Language and Semantic Knowledge Systems

What is a concept?

Perceptually-grounded symbols, conjunction of perceptual, motor etc reps involved in experiences with instances of the concept 

What is family resemblance?

Concept categories are structured around similarity (perceptual-motor or amodal) 

• BUT features are probabilistic, not necessary/sufficient 

How was Malik-Moraleda’s (2022) study into universal attributes of language conducted (design)?

• Language localizers 

  • English localizer: reading sentences vs. nonwords. 

  • Native-language localizer (critical task): 

    • Listening to short passages from Alice in Wonderland in: 

      • Their native language 

      • An acoustically degraded version (speech-like but unintelligible) 

      • An unfamiliar foreign language 

• Non-linguistic control tasks 

  • Spatial working memory task 

  • Arithmetic (math) task 

• Naturalistic cognition 

  • Listening to a coherent story in the native language 

  • Resting-state scan 

• Properties tested: 

  • Topography – location in frontal, temporal, and parietal cortex 

  • Left-hemisphere lateralization 

  • Functional integration – strong correlations among language regions 

  • Functional selectivity – stronger responses to language than to non-linguistic tasks 

What were the findings of Malik-Moraleda’s (2022) study into universal attributes of language?

• The neural architecture supporting language is universal, despite dramatic surface-level differences between languages 

• Universal features: 

  • Consistent anatomical location 

  • Predominant left lateralization 

  • Strong internal functional connectivity 

  • Selectivity for linguistic processing 

    • These properties likely reflect shared biological constraints shaped by evolution 

Neural basis of speech perception (diagrams)

Speech comprehension (diagrams)

How are semantic features distributed?

Across modality-specific systems 

• Visual features → ventral temporal cortex 

• Auditory features → temporal cortex 

• Motor features → frontoparietal cortex 

What does recognition involve?

Convergence

What is semantic cognition? What does it involve?

Brain's ability to acquire knowledge across a lifetime, store meanings of words/objects/people/events, generalise that knowledge to new situations, flexibly use meaning to guide (non)verbal behaviour 

• Divergence or pattern completion

• Hub + spokes → hub in anterior temporal lobes

What does semantic representation involve?

The hub-and-spoke model 

• Concepts are built from spokes (modality-specific systems e.g vision, emotion, lang) + hub (transmodal region that integrates info across modalities) 

What is the semantic hub?

• Located in the anterior temporal lobes (ATL), bilaterally 

• Integrating modality-specific reps/multimodal features

  • Allows generalization across contexts (e.g. knowing that dogs bark even if you’ve never seen this dog) 

• Supports abstraction beyond surface similarity 

• Enables category membership judgments

• Applies to objects, actions, + abstract words 

• Ultimate convergence zone 

What is key evidence for the semantic hub?

• Semantic dementia

  • Neurodegenerative disorder 

  • Follows category structure → progressive loss of specific info whilst retaining general info (breakdown of semantic knowledge)

  • Starts in anterior temporal lobe 

  • Patients show impairment across all concept types, effects driven by familiarity, typicality + specificity, highly consistent deficits across tasks + modalities 

• fMRI (with distortion correction): ATL activates for meaning across modalities 

• TMS: disrupting ATL slows semantic processing across domains 

• Electrocorticography: ATL shows early semantic coding (~200 ms) 

• Computational models: hub damage reproduces SD-like patterns 

What does semantic cognition support?

• Understanding language 

• Recognizing objects 

• Making inferences (e.g. what objects are for) 

• Using tools appropriately 

What does semantic cognition depend on?

The controlled cognition framework:

• Semantic rep system

• Semantic control system

What is the semantic representation system?

• Stores conceptual knowledge 

• Builds abstract, generalisable concepts from experience 

What is the semantic control system?

• Regulates how semantic knowledge is accessed/used 

• Shapes meaning according to task, context + goals 

What does semantic control enable us to do?

• Focus on task-relevant meanings 

• Suppress dominant but irrelevant associations 

• Retrieve weak or unusual meanings 

• Adapt meaning to context 

  • E.g. using a knife differently (cutting, spreading, scooping) 

What does semantic control rely on?

A distributed network 

• Ventral and inferior prefrontal cortex (vPFC / IFG) 

• Posterior middle temporal gyrus (pMTG) 

• Intraparietal sulcus (IPS) 

• Pre-SMA and anterior cingulate cortex 

What is semantic aphasia?

• Damage: prefrontal and/or temporoparietal regions 

• Problem: failure to control semantic activation 

• Errors: inconsistent, context-dependent 

• Cueing: helps a lot 

• Strong susceptibility to distraction and interference 

What is semantic dementia?

• Damage: ATL hub 

• Problem: loss of representations 

• Errors: consistent, frequency-sensitive 

• Cueing: does not help 

  • Double dissociation supports separate systems for rep + control 

How do computational models relate to semantic control?

Show that a separate control system is necessary to preserve generalisation + allow flexible, task-specific behaviour 

• If task context is mixed directly into semantic reps then concepts fail to generalise properly 

• Representation = stable structure 

• Control = flexible modulation 

What are some other semantic contributors?

• IFG: semantic control + conflict resolution 

• Angular gyrus: integrative semantic functions 

• Posterior MTG: lexical semantic reps 

What are category-specific semantic deficits?

Semantic deficits following stroke can affect some categories more than others 

• Could be due to different feature types: sensory-functional distinction 

  • Animals + fruit: defined more by sensory knowledge (colour, shape, four legs, etc.) 

  • Inanimate objects (e.g. tools): defined more by their functions + associated actions 

  • Converging evidence: gemstones + musical instruments tend to be impaired with living things (sensory) but body parts tend to be impaired with nonliving things (functional)

• Explains why some patients have general semantic loss (e.g. semantic dementia) + others show category-specific deficits (e.g. tools vs animals) 

  • Hub damage → category-general impairment 

  • Spoke damage → category-specific impairment

What is there a double dissociation for?

Living things + nonliving things

What does sentence comprehension rely on?

Left-lateralised distributed network 

What are the components of the left-lateralised distributed network involved in sentence comprehension?

• Posterior MTG 

• Posterior IFG (Broca’s area) 

• ATL 

• Temporoparietal junction/AG

• Phonological loop 

What is the function of the posterior MTG?

• Accesses morphosyntactic features 

• Reps grammatical category alternatives

What is the function of the posterior IFG (Broca’s area)?

• Top-down selection 

• Resolves ambiguity 

• Possibly supports sequencing or control 

  • Theoretically controversial due to mixed lesion evidence 

What is the function of the ATL?

• Combinatorial parsing 

• Compositional semantic integration 

What is the function of the temporoparietal junction/AG? 

Participant role assignment (“who did what to whom”) 

What is the function of the phonological loop?

• Supports comprehension of complex sentences 

• Not strictly necessary in all cases 

What is involved in sentence production?

• Less understood 

• Agrammatism is heterogeneous, not a single syndrome 

• Lesions vary widely across patients 

• fMRI suggests shared grammatical resources for comprehension + production 

  • Posterior MTG + IFG likely contribute to both 

• Unresolved precise functional roles 

What does perception of spoken language involve?

• Early auditory processing

  • Spectrotemporal analysis in STG 

• Phonological processing

• Hemispheric differences

Outline the process of auditory processing

Cochlea → brainstem → thalamus → primary auditory cortex (Heschl’s gyrus) 

What does phonological processing involve?

• Posterior STG + STS form a phonological network 

• Hierarchical processing from simple sounds to word forms 

• Representations are distributed, not localized to single spots 

Describe the differences between hemispheres

• LH → rapid temporal processing (phonemes) 

• RH → slower temporal integration (syllables, prosody) 

In perception of spoken language, what occurs after phonological recognition?

Processing splits in 2 → dual-stream model

What is are the dual streams of spoken language?

• Speech production: dorsal stream (inferior parietal and frontal) 

  • Related to skilled action (dorso-ventral visual stream) + action planning 

• Speech comprehension: ventral stream (superior temporal) 

What is the dorsal stream?

• Sound → action

• Area Spt → frontal articulatory regions 

• Supports repetition, verbal short-term memory, speech learning 

• Strongly left-lateralized 

What is the ventral stream?

• Sound → meaning

• Posterior MTG → anterior temporal lobe (ATL) 

• Supports lexical–semantic processing 

• Bilateral but left-dominant 

Dual streams of spoken language deficits (diagrams)

How does motor involvement relate to perception of spoken language?

Exists but is modulatory, not essential + remains debated 

Language sub-systems (diagram)

What does spoken language production involve?

1. Conceptual selection 

2. Morphosyntactic processing 

3. Phonological encoding 

4. Syllabification and articulatory planning 

5. Motor execution

What does conceptual selection involve?

• Meaning selected, strongly involving the ATL 

• IFG contributes control + selection

What does morphosyntactic processing involve?

Likely involves mid/posterior MTG 

What does phonological encoding involve?

• Posterior STG/STS retrieves phoneme sequences 

• Debate over single vs dual phonological lexicons 

What does syllabification and articulatory planning involve?

• Posterior IFG + anterior insula 

• Frequent syllables may be stored as motor “chunks” 

What does articulatory planning involve?

Segment-level deficits

• Ghost → ‘goath’

• Phoneme distortions

What does sentence planning involve?

Sentence-level deficits

• Global fluency + informativeness

• Mean length of utterances

• Words in sentences

Sentence planning as action planning (diagrams)

What does motor execution involve?

Ventral precentral gyrus (somatotopic vocal tract map) 

What is the function of the auditory feedback loop?

Compares expected vs actual sound 

What is the function of the somatosensory feedback loop?

• Monitors vocal tract sensations 

• Allows rapid, unconscious correction 

What does reading involve?

A central visual processing hierarchy 

• Visual cortex → occipitotemporal regions → visual word form area (VWFA) 

What are the properties of the visual word form area?

• Invariant to size, font, case, position 

• Prefers real words over pseudowords 

• Script-general (alphabetic, logographic, Braille) 

• Develops through learning (not evolution)

What occurs after VWFA recognition?

• Phonology accessed via perisylvian speech circuits 

• Semantics accessed via inferior temporal and ATL systems 

How are regular and irregular words read?

• Regular → sublexically

• Irregular → may rely more on semantics (controversial)

What does writing involve?

• Orthographic retrieval

• Graphemic buffer 

• Allographic conversion

• Graphomotor planning 

What is orthographic retrieval?

Abstract grapheme strings accessed in the VWFA 

What is a graphemic buffer?

• Maintains letter identities + order 

• Controlled by posterior IFG 

What is allographic conversion?

Abstract letters → specific forms 

What is graphomotor planning?

• Stroke sequences for handwriting 

• Frontoparietal motor regions 

How does typing relate to writing?

Uses related but distinct mechanisms

What aspect of the brain does language primarily rely on? How is this area organised?

Cerebral cortex 

• Organised by: 

  • Lobes (frontal, temporal, parietal, occipital, insula) 

  • Gyri and sulci 

  • Cytoarchitectonic regions (e.g. Brodmann areas) 

What does language depend on?

Large-scale distributed networks → don’t work in isolation

• Communicate via white-matter pathways 

• Broca’s area (left IFG) + temporal lobe regions are highlighted as major hubs → BUT always as parts of wider circuits (not standalone “modules”)

How are brain mapping methods used?

Converging evidence across methods (as no single method is sufficient)

What are the different brain mapping methods?

• Hemodynamic imaging (PET, fMRI)

• Lesion studies (neuropsychology)

• Transcranial magnetic stimulation (TMS)

• Electrophysiology (EEG, MEG, intracranial recordings)

Evaluate hemodynamic imaging

• Good spatial resolution 

• BUT poor temporal resolution, correlational

Evaluate lesion studies

• Provide causal evidence 

• Reveal dissociations between language components 

• Have improved due to better imaging and testing methods 

Evaluate TMS

• Temporarily disrupts or facilitates specific regions 

• High temporal + spatial precision 

• BUT limited to surface cortex 

Evaluate electrophysiology

• Excellent temporal resolution 

• Closer to neural firing 

• BUT often limited in spatial precision or availability