Neuropsychology: The Speaking Brain Flashcards
Which steps are involved in speech comprehension?
-Speech sound heard
-Early auditory processing
-Recognize speech sounds
-Recognize spoken words
-Retrieve word meaning and parse and comprehend sentences
-Integrate with knowledge about speaker and word
What two concepts are important in spoken word recognition?
-Phonological lexicon
-Lexical acces
What is phonological lexicon?
-Concept in spoken word recognition
-Store of abstract speech sounds that make up known words
What is lexical acces?
-Concept in spoken word recognition
-Process of matching perceptual description of word on to stored memory description of that word
What is the cohort model of speaking?
Model for recognizing spoken words
-All candidates considered in parallel
-Candidates eliminated as more evidence available in speech input
-Uniqueness point occurs when only 1 candidate remains
-Uncommon words activated less (speech > species)
-However: semantic context does not alter pattern
-Suggests semantics occurs late (after spoken word recognition)
What neural evidence is there for semantics coming after word recognition?
-N400 in ERPs
-N400: negative value that occurs 400msecs after stimulus onset
-Results
–>Lowest N400 in semantically correct sentence
–>Highest N400 in semantically incorrect sentence
-Explains why semantic context has not much effect on spoken word recognition
What is semantic memory?
-Important in recognition of language
-Represents conceptual knowledge of world: meaning of words and objects, factual knowledge
-Central role in human cognition: at interface of language, memory and perception
What are characteristics of models of semantic memory?
All models propose that concepts are comprised of constellation of constituent features, models of semantic memory differ ito:
-What format do features take: amodal vs grounded
-How features are organised: hierarchical vs non-hierarchical
-How category info is represented: in addition to feature level info vs purely emergent properties of features
What format of features can the semantic memory have?
-Amodal concepts
-Grounded/embodied concepts
-Combination: Hub-and-Spoke model
What are amodal concepts of the semantic memory?
-Amodal representations: representations of concepts exist independent from perception of concepts and independent of input/output modality
-Originally theories of semantic memory thought that semantic memory was amodal
-Symbol grounding-problem
–>Concepts not defined in terms of each other
–>Concepts defined in terms of experiences and interactions with world
What are grounded/embodied concepts of the semantic memory?
-Grounded representations: representations of concepts exist in terms of experiences and interactions with world
–>Reaction to symbol grounding problem with amodal representations
-Perceptual systems distributed in brain, so semantic knowledge also distributed
-Not necessarily linked to innate knowledge, but rather to shared experience
-Problem for grounded/embodied concepts: abstract concepts, but some concepts can be explained
–>Claim that number and time concepts are processed spatially
–>Emotions may be embodied feeling states linked to certain contexts/stimuli
What is the Hub-and-Spoke model of the semantic memory?
Patterson et al. (2007)
-Combination of amodal and grounded concepts
–>Amodal semantic hub in anterior temporal lobes, important for atypical features
–>Grounded/embodied semantic spokes in rest of brain, sustain typical categorization
-People with damage in hub can have semantic dementia
What is semantic dementia?
-Damage to anterior temporal lobe (“hub” of semantic memory)
–>”Spokes” sustain typical feature probabilities, but not knowledge of exceptions
-In drawings: omitting features of model important for distinction
-In categorization: errors in atypical examples of categories
What is Collins & Quinlan’s (1969) model of semantic memory?
-Early, (amodal) hierarchical model of semantic memory
-Distance effects: faster in classifying robin as bird than as animal
-Criticism
(image)
What criticism is there for the Collins & Quinlan’s (1969) model of semantic memory?
-Distance effects could depend on frequency of co-occurrence rather than hierarchy
-Not all concepts have hierarchical relationship
What clear effects of hierarchy have been seen in brain activity in fMRI-studies?
Rogers et al. (2006): sub-ordinate and super-ordinate info in brain (substrates)
-fMRI study of naming and categorisation
-Processing at specific level activates anterior temporal pole (same region as in semantic dementia), but other levels activate posterior temporal lobes
-Patients with ATL (anterior temporal lobe) damage: retain ability in superordinate classification, but struggle more with item and subordinate-level classifications
What different views are there on category specificity in semantic knowledge?
-Animate-inanimate category specificity
-Sensory-functional distinction
What evidence is there for animate-inanimate category specificity in semantic knowledge?
-Warrington & McCarthy (1983): patient with good knowledge of animals, foods and flowers, but not good knowledge of inanimate objects
-Warrington & Shallice (1984): patients with good knowledge of inanimate objects, but not good knowledge of animals, foods and flowers
-Amodal deficits: impairments found at comprehending pictures and words, naming pictures and matching pictures with words
-Explained using sensory-functional distinction: certain regions process certain features, so no categoric selective regions
-Animals defined by sensory properties, inanimate objects (especially tools) defined by function
What evidence is there against sensory-functional distinction in semantic knowledge?
-Evidence:
–>Some patients with category-specific impairments don’t show difference between knowledge of sensory vs functional facts
–>Some patients have selective difficulties in comprehending sensory properties, but don’t have category-specific impairments
–>Some patients with particularly selective deficits for 1 category
-Suggests categories and features are represented separately (and can be damaged separately) rather than 1 being based upon other
What characteristics are important for understanding and producing sentences?
-Broca’s area and sentence processing
-Relation between syntax and semantics
What is syntax?
-Part of parsing process: putting words into sentences
-Syntax: structure
What is semantics?
-Part of parsing process: putting words into sentences
-Semantics: meaning
How is Broca’s area related to sentence processing?
-Broca’s area important for syntax (not related to speech production)
-Broca’s aphasia
-Posterior regions of Broca’s: important for complex syntax
-Anterior regions of Broca’s: important for working memory and control of complex semantics
What is Broca’s aphasia?
-Damage in Broca’s area
-Impairment in speech comprehension and production, but only when syntax is crucial
-Syntax problems (structure), also in non-language syntax
-Linked to symptom of agrammatism
What is agrammatism?
Halting speech production that is devoid of function words, bound morphemes and often verbs
What relation is there between syntax and semantics?
-Interaction between syntax and semantics important for creating sentences
-Bias in humans: considering most logical sentence given what has been read
–>Problem with garden path sentence
–>Bias in humans: semantics can bias syntax
What is the problem with garden path sentences?
-Early part biases wrong interpretation
-Involves syntactic reanalysis on encountering unexpected word
-In EEG: P600 linked to these words
–>N400 linked to unexpected semantic context
What is P600 in an EEG?
-Positive value that occurs 600msecs after onset stimulus
-Stronger P600 activation in
–>Ungrammatical sentences
–>Grammatical but unexpected/challenging (garden path) sentences
–>Even when sentence semantically meaningless
-Might reflect syntactic analysis or reanalysis
What is Levelt’s discrete stages model for phonological code for retrieving and producing spoken words?
-After forming communication intention to speak, person has to decide which words to select: 3 stages
-Discrete stages have no interaction
What 3 stages are there in Levelt’s discrete stages model?
-Lexicalization
-Lemma retrieval
-Lexeme retrieval
What is lexicalization according to Levelt’s discrete stages model?
-Selecting single word based on meaning person wishes to convey
-Choosing semantic concept
What is lemma retrieval according to Levelt’s discrete stages model?
-Choosing grammatical properties of word
-Access syntactic properties
What is lexeme retrieval according to Levelt’s discrete stages model?
-Choosing actual word form
-Phonological encoding (syllabification, prosodification)
What evidence is there in favor of Levelt’s discrete stages model?
-Explains tip-of-tongue phenomenon
-Explains patients with anomia
-Discrete stages because: sheep primes goat (competition at semantic level), goat primes goal (competition at phonological leven), but sheep doesn’t prime goal (two stages of competition don’t interact)
How does Levelt’s discrete stages model explain the tip-of-the-tongue phenomenon?
-Retrieval of lemma completed
-Partial or no retrieval of lexeme
What is anomia?
-Pathological word-finding problems
-Problem with choosing specific word: distinguishing between concepts
-Problem with articulation: unable to retrieve phonological info
What evidence is there against Levelt’s discrete stages model?
High proportion of mixed errors
-With both semantic and phonological characteristics
-Suggests interaction between levels
-Explained by Dell’s interactive stages model: interactivity between stages causes errors
What problem can there be with articulation?
Verbal dyspraxia
How is Broca’s area involved in speech production?
-Involved in over and covert planning of speech production, but no motor commands reside there
-Evidence for mirror neurons in Broca’s could be consistent with this
What is verbal dyspraxia?
-Apraxia of speech: can sound like foreign accent sometimes
-Articulation problems
-Lesions in insula and basal ganglia (NOT Broca’s)
What are characteristics of aphasia?
-Encountered a lot in clinical practice
-Inability to comprehend or formulate language due to brain damage
-Different criteria for diagnosis
-Exclusion criteria
-Language problems
-Distinction in common types of aphasia
What criteria are there for a diagnosis of aphasia?
-Acquired language disorder caused by localized brain damage
-Problems with understanding/producing language
-Involves multiple modalities and multiple linguistic components
What exclusion criteria are there for aphasia?
-No developmental disorder: specific language impairment
-No general psychological factors, no diffuse deficit: dementia
-No specific speech production disorder
What language problems can there be in aphasia?
-Word finding problems
-Omission or substitution of words: production of paraphasia
-Deficits in fluency, grammar, comprehension, repetition, reading and writing
What word finding problems can there be in aphasia?
-Semantic anomia: deficit in activating lemma’s
-Word form anomia: deficit in activating phonological form
What problems in omission or substitution of words can there be in aphasia?
Production of paraphasia
-Lexical/verbal paraphasia: substitution with existing word
-Phonological paraphasia (stoon instead of spoon)
-Neologism: new words
What distinction can be made in common types of aphasia?
-Fluent aphasia: Wernicke’s aphasia
-Nonfluent aphasia: Broca’s aphasia
-Global aphasia
What is fluent or Wernicke’s aphasia?
-Ability to speak in complete but nonsense sentences, with paraphasias and neologisms
-Difficulty in understanding speech
-Damage in left temporal lobe
What is nonfluent or Broca’s aphasia?
-Ability to speak with short phrases, but grammatical mistakes and omissions
-Damage in left frontal cortex
-Often also motor problems
What is global aphasia?
Problems in all aspects of language
