Most observations on the physiology of language have been made through work with subjects who have sustained head injuries. When we say that verbal behavior is a lateralized function, we mean that both hemispheres of the brain are equally important for speech. People with Broca's aphasia speak fluently, but have anomia.
Anomia is a difficulty in finding the correct word to describe an object, action, or situation.
People with Wernicke's aphasia speak fluently but without meaning and have poor comprehension. Research with people who have transcortical sensory aphasia suggests that the ability to understand is necessary for accurate memorization. Pure word deafness is the inability to comprehend the meaning of words. Damage to the posterior language area disrupts the ability to recognize written or spoken words. It conveys meanings of words but not sounds.