Decreased motivation - Iyokugentai

...When this abnormally increases and one act after another is performed, it is called compulsion to act, and is seen in mania. <Hypobulia> A state in which drive is reduced and there is no spontaneous volitional action, leading to a life of idleness and nothing to be done. It appears in schizophrenia with emotional blunting and organic brain diseases (frontal lobe damage, widespread brain damage, etc.).

*Some of the terminology explanations that mention "loss of motivation" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…これが異常に亢進して次々と行為をするものを行為心迫といい，躁病にみられる。〈意欲減退hypobulia〉　欲動が低下し意志行為の自発的発動がない状態で，なんらなすところなく無為な生活を送る。情意鈍麻のある精神分裂病や脳器質的疾患(前頭葉障害や脳の広範な障害など)にあらわれる。…

※「意欲減退」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報