Report - Language and The Brain [PDF]

Zitiervorschau

St. Paul University Philippines Tuguegarao City, Cagayan 3500

DRL 305: Psycholinguistics

Language and the Brain Bryan B. Echanique PhD RL Student First Trimester, 2019-2020

Objectives

1. Present a brief survey of brain structure; 2. Point out the parts of the brain which are critical to language production and comprehension; 3. Differentiate language localization and lateralization; 4. Discuss some types of brain disturbance that result from brain damage; 5. Explain brain plasticity; 6. Affirm the autonomy of language faculty; 7. Draw the implications of researches on aphasia.

Outline

1. Brain structure 2. Language areas in the brain 3. Localization and lateralization 4. Brain disturbance and speech disorders 5. Brain plasticity 6. Language autonomy 7. Research on aphasia

Language and the brain

Neurolinguistics The study of the relationship between language and the brain.

The human brain

▪ Composed of +/- 10 billion nerve cells (neurons) ▪ The highest level of the brain is the cerebral cortex (found only in mammals, and human has the greatest proportion of cortex). ▪ Language representation and processing occurs in the cortex. Figure 1. The cerebral cortex (“Language and the human brain,” n.d.)

Cerebral hemispheres The brain is composed of cerebral hemispheres: ▪ Right hemisphere: supervises left side of body ▪ Left hemisphere: supervises right side of body “Contralateral brain function”/ “Contralateral neural control” Figure 2. Brain hemispheres (Mayo Clinic, n.d.)

Contralateral brain function

Figure 3. Right-handedness and the brain (Mastin, 2012)

Corpus callosum The corpus callosum connects the left and right hemispheres. ▪ Network of two million fibers ▪ Location: Above the thalamus, under the cortex ▪ Function: Allows the left and right hemispheres to communicate by transmitting neural messages between them

Figure 4. Corpus callosum (Brain Made Simple, n.d.)

Modularity of the brain The brain is divided into distinct anatomical faculties that are directly responsible for specific cognitive functions. - Left hemisphere is superior for language, rhythmic perception, temporal-order judgments, and mathematical thinking skills - Right hemisphere does better in pattern-matching tasks, recognizing faces, and spatial orientation.

Figure 5. Left and right brain hemispheres (MC2.Bid4Papers, 2017)

Localization and Lateralization

▪ Localization: Different human cognitive abilities and behaviors are localized in specific parts of the brain. o e.g., speech comprehension is controlled by the Wernicke’s area ▪ Lateralization: Any cognitive function that is localized primarily in one side of the brain o e.g., language is lateralized to the left hemisphere

Localization and Lateralization

Localization

Figure 3. Brain localization (Mastin, 2012) Figure 6. Lateralization of cerebral functions (Tejano, 2016)

Language lateralization ▪ Split-brain patients: evidence for lateralization o In the past, some cases of severe epilepsy were treated by cutting the corpus callosum, severing the connection between the two hemispheres.

▪ Messages sent to the hemispheres cause different responses in split-brain patients. o Object placed in the left hand (right hemisphere): object can be used but not named o Object placed in the right hand (left hemisphere): object can be named and described immediately

Language areas in the brain

1. Broca’s area (or anterior speech cortex) - Located in the frontal part of the left hemisphere of the brain - Discovered in 1861 by French surgeon Paul Broca, who found that it serves a vital role in the generation of articulate speech - Responsible for speech production

Language areas in the brain

2. Wernicke’s area (or posterior speech cortex) - Located in the posterior third of the upper temporal convolution of the left hemisphere of the brain - First described in 1874 by German neurologist Carl Wernicke - Contains motor neurons involved in the comprehension of speech

Language areas in the brain

3. Motor cortex - An area that generally controls movement of the muscles - Initiates impulses that travel through the brain stem to produce audible sounds

Language areas in the brain

4. Acuate fasciculus - A bundle of axons (or nerve fibers) that connects Broca’s area and Wernicke's area in the brain

Brain disturbance and speech disorders

1. Broca’s aphasia - Results from damage to the frontal lobe of the brain - Individuals with this form of aphasia are able to comprehend speech but have great difficulty expressing their thoughts. - People with Broca aphasia speak in short phrases that include only nouns and verbs (telegraphic speech).

Brain disturbance and speech disorders

1. Broca’s aphasia - Effects: ▪ intelligence not necessarily affected ▪ understanding not necessarily affected ▪ production severely impaired o Trouble with function words (e.g., articles, prepositions, pronouns) o Trouble with inflectional morphology (e.g., -ed, -s) o Difficulties forming grammatical sentences o Difficulties understanding complex sentences (e.g., passives) (“Language and the Human Brain,” n.d.).

Brain disturbance and speech disorders

1. Broca’s aphasia - Example: Eliminates inflections such as -ed or end of the word such as -er (in ‘after’).

Brain disturbance and speech disorders

1. Broca’s aphasia - Example: “Yes ... Monday ... Dad, and Dad ... hospital, and ... Wednesday, Wednesday, nine o’clock and ... Thursday, ten o'clock ... doctors, two, two ... doctors and ... teeth, yah. And a doctor ... girl, and gums, and I.”

- Example: “Me ... build-ing ... chairs, no, no cab-in-ets. One, saw ... then, cutting wood ... working ...”

Brain disturbance and speech disorders

2. Wernicke’s aphasia - Results from damage to the temporal lobe of the brain - Individuals with Wernicke aphasia speak in long, garbled sentences (word salad) and have poor speech comprehension.

Brain disturbance and speech disorders

2. Wernicke’s aphasia - Effects: ▪ Fluent speech ▪ Good intonation ▪ Lexical errors ▪ Nonsense words ▪ “Word salad” ▪ Comprehension impaired (“Language and the Human Brain,” n.d.).

Brain disturbance and speech disorders

2. Wernicke’s aphasia - Example: When asked to repeat the word glass, he or she might say ‘window’ or something related to glass.

Brain disturbance and speech disorders

2. Wernicke’s aphasia - Example: DOCTOR: How do you feel? PATIENT: I felt worse because I can no longer keep in mind from the mind of the minds to keep me from mind and up to the ear which can be to find among ourselves.

Brain disturbance and speech disorders

2. Wernicke’s aphasia - Example: D: How are you today, Mrs. A? P: Yes. D: Have I ever tested you before? P: No. I mean I haven’t. D: Can you tell me what your name is? P: No, I don’t I…right I’m right now here. D: What is your address? P: I cud if I can help these this like you know… to make it. We are seeing for him. That is my father.

Broca’s and Wernicke’s areas

Broca’s area controls syntax. Wernicke’s area controls semantics.

Brain disturbance and speech disorders

3. Global aphasia - Results from extensive brain damage - Individuals with global aphasia exhibit symptoms of both Broca and Wernicke aphasia.

Speech therapy

Speech therapy may be useful to treat aphasia. In some instances, improvement may be due to assumption of some language functions by other areas of the brain, but recovery is usually incomplete.

Aphasia therapy

“Several studies feature stateof-the-art computer technology, using a virtual therapist to deliver intensive therapy. Therapy can be done independently in the participant’s home” (Center for Aphasia Research and Treatment, 2017).

Hemispherectomy Hemispherectomy: a medical procedure that involves removing one hemisphere of the brain In adult hemispherectomy patients: ▪ Left cerebral hemisphere removed o lose most but not all of their linguistic competence o lose the ability to speak and process complex syntactic patterns o retain some language comprehension ability ▪ Right cerebral hemisphere removed o difficulty in understanding jokes and metaphors o cannot use loudness and intonation as cues to whether a speaker is angry, excited, or merely joking. Thus: The right hemisphere also has a role in normal language use!

Plasticity To some extent, the brain may reassign functions to different areas of the brain. This is due to the plasticity of the brain. ▪ Left hemisphere is predisposed to learn language. ▪ During language development, the right hemisphere can take over many language functions if necessary.

Plasticity ▪ Child hemispherectomy patients are able to reacquire a linguistic system, albeit delayed.

▪ In adults, the right hemisphere cannot take over linguistic functions anymore. ▪ Plasticity of the brain decreases with age.

Language autonomy Is language faculty already present at birth, or is it derived from more general intelligence? Children with SLI (Specific Language Impairment): ▪ have difficulties in acquiring language, BUT ▪ do not have brain lesions responsible for language difficulties ▪ have no other cognitive deficits

Therefore: Language ability ≠ General cognition Grammatical faculty is separate from other cognitive abilities.

Language autonomy Christopher (IQ = 60-70) ▪ Unable to button his shirt or play tic-tactoe BUT… ▪ Remarkable language skills ✓ Could read at age 3 ✓ Knows many languages from different families (Germanic, Slavic, Turkic) – polyglot ✓ Easily learns new languages Hence: Language ability ≠ General cognition Figure 8. Christopher (“Language and the Human Brain,” n.d.)

Language autonomy

Evidence from aphasia, SLI, and the asymmetry of abilities in linguistic savants strongly supports the view that language faculty is autonomous, genetically determined, and consists of multiple brain modules. It is not derived from more general intelligence.

Research on aphasia

“Research shows that people with aphasia can continue to improve their language even years after their stroke, and that intensive therapy is essential for making changes in the brain” (Center for Aphasia Research and Treatment, 2017).

References Anggraini, L. F., & Farida, N. U. (2014, October 14). Language and the brain (PDF document). Retrieved from https://www.slideshare.net/noviiummiy/language-and-the-brain-40247158?from_action=save Brain hemispheres (Online image). Retrieved from Mayo Clinic website: https://www.mayoclinic.org/tests-procedures/ epilepsy-surgery/multimedia/brain-hemispheres/img-20008029 Bandith, B. (2011, June 8). Chapter 6: Language and the brain (PDF document). Retrieved from https://www.slideshare.net/bandith/language-and-the-brain-8242180 Center for Aphasia Research and Treatment. (2017). Aphasia research studies. Retrieved from Shirley Ryan Ability Lab website: https://www.sralab.org/aphasiaresearch

Christopher (Online image). (n.d.). Retrieved from http://udel.edu/~dlarsen/ling101/slides/brain.pdf Corpus callosum (Online image). (n.d.). Retrieved from Brain Made Simple website: http://brainmadesimple.com/corpuscallosum.html

Joynt, R. (2019, January 31). Aphasia. In Encyclopædia Britannica. Retrieved from https://www.britannica.com/science/ aphasia-pathology

References Language and the human brain (PDF document). (n.d.). Retrieved from http://udel.edu/~dlarsen/ling101/slides/brain.pdf MC2.Bid4Papers. (2017, December 20). Left and right brain hemispheres (Online image). Retrieved from https://mc2.bid4papers.com/blog/8-ways-left-brain-thinkers-boost-creativity/ Mastin, L. (2012). Right-handedness and the brain (Online image). Retrieved from https://www.rightleftrightwrong. com/brain.html Tejano, J. (2016). Lateralization of cerebral functions. Retrieved from https://sites.google.com/site/sociopsychotejano/brainhemispheric-dominance The cerebral cortex (Online image). (n.d.). Retrieved from http://udel.edu/~dlarsen/ling101/slides/brain.pdf