Particular hexahydropyrano [3,2-b] [1,4] benzothiazine derivatives represented by the following general formula (I) or pharmaceutically acceptable acid-addition salts thereof. ##STR1## The compounds can facilitate the metabolic turnover of inositol phospholipids at a hippocampus playing an important part in memory, and improve cerebral function leading the memory. The compounds can be utilized as agents for activating brain metabolism and improving cerebral function.