B, Jamali S, Tremblay KL - BMC Neurosci (2013)

Bottom Line: The amplitude of the earlier N1m wave, which is related to processing of sensory information, did not change over the time course of the study.The P2m amplitude increase and its persistence over time constitute a neuroplastic change.Different trajectories of brain and behaviour changes suggest that the preceding effect of a P2m increase relates to brain processes, which are necessary precursors of perceptual learning.

View Article: PubMed Central - HTML - PubMed

Affiliation: Rotman Research Institute, Baycrest Centre, 3560 Bathurst Street, Toronto M6A 2E1, ON, Canada. bross@research.baycrest.org.

ABSTRACT

Background: Auditory perceptual learning persistently modifies neural networks in the central nervous system. Central auditory processing comprises a hierarchy of sound analysis and integration, which transforms an acoustical signal into a meaningful object for perception. Based on latencies and source locations of auditory evoked responses, we investigated which stage of central processing undergoes neuroplastic changes when gaining auditory experience during passive listening and active perceptual training. Young healthy volunteers participated in a five-day training program to identify two pre-voiced versions of the stop-consonant syllable 'ba', which is an unusual speech sound to English listeners. Magnetoencephalographic (MEG) brain responses were recorded during two pre-training and one post-training sessions. Underlying cortical sources were localized, and the temporal dynamics of auditory evoked responses were analyzed.

Results: After both passive listening and active training, the amplitude of the P2m wave with latency of 200 ms increased considerably. By this latency, the integration of stimulus features into an auditory object for further conscious perception is considered to be complete. Therefore the P2m changes were discussed in the light of auditory object representation. Moreover, P2m sources were localized in anterior auditory association cortex, which is part of the antero-ventral pathway for object identification. The amplitude of the earlier N1m wave, which is related to processing of sensory information, did not change over the time course of the study.

Conclusion: The P2m amplitude increase and its persistence over time constitute a neuroplastic change. The P2m gain likely reflects enhanced object representation after stimulus experience and training, which enables listeners to improve their ability for scrutinizing fine differences in pre-voicing time. Different trajectories of brain and behaviour changes suggest that the preceding effect of a P2m increase relates to brain processes, which are necessary precursors of perceptual learning. Cautious discussion is required when interpreting the finding of a P2 amplitude increase between recordings before and after training and learning.

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Behavioural performance in stimulus identification during the five training sessions. A: Labeling the speech sound with 20 ms pre-voicing time as ‘mba’ was considered as correct response. The group mean of correct responses increased over training sessions (red line). The group mean frequency of mistakenly labeling the 10-ms pre-voicing sound as ‘mba’ decreased during the training (blue line). (Error bars denote the 95%-confidence limits for the mean). B: The signal discrimination index d-prime (red line) increased significantly between the third and fourth and between the fourth and fifth training session, whereas the performance increase was not significant during the first half of the training. A response bias (blue) was not significant (blue line). C: Individual change in correct responses (red) and false alarms (blue) between the first and last training sessions. D: Individual changes in the signal discrimination index d-prime. Despite individual variability the d-prime measure increased for all participants during the training.
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Figure 1: Behavioural performance in stimulus identification during the five training sessions. A: Labeling the speech sound with 20 ms pre-voicing time as ‘mba’ was considered as correct response. The group mean of correct responses increased over training sessions (red line). The group mean frequency of mistakenly labeling the 10-ms pre-voicing sound as ‘mba’ decreased during the training (blue line). (Error bars denote the 95%-confidence limits for the mean). B: The signal discrimination index d-prime (red line) increased significantly between the third and fourth and between the fourth and fifth training session, whereas the performance increase was not significant during the first half of the training. A response bias (blue) was not significant (blue line). C: Individual change in correct responses (red) and false alarms (blue) between the first and last training sessions. D: Individual changes in the signal discrimination index d-prime. Despite individual variability the d-prime measure increased for all participants during the training.

Mentions: Participants were trained to identify the speech sound with the longer pre-voicing time as ‘mba’ and the one with shorter pre-voicing as ‘ba’. During the five days of training, correctly identifying ‘mba’ (a hit) increased across the group from 72.7% to 81.3% while mistakenly labeling ‘ba’ as ‘mba’ (a false alarm) decreased from 30.2% to 18.2% (Figure 1A). Correspondingly, the d’-measure increased from 1.12 to 1.80 (F(1,13) = 8.29, p = 0.013). A response bias was not significant in any training session (Figure 1B). Although the amount of increase in the hit rate of was variable across participants (Figure 1C) all individuals improved their performance as indicated by the d’-measure (Figure 1D). Identification performance did not increase significantly within the first three training sessions but improved between the third and fourth and between the fourth and fifth session (p < 0.05 both). This means that behavioural accounts of learning occurred relatively late after an accumulation of stimulus experience, beyond the initial intervals that could have involved procedural learning.


Plasticity in neuromagnetic cortical responses suggests enhanced auditory object representation.

Ross B, Jamali S, Tremblay KL - BMC Neurosci (2013)

Behavioural performance in stimulus identification during the five training sessions. A: Labeling the speech sound with 20 ms pre-voicing time as ‘mba’ was considered as correct response. The group mean of correct responses increased over training sessions (red line). The group mean frequency of mistakenly labeling the 10-ms pre-voicing sound as ‘mba’ decreased during the training (blue line). (Error bars denote the 95%-confidence limits for the mean). B: The signal discrimination index d-prime (red line) increased significantly between the third and fourth and between the fourth and fifth training session, whereas the performance increase was not significant during the first half of the training. A response bias (blue) was not significant (blue line). C: Individual change in correct responses (red) and false alarms (blue) between the first and last training sessions. D: Individual changes in the signal discrimination index d-prime. Despite individual variability the d-prime measure increased for all participants during the training.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3924184&req=5

Figure 1: Behavioural performance in stimulus identification during the five training sessions. A: Labeling the speech sound with 20 ms pre-voicing time as ‘mba’ was considered as correct response. The group mean of correct responses increased over training sessions (red line). The group mean frequency of mistakenly labeling the 10-ms pre-voicing sound as ‘mba’ decreased during the training (blue line). (Error bars denote the 95%-confidence limits for the mean). B: The signal discrimination index d-prime (red line) increased significantly between the third and fourth and between the fourth and fifth training session, whereas the performance increase was not significant during the first half of the training. A response bias (blue) was not significant (blue line). C: Individual change in correct responses (red) and false alarms (blue) between the first and last training sessions. D: Individual changes in the signal discrimination index d-prime. Despite individual variability the d-prime measure increased for all participants during the training.
Mentions: Participants were trained to identify the speech sound with the longer pre-voicing time as ‘mba’ and the one with shorter pre-voicing as ‘ba’. During the five days of training, correctly identifying ‘mba’ (a hit) increased across the group from 72.7% to 81.3% while mistakenly labeling ‘ba’ as ‘mba’ (a false alarm) decreased from 30.2% to 18.2% (Figure 1A). Correspondingly, the d’-measure increased from 1.12 to 1.80 (F(1,13) = 8.29, p = 0.013). A response bias was not significant in any training session (Figure 1B). Although the amount of increase in the hit rate of was variable across participants (Figure 1C) all individuals improved their performance as indicated by the d’-measure (Figure 1D). Identification performance did not increase significantly within the first three training sessions but improved between the third and fourth and between the fourth and fifth session (p < 0.05 both). This means that behavioural accounts of learning occurred relatively late after an accumulation of stimulus experience, beyond the initial intervals that could have involved procedural learning.

Bottom Line: The amplitude of the earlier N1m wave, which is related to processing of sensory information, did not change over the time course of the study.The P2m amplitude increase and its persistence over time constitute a neuroplastic change.Different trajectories of brain and behaviour changes suggest that the preceding effect of a P2m increase relates to brain processes, which are necessary precursors of perceptual learning.

View Article: PubMed Central - HTML - PubMed

Affiliation: Rotman Research Institute, Baycrest Centre, 3560 Bathurst Street, Toronto M6A 2E1, ON, Canada. bross@research.baycrest.org.

ABSTRACT

Background: Auditory perceptual learning persistently modifies neural networks in the central nervous system. Central auditory processing comprises a hierarchy of sound analysis and integration, which transforms an acoustical signal into a meaningful object for perception. Based on latencies and source locations of auditory evoked responses, we investigated which stage of central processing undergoes neuroplastic changes when gaining auditory experience during passive listening and active perceptual training. Young healthy volunteers participated in a five-day training program to identify two pre-voiced versions of the stop-consonant syllable 'ba', which is an unusual speech sound to English listeners. Magnetoencephalographic (MEG) brain responses were recorded during two pre-training and one post-training sessions. Underlying cortical sources were localized, and the temporal dynamics of auditory evoked responses were analyzed.

Results: After both passive listening and active training, the amplitude of the P2m wave with latency of 200 ms increased considerably. By this latency, the integration of stimulus features into an auditory object for further conscious perception is considered to be complete. Therefore the P2m changes were discussed in the light of auditory object representation. Moreover, P2m sources were localized in anterior auditory association cortex, which is part of the antero-ventral pathway for object identification. The amplitude of the earlier N1m wave, which is related to processing of sensory information, did not change over the time course of the study.

Conclusion: The P2m amplitude increase and its persistence over time constitute a neuroplastic change. The P2m gain likely reflects enhanced object representation after stimulus experience and training, which enables listeners to improve their ability for scrutinizing fine differences in pre-voicing time. Different trajectories of brain and behaviour changes suggest that the preceding effect of a P2m increase relates to brain processes, which are necessary precursors of perceptual learning. Cautious discussion is required when interpreting the finding of a P2 amplitude increase between recordings before and after training and learning.

Show MeSH
Related in: MedlinePlus