This is page is an unedited draft from Marcello’s manuscript. It needs citations, figures, cross-links, and other work to be done. It will take a while!
It is here so you can see the general gist of Marcello’s argument across the whole essay.
Feel free to visit from time to time for updates.
The patterns of activity during general anaesthesia resemble significantly those during deep sleep. Anaesthetics have been shown to activate sleep-promoting neurons in the hypothalamus and inhibit major arousal nuclei in the brainstem.
Spontaneous slow and fast rhythmic activity generated in different regions of the mouse cortex was recorded under ketamine anaesthesia. Under this kind of anaesthesia rhythmic activity was observed in the primary visual, somatosensory, and motor cortex and medial prefrontal cortex. These rhythms consisted of periods of neuronal firing or UP states, interspersed with silent periods or DOWN states. These slow waves had a frequency of <1 Hz. During UP states different frequencies superimposed on the slow waves were generated, including high frequency firing in the gamma frequency range. The slow waves preferentially propagated from front to back. Similar patterns of activity have been recorded in cortical slabs of anaesthetised cat.
With multichannel recordings under anaesthesia, low frequency spreading depolarisations have also been observed in the visual cortex of anaesthetised rat, cat and macaque. In rats anaesthetised with ketamine diverse types of patterns of brain activity, including stationary, travelling and spirals waves were recorded.
General anaesthesia reduces connectivity, increases in spectral power of slow oscillations, and reduces spatiotemporal complexity.