Presentation on theme: "Language and Aphasia CSE 140 etc.. Outline Review the relationships between lesions and linguistic effects Review of the traditional picture about Broca’s."— Presentation transcript:
Language and Aphasia CSE 140 etc.
Outline Review the relationships between lesions and linguistic effects Review of the traditional picture about Broca’s aphasia, and agrammatism Examine how a particular study arrived at a more detailed picture of the deficit in Broca’s aphasia
Cortical Regions Although we have seen large scale brain structures (e.g. lobes), Damasio refers to cortical regions by number in the reading. Pink: Frontal Blue: Parietal Green: Temporal Yellow: Occipital
Brodmann Areas Distinct brain areas identified in terms of anatomical structure So e.g. Broca’s area is sometimes defined as consisting of 44,45; much of the literature uses these numbers because of their precise definitions.
Traditional Distinction Broca’s: Non-fluent speech; function words and morphemes omitted; comprehension ok. Wernicke’s: Fluent speech, but filled with non-sense or filler words; comprehension impaired. From a traditional point of view:
Areas and Connections Broca Wernicke Arcuate Fascisculus
Causes Stroke Head injury Tumors Degenerative conditions (e.g. Alzheimer’s)
Types Broca’s (more later) Wernicke’s: Damage to posterior area Conduction: Arcuate + cortex above Global: Entire set of language areas
Wernicke’s Speech: Fluent and well-articulated; but contains many non-words, or filler words Comprehension: Poor Basic Idea: Damage to areas in which words are stored, or in which the phono- logical forms of words are associated with meanings.
Conduction Aphasia Lesion: Affects areas connecting Wernicke’s and Broca’s areas Supramarginal gyrus Also arcuate, which is underneath
Conduction Continued Speech: Relatively unimpaired; but many speech errors, or non-words are used. Also defective naming ability. Comprehension: Also good, unlike Wernicke’s, but repetition is not possible Idea: Network that builds meaningful units out of speech sounds is disabled.
Global Aphasia Lesion: Covers entire system of language areas in the dominant hemisphere Abilities: Almost total inability to produce or comprehend speech. Idea: Combines features of Broca’s and Wernicke’s aphasias
Additional Specific Deficits The Temporal lobe is shown in green. Left temporal pole Areas 20,21
Temporal Lobe Problems Damage to the temporal pole and areas 20, 21 impairs subjects’ ability to retrieve words. Other abilities seem to remain more intact. Temporal pole alone: proper nouns (John, Washington, etc.) are affected, not common nouns like dog, cat, etc. Lesion in 20,21: retrieval of both noun types is severely impaired.
Summary Very specific linguistic effects for lesions in certain areas. Primary role of Broca’s and Wernicke’s areas for language, along with the areas and fibers connecting them Remaing questions: how the specifics of a deficit as complicated as e.g. Broca’s aphasia are studied
Grammaticality Judgments Reviewing a study by Linebarger et al. (1983) that shows a surprising aspect of Broca’s aphasia Background: Knowledge that Broca’s aphasics have difficulty with word-order, and assigning roles to participants: He showed her baby the pictures. He showed her the baby pictures. The cat that the dog is biting is black. The dog that the cat is biting is black. The theory at the time: Broca’s patients are unable to construct syntactic representations.
Idea behind the study Basic Idea: Test the idea that Broca’s aphasics cannot construct syntactic representations by presenting them with a mixture of grammatical and ungrammatical sentences, and having them make a judgment. Procedure: Subjects listened to sentences of ten types, grammatical and ungrammatical versions, and had to accept or reject them.
Some sentence types Syntactic frames: He came to my house at six o’clock. *He came my house at six o’clock. Auxiliary Inversion: Is the boy having a good time? *Is the boy is having a good time? Gapless relative clauses: Mary ate the bread that I baked. *Mary ate the bread that I baked a cake.
More sentence types Tag Questions: The little boy fell down, didn’t he? *The little boy fell down, didn’t it? Reflexive Sentences: I helped myself to the birthday cake. *I helped themselves to the birthday cake. Auxiliary verb in tag question: John is very tall, isn’t he? *John is very tall, didn’t he?
Predictions The study is designed to test the theory that Broca’s aphasics cannot construct syntactic structures. Prediction of that theory: Broca’s aphasics should not show knowledge of grammaticality or ungrammaticality. They are not able to construct syntactic representations, so they should have to guess.
Results from one subject Sentence Good Sentence Bad Accept17813 Reject52208 I.e., the subjects could tell for the majority of cases which sentences were grammatical and which not. The behavior of one subject, indicative of the rest:
Interpreting the results The Broca’s patients showed remarkably good results, suggesting that they are capable of performing syntactic analyses. Two further points: 1. They did not perform equally well on all sentence types. 2. What does this result show, given that these patients do have difficulty in tasks that require them to identify Agents, Patients, and so on?
The problematic cases Tag-questions and reflexives were considerably more difficult for the subjects: The little boy fell down, didn’t he? *The little boy fell down, didn’t it? John is very tall, isn’t he? *John is very tall, didn’t he? I helped myself to the birthday cake. *I helped themselves to the birthday cake.
One possibility These sentences involve storing the gramma- tical features of an element, for use later: The little boy fell down, didn’t he? (boy = Masculine) John is tall, isn’t he? (Aux = 3rd Person of be) I helped myself to the cake. (Subject = Ist Person I) SentenceStorage One idea is that the syntactic analysis is good, but at the cost of a shallow semantic analysis. That is, the patients parse the structure correctly, but do not retain the features noted above, in this type of case.
The larger pattern The authors suggest that there is a tradeoff between syntax and semantics. If tasks like picture naming tax each, then deficits will be more apparent. In any case the result is interesting and surprising, because it shows grammatical sensitivity in a population thought to be incapable of syntactic analysis. Once again, the study shows the integration of linguistic and experimental techniques.