Language 

(what we know)

1.  It is quite difficult to link our concept of language to a specific area in the brain 

2. Broca's aphasia patients/ lesions are bigger than brocas area and they have huge language impairment 

3. With language aphasia it is often that motor control is affect 

1. Wernicke-Geschwind Model

• Wernicke’s Area (Posterior Superior Temporal Gyrus – Left Hemisphere)

• Wernicke’s aphasia - fluent aphasia - their speech production is normal but agrmmatical 

• Broca’s Area (Left Inferior Frontal Gyrus)

• Damage here causes Broca’s aphasia → Difficulty forming speech, but comprehension remains intact.

• Arcuate Fasciculus (Connection Between Wernicke’s & Broca’s Areas)

• Damage here causes conduction aphasia → Difficulty repeating words, even though comprehension and speech production remain mostly intact.

• Angular Gyrus (Parietal Lobe – Near Wernicke’s Area)

• Damage here can cause alexia (inability to read) and agraphia (inability to write)

How do they explain language comprehension? 

1. Sound enters Primary Auditory Cortex → Recognized as speech.

2. Wernicke’s Area processes meaning.

3. Information travels via the Arcuate Fasciculus to Broca’s Area.

4. Broca’s Area forms a motor plan for speech.

5. Primary Motor Cortex executes speech by controlling the mouth and vocal muscles.

2. Challenges and alternatives to the model 

• Sentence comprehension does not always require grammaticality - e.g. boy, kick, ball 

• But some sentences (semantically reversible sentences require interpretation of sentence structure) 

• People with Brocas aphasia struggle with semantically reversible sentences because grammar is super relevant - this suggests that brocas area is more than just planning motor for speech 

• Voxel-based lesion symptoms mapping onto 101 aphasic stroke survivors → what voxels will you see damdge and how does this relate to the symptom they are showing (language) → the most affected area was not Broca or Wernickes are → This study showcases that while Previously, speech production issues were thought to be only due to Broca’s area damage. This study shows that other regions (insula & deep white matter) are just as important.

3. Declaractive/procedural model of language 

language processing relies on two distinct memory systems, rather than simply dividing language into comprehension vs. production.

• Declarative = what = lexicon = hippocampus, middle temporal gyrus).

• Procedural = how = the grammar rules - how to we go from present to past tense = basal ganglia and frontal cortex

  • This explains the damage from other regions 

  • Broca’s aphasia → Often affects grammar, consistent with procedural memory impairment.

  • Wernicke’s aphasia → Often affects word retrieval, consistent with declarative memory impairment.

4. Memory, Unification, Control → emphasis on the relationship between different network

• These 3 functions work together  

5. Holistic vs. analytic processing - is the difference between lexicona nd grammar enough to explain behaviour? 

• Holistic processing: A person might interpret a sentence based on the overall meaning, considering the tone and context of the conversation.

Analytic processing: A person might focus on individual words or grammar rules to understand the meaning of the sentence.