Neurobiology of Consciousness - Neuroscience and Ancient Perspectives

Awareness and alertness are important aspects of consciousness. A person is said to be conscious when the person is totally alert or aware of the external environment. The opposite state of consciousness is sleep when the awareness of the external environment is low. Sleep is characterized by two main stages: rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. NREM is deep sleep and further comprised of three stages. EEG studies have shown the difference between different stages of sleep and REM sleep, and has an EEG pattern similar to wakefulness stage. Neuronanatomical structures such as anterior hypothalamus, cortical neurons and ultradian oscillator are sleep promoting areas and the posterior and lateral hypothalamus, dorsal raphe, thalamus, and brainstem are arousal regions. These different areas work in tandem to regulate the sleep–wake cycles. In addition, Melatonin is also known as sleep hormone involved in the regulation of sleep. In ancient perspectives, consciousness has four states, awake (Jagrata), dream state (Svapna), deep sleep (Sushupti). Further two states of sleep that are beyond the comprehension of a common man are Turiya and Turiyatita. The neuroscience and ancient perspectives of consciousness shall be understood and studied together to enhance our understanding of consciousness. Understanding of both perspectives in combination may help in advancing the polysomnography research.