In the Physical functioning,
consciousness works in three levels simultaneously. Sensual perceptions are in
the material consciousness. In this level of the consciousness we need effort.
When there is no effort, we go to the sub-consciousness state. When we are in
this level we are able to understand many secrets of the nature.
When we sleep, the
conscious mind stops. Always the sub-conscious mind does not stop functioning.
That is the reason we dream arises while on sleep. Based on the food we in
took, tensions or emotional moods may disturb the brain cells. So, in sleep
such disturbances cause dreams.