7.1 localization of language

localization of language

Why is studying neural basis of language complex?

• Most of the brain takes part in language in one way or another

• Most patients who add information to studies of language have had strokes, usually of the middle cerebral artery.

• Immediately following stroke, symptoms are generally severe but improve considerably as time passes.

• Aphasia syndromes described as nonfluent (Broca’s) or fluent (Wernicke’s) have many varied symptoms, each of which may have different neural basis.

• Other cognitive functions are also relevant, such as EF, WM, memory, attention & perception.

Anatomical areas associated with language

• Inferior frontal gyrus, superior temporal gyrus & surrounding areas: ventral parts of the precentral & postcentral gyri, supramarginal gyrus, angular gyrus & medial temporal gyrus.

• Areas 45 and 44 (Broca’s area), area 22 (Wernicke’s area) & parts of areas 4, 6, 9, 3-1-2, 40, 39 & 21.

• Insula, Heschl’s gyrus & aSTP & pSTP.

Anterior & Posterior language regions:

• Subdivisions of Broca’s area

Subdivisions of Broca’s area:

• Anterior & posterior region in area 45.

• Dorsal & ventral region in area 44

• Ventral premotor area 6 (facial movements)

• Surrounding areas containing mirror neurons

Dronkers et al. (2017)

• Selective damage to Broca’s area & Wernicke’s area do not produce its equivalent in aphasia.

• To produce a Broca aphasia a larger area needs to be affected.

• It doesn’t just manifest an aphasia, also cognitive & memory deficits as well.

Anatomical areas associated with language

Dual pathways for language

• two pathways → dorsal & ventral

• the information flows both ways between temporal & frontal cortex

Ventral or what pathway

• Transform sound information into meaning (phonological → semantics).

• It assigns meaning to words : semantics

Dorsal or where pathway

• transform sound information into motor representation (phonological → articulation)

• phonemes

Integration of semantic-syntactic

• information through Broca’s area & Insular cortex.

Inferior Fronto-occipital fasciculus

• cerebral areas:

  • inferior frontal cortex

  • temporal cortex

  • occipital cortex

  • parietal cortex

• functions of the fasciculus:

  • semantic process

  • visual mapping of the words with the semantic meaning (reading)

Uncinate fasciculus 

• Cerebral areas:

  • Anterior Broca’s area (AB45 → triangular area),

  • Area Broadmann 47

  • Temporal lobe

• functions of the fasciculus:

  • Semantic processing of the word (lexicon-semantic access, categorizing & judgement), of the phrase (plausible semantic)

Arcuate fasciculus 

• Cerebral areas:

  • Posterior area of Broca (AB44 → opercular area)

  • Wernicke area (medial posterior & superior temporal gyrus)

• functions of the fasciculus:

  • Complex syntax by prediction top-down for entering words.

  • Activation related to the complexity.

  • Comprehension of the semantic structure

  • Phonological processing related to phonological knowledge.

Superior longitudinal fasciculus

• cerebral areas:

  • Dorsal premotor cortex

  • Parietal cortex

  • Medial & superior temporal gyrus

• functions of the fasciculus:

  • A guideline from what I hear to the praxia.

  • A guideline of the representation of the grapheme to a motor representation.

  • Repetition of the words that are heard