Final answer:
Signals for written and spoken language are processed via the primary visual or auditory cortex, respectively, and converge at language processing centers like Broca's area and the motor cortex. Broca's area, which is crucial for speech production, and the frontal eye fields are critical in the pathway; damage to these areas can result in communication issues like Broca's aphasia or visual-motor coordination problems.
Step-by-step explanation:
Signals of written and spoken words follow distinct pathways to reach the motor cortex. For written words, the process begins as visual information, which is captured by the eyes and transmitted to the primary visual cortex in the occipital lobe. The visual input here is primarily processed for basic shapes and depth, and then it is directed along the dorsal and ventral streams for more complex processing related to spacial relations and object recognition, respectively. In contrast, spoken words, after being processed by the ear, are sent to the auditory cortex before they reach language processing centers.
Broca's area, located in the frontal lobe anterior to the premotor and primary motor cortex, is responsible for planning the movements required for speech production. Damage to Broca's area can cause difficulty in speech production, known as Broca's aphasia, although the person's understanding of language typically remains intact. Nearby, the frontal eye fields are critical for eye movement coordination in response to visual stimuli, connecting to the superior colliculus, and any impairment can lead to issues with visual-motor coordination.
From these processing and planning regions, the pathways converge onto the motor cortex, where motor commands are initiated. The corticospinal and corticobulbar tracts transmit these commands to the opposite side of the body due to their largely contralateral structure, meaning that the right motor cortex controls the left side of the body and vice versa. This intricate network ensures that cognitive recognition of words, either written or spoken, can be translated into appropriate verbal or motor responses.