title: Robust discrimination between EEG responses to categories of environmental sounds in early coma.
abstract: Humans can recognize categories of environmental sounds, including vocalizations produced by humans and animals and the sounds of man-made objects. Most neuroimaging investigations of environmental sound discrimination have studied subjects while consciously perceiving and often explicitly recognizing the stimuli. Consequently, it remains unclear to what extent auditory object processing occurs independently of task demands and consciousness. Studies in animal models have shown that environmental sound discrimination at a neural level persists even in anesthetized preparations, whereas data from anesthetized humans has thus far provided null results. Here, we studied comatose patients as a model of environmental sound discrimination capacities during unconsciousness. We included 19 comatose patients treated with therapeutic hypothermia (TH) during the first 2 days of coma, while recording nineteen-channel electroencephalography (EEG). At the level of each individual patient, we applied a decoding algorithm to quantify the differential EEG responses to human vs. animal vocalizations as well as to sounds of living vocalizations vs. man-made objects. Discrimination between vocalization types was accurate in 11 patients and discrimination between sounds from living and man-made sources in 10 patients. At the group level, the results were significant only for the comparison between vocalization types. These results lay the groundwork for disentangling truly preferential activations in response to auditory categories, and the contribution of awareness to auditory category discrimination.
authors.affiliation: Electroencephalography Brain Mapping Core, Center for Biomedical Imaging (CIBM), University Hospital Center, University of Lausanne Lausanne, Switzerland ; Department of Radiology, University Hospital Center, University of Lausanne Lausanne, Switzerland.
authors.forename: Natacha
authors.initials: N
authors.lastname: Cossy
authors.affiliation: Electroencephalography Brain Mapping Core, Center for Biomedical Imaging (CIBM), University Hospital Center, University of Lausanne Lausanne, Switzerland ; Department of Radiology, University Hospital Center, University of Lausanne Lausanne, Switzerland.
authors.forename: Athina
authors.initials: A
authors.lastname: Tzovara
authors.affiliation: Department of Clinical Neurosciences, University Hospital Center, University of Lausanne Lausanne, Switzerland.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Simonin
authors.affiliation: Department of Clinical Neurosciences, University Hospital Center, University of Lausanne Lausanne, Switzerland.
authors.forename: Andrea O
authors.initials: AO
authors.lastname: Rossetti
authors.affiliation: Electroencephalography Brain Mapping Core, Center for Biomedical Imaging (CIBM), University Hospital Center, University of Lausanne Lausanne, Switzerland ; Department of Radiology, University Hospital Center, University of Lausanne Lausanne, Switzerland.
authors.forename: Marzia
authors.initials: M
authors.lastname: De Lucia
keywords: auditory processing; coma; environmental sounds; multivariate decoding; single-trial EEG; voice