llimba Flashcards
where is language located
over 95% of humans have left-hemisphere specialisation
what is the role of the right hemisphere in language
right hemisphere has some verbal abilities but these are limited
- how do we know that language is mainly represented on the left side of the brain
in the 19th century, paul broca and carl wernicke idenitifed specific areas of the brain involved in language:
- brocas area (LEFT FRONTAL LOBE) is responsible for speech production
- werncieks area (LEFT TEMPORAL LOBE) is critical for language comprehension
both areas are in the left hemisphere
- how do we know that language is mainly represented on the left side of the brain
split-brain studies
in individuals with surgically severed corpus callosums (e.g. for epilepsy treatment), experiments show that language is predominantely processed in the left hemisphere
e.g. if an object is presented to the left visual field (processed by the right hemisphere), individuals often cannot verbally name it, but they can identify it non-verbally.
e.g. they are presented with word key in their left visual field, and name it ring which is what they see in their right visual field but pick up key
- how do we know that language is mainly represented on the left side of the brain
stroke patients
most stroke-induced language deficits (aphasia) are linked to damage in the left hemisphere, reinfocring its domaincnce in langugae
- how do we know that language is mainly represented on the left side of the brain
neuroimaging studies
studies often observe greater blood flow and neural activation in the left hemsiphere during language related tasks comapred to the right hemsipehre
- how do we know that language is mainly represented on the left side of the brain
Wada test
in this procedure, a short-acting anaesthetic is injected into one hemsiphere of the brain
when the left hemisphere is anesthetized, most people become temporarily unable to speak, confirming its role in language
what is the role of the right hemisphere in language
for processing the intonation, rhythm and emotional tone of speech, collectively known as prosody
damage to the right hemispehre can result in:
- aprosodia: difficulty interperting or producing the emotional tone of speech
what are the different clinical manifestations of aphasia
broca aphasia
wernicke apahsia
conduction apahsia
transcrotical aphasia
what is aphasia
language comprehension and production disroders following brian damage
what are the different approaches to studying language disorders
study brain areas involved - group studies
study breakdown of cognitive process - case studies
what is brocas aphasia
difficulties in planning and organising speech
problems with speech prpoduction
what is brocas aphasia related to
the articulation problem is related to the motor control of speech
this is different from dysarthria, which is often related to subcortical areas (such as basal ganglia). Dysarthria is an impairment of all speech sound indiscriminately as there is a loss of control for articulator muscles
what are the different characteristics of brocas aphasia
anomia - several pauses
semantic paraphasia - saying the wrong word e.g. arm instead of leg
phonological pharaphasia - incorrect word sounds like the correct one
telegraphic speech - short simple sentences made up primarily of content words
where is brocas aphasia localised
left frontal third gyrus
what are the criticisms about brain localisation
patients with lesion in brocas areas - not showing the related aphasia
Dronkers examined 22 patients with lesions in brocas area
only 10 showed brocas aphasia
Penfield and roberts observed that surgical removal of brocas area usually results in temporary language impairment
patients showing brocas aphasia - lesion anterior to brocas area or subcortical brain damage
Vanier and caplan describe 20 patients showing brocas aphasia - 3 had subcortical lesions
what is wernickes aphasia
disorder of language comprehension
the impairment may concern spoken or written language
fluent speech but meaningless
what are the characteristiscs of wernickes aphasia
mostly meaningless
some repetitions
some non-wrods = neologism
how do wernickes patients compensate
wernickes patients tend to compensate for word-finding difficulties using circomlocutions
what are circomlocutions
description of words rather than naming them
e.g. the farm animal that needs to be milked = cow
what is neologisms
new words invented by the patient
when neologisms are frequent = jargon
where is the brain lesion in wernickes aphasia
left posterior third of the superior temporal gyrus
also supramarginal and angular gyrus
what is global aphasia
non fluent aphasia
there may be complete loss of speech
associated with verbal comprehension deficits
what are the characteristics of global aphasia
comprehension difficulties tend to recover but les imporvement has been observed in expression
this may be due to the fact that passive comprehension activates both hemisphere while speech involved mainly left unilateral areas
