Why does damage to Wernicke's area leave speech fluent but full of wrong words? · Grey Matter

The frontal machinery that produces the rhythm, melody and grammar of speech is intact, so words keep coming at a normal rate.

Why does damage to Wernicke's area leave speech fluent but full of wrong words?

The frontal machinery that produces the rhythm, melody and grammar of speech is intact, so words keep coming at a normal rate. What is lost is the region that links word sounds to their meanings and checks what is about to be said against what was meant, so the wrong sounds and the wrong words get through: paraphasias, invented words, sometimes jargon. The same damage breaks comprehension of others' speech, and because the patient's own monitoring is broken too, many are unaware that they are not making sense.