The stimulus-evoked neural response is a widely explored phenomenon. Conscious awareness is associated in many cases with the corresponding selective stimulus-evoked response. For example, conscious awareness of a face stimulus is associated with or accompanied by stimulus-evoked activity in the fusiform face area (FFA). In addition to the stimulus-evoked response, spontaneous (i.e. task-unrelated) activity in the brain is also abundant. Notably, spontaneous activity is considered unconscious. For example, spontaneous activity in the FFA is not associated with conscious awareness of a face. The question is: what is the difference at the neural level between stimulus-evoked activity in a case that this activity is associated with conscious awareness of some content (e.g. activity in the FFA in response to fully visible face stimuli) and spontaneous activity in that same region of the brain? To answer this question, in the present study, we had a rare opportunity to record two face-selective multi-units in the vicinity of the FFA in a human patient. We compared multi-unit face-selective task-evoked activity with spontaneous prestimulus and a resting-state activity. We found that when activity was examined over relatively long temporal windows (e.g. 100–200 ms), face-selective stimulus-evoked firing in the recorded multi-units was much higher than the spontaneous activity. In contrast, when activity was examined over relatively short windows, we found many cases of high firing rates within the spontaneous activity that were comparable to stimulus-evoked activity. Our results thus indicate that the sustained activity is what might differentiate between stimulus-evoked activity that is associated with conscious awareness and spontaneous activity.

中文翻译：

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比较人后梭状回面部选择性多单元的刺激诱发和自发反应

刺激诱发的神经反应是一种广泛探索的现象。在许多情况下，有意识的意识与相应的选择性刺激诱发反应有关。例如，面部刺激的有意识意识与梭状面部区域 (FFA) 中的刺激诱发活动相关或伴随。除了刺激诱发的反应，大脑中的自发（即与任务无关的）活动也很丰富。值得注意的是，自发活动被认为是无意识的。例如，FFA 中的自发活动与对一张脸的有意识的认识无关。问题是：如果刺激诱发的活动与对某些内容的有意识的认识相关（例如 FFA 响应完全可见的面部刺激的活动）和大脑同一区域的自发活动？为了回答这个问题，在本研究中，我们有一个难得的机会在人类患者的 FFA 附近记录两个面部选择性多单元。我们将多单元面部选择性任务诱发活动与自发预刺激和静息状态活动进行了比较。我们发现，当在相对较长的时间窗口（例如 100-200 毫秒）内检查活动时，记录的多单元中面部选择性刺激诱发的放电远高于自发活动。相反，当在相对较短的窗口内检查活动时，我们发现许多自发活动中的高放电率与刺激诱发的活动相当。