The Brain Determines the Strength of Consciousness Functions

What is the difference between the solitary mental consciousness in dreams and the solitary mental consciousness outside of dreams? During sleep, the circulation of qi and blood weakens, and the circulation of qi and blood in the brain also weakens. The six consciousnesses arise and operate depending on the brain as the supreme faculty (rūpa-prasāda). After the solitary mental consciousness arises in a dream, due to the condition of the supreme faculty, the mind consciousness functions rather weakly; its discernment within the dream is not clear or detailed enough, and what it remembers is not firmly retained. If the manas considers the dream to be very important, and it is strongly stimulated by it, the impression will be deep, and the manas will cause the solitary mental consciousness to deepen the impression. After waking up, the mind consciousness can remember it vividly and recall the dream very clearly. 

Due to external forces damaging the brain and causing unconsciousness, the six consciousnesses cease. After waking up, some people will suffer amnesia. This is because the brain has been damaged, obstructing the functioning of the mind consciousness; the mind consciousness's function of integrating information becomes disordered or weakened, resulting in the inability to recall people and events from a certain period of time. Once the brain receives a strong stimulus, the mind consciousness may possibly recover its memory and recall people and events from the past. The memories of childhood and early years are not firm because the brain is not fully developed, causing the functions of the mind consciousness to be weak and the memory to be insecure. The mind consciousness of the elderly is generally weaker in function than in their youth; their discernment is not detailed and their minds are coarse—this is what is called senility. 

When the circulation of qi and blood is not smooth, it will damage the brain, and a person will become foolish, dull, and senile. Therefore, the six consciousnesses are of the nature of dependent arising, are dharmas born of causes and conditions, are extremely illusory, and cannot be relied upon; the six consciousnesses are not the self, nor are they what belongs to the self. In the neutrino-body (antarā-bhava), the functions of the mind consciousness are even weaker, because the antarā-bhava arises temporarily, its four great elements are coarse and inferior, far inferior to the human body, and severely obstruct the functions of the mind consciousness. Therefore, in the antarā-bhava, the mental activities of the manas are dominant; the mind consciousness cannot effectively regulate the manas, and the inherent nature of the manas determines the destination of the next life. Therefore, realizing the fruits through the mind consciousness is a fruit made of paper.