The Compendium of Caraka 4.4.15

4.4.15

tasya yatkālamevendriyāṇi saṃtiṣṭhante, tatkālameva cetasi vedanā nirbandhaṃ prāpnoti;tasmāttadā prabhṛti garbhaḥ spandate, prārthayate ca janmāntarānubhūtaṃ yat kiṃcit, taddvaihṛdayyamācakṣate vṛddhāḥ/

At the very time when its sense organs become established, at that very time sensation attains an unbroken continuity in the mind; therefore, from then on the embryo throbs and longs for whatever it experienced in another birth. The elders call this the state of having two hearts (dvaihṛdayya).