How can I update particular fields of model with validation in Ruby on Rails?

There is an AcviteRecord Model named User like this:

class User < ActiveRecord::Base
  validates :name, :presence => true
  validates :email, :presence => true, :uniqueness => true

  validates :plain_password, :presence => true, :confirmation => true
  validates :plain_password_confirmation, :presence => true
  #...other codes
end

It requires that the update of name and email and the update of password are separated.

When only update name and password, using update or update_attributes will cause password validation which is not needed. But using update_attribute will save name and email without validation.

Are there any ways to update particular fields of model with validation without causing the other fields' validation?