A patient has a lesion in the arcuate fasciculus (the white matter tract connecting Broca's and Wernicke's areas). They understand speech well and produce spontaneous speech fluently, but cannot repeat sentences spoken to them. What does this pattern of conduction aphasia best support?
AThe classical two-region model, since both Broca's and Wernicke's areas are anatomically intact
BA network model of language, where the white matter connections between regions are critical components, not just the regions themselves
CRight-hemisphere language processing, since the left-hemisphere lesion causes the deficit
DThe modular view that production and comprehension are fully independent systems
Conduction aphasia is a decisive challenge to the strict two-region model. If language were simply two modules (Broca's = production, Wernicke's = comprehension), then intact Broca's and Wernicke's areas should produce intact language — but the patient cannot repeat. A network model explains this naturally: repetition requires transmission between the comprehension and production systems, and severing the arcuate fasciculus breaks that transmission. The deficit is in a connection, not a module. This is why modern neurolinguistics emphasizes networks of regions connected by white matter tracts rather than isolated processing centers.
Question 2 Multiple Choice
Modern fMRI studies of neurologically intact speakers performing language tasks find which of the following?
AOnly Broca's area activates during speech production; only Wernicke's area activates during comprehension, confirming the classical model
BBoth Broca's and Wernicke's areas activate across a wide variety of language tasks, as part of a broadly distributed bilateral network
CLanguage processing is evenly distributed across both hemispheres with no left-hemisphere advantage for any task
DThe classical two-area model is fully confirmed: only Broca's and Wernicke's areas are necessary and sufficient for all language tasks
Neuroimaging has complicated the classical model in multiple directions. Both Broca's and Wernicke's areas activate across diverse language tasks — not just 'their' assigned functions — and processing extends into prefrontal, parietal, temporal, and subcortical regions. The picture is a distributed network, not two encapsulated modules. Left-hemisphere dominance for language is real but probabilistic (~95% of right-handers), and the right hemisphere contributes meaningfully to prosody, figurative language, and discourse coherence. The classical model remains clinically useful as a rough guide but is descriptively incomplete.
Question 3 True / False
The right hemisphere plays no significant role in language processing — language is exclusively a left-hemisphere function.
TTrue
FFalse
Answer: False
Left-hemisphere dominance for language is real but does not mean exclusive. The right hemisphere contributes substantially to prosody (the melody and rhythm of speech), discourse coherence, figurative language interpretation (metaphors, idioms), and pragmatic processing (inferring speaker intent, understanding indirect speech acts). Right-hemisphere damage can impair these functions even when the patient's basic sentence production and comprehension remain intact. Language is a left-hemisphere-dominant but bilateral function.
Question 4 True / False
Aphasic patients often retain underlying grammatical competence that surfaces under certain conditions, suggesting that aphasia typically disrupts access to language rather than destroying the grammar itself.
TTrue
FFalse
Answer: True
This is a crucial insight about what aphasia is and is not. Aphasic patients are not simply people who have 'lost their grammar.' Many show residual competence under facilitated conditions — they can sometimes complete familiar phrases, respond to yes/no questions, or produce words in constrained tasks that they fail in free production. This pattern suggests the grammatical knowledge is largely intact but access to it is disrupted by damaged processing pathways. Aphasia is a performance impairment, not a competence deletion — a distinction that has important clinical and theoretical implications.
Question 5 Short Answer
Describe one piece of evidence that challenges the classical two-region model of language (Broca's area = speech production; Wernicke's area = comprehension), and explain what it reveals about how language is actually organized in the brain.
Think about your answer, then reveal below.
Model answer: Conduction aphasia is the clearest challenge. Patients with damage to the arcuate fasciculus — the white matter tract connecting Broca's and Wernicke's areas — have intact spontaneous speech and intact comprehension but cannot repeat sentences. The classical model predicts intact language if both regions are intact; it has no explanation for this pattern. The network account explains it naturally: repetition requires transmitting information from the comprehension system to the production system, and severing the connecting tract breaks that transmission. The deficit is in the connection, not the modules. This reveals that language function depends on the integrity of white matter pathways, not just the cortical regions themselves — the brain's language system is a network of interconnected components, not two isolated processors.
Other valid evidence includes fMRI showing both regions activate across diverse tasks (not just their 'assigned' functions), and right-hemisphere contributions to prosody and discourse that the classical model cannot account for. Any of these illustrate the same point: language is more distributed and interconnected than a two-region model allows.