Ch 11 - Language Cognitive Neuroscience

language output requires

coordinated motor movements and precise temporal control to produce speech, writing, or signs

left hemisphere

grammar, vocab, literal meaning

right hemisphere

emotional and contextual aspects of language, incl prosody, tone of voice, figurative language, and humor

aphasia

an acquired language disorder involving impaired language COMPREHENSION and/pr production, even though articulatory mechanisms are intact

dysarthria

a motor speech disorder caused by impaired control over articulatory muscles

speech apraxia

a motor speech problems via motor planning or programming of movement of articulation

anomia

a form of aphasia characterized by an inability to name object (the tip-of-the-tongue problem)

broca’s aphasia

known as anterior aphasia, nonfluent aphasia, or expressive aphasia

problems with speech production and some comprehension deficits involving complex syntax

difficulty finding appropriate words and organizing them into sentences during speech production

variability in speech output: words, phrases, unintelligible speech; often telegraphic (containing primarily content words)

Wernicke’s Aphasia

known as posterior aphasia or receptive aphasia

deficits primarily involves language comprehension

speech is fluent but may be nonsensical with impaired meaning and word selection

damage to posterior regions of the superior temporal gyrus and may involve adjacent posterior temporal and parietal regions or underlying white matter tracts

arcuate fasciculus

the bundle of axons that connect Wernicke’s and Broca’s areas

Conduction aphasia

understand spoken and written language and recognize their speech errors but cannot correct them; problems with spontaneous speech, repeating speech, and incorrect word use

Mental Lexicon

meaning; mental store of information about words

• semantic info

• syntactic info (how words are combined)

• details of word forms (spelling and sound patterns)

phonological form: orthographic form

sound: vision

language comprehension includes 3 general functions:

lexical access, lexical selection, lexxical integration

semantic network model

word meanings are represented in a semantic network in which words(concepts), depicted as conceptual nodes, are connected to each other

dysarthria cases:

Amyotrophic Lateral Sclerosis (ALS) aka motor neuron disease, is a rare, progressive, and ultimately fatal neurological disorder

it causes the degeneration of motor neurons in the brain and spinal cord, progressively impairing the voluntary muscle movements involved in functions such as speaking, swallowing, and moving

phonemes

smallest units of sound that distinguish meaning

segmentation problem

identify individual words in a continuous stream of speech

prosodic information

use rhythm, stress, and pitch to help interpret speech

acoustic sensitivity is highest in where

primary auditory cortex - A1

left posterior inferior temporal cortex

involved in accessing and integrating semantic representations

alexia

a condition in which patients have difficulty or are unable to read words, even though other aspects of language are relatively preserved

visual word form area

is heavily interconnected with regions of the language system, including the inferior frontal, temporal, and inferior parietal cortices

3 Contextual Representation in Word Comprehension

1. Modular/autonomous models

2. Interactive models

3. Hybrid models

Modlar/autonomous models

language-processing modules operate separately and independently

Interactive models

context can influence word recognition even before sensory information is fully available by changing the activation levels of word-form representations in the mental lexicon

Hybrid models

lexical access is autonomous, but lexical selection can be influenced by contextual information

syntax

plays a critical role by organizing sentence structure and defining relationships between words

syntactic parsing

enable comprehension of novel sentences, including sentences not previously encountered or stored in memory

MTG & STG

middle temporal gyrus and superior temporal gyrus are important for mapping speech sounds onto word meanings

IFG

left inferior frontal gyri is involved in lexical selection among many candidates

N400 Wave

reaches its peak amplitude around 400 ms, with greater amplitude in response to semantically incongruent words or events,

specific to semantic analysis

P600 Wave

the P600 response aka the syntactic positive shift (SPS), thought to be elicited by hearing or reading grammatical errors and other syntactic anomalies

Electrophysiological Measures of Language Processing

1. prelinguistic sensory processing occurs early, as reflected by the P1 component at 100ms

2. orthographic analysis of written words is reflected by the posterior N1 component at approximately 150-200 ms

   1. Phonological/phonetic analysis occurs around 200-300 ms, as reflected by the PHONOLOGICAL MISMATCH NEGATIVITY (pMMN) in response to phonological incongruities in auditory and visual stimuli

Memory-unification-control (MUC) model

1. Memory: stores linguistic knowledge, including lexical and grammatical information

2. Unification: integrates phonological, semantic, and syntactic information to construct coherent representations

3. Control: coordinates language use with social interactions and communicative goals, including joint action (ex: taking turns during a conversation)

ventral pathway

connects the temporal cortex with the inferior frontal cortex and supports semantic processing

elementary combinatorial processes

combining words into simple phrases in language - in ventral pathway connecting the most ventral portion of the inferior frontal cortex

dorsal pathway

connects the auditory cortex with the premotor cortex (PMC) is involved in speech preparation

syntactic processing

the dorsal pathway connecting Broca’s area (BA44) with the superior temporal gyrus (STG) and superior temporal sulcus (STS)

macroplanning

deciding what to express (what message to communicate)

microplanning

deciding how to express it (how to formulate the message in words and sentences)

stages of word production

1. conceptual preparation

2. lexical selection

3. morphological and phonological encoding

4. phonetic encoding

5. articulation

speakers monitor their own speech by making use of their comprehension system

Hierarchical State Feedback Control (HSFC) model

proposes that speech motor control occurs at multiple hierarchical levels, with feedback loops operating at each level

allows real-time error detection and correction by compairing auditory targets and sensory feedback from the articulators with the intended speech output

uses a FORWARD MODEL to predict the sensory consequences of motor commands, helping the speaker anticipate and detect errors

lexigrams

abstract visual symbols used by a bonobo to communicate

arcuate fasciculus

a prominent projection of the arcuate fasciculus into the temporal lobe is significantly smaller or absent in nonhuman primates compared with humans

this anatomical difference may be relevant to the evolution of human language -left-hemisphere dominance and specialization

Explain Broca’s aphasia, Wernicke’s aphasia, and conduction aphasia in terms
of their characteristic symptoms and underlying neural substrates. How are these
three types of aphasia related in terms of the brain regions and neural pathways
involved in language processing?