Research Group "Subcortical Contributions to Comprehension", Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
Cortex. 2013 Oct;49(9):2449-61. doi: 10.1016/j.cortex.2012.12.012. Epub 2012 Dec 21.
In everyday life we frequently make the fundamental distinction between sensory input resulting from our own actions and sensory input that is externally-produced. It has been speculated that making this distinction involves the use of an internal forward-model, which enables the brain to adjust its response to self-produced sensory input. In the auditory domain, this idea has been supported by event-related potential and evoked-magnetic field studies revealing that self-initiated sounds elicit a suppressed N100/M100 brain response compared to externally-produced sounds. Moreover, a recent study reveals that patients with cerebellar lesions do not show a significant N100-suppression effect. This result supports the theory that the cerebellum is essential for generating internal forward predictions. However, all except one study compared self-initiated and externally-produced auditory stimuli in separate conditions. Such a setup prevents an unambiguous interpretation of the N100-suppression effect when distinguishing self- and externally-produced sensory stimuli: the N100-suppression can also be explained by differences in the allocation of attention in different conditions. In the current electroencephalography (EEG)-study we investigated the N100-suppression effect in an altered design comparing (i) self-initiated sounds to externally-produced sounds that occurred intermixed with these self-initiated sounds (i.e., both sound types occurred in the same condition) or (ii) self-initiated sounds to externally-produced sounds that occurred in separate conditions. Results reveal that the cerebellum generates selective predictions in response to self-initiated sounds independent of condition type: cerebellar patients, in contrast to healthy controls, do not display an N100-suppression effect in response to self-initiated sounds when intermixed with externally-produced sounds. Furthermore, the effect is not influenced by the temporal proximity of externally-produced sounds to self-produced sounds. Controls and patients showed a P200-reduction in response to self-initiated sounds. This suggests the existence of an additional and probably more conscious mechanism for identifying self-generated sounds that does not functionally depend on the cerebellum.
在日常生活中，我们经常对源自自身行为的感觉输入和外部产生的感觉输入做出基本区分。有人推测，这种区分涉及使用内部前馈模型，该模型使大脑能够调整其对自身产生的感觉输入的反应。在听觉领域，这一观点得到了事件相关电位和诱发磁场研究的支持，这些研究表明，与外部产生的声音相比，自我启动的声音会引起抑制的 N100/M100 脑反应。此外，最近的一项研究表明，小脑损伤的患者不会产生明显的 N100 抑制效应。这一结果支持了小脑对于产生内部前馈预测至关重要的理论。然而，除了一项研究之外，所有研究都在单独的条件下比较了自我启动和外部产生的听觉刺激。这种设置使得在区分自我和外部产生的感觉刺激时，无法对 N100 抑制效应做出明确的解释：N100 抑制也可以通过在不同条件下注意力的分配差异来解释。在当前的脑电图（EEG）研究中，我们在改变的设计中研究了 N100 抑制效应，将（i）自我启动的声音与混合有这些自我启动的声音的外部产生的声音进行比较（即，两种声音类型都出现在同一条件下），或者（ii）自我启动的声音与外部产生的声音进行比较在不同条件下发生的声音。结果表明，小脑会针对自我启动的声音产生选择性预测，而与条件类型无关：与健康对照组相比，小脑损伤的患者在与外部产生的声音混合时，不会对自我启动的声音产生 N100 抑制效应。此外，该效应不受外部产生的声音与自我产生的声音之间的时间接近度的影响。对照组和患者对自我启动的声音表现出 P200 减少。这表明存在一种用于识别自我产生声音的额外机制，可能更有意识，并且该机制不依赖于小脑。
