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The field of Consciousness Studies combines neuroscientists/neurologists and psychologists to study consciousness beginning in the 1980s.

They publish in journals such as consciousness and Cognition and the Journal of consciousness Studies, and hold regular conferences by groups such as the Association for the Scientific Study of Consciousness.

The Spectrum of Consciousness by Ken Wilber is the most thorough account of the spiritual approach to consciousness which compares western and eastern ways of thinking about the mind.

for more scientific approaches on consciousness follow the wiki link below.

You have to define more closely what you mean by conciousness. More typically thought of as self awareness in philosophy the study of conciousness in psychology and sociology, more particularly, looks at the areas as how do we know we exist, how can we prove we exist. It also looks at the degree to which we are shaped by and are shaping others through our conciousness.

If you want to study sleep this is more the realm of the life sciences - from which psychology often borrows ideas - and should direct your focus there.