| dc.description.abstract | Consciousness is always the high-level cognitive function that attracts the neuroscientists or even philosophers. However, the current research has not successfully disclosed the linkage between the brain functions and consciousness. Previous studies have found that under the near-death experience, the blood contains a higher concentration of carbon dioxide and the brain research indicates a strong change across multiple frequency ranges. These studies imply that during near-death state, when the brain undergoes the dying process, the speeds of perishing vary across multiple brain networks, resulting in the swift memory flashes before dying. To verify the speculation, we established a standard processes for animal sacrifice procedure and observe the brain dynamics of sacrificing procedure by functional magnetic resonance imaging (fMRI), which allows us to understand the dynamic loss of consciousness in death.
We used 11 normal SD rats in our experiment. The total acquisition time was 15 minutes and the injection of potassium chloride ( KCl ) was at the 5th minute. Functional connectivity was observed under 3 conditions: (1) the first 300 seconds before KCl injection (anesthesia), (2) the dynamic perish process between the 300~600 seconds (near-death), and (3) the last 300 seconds without vital signs (sacrifice). We first compared the functional connectivity patterns across (1) and (3), and then analyzed the dynamic indices to realize the regional difference in the (2) condition. The dynamic indices included the time to reach the maximum after KCl injection, the time to reach minimum after KCl injection, and slope of the signal drop. Seed were selected on multiple brain regions: motor cortex, somatosensory cortex, the default mode network (DMN), caudate putamen (CPu), thalamus. The results showed the huge change of functional connectivity on rat brain. The dynamic indicators showed that the cortical area, such as somatosensory cortex and DMN regions , required longer time to reach the maximum, and the subcortex spent less time to reach the maximum intensity. In time to minimum, we could see that thalamus had longer time to reach the valley and the caudate putamen (CPu) had shortest time to minimum. Our findings unveiled not only the regional specificity along the near-death process, but also built up an animal fMRI experimental environment for further consciousness investigations. | en_US |