What type of aphasia is characterized by posterior lesions affecting fluency?

The type of aphasia characterized by posterior lesions affecting fluency is fluent aphasia. Fluent aphasia typically arises from damage to areas in the posterior part of the left hemisphere of the brain, especially in regions associated with language processing, such as Wernicke's area. Individuals with fluent aphasia produce speech that is generally smooth and grammatically correct, but they may have significant difficulties in understanding language and producing meaningful content.

In fluent aphasia, while the flow of speech is intact, the individual often produces sentences that contain nonsensical words or irrelevant information, making their speech difficult to follow. This contrasts with non-fluent aphasia, where speech production is halting and labored, and associated comprehension is typically better than production. Global aphasia represents a more severe form, affecting both expressive and receptive language, while transcortical aphasia involves preserved repetition abilities but disruption in spontaneous speech and comprehension, often related to lesions in regions outside the classic language areas.