Consciousness is a very difficult concept to define, let alone study scientifically. It is often overlooked in introductory psychology classes, I think because discussing it quickly becomes a tangled briar of contradictions and confusion. It’s a shame because it is one of the most important concepts in human experience.
See this recent article in the New York TImes about consciousness and some scientific studies on it. One vexing thing about these studies is the questions of why, when the neocortical regions are inactivated, can participants understand the language used as commands to perform some function? If Wernicke’s area is inactivated by anesthetics, how is the language comprehended? The article does not provide any explanation of this.