Patients with prolonged disorders of consciousness (PDOC) are often unable to communicate their state of consciousness. Determining the latter is essential for the patient's care and prospects of recovery. Auditory stimulation in combination with neural recordings is a promising technique towards an objective assessment of conscious awareness. Here, we investigated the potential of complex, acoustic stimuli to elicit EEG responses suitable for classifying multiple subject groups, from unconscious to responding.

We presented naturalistic auditory textures with unexpectedly changing statistics to human listeners. Awake, active listeners were asked to indicate the change by button press, while all other groups (awake passive, asleep, minimally conscious state (MCS), and unresponsive wakefulness syndrome (UWS)) listened passively. We quantified the evoked potential at stimulus onset and change in stimulus statistics, as well as the complexity of neural response during the change of stimulus statistics.

On the group level, onset and change potentials classified patients and healthy controls successfully but failed to differentiate between the UWS and MCS groups. Conversely, the Lempel-Ziv complexity of the scalp-level potential allowed reliable differentiation between UWS and MCS even for individual subjects, when compared with the clinical assessment aligned to the EEG measurements. The accuracy appears to improve further when taking the latest available clinical diagnosis into account.

In summary, EEG signal complexity during onset and changes in complex acoustic stimuli provides an objective criterion for distinguishing states of consciousness in clinical patients. These results suggest EEG-recordings as a cost-effective tool to choose appropriate treatments for non-responsive PDOC patients.

长期意识障碍（PDOC）的患者通常无法传达其意识状态。确定后者对于患者的护理和康复前景至关重要。听觉刺激与神经记录相结合是一种有前途的技术，可用于客观评估意识意识。在这里，我们研究了潜在的复杂声刺激诱发脑电图反应的潜力，该反应适用于对从无意识到反应的多个受试者类别进行分类。

我们向听众展示了自然的听觉纹理，其统计数据出乎意料地发生了变化。醒着的主动听众被要求通过按下按钮来指示变化，而所有其他组（醒着的被动，睡眠，最低意识状态（MCS）和无反应的清醒综合症（UWS））则被动地听。我们量化了刺激发生和刺激统计变化时诱发的电位，以及刺激统计变化期间神经反应的复杂性。

在组水平上，发病和改变潜能成功地将患者和健康对照分类，但未能区分UWS组和MCS组。相反，与针对脑电图测量的临床评估相比，头皮水平电势的Lempel-Ziv复杂度允许UWS和MCS可靠区分，即使对于单个受试者也是如此。考虑到最新的临床诊断，准确性似乎进一步提高。

总之，在发作和复杂声刺激变化期间的脑电信号复杂性为区分临床患者的意识状态提供了客观标准。这些结果表明，脑电图记录是为无反应的PDOC患者选择合适治疗方法的一种经济有效的工具。