Consciousness is one of final questions for humans to tackle in neuroscience. Due to the lack of understanding of the basic brain network and mechanisms of functions, our knowledge of consciousness remains at the theoretical level. Recent studies using brain imaging in humans and modern neuroscience techniques in animal studies reveal a basic brain network for consciousness. The projection from the thalamus to different cortical regions form a network of activities to maintain consciousness in human and animals. These feedback and feedforward circuits maintain the consciousness even in certain brain injury conditions. Proteins and ion channels that contribute to these circuit neural activities are targets for drugs and manipulations that affect consciousness, such as anesthetic agents. Synaptic plasticity that trains synapses during learning and information recall, modify circuits and contribute to a high level of consciousness in certain populations.