The Neural Basis of Language

Steps of Auditory Comprehension:

1.Cochlea to cochlear nuclear complex (CNC) via cranial nerve VIII

2.CNC to thalamus

3.Thalamus to primary auditory cortex (41,42)

4.Primary auditory cortex to Wernicke’s area (22)

5.Wernicke’s to BA 44 of Broca’s area (syntax)

Steps of Visual Comprehension (Reading):

1.Eyes to LGN of thalamus via optic tracts

2.LGN to visual cortex (17,18,19) via geniculocalcarine tract

3.Visual areas to ventral and dorsal streams of vision

4.For reading, 3 other cortical areas involved:

–Parietotemporal system

• Word analysis: Decoding semantics

–Occipitotemporal system•Word form recognition: Sight reading

–Anterior reading system•Word analysis: Decoding syntax?

Steps of Oral Production: 

1.Decision to speak formed in prefrontal cortex.

2.Decision sent to Broca’s area (44,45) for language encoding and speech planning.

3.Speech plans sent to SMA (6), which activates the plans.

4.SMA (6) sends to motor cortex (4), which sends activated plans to speech muscles.

Steps of Written Expression: 

1.Decision to write formed in prefrontal cortex.

2.Decision sent to Broca’s area (44,45) for language encoding.

3.Writing plans sent to premotor area (6), which forms grapheme motor plans.

4.Premotor area (6) sends to motor cortex (4), which sends plans to hand muscles.

5.Areas 5 and 7 aid visual spatial elements of writing.