In recent years, with the great breakthroughs in the treatment of brain injury, neurological dysfunction and other serious diseases, more and more patients have been referred to disorders of consciousness (DOC). In clinical work, accurate assessment of DOC is critical to its treatment, and how to assess the level of consciousness and prognosis of patients after treatment has become a hot research topic in recent years. The model of consciousness loss and recovery is an ideal tool to understand the neural mechanism of consciousness, but clinical trials are easily restricted by many factors such as ethics, so animal models are often used as preclinical basic experiments, while non-human primates (NHP) are closely related to humans and are ideal models for studying human diseases. Currently, there are many tests to assess the level of consciousness of NHP, and there are different methods, all of which have certain advantages and limitations. This article reviews the current literature on the current status of the NHP consciousness scale assessment tool, and find that the assessment of NHP consciousness is mainly divided into stimulus response-based assessment after anesthesia experiments, behavioral task completion-based assessment after stimulus-reward experiments, and comprehensive multi-indicator assessment of NHP consciousness level. Therefore, this article provides an overview of the current status of each NHP consciousness scale assessment tool and its advantages and disadvantages in order to provide new thoughts on assessing consciousness from the perspective of animal models in the hope of finding a more appropriate assessment tool.
Prolonged disorders of consciousness (pDOC) are pathological conditions of alterations in consciousness caused by various severe brain injuries, profoundly affecting patients’ life ability and leading to a huge burden for both the family and society. Exploring the mechanisms underlying pDOC and accurately assessing the level of consciousness in the patients with pDOC provide the basis of developing therapeutic strategies. Research of non-invasive functional neuroimaging technologies, such as functional magnetic resonance (fMRI) and scalp electroencephalography (EEG), have demonstrated that the generation, maintenance and disorders of consciousness involve functions of multiple cortical and subcortical brain regions, and their networks. Invasive intracranial neuroelectrophysiological technique can directly record the electrical activity of subcortical or cortical neurons with high signal-to-noise ratio and spatial resolution, which has unique advantages and important significance for further revealing the brain function and disease mechanism of pDOC. Here we reviewed the current progress of pDOC research based on two intracranial electrophysiological signals, spikes reflecting single-unit activity and field potential reflecting multi-unit activities, and then discussed the current challenges and gave an outlook on future development, hoping to promote the study of pathophysiological mechanisms related to pDOC and provide guides for the future clinical diagnosis and therapy of pDOC.