The study design is a single-center prospective pilot study. Hypothesis: Results of cerebral fNIRS examination in unconscious patients with severe hemorrhagic or ischemic stroke in the ICU are congruent with the results of SSEP and AEP. Hence, making it a potential prognostic tool for unconscious ICU patients. In a specific subgroup of unconscious patients after cardiac arrest and cardiopulmonary resuscitation the fNIRS measurement is congruent with the results of electroencephalography (EEG). The primary purpose of this study is to evaluate the agreement of the results of fNIRS examination to those of evoked potentials and EEG in unconscious ICU patients with severe hemorrhagic, or ischemic strokes or hypoxic brain injury after cardiac arrest and cardiopulmonary resuscitation. fNIRS will be compared to evoked potentials in an experimental group consisting of unconscious neuro-intensive care patients and in a control group consisting of healthy, conscious subjects. To compare fNIRS with evoked potentials there are two test phases: 1. The cerebral response to a somatosensory stimulus (peripheral nerve stimulation) is measured by fNIRS and SSEP 2. The cerebral response to an auditory stimulus is measured by fNIRS and AEP To avoid biases the following has to be considered: * The timing of the measurements plays an important role. A time difference between compared measurements can influence the outcome significantly due to deterioration or recovery of the neuronal network during the time gap. Therefore, fNIRS and evoked potentials will be measured simultaneously. * If the compared measurement methods are conducted by the same researcher the possibility of bias is high. Hence, two different researcher will conduct each one measurement without knowing the results of each other during the measurement.