Target creature's Intelligence and Charisma scores each drop to 1. The affected creature is unable to use Intelligence- or Charisma-based skills, cast spells, understand language, or communicate coherently. Still, it knows who its friends are and can follow them and even protect them. The subject remains in this state until a heal, limited wish, miracle, or wish spell is used to cancel the effect of the feeblemind. A creature that can cast arcane spells, such as a sorcerer or a wizard, takes a -4 penalty on its saving throw.
So its clear that int and cha casters are shut down hard by the spell when they are affected. But I dont feel that its exactly clear on how wis casters (usually divine) are affected.
Take for example a cleric. Their casting ability score is not affected so they can still cast all their spell levels. The spell says that they are unable to cast spells, but it reads like an effect of the reduced int/cha, or the inability to speak clearly. So spells prepared with silent spell would help.
Are Wisdom-based casters able to still cast spells?