Vāsudeva is worshiped within the heart by meditation because He is the predominating Deity of the heart.
Saṅkarṣaṇa, the second expansion, is Vāsudeva’s personal expansion for pastimes, and since He is the reservoir of all living entities, He is sometimes called jīva. The beauty of Saṅkarṣaṇa is more than that of innumerable full moons radiating light beams. He is worshipable as the principle of ego. He has invested Anantadeva with all the potencies of sustenance. For the dissolution of the creation, He also exhibits Himself as the Supersoul in Rudra, irreligiosity, sarpa (the snake), antaka (death) and the demons.
Pradyumna, the third manifestation, appears from Saṅkarṣaṇa. Those who are especially intelligent worship this Pradyumna expansion of Saṅkarṣaṇa as the principle of the intelligence. The goddess of fortune always chants the glories of Pradyumna in the place known as Ilāvṛta-varṣa, and she always serves Him with great devotion. His complexion appears sometimes golden and sometimes bluish like new monsoon clouds in the sky. He is the origin of the creation of the material world, and He has invested His creative principle in Cupid. It is by His direction only that all men and demigods and other living entities function with energy for regeneration.
Aniruddha, the fourth of the quadruple expansions, is worshiped by great sages and psychologists as the principle of the mind. His complexion is similar to the bluish hue of a blue cloud. He engages in the maintenance of the cosmic manifestation and is the Supersoul of Dharma (the deity of religiosity), the Manus (the progenitors of mankind) and the devatās (demigods). The Mokṣa-dharma Vedic scripture indicates that Pradyumna is the Deity of the total mind, whereas Aniruddha is the Deity of the total ego, but previous statements regarding the quadruple forms are confirmed in the Pañcarātra tantras in all respects.
Ref >> Srila Prabhupada Vani.