Д190
ВПАДАТЬ/ВПАСТЬ В ДЕТСТВО (B МЛАДЕНЧЕСТВО)
VPsubj:
human 1. to lose one's mental faculties because of old age
X впадает в детство - X is entering (falling into) his second childhood
X is getting (becoming) senileX is in his dotage.
2. Also: ВПАДАТЬ/ВПАСТЬ В РЕБЯЧЕСТВО to act, think etc as a child would
X впадает в детство = X behaves like a (little) child (kid)
(in limited contexts) X is experiencing (enjoying
etc) his second childhoodX is being childish.