In the present dissertation we have attempted to correlate the functioning of the brain with mental activity i.e. mind. The objects or events provide external stimuli to form a mental image in the brain. The brain in turn operates on mental image and makes a decision. Thus an operator of brain which is termed as brain operator (Г), operates on mental image (C) and makes decision (D), which can be expressed as: Г(C)=D The brain operator essentially is a synonym of mind. The brain operator acting upon the mental image formed after encountering with the environment, makes decision by processing it through noncommutative acquisition (Гa) and organic (Гo) operators respectively. Decision making when associates with external bioenergy generates response which is translated into behaviour. Further, a model of brain-computer has been presented showing the mechanism of subconscious and conscious minds. This model clearly points out the limitation of the most sophisticated electronic computer in the sense that electronic computer lacks the Self Generating Programme (SGP) stage of its brain counterpart.