Becker Frank, Reinvang Ivar
Sunnaas Rehabilitation Hospital, Faculty Division Ullevål University Hospital, University of Oslo, 0318 Oslo, Norway.
Behav Brain Funct. 2007 Jan 19;3:6. doi: 10.1186/1744-9081-3-6.
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.
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.
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.
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 varies depending on factors as lesion site, time after injury, and language task.
声音和语音处理受损在失语症听觉语言理解缺陷中所起的作用尚不清楚。对于即使是严重听觉理解缺陷患者也可辨别的刺激，尚未进行关于失语症中参与的语音处理的电生理研究。
事件相关脑电位（ERP）被用于研究失语症患者在音节检测任务中的语音处理。在一个oddball范式中，参与者必须在频繁出现的标准音节/ba:/中检测出不频繁出现的目标音节/ta:/。将10名中度听觉理解受损患者和10名重度听觉理解受损患者与11名健康对照者进行比较。
N1波幅降低表明初级刺激分析受损；N1降低是听觉理解受损的一个预测指标。N2波幅衰减表明参与的刺激分类和辨别减少。然而，所有失语症患者几乎都能无误地辨别刺激，并且与目标识别相关的过程（P3）没有显著减少。失语症受试者可能通过纯粹的听觉差异辨别刺激，而ERP结果显示与语言相关的处理减少，然而这并未妨碍完成任务。失语症亚组与对照组之间的地形差异表明激活存在代偿性变化。
失语症患者早期时间窗（N1、N2）的刺激处理发生改变，对复杂语言材料的听觉理解产生不利影响，同时允许完成更简单的任务（音节检测）。在音节检测中可能会激活语音处理的代偿模式，但在更复杂的任务中可能不起作用。代偿过程能够被激活的程度可能因病变部位、损伤后时间和语言任务等因素而有所不同。
