Successful syllable detection in aphasia despite processing impairments as revealed by event-related potentials
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BioMed Central
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Successful syllable detection in aphasia despite processing impairments as revealed by event-related potentials Frank Becker*1,2 and Ivar Reinvang3 Address: 1Sunnaas Rehabilitation Hospital, Faculty Division Ullevål University Hospital, University of Oslo, 0318 Oslo, Norway, 2Dept. of Research, Sunnaas Rehabilitation Hospital, 1450 Nesoddtangen, Norway and 3Dept. of Psychology, University of Oslo, 0317 Oslo, Norway Email: Frank Becker* - [email protected]; Ivar Reinvang - [email protected] * Corresponding author
Published: 19 January 2007 Behavioral and Brain Functions 2007, 3:6
doi:10.1186/1744-9081-3-6
Received: 07 September 2006 Accepted: 19 January 2007
This article is available from: http://www.behavioralandbrainfunctions.com/content/3/1/6 © 2007 Becker and Reinvang; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: The role of impaired sound and speech sound processing for auditory language comprehension deficits in aphasia is unclear. No electrophysiological studies of attended speech sound processing in aphasia have been performed for stimuli that are discriminable even for patients with severe auditory comprehension deficits.
Methods: Event-related brain potentials (ERPs) were used to study speech sound processing in a syllable detection task in aphasia. In an oddball paradigm, the participants had to detect the infrequent target syllable /ta:/ amongst the frequent standard syllable /ba:/. 10 subjects with moderate and 10 subjects with severe auditory comprehension impairment were compared to 11 healthy controls. Results: N1 amplitude was reduced indicating impaired primary stimulus analysis; N1 reduction was a predictor for auditory comprehension impairment. N2 attenuation suggests reduced attended stimulus classification and discrimination. However, all aphasic patients were able to discriminate the stimuli almost without errors, and processes related to the target identification (P3) were not significantly reduced. The aphasic subjects might have discriminated the stimuli by purely auditory differences, while the ERP results reveal a reduction of language-related processing which however did not prevent performing the task. Topographic differences between aphasic subgroups and controls indicate compensatory changes in activation. Conclusion: Stimulus processing in early time windows (N1, N2) is altered in aphasics with adverse consequences for auditory comprehension of complex language material, while allowing performance of simpler tasks (syllable detection). Compensational patterns of speech sound processing may be activated in syllable detection, but may not be functional in more complex tasks. The degree to which compensational processes can be activated probably varie
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