Nirodha-samāpatti: 'attainment of ceasing' S. XIV, 11, also called saññā-vedayita-nirodha, ceasing of feeling and perception', is the temporary suspension of all consciousness and mental activity, following immediately upon the semi-conscious state called 'sphere of neither-perception-nor-non-perception' see: Jhanas. The absolutely necessary pre-conditions to its attainment are said to be perfect mastery of all the 8 absorptions jhanas as well as the previous attainment of Anagami or Arahantship see: ariya-puggala
According to Vis.M XXIII, the entering into this state takes place in the following way: by means of mental tranquillity samatha and insight vipassanā one has to pass through all the 8 absorptions one after the other up to the sphere of neither-perception-nor-non-perception and then one has to bring this state to an end. If, namely, according to the Vis.M, the disciple Anāgāmi or Arahat passes through the absorption merely by means of tranquillity, i.e. concentration, he will only attain the sphere of neither-perception-nor-non-perception, and then come to a standstill; if, on the other hand, he proceeds only with insight, he will reach the fruition phala of Anāgāmi or Arahatship. He, however, who by means of both abilities has risen from absorption to absorption and, having made the necessary preparations, brings the sphere of neither-perception-nor-non-perception to an end, such a one reaches the state of ceasing. Whilst the disciple is passing through the 8 absorptions, he each time emerges from the absorption attained, and regards with his insight all the mental phenomena constituting that special absorption, as impermanent, miserable and impersonal. Then he again enters the next higher absorption, and thus, after each absorption practising insight, he at last reaches the state of neither-perception-nor-non-perception, and thereafter the full ceasing. This state, according to the Com., may last for 7 days or even longer. Immediately at the rising from this state, however, there arises in the Anāgāmi the fruition of Anāgāmiship anāgāmi-phala in the Arahat the fruition of Arahatship arahatta-phala.
With regard to the difference existing between the Bhikkhu abiding in this state of ceasing on the one hand, and a dead person on the other hand, M 43 says:;In him who is dead, and whose life has come to an end, the bodily in-and-outbreathing, verbal thought-conception and discursive thinking, and mental functions see: sankhāra 2 have become suspended and come to a standstill, life is exhausted, the vital heat extinguished, the abilities are destroyed. Also in the Bhikkhu who has reached 'ceasing of perception and feeling' saññā-vedayita-nirodha the bodily, verbal and mental functions have been suspended and come to a standstill, but life is not exhausted, the vital heat not extinguished, and the abilities are not destroyed.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.