Vedantic thought overlays the five koshas with a coarser scheme of three bodies, or sharira: the gross, sthula sharira, the subtle, sukshma sharira, and the causal, karana sharira. Vijnanamaya, the wisdom sheath, belongs to the subtle body along with the vital and mental sheaths, distinct from Annamaya, the food sheath, which alone is identified with the gross body and left behind at death.
Because Vijnanamaya lies within the subtle body, the tradition holds it to persist beyond physical death, carrying the faculty of discernment forward until liberation dissolves both the subtle and causal bodies; this sheath is also given particular weight in Vedantic practice because it is the faculty said to be capable of recognising the difference between the true self and the sheaths that cover it, a recognition liberation itself depends on.
Vijnanamaya's role as discriminator sets it apart from Manomaya, the more reactive mental sheath just outside it: where Manomaya processes sensory input automatically, Vijnanamaya is held to judge and decide, the faculty of buddhi that a serious meditator is trained to strengthen against the pull of unconsidered reaction. Twentieth century Theosophical writers later adapted kosha vocabulary into a separately bounded scheme of subtle bodies, a distinct later Western system rather than a continuation of this Vedantic teaching.
Sources The Principal Upanishads with Rainbow Body: A History of the Western Chakra System from Blavatsky to BrennanKurt Leland