Aphasia

The table below lists the major types of aphasia. Remember that dysarthria is different and refers to a motor speech disorder.

This area 'forms' the speech before 'sending it' to Broca's area. Lesions result in sentences that make no sense, word substitution and neologisms but speech remains fluent - 'word salad'

Comprehension is impaired | | Broca's (expressive) aphasia | Due to a lesion of the inferior frontal gyrus. It is typically supplied by the superior division of the left MCA

Speech is non-fluent, laboured, and halting. Repetition is impaired

Comprehension is normal | | Conduction aphasia | Classically due to a stroke affecting the arcuate fasiculus - the connection between Wernicke's and Broca's area

Speech is fluent but repetition is poor. Aware of the errors they are making

Comprehension is normal | | Global aphasia | Large lesion affecting all 3 of the above areas resulting in severe expressive and receptive aphasia

May still be able to communicate using gestures |

Diagram showing the main types of aphasia

When replying to a conversation, we can imagine how Wernicke's and Broca's areas may interact:

Spoken word is heard at the ear. This passes to Wernicke's area in the temporal lobe (near the ear) to comprehend what was said. Once understood, the signal passes along the arcuate fasciculus, before reaching Broca's area. The Broca's area in the frontal lobe (near the mouth) then generates a signal to coordinate the mouth to speak what is thought (fluent speech).