Neurophysiological indicators for consciousness state recognition using auditory textures.

Research project objectives/hypothesis
The research domain of this project is the development of a measurement protocol that uses auditory stimuli together with the registration of human electric brain activity and would be able to determine the actual level of consciousness. This study is motivated by the lack of reliable clinical methods which can clearly differentiate between various states of consciousness for patients with disorders of consciousness (DOC) after severe brain injuries. The method proposed here is based on the assumption that perception of complex auditory textures requires the brain to detect certain statistical pattern and integrate statistical information which can only occur in the presence of consciousness. An essential goal of this project is comprehensive test of its hypotheses on a group of healthy subjects in sleep and awake condition, on DOC patients as well as on mice during direct registration of neuronal responses in the auditory cortex where manipulation with the level of consciousness is obtained with anesthesia.

Research project methodology
Electrophysiological techniques are the principal research methods in the presented project. Electroencephalography will be used as the basic measurement technique in healthy human and DOC patients whereas the experiments in mice will be performed with chronically implanted electrodes for recording from multiple neurons. This approach will allow us to analyze the neural response to the same stimulus on different levels, i.e. reaching from single to populations of neurons. The main experimental paradigm is auditory texture method which would be analysed considering changes in time (e.i. ERP) and time-frequency, additionally with connectivity analysis. We plan to use a total of approx. 20 healthy subjects in each condition and the same number of DOC patients with various behavioral diagnosis. The obtained results would be compared to the outcomes of other neuroimaging methods to determine the actual level of consciousness on the same group of patients. The research on ~10 mice undergoing increasing depths of anesthesia would be carried out at Radboud University Nijmegen at the Netherlands.

Expected impact of the research project on the development of science
Reliable diagnosis of disorders of consciousness appears as a serious problem of current medicine and poses a real challenge for the science. The ambiguity of the externally observable symptoms in patients leads to a high rate of incorrect classification of the state of consciousness (~40%). The method used in the present project could provide a relatively low-cost alternative that is easy to use and interpret and was never tested before. Additionally, this research is innovative due to its interdisciplinary nature where brain activity after textures stimuli would be described both on the level of single neurons as well as neuronal populations. Further, the project would broaden scientific knowledge about the representation of auditory stimuli in the brain, especially the auditory textures which have hardly been researched. At the same time it would deepen the understanding of the brain mechanisms underlying consciousness in general and situations in which consciousness is lost fully or partially.