Computer aided tomography (CAT) scans are used to create images of the brain; this technique uses radiation in the [ Select ] X-ray Gamma Radio wave Microwave range. Positron emission tomography (PET) uses radiation in the [ Select ] Gamma Microwave Radio wave X-ray radiation range. Of these two imaging methods, [ Select ] PET CAT is better able to provide functional information about brain regions. MRI uses radiation in the [ Select ] X-ray gamma radio visible frequency.   Because the larger neurons in the cerebral cortex all have the same (approximate) radial orientation, their activity produces electrical potentials that can be detected at the external surface of the head – the amplitude of these Electroencephalography (EEG) signals depends on the degree of [ Select ] Noise Gamma Synchrony Variability of the neurons contributing to the signal. High amplitude, low frequency EEG signals are most evident when we are [ Select ] Awake Dreaming Sleeping .多重下拉选择题