Here’s a brief explanation of the four aspects of the human mind, and the influence that meditation has over each of them.
Manas, the everyday conscious mind, is the coordinator of the senses and the mental screen on which thoughts and images occur. In meditation, manas is calmed. Its energies are collected rather than allowed to shift about. Sense activities quiet, meandering thoughts settle down, and attention becomes focused.
As manas is calmed, a more discerning dimension of the mind, the buddhi, awakens. The buddhi assigns meaning and value to experience. Through the practice of meditation, the buddhi witnesses mental activity, lending a sense of dispassion to inner life. When it is purified, the buddhi provides a refined reflection of consciousness itself.
The chitta is the unconscious storehouse of past thoughts and experiences—the bed of memory. It accumulates impressions and blends them with current mental imagery to give understanding and richness to experience. Stored impressions are propelled back onto manas in the form of habitual behaviors or desires. In meditation this can take the form of a fantasy, a distracting thought, a simple desire, or a powerful emotional urge. However, the process of meditation deposits impressions of peace and concentration in the chitta. These provide support during future periods of meditation.
The mind as ahamkara is the maker of an “I.” When we use the word “I,” we imply an identity constructed within the mind itself. With its lesser side, we cling to a limited self—we grasp the ego and the things with which it identifies. Yet each of us is also a manifestation of a vast field of pure consciousness, our true Self. Meditation gradually dispels the falseness of self-identity and reveals a deep and true Self.