2 Neuroscience2.7 Neural circuits

2.7.1.16 Language networks

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Written by Resident Doctor Committee · Published

New in the 2027 syllabus

The College added this topic for exams from January 2027.

From sound to meaning and speech

  • Language depends on temporal, parietal and frontal networks that interact. You cannot assign understanding and speaking to two isolated cortical centres.

  • Early auditory processing analyses speech sounds in the superior temporal regions on both sides. Processing then divides into lexical and semantic processing (words and meaning) and articulatory processing (producing speech).

  • The ventral stream links speech sounds to meaning through temporal networks. It is more bilateral than classical accounts suggest.

  • The dorsal stream links speech sounds to articulatory plans through temporoparietal and frontal regions. It is more strongly left-lateralised.

  • Inferior frontal regions help with speech planning, selection and grammatical processing. Temporal regions support lexical and semantic representations (the store of words and their meanings).

Clinical pattern

Typical language findings

What it suggests about the network

Non-fluent aphasia

Effortful speech with reduced grammar. Comprehension may also be impaired

Usually damage to left frontal regions and connected networks

Fluent receptive aphasia

Fluent speech that carries little information, with impaired comprehension

Usually posterior temporal network damage

Conduction aphasia

Repetition impaired out of proportion to other skills, with phonological (speech-sound) errors

Disrupted auditory-motor integration

Semantic impairment

Loss of knowledge of words and concepts

Anterior temporal network dysfunction

A functional schematic rather than an anatomical tract map. Language depends on interacting networks; the two routes do not assign comprehension and expression to isolated centres. Original illustration drawn in Python for MRCPsychiatrist; see images/ATTRIBUTION.md

Clinical distinctions

  • Aphasia is a disorder of language itself. Dysarthria impairs the motor execution of speech. Apraxia of speech impairs the planning of speech movements.

  • Assessment tests fluency, naming, repetition, comprehension, reading and writing separately. Do not judge language function from conversation alone.

  • Prosody and pragmatics (the tone of speech and how language is used in context) draw on distributed networks. The right hemisphere contributes to emotional tone and contextual meaning.

  • Formal thought disorder is a problem with how thought is organised and communicated. Do not automatically put it down to a focal aphasia.

Revision material for the MRCPsych examinations. Not clinical guidance, and not for use in patient care.