Speech Perception and Concepts

Speech Perception

• Speech perception involves three key components: novel auditory categories, sine-wave speech sounds, and familiar phonemes.
• Processing shifts to more basic functions in the posterior brain areas.
• Speech comprehension follows a hierarchical structure: phonemes to words, then to phrases. More complex functions are processed further in the brain (even bilaterally).
• A study across 45 languages (12 language families) shows a consistent pattern of activity in the anterior temporal lobe during language processing.
• Activity in the left hemisphere (LH) language network is assessed, measuring native language comprehension, degraded native language comprehension, and comprehension of unfamiliar languages.
• Working memory and mathematical tasks showed no initial activity (likely controlling for non-language cognitive processes).

Concepts

• Concepts are perceptually-grounded symbols, combining perceptual, motor, and other representations related to experiences.
• Concept categories are structured by family resemblance–similarity among members.
• Concept features are probabilistic, not necessary (e.g., chairs).

Convergence and Divergence in Semantic Processing

• Semantic processing involves a model controlled by higher-order association cortices.
• This model has different components for motor, somatosensory, visual, and auditory information.
• Recognition involves convergence of information.
• Semantic cognition involves divergence or pattern completion, requiring simulation and re-enactment of the item.

Semantic Hub

• The semantic hub integrates various representations, acting as the ultimate convergence zone.
• Specialized hubs develop progressively during brain development.
• Damage to the semantic hub affects overall semantic representation.
• Damage to a spoke (specific category) affects knowledge of that category.

Semantic Dementia

• Semantic dementia demonstrates breakdowns in semantic knowledge.
• It involves progressive neurodegeneration in the anterior temporal lobe, causing damage to the semantic hub.
• The impairment also manifests in drawing, with degeneration of specific characteristic details.

Sensory-Functional Distinction

• Sensory and functional features distinguish knowledge types.
• Living things (e.g., animals, fruits) are more defined by sensory characteristics (color, shape, legs).
• Inanimate objects (e.g., tools, furniture) are defined by their functions, related actions, and the way they are used.
• Tests showed converging evidence, such as impairments in knowledge about gemstones and instruments being similar to the impairments in living things, while body part knowledge was impaired in non-living things.
• Knowledge of various categories is situated in multiple parts of the brain (primarily temporal and parietal).

Language Processing Locations

• Speech production is associated with a dorsal stream.
• Speech comprehension utilizes the ventral stream.
• These brain regions are connected by white matter tracts.

Language Impairments

Articulatory Planning

• the precise coordination and motor execution of individual speech sounds or phonemes.
• Segment-level deficits show distortions in phonemes (e.g., "Ghost" to "Goath").

Sentence Planning

• the broader organisation and construction of sentences during speech, including word order, grammar, and fluency.

• Segment-level deficits show distortions in phonemes.

• Sentence-level deficits involve issues with global fluency, informativeness, and sentence components like word choice and utterance length.

Language Processing Sequences

• Sentence planning is potentially akin to action planning.
• It follows specific sequences, involving planning and an execution phase.