" Which", vegetable , improves , " Brain memory"?

Don't eat specific foods to target specific things like memory.  (Unless you have a particular condition and you have been given advice by a doctor.)

Instead, eat a healthy diet.  We all know what a healthy diet is: it contains lots of food for humans.  Fruit, vegetables, nuts, seeds, meat, fish, dairy, grains, etc.   It does not include lots of things which are manufactured.  Just because something is edible doesn't mean it's food.

Also important for memory is adequate sleep.