Primary Consciousness - Neurophysiological Basis

Neurophysiological Basis

Physiologically, three fundamental facts stand out about primary consciousness:

1. Waking consciousness is associated with low amplitude, irregular EEG activity in the 20–70 Hz range.
   • Conversely, unconscious states like deep sleep, coma, general anesthesia, and epileptic states of absence show a predominance of low frequency, high-amplitude and more regular voltages at less than 4Hz.
2. Consciousness seems to be instinctively associated with the thalamus and cortex, even if the extent to which this true is argued among scientists.
   • Damage to the brainstem or thalamus can abolish consciousness, while damage to the sensory cortex appears to delete specific conscious features such as color vision, visual motion, conscious experiences of objects and faces, and the like.
3. Consciousness is distinctively associated with widespread brain activation related to the conscious content.
   • Perhaps two dozen experiments show that sensory input supporting consciousness spreads from the sensory cortex to parietal, prefrontal, and medial-temporal cortex, while closely matched input that does not reach consciousness activates mainly local sensory regions. Further, the widespread activity appears to involve more globally coordinated activity.