The amount of knowledge on human consciousness has created a multitude of viewpoints and it is difficult to compare and synthesize all the recent scientific perspectives. Indeed, there are many definitions of consciousness and multiple approaches to study the neural correlates of consciousness (NCC). Therefore, the main aim of this article is to collect data on the various theories of consciousness published between 2007–2017 and to synthesize them to provide a general overview of this topic. To describe each theory, we developed a thematic grid called the dimensional model, which qualitatively and quantitatively analyzes how each article, related to one specific theory, debates/analyzes a specific issue. Among the 1130 articles assessed, 85 full texts were included in the prefinal step. Finally, this scoping review analyzed 68 articles that described 29 theories of consciousness. We found heterogeneous perspectives in the theories analyzed. Those with the highest grade of variability are as follows: subjectivity, NCC, and the consciousness/cognitive function. Among sub-cortical structures, thalamus, basal ganglia, and the hippocampus were the most indicated, whereas the cingulate, prefrontal, and temporal areas were the most reported for cortical ones also including the thalamo-cortical system. Moreover, we found several definitions of consciousness and 21 new sub-classifications.

Recent studies suggest that COVID-19 survivors may experience long-term health consequences: in particular, neurological and mental health symptoms might be associated with long-term negative outcomes. This study is a secondary analysis of a larger cohort study and aims to determine the extent to which neurological and mental health sequelae are associated with survivors’ disability. Participants include COVID-19 survivors, with no pre-morbid brain conditions, who were discharged from the COVID-19 Unit of the ASST Spedali Civili Hospital between February and April 2020. At an average of 3.5 months after discharge, they were submitted to a neurological examination and completed the WHO Disability Assessment Schedule (WHODAS-12), the Hospital Anxiety and Depression Score, the Pittsburgh Sleep Quality Index and the Montreal Cognitive Assessment. Multivariable regression analysis was carried out to analyze variables that explain WHODAS-12 variation. In total, 83 patients (63 males, average age 66.9, 95% CI: 64.2–69.7) were enrolled; average WHODAS-12 was 13.2 (95% CI: 9.7–16.6). Cognitive dysfunction, anxiety, fatigue, and hyposmia/hypogeusia explained 28.8% of WHODAS-12 variation. These findings underline the importance and need for longitudinal follow-up assessments after recovery from COVID-19 and suggest the need for early rehabilitation of residual symptoms to enhance patients’ functioning.

Introduction: Consciousness relies on both cortical and subcortical structures and their feedforward and feedback pathways. Within this framework, the thalamus represents a relay station enabling the transmission, reception, and integration of information. However, it is divided into several nuclear groups each composed of functionally heterogeneous nuclei, and, to date, an agreement on which nuclei are most involved in the generation, maintenance, and modulation of consciousness is still lacking.Methods: To fill this gap, we performed a systematic review by querying 5 electronic databases (MEDLINE/Pubmed, Scopus, EMBASE, Web of Science, and Cinahl Complete) about studies published in the last 20 years exploring the relationship between specific thalamic nuclei/nuclear groups and consciousness. For each included study, we extracted data supporting (i.e., positive evidence) or not (i.e., negative evidence) the relationship between a specific nucleus/nuclear group and the consciousness.Results: 167 articles were included leading to 346 pieces of evidence of which 284 were positive. Most of the retrieved positive evidence pertained to the intralaminar nuclear group, followed by the mediodorsal and ventral nuclear groups. Furthermore, when considering the specific nuclei within the intralaminar nuclear group, results highlighted the centromedian-parafascicular complex (CM-Pf) as the nucleus most related to consciousness. Despite the high heterogeneity characterizing the adopted methodologies (e.g., brain stimulation, anesthesia, brain damage), as well as the study population (e.g., either healthy and pathological humans or animals) across studies, the greatest amount of evidence supported a key role of CM-Pf for the generation, modulation, and maintenance of the level of consciousness.Discussion: Though there is more research on the role of intralaminar nuclei, there is proportionally more positive evidence supporting these nuclei (particularly the CM-Pf) as key nodes in the network underlying consciousness compared to other thalamic nuclei. These results support ongoing therapeutic approaches to disorders of consciousness by reinforcing the rationale behind brain stimulation targeting CM-Pf and paving the way for other potential candidates for targeted interventions.

Neuroimaging tools could open a window on residual neurofunctional activity in the absence of detectable behavioural responses in patients with disorders of consciousness (DOC). Nevertheless, the literature on this topic is characterised by a large heterogeneity of paradigms and methodological approaches that can undermine the reproducibility of the results. To explicitly test whether task-related functional magnetic resonance imaging (fMRI) can be used to systematically detect neurofunctional differences between different classes of DOC, and whether these differences are related with a specific category of cognitive tasks (either active or passive), we meta-analyzed 22 neuroimaging studies published between 2005 and 2017 using the Activation Likelihood Estimate method. The results showed that: (1) active and passive tasks rely on well-segregated patterns of activations; (2) both unresponsive wakeful syndrome and patients in minimally conscious state activated a large portion of the dorsal-attentional network; (3) shared activations between patients fell mainly in the passive activation map (7492 voxels), while only 48 voxels fell in a subcortical region of the active-map. Our results suggest that DOCs can be described along a continuum—rather than as separated clinical categories—and characterised by a widespread dysfunction of brain networks rather than by the impairment of a well functionally anatomically defined one.