PY2507.5 ~ {Ataxia, Apraxia & Agnosia}
schematic model of single word processing
from perception to comprehension starting with auditory input then its transformed into phonemes thismphonological representation needs to be held for a long time as the brain looks for any previous representations to then associate it with that to create a word or semantic meaning
how does the schematic model of auditory processing go
auditory input ± auditory-phonological conversion ± phonological input buffer ± phonological input lexicon ± semantic system
impairments speech perception
so damage to any of the stages results in different kinds of linguistic impairments - which include cortical deafness ± word deafness ± lexical deafness ± semantic deafness
cortical deafness
results from damage to auditory parts of brain [areas 41 & 42] - Heschl's gyrus [lesions to AC don't result in deafness but more subtle deficits in sound freq + intensity discrimination]
loss of perception is caused by damage to what areas
primary visual + somatosensory cortex
what areas are involved in processing sounds
areas 41,42 {Brodmann areas] hidden within the lateral fissure + area 22 on lateral surface of the TL is also partially involved in processing sounds [Wernicke's area]
bilateral lesions in cortical deafness - what does it result it
patients can still typically recover, initially patients may loose sound awareness but this is generally recovered
word deafness [aka verbal agnosia]
when the auditory-phonological conversion is damaged have severe difficulties in understanding linguistic sounds [speech or phonological representation] - but the patients are not deaf
word deafness symptoms
normal perfomance in audiometric tests + can identify melodies or enviro sounds + can understand written language + complain that words are spoken too fast or sound foreign + struggle with repetition & venues with lots of noise like the airport
pure word deafness experiments results
probs with repetition of words & non-words + words in isolation understood better than words in sentences + vowels discriminated better than consonants which involve faster changes + deficit in processing rapidly changing non-speech stimuli
what do lexical + semantic word deafness have in common
damage happens later on, so they can decode acoustic inputs but they can't make contact with lexical representations so the impairment occurs after phonological representation in addressing the lexicon
lexical deafness
[they can repeat the word the word table but can't point to it or define it] so poor lexical decision + poor comprehension
semantic deafness
good auditory lexical decision + poor comprehension [so damage can occur before phonological input lexicon or after - which is before the semantic system]
lexical decision task
psych experiment used to study how people recognize + process words. participants are presented with a series of stimuli then asked to quickly decide whether each one is a real word or a non-word
lexicon
mental repository of words + their meanings that a person knows + can access when needed - like an internal dictionary
the semantic system
component in our mind that represents meaning of words
Levelt, 1992 - semantic system
a single meaning corresponds to each word [not as common]
Dell, 1988 - semantic system
more common - meanings are represented decomposed in a number of semantic features which are shared across words - these shared features explains semantic priming + occurrence of semantic errors in aphasia
in the cog architecture what position is the semantic system
occupies central position since it is used across tasks [spoken language, comprehension + production]
semantic impairments characteristics [inputs]
categorizing pics or words in semantic cats if they're close enough + deciding which are the right attributes corresponding to a word or depicted item + in word-picture matching, words with similar meanings are confused
semantic impairments characteristics [outputs]
semantic errors in: pic naming + spontaneous speech + across diff output modalities [both in spoken & written production] + cat specific deficits [patients show worse comprehension + naming for living over non-living cats]
anomia
difficulties arise when someone cant go from word meanings to phonological lexicon, so finding the right word for a concept [having a word on the tip of the tongue]
defining characteristics of anomia
no problems with repetition + susceptible to cueing + probs more severe for uncommon words + no probs in word-picture matching tasks
errors made in anomia
include 'don't know' circumloctutions + few or no phonological paraphasias + semantic errors if the deficit is between semantic system & the lexicon but restricted to one modality
semantic error
mistake related to the meaning of words [saying apple when you mean orange]
phonological impairments [conduction/wernickes/jargon] aphasia
sound form of words is produced in an inaccurate or jumbled up fashion [in extreme cases jargon target is completely unrecognizable] mild version is conduction whilst most severe is jargon aphasia
defining characteristics of phonological impairments
deficit across all tasks involving spoken output [reading + repetition + spontaneous speech + pic naming] + not susceptible to cueing + no effect of grammatical class, no or weak effect of freq, effects of length
phonological impairments main error types
phonological paraphasias + neologisms [more complex transformations - characteristic of jargon aphasia]
difference between phonological deficits and anomia
impaired retrieval to phonological lexicon = anomia [getting to word level is the prob]
impaired retrieval to phoneme = pd [getting word sounds is the prob]
2 layers in the lexicons
representing word units [addressed from semantics] or representing phonemes and their order addressed from the word nodes
apraxia speech
prob in articulatory planning [strong integration between the sounds [coarticulation] which requires a lot of planning] , sound errors made, cues don't help, little effect of semantic variables
why is apraxia difficult to distinguish from phonological impairments
they both struggle with sound errors in speech, defining characteristic of apraxia is production of phonetic errors + phonological errors
diff between apraxia & phonological impairments
pi = sounds are incorrectly selected but produced correctly
a = sounds produced in a distorted way [slurred] producing phonetic errors
phonetic errors vs phonological errors
pl - arise from prob with phonological representation prob in selecting the right phoneme [speech sound]
pt - prob is with realization of this phoneme [having an accent speaking english if you're from italy]
anarthria or dysarthria
often from non-cortical lesions [upper motor neurons] prob in moving muscles that initiate articulatory planning, motor-sensory impairment + impairments are much more consistent across most words, some phonemes are always mispronounced regardless of context + make little attempts to self-correct
anarthria / dysarthria characteristics of voice of patient
strained-strangled voice [spastic dysarthria]+ mono-tonic + reduced loudness [hypokinetic dysarthria] + hoarseness + slurred articulation
sentence processing
in order to understand a sentence you need to understand meaning of individual words, word order + inflections & function words [prepositions, articles, pronouns]
impairments of sentence comprehension
aphasic participants are fine in understanding content words but struggle with understanding grammar [so semantically irreversible sentences] this is called aggramatic comprehension
impairments of sentence production
sentences lack any grammatical structure, inflections + function words omitted [speech has telegraphic quality] the opp of anomia
STM - short term memory
capacity to keep simultaneously in mind a certain amount of info, capacity is linked to working memory cause info held in STM usually used to carry out a cog. task
impairments to STM verbal info vs visuo spatial
v = inability to learn new words + probs understanding particular types of sentences esp in conditions which slow down processing [noisy area then competency is reduced
vs = difficulties in orienting new enviros
how did dejerine describe dyslexia (1882)
alexia with agraphia [reading + spelling impairment] - lesion of [above wernickes area] angular gyrus of LPL and alexia w/o agraphia [disconnection syndrome] - lesion of LOL + splenium of corpus callosum
agraphia (1882)
seen as a result of a confusion state [back in the day before it was viewed as an actual impairment] which leads to probs of concentration and shifting of attention
dyslexia: Marshall and Newcombe (1973)
described diff error patterns corresponding to damage to diff cog components = surface + deep + phonological dyslexia
reading + spelling impairment = selective impairment
agraphia: Basso, Taborelli and Vignolo (1978)
described selective writing probs not secondary to either aphasia / apraxia, similar dissociations were described in reading + spelling
phonological dyslexia
trouble sounding out words using phonics + can still read familiar words but struggles with unfamiliar / non-words, because brain pathway that connects letters to sounds [phonological route] is damaged
surface dyslexia
trouble recognizing whole words by sight [esp irr words that don't follow typical spelling rules e.g. yatcht] + can sound out normal words using phonics, because brain's visual route- direct lexical route [for recognizing words instantly] is damaged
deep dyslexia
both phonological + visual route damaged + so reading familiar + unfamiliar + nonwords is difficult + make semantic errors saying word with a related meaning instead of actual word, because damage is more widespread in reading network
model of spelling to dictation [lexical semantic route]
auditory buffer kept in phonological input buffer then that auditory phonologocal representation connects with corresponding info in p lexicon that activates representation in semantic system then orthographic lexicon then graphemic buffer [translation]
orthographic lexicon
part of the brain that stores written forms of words [how words look when spelled]
from semantic system to orthographic lexicon [lexial -semantic route]
usually used when writing words so you think of a concept or meaning then you ss identifies meaning of concept then brain accesses ol to find out how word is spelled then motor system writes it down
surface dysgraphia
writing disorder where people rely on sounding out words but struggle with irr spelling, occurs when connection between ss and ol is damaged so yk what word means but can't remember how to spell it [esp irr + less common words] so you guess spelling and produce semantic neighbour or word that sounds similar
non-lexical route {phonological]
converting phonology into autonomy bit by bit, we know the sounds so we know that certain sounds correspond to certain combinations of letters [helpful when spelling irr word] we can then produce a plausible version of word.
graphemic buffer
after your brain figures out how a word is spelled [from ol] the gb temporarily stores letters in right order then your motor system uses info to write or say word
damage to graphemic buffer
you mix up, leave out or add extra letters, these errors are more common in longer wordsv[harder to hold them in memory] - person might know how word is spelled but will still make errors because buffer can't hold it properly
why is non-lexical route important
helps in spelling even novel words, esp in development when still learning to read and write, you can direct mental + memory resources to remeber irregularities in words
direct lexical route
brain's fast lane for reading [how we instantly recognize familiar whole words without needing to sound them out] straight from written word to mental dictionary [ol] to meaning [ss]
phonological dysgraphia
prob with spelling novel words, spelling ocurs through lexical route only, so good spelling at familiar words + so won't make phonological errors, hearing + speaking is fine as well [patient PR]
deep dsygraphia [patient JC]
spelling errors through lexical route + access from semantic system is reduced, so in writing: semantic + morphological errors + can spell easier words + inability to write non-words but no semantic errors in spoken picture naming, repeptition + reading
peripheral dysgraphia
writing disorder that affects physical process of writing [so ss, ol or meaning but getting letters onto page correctly so motor output stage]
allographic + afferent / spatial
allographic dysgraphia
better oral than spelling + mixing fonts [trouble producing correct letter shapes but spelling is fine but letter formation is inconsistent]
afferent dysgraphia
stroke errors + deletions or additions of letters + strokes + wide left margin & sloping writing + often but not always RH lesion & concurrent with deficits of visual attention
central vs peripheral dysgraphia
c - prob with language system [spelling: ol, word meaning:ss + grammar + sound-letter link: p route]
p - prob with motor output or letter formation system [actual act of writing]
difference between lexicon and semantic system
lexicon = vocabulary, a collection of words and their meanings, while semantic system = broader framework that analyzes and understands the relationships and meanings within that vocabulary.
alexia
an acquired reading disorder resulting from brain damage, causing the inability to read despite having previously been able to do so
articulatory planning
cognitive process of sequencing and coordinating the physical movements of the speech organs [tongue, lips] to produce speech sounds