Biological Foundations of Language
Prosopagnosia
- - also called face blindness, is a cognitive disorder of face perception in which the ability to recognize familiar faces, including one's own face (self-recognition), is impaired, while other aspects of visual processing and intellectual functioning remain intact.
Sulci
- A fold in the cerebral cortex
Gyrus
- A gyrus (pl. gyri) is a bump on the cerebral cortex.
Phineas Gage
- A railroad worker who set of an explosion which resulted an iron bar shooting up through his skill. - The heat cauterizing the wound. - His frontal lobe was very much damaged and thus he lost his ability to plan and maintain socially accepted behaviour.
Angular Gyrus and its Functions
- A region of the parietal lobe which lies near the temporal lobe. - The angular gyrus plays a central role in mediating between visual and auditory language.
Hemispherical processing for right handers
- Broadly speaking, in most right handed people the left hemisphere is particularly concerned with analytic, time-based processing, while the right hemisphere is particularly concerned with holistic, spatially based processing - For the great majority (96%) of right-handed people, language functions are predominately localized in the left hemisphere. We say that this hemisphere is dominant - even 70% of left-handed people are left hemisphere dominant.
Conduction Aphaisa
- Caused by disconnection between both broca and wernickes areas. - Speech production ok. - Problems repeating heard words - Deficit in accessing the code of words received through sight and sound.
Damage to the Arcuate Fasciculus
- Damage to the arcuate fasciculus results in difficulties repeating language, while comprehension and production remain otherwise unimpaired. - This pattern is an example of a disconnection syndrome.
Broca's Aphasia aka Expressive aphasia
- Difficulty with production, not comprehension. - Agrammatism (absence of function words in telegraphic system). - Can't use syntax to differentiate. (Leopard/lion). - Slow laboured speech, anomia (no names), difficulty finding words. - Paraphasic errors "plashing... flashing... running [splashing]". - Telegraphic speech (no or few function words). - Extreme cases = only a few syllables, words/phrases.
What is Disconnection?
- Disconnection occurs when the connection between two areas of the brain is damaged without damage to the areas themselves.
Wernicke's Aphasia aka Receptive Aphasia
- Disturbance in auditory comprehension; fluent speech - Problems understanding written/spoken language. - Communication cut off. - Fluent but meaningless speech. - Semantic paraphasia substituting words related to meaning (e.g. cat, dog, horse= domestic animals). - Difficulty connecting meaning.
What area is linked to prosopagnosia, dyslexia and synesthesia?
- Fusiform face area. - It is located in the Inferior temporal cortex
Fissures
- Larger sulci
The Language Acquisition Mechanism
- Learning spoken language is different from other types of learning in that it does not require instruction. - Reading and writing however require specific instruction to be learnt. - This indicates that language acquisition is a biologically determined phenomenon.
Musical Stimuli and Lateralisation
- Nevertheless, speech sometimes elicits left-ear advantages, and right-ear advantages for musical stimuli have been found. The distinction between holistic and relational processing appears to capture a salient difference in how the two hemispheres do their work.
Limitations of the Geschwind Model
- Other areas minus brocas and wernickes affect language. - Brain damage does not have an effect on the model.
Localisation of Brain Function
- Parts of the brain are specialized for specific tasks.
Dichotic Listening and lateralisation
- Studies of dichotic listening with normal individuals typically reveal right-ear advantages for speech stimuli and left-ear advantages for non-speech stimuli.
Wernicke's area
- The Wernicke's area is located in the temporal lobe on the left side of the brain and is responsible for the comprehension of speech.
Dichotic Listening Task
- The dichotic listening task (di = 2; otic = ear) is a very useful way to study selective attention. (Cherry, 1953). - The task asked an observer pay attention to one of two different messages, each delivered to one ear over stereo earphones. For example, the left earphone may present Lincoln's Gettysburg Address, and the right earphone may give a list of random words. The observer is asked to pay attention to the Gettysburg Address and ignore the random words in the other ear
Lateralization examples
- The left hemisphere is more linguistically sophisticated than the right, especially in the areas of syntactic and phonetic processing - The right hemisphere is more adapted at understanding the multiple meanings of ambiguous words and in comprehending pragmatic aspects of language such as indirect speech acts.
Function of the Corpus Callosum
- The primary function of the corpus callosum is to integrate motor, sensory, and cognitive performances between the cerebral cortex on one side of the brain to the same region on the other side.
Broca's area
- This area, located in the frontal part of the left hemisphere of the brain, was discovered in 1861 by French surgeon Paul Broca, who found that it serves a vital role in the generation of articulate speech.
Information Processing of the hemispheres
- When a stimulus is presented to the left visual field, the right hemisphere of a split-brain patient becomes aware of the stimulus and is able to communicate that awareness in nonverbal ways = grabbing an object with left hand -> controlled by right hemisphere = speech is predominantly controlled by the left hemisphere the patient is unable to describe what she has seen
Visual Pathways
- When fixating on a point, each eye sees both visual fields but sends information about the right visual field only to the left hemisphere and information about the left visual field only to the right hemisphere. - The visual areas of the left and right hemisphere normally communicate through the corpus callosum.
Fusiform face area and Logograms
- When reading Chinese letters (logography), they elicit a response in FFA. - Damage to FFA may result in inability to identify such letters
Geschwind Model for Speech Production (Auditory)
- When we hear a word, information is transmitted from the part of the cortex responsible for processing auditory information to Wernicke's area. - If we then speak that word, information flows to Broca's area where articulatory information is activated, and is then passed on to the motor area responsible for speech.
Arcuate Fasciculus
- a bundle of axons that connects broca and wernickes areas.
Logogram
- a written character that represents a word or phrase. Chinese characters and Japanese kanji are logograms
What is aggramatism?
- absence of function words in telegraphic system
Frontal Lobe and location
- executive thinking - Imagination -center for fluent expression, syntax
What is synesthesia?
- is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway
FOXP2
- is required for proper development of speech and language - The gene is located on chromosome 7 (7q31, at the SPCH1 locus), and is expressed in fetal and adult brain, heart, lung and gut. - In humans, mutations of FOXP2 cause a severe speech and language disorder - Versions of FOXP2 exist in similar forms in distantly related vertebrates; functional studies of the gene in mice and in songbirds indicate that it is important for modulating plasticity of neural circuits
Split Brain Research
- language deficits are associated with damage to the left hemisphere of the brain more often than to the right hemisphere. - In animal studies where the corpus callosum was severed, it was found that there was little to no transfer of information between hemispheres.
Temporal Lobe and Location
- speech and Sound processing -center for language comprehension, semantics
Main feature of Broca's Aphasia
- the loss of the ability to express grammatical relationships, either in speech or in writing.
Lateralization
- the tendency for a given psychological function to be served by one hemisphere, with the other hemisphere either incapable or less capable of performing the function.
Hand Gestures and both Aphasia's
Two kinds of gestures appear in normal speech (Bavelas et al., 1992; McNeill, 1985): - those that refer to some aspect of the content of the conversation - those that appear to be more interactive in nature. =Broca's aphasics tend to have impairments in the second type of gesture; Wernicke's aphasics have more problem with the first type
Geschwind Model for Speech Production (Visual)
Visual association cortex -> Angular gyrus -> Wernicke's Area -> Broca's Area (activation of articulatory info) -> motor area
Does Language involves in the LEFT hemisphere of the brain only?
-FALSE - morphology (grammar), syntax, grammatical more left -pragmatics/semantics more right
