Broca's aphasia is caused by damage to a specific area of the brain known as Broca's area, which is usually located in the left hemisphere. This area is responsible for controlling the motor functions involved in speech production, such as moving the mouth and tongue. Because Broca's area is located in the left hemisphere, which controls the right side of the body, damage to this area often results in partial paralysis on the right side of the body.
On the other hand, Wernicke's aphasia is caused by damage to an area of the brain known as Wernicke's area, which is also usually located in the left hemisphere. This area is responsible for understanding and processing language. Because Wernicke's area is not directly involved in motor functions, damage to this area does not typically result in paralysis or weakness on either side of the body.