Language COG NRSC

This Week’s Learning Objectives: • Describe the major brain regions and pathways that support language comprehension and production. • Compare classical and contemporary models of language processing. • Explain how the brain processes meaning in spoken and written language, from words to sentences. • Understand how language disorders such as aphasia, dyslexia, and apraxia reveal how the system works. • Discuss how language organization varies across individuals, development, and evolution.

Human language is…

1. symbolic

2. rule-governed and generative

3. able to refer to the past, future, and hypothetical

4. built from hierarchical, recursive structure

5. suited for storytelling and complex social thought

It’s important to know that animals communicate through visual, auditory, tactile, and chemical signals.

Non-human primates don’t speak because…

They can’t produce human speech due to limited:

1. vocal anatomy

2. reduced fine motor control for speech

3. less voluntary control over vocalization

4. less precise breath control

They are still effective communicators as their calls are tied to specific emotional or social contexts.

Can apes learn human-like languages?

They can learn symbols or signs for objects, actions, and simple concepts but their communication is often…

1. short

2. tied to immediate context

3. limited in syntax and combinatorial complexity

However, they don’t show open-ended, generative structure of human language.

Language in the Brain System

• Human language may be a uniquely human cognitive system

• There is no clear animal model of full human language

• Neural basis is harder to study than vision or memory

• Knowledge comes from lesion studies, neuroimaging, and EEG

• Language is strongly lateralized in the brain

Evolutionary Clues about Language

• Humans show strong connectivity in left perisylvian language networks, with major dorsal and ventral pathways linking temporal, parietal, and inferior frontal cortex

• Similar pathways exist in other primates, but they are less extensive, with minimal projections into lateral and inferior temporal cortex

Aphasia

• Partial or complete loss of language abilities caused by brain damage

  • Commonly from stroke

    • distinct from motor speech disorders such as dysarthria and apraxia of speech

• Affects speaking, comprehension, reading, writing, and grammar

• Severity depends on lesion location, size, and individual factors and different syndromes show different patterns of impairment

Broca’s Aphasia: Nonfluent/Expressive Language Impairment

• Characterized by slow, effortful, telegraphic speech, and limited vocabulary

  • Speech articulation may be impaired, deficits to syntax and writing

  • Comprehension is generally preserved for simple sentences and impairs for syntactically complex ones

• Patients are often aware of their language deficits

• Most often associated with lesions in the left inferior frontal lobe (including Broca’s area…think of patient ‘tan‘)

Wernicke’s Aphasia: Fluent/Receptive Speech with Impaired Comprehension

• Speech well formed, but lacks meaningful content

• Severe impairments in comprehension of spoken and written language

• Patients are often unaware of their deficits

• Associated with damage in the left posterior superior temporal cortex and underlying white matter