Rinne Teemu
Institute of Behavioural Sciences, University of Helsinki, Finland.
Open Neuroimag J. 2010;4:187-93. doi: 10.2174/1874440001004010187. Epub 2010 Dec 23.
The present study was designed to directly test the hypothesis that suppression of activations to task-irrelevant sounds contributes to the attention-related modulations of auditory cortex (AC) activations observed in previous fMRI studies. Subjects selectively attended to auditory (broadband noise bursts with pitch) or visual (Gabor gratings) asynchronous fast-rate stimulus streams concurrently presented to left-ear, right-ear, above-fixation, or below-fixation. Auditory and visual task difficulty was parametrically manipulated in three levels. Behavioral data obtained during fMRI indicated that subjects achieved acceptable performance levels in all tasks and that the task-difficulty manipulation was effective. Consistent with previous studies, AC activations strongly depended on the direction of attention. AC activations to sounds were higher during auditory than during visual tasks and AC activations were higher in the hemisphere contralateral to the attended ear. However, the effects of task difficulty on AC activations were weak or non-existent. In particular, increasing task difficulty was not associated with a systematic decrease of AC activations in areas that were modulated by attention. These results suggest that suppression of AC activations to task-irrelevant sounds is likely to be small or negligible as compared with the strong activation enhancements observed in fMRI during active auditory tasks.
本研究旨在直接验证一个假设，即对与任务无关声音的激活抑制有助于解释先前功能磁共振成像（fMRI）研究中观察到的听觉皮层（AC）激活的注意力相关调制。受试者选择性地关注同时呈现给左耳、右耳、注视点上方或注视点下方的听觉（带音高的宽带噪声突发）或视觉（Gabor光栅）异步快速刺激流。听觉和视觉任务难度在三个水平上进行参数化操作。fMRI期间获得的行为数据表明，受试者在所有任务中都达到了可接受的表现水平，并且任务难度操作是有效的。与先前的研究一致，AC激活强烈依赖于注意力方向。在听觉任务期间，对声音的AC激活高于视觉任务期间，并且在被关注耳朵对侧的半球中AC激活更高。然而，任务难度对AC激活的影响较弱或不存在。特别是，任务难度增加与在受注意力调制的区域中AC激活的系统性降低无关。这些结果表明，与在活跃听觉任务期间fMRI中观察到的强烈激活增强相比，对与任务无关声音的AC激活抑制可能很小或可忽略不计。
