Language and Lateralization

Question 1

Define the terms language, communication, and grammar.

Answer 1

Communication: the transmission of information between individuals

Language: the highly specialized form of communication where arbitrary symbols are assembled and reassembled in almost infinite variety and associated with a a vast range of things, actions, and concepts.

Grammar: a strict set of rules for language that allows us to share information with speakers of the same language.

Question 2

What is cerebral lateralization?

Answer 2

Cerebral lateralization: the division of labour between the two hemispheres so that each is specialized for particular types of processing.

For example, verbal abilities are associated with the left hemisphere of the brain while spatial cognition is associated with the right.

Question 3

What does it mean to say that stimulus are processed by the contralateral hemisphere?

Answer 3

This means that stimulus that is perceived by one half of the body will be processed by the opposite hemisphere of the brain. For example, if you feel something with your left hand, or see something in the left field of vision, than you will process this stimulus in the right hemisphere first.

Question 4

What is a split brain individual?

Answer 4

Someone who has had their corpus callosum severed. Results in the two hemispheres being unable to communicate.

Question 5

What concept is being referred to in the “right ear advantage”?

Answer 5

Right ear advantage is referring to the fact that, in right handed individuals, their right ear has an advantage when listening to dichotically presented stimulus (different stimulus presented simultaneously to different ears).
Why? Because information presented to the right ear goes to the left hemisphere’s auditory cortex and then to language processing in the same hemisphere while information presented to the left ear goes to the right hemisphere’s auditory cortex and then has to cross the corpus callosum and get to the left hemisphere before it can be processed by the language centres.

Question 6

What are tachistoscope tests and what do they tell us?

Answer 6

Tachistoscope tests are when information is presented for less than 150ms to one visual field. This amount of time is too brief for the brain to move the eyes/head to bring the stimulus into both visual fields thereby ensuring that the stimulus is only processed by the visual field it is exposed to.

These tests have told us that the left visual field (right hemisphere) is better at processing nonverbal stimuli while the right visual field (left hemisphere) is better at processing verbal stimuli.

Question 7

What is the planum temporale area?

Answer 7

It is in the auditory region of the cortex and is larger on the left than it is in the right, even before exposure to language. Is believed to play a role in communication

Question 8

How is music perceived?

Answer 8

The right hemisphere largely processes music stimulus UNLESS the person has perfect pitch/musical experience, then the left hemisphere is also largely involved.

Question 9

Is language ever a right hemisphere dominant process?

Answer 9

Yes but rarely. When it does occur, it is usually in left-handed individuals

Question 10

What is involved in spatial processing?

Answer 10

Spatial processing includes geometric shape recognition, direction sense and navigation abilities, face processing, and imagined 3D rotation of objects in the mind’s eye.

Question 11

What is Prosopagnosia? What causes it?

Answer 11

Also called Face blindness, is the inability to recognize faces, including one’s own. Is caused by damage/abnormalities in the fusiform gyrus in the right hemisphere, the area of the brain that is specialized to recognize faces. Prosopagnosia can be acquired due to brain damage or lesions in the fusiform gyrus, or it can be congenital (from birth).

Prosopagnosia is often associated with other forms of agnosia (inability to identify individual objects)

Question 12

What is the Wada test?

Answer 12

The Wada test is when one hemisphere of the brain is given anesthetic to localize functions to a specific hemisphere (e.g. giving anesthetic to the right hemisphere and then asking the person to speak would confirm if their language centres are in the left hemisphere).

Question 13

What are the following disorders and how are they related?

• Aphasia
• Paraphasia
• Agraphia
• Alexia
• Apraxia

Answer 13

Aphasia is an impairment in language ability by varying degrees and is caused by brain injury (e.g. stroke) in the left hemisphere.
Paraphasia is a type of aphasia, it is when the individual substitutes words with sounds, incorrect words, or unintended words.

Agraphia, Alexia, and Apraxia often co-occur with aphasia:

• Agraphia –> impairment in writing
• Alexia –> Impairment in reading
• Apraxia –> motor impairment characterized by a difficulty making a sequence of movements.

Question 14

What are the six main language areas of the left hemisphere?

Answer 14

1. Primary Motor Cortex
2. Supramarginal gyrus
3. Angular Gyrus
4. Primary Auditory Area
5. Wernicke’s Area
6. Broca’s area

Question 15

What is Broca’s Aphasia?

Answer 15

Also called nonfluent aphasia. It is when there is a difficulty producing speech but comprehension of language is good. Is caused by damage to the left inferior frontal region (i.e. Broca’s regions)

Is associated with Hemiplegia (paralysis of one side, usually the right) or hemiparesis (weakness of one side, usually the right)

Question 16

What is Wernicke’s Aphasia?

Answer 16

Also called fluent aphasia, is complex verbal output with many Paraphasia that make the speech unintelligible, is associated with a lack of language comprehension and anomia (inability to name persons and objects). Is caused by damage to the left posterior temporal cortex (i.e. Wernicke’s area).

Question 17

What is Global Aphasia?

Answer 17

Is the total loss of the ability to produce or understand language. Is caused by widespread damage to the left hemisphere affecting many or all speech zones. There is very little chance of recovery from global aphasia (other forms of aphasia can have some improvement with intensive therapy.)

Question 18

What is the connectionist Model of Language (aphasia)? What are criticisms of this model?

Answer 18

Also called the Wernicke-Geschwind Model.

Claims that deficits result from disconnection between brain regions. Says that each region is involved with a particular feature of language and that lesions disrupt the connection between these regions resulting in an inability to put these features together.

Criticisms:

• This model oversimplified the neural mechanisms of language
• We now know that the brain is not as modular as this theory suggests
• improved imaging tech shows that areas we thought were connected (at the time of the connectionist model) are not connected in the way we thought.

Question 19

What is the neurological mechanism behind speaking a heard word according to the connectionist model

Answer 19

1. Primary auditory cortex sends information to Wernicke’s area
2. Wernicke’s area decodes the sounds then transmits the information to the arcuate fasciculus.
3. Arcuate fasciculus sends the information to Broca’s area
4. Broca’s area makes a speech plan and sends that information to the motor cortex
5. The motor cortex produces speech

Question 20

What is the neurological mechanism behind speaking a written word?

Answer 20

1. The primary visual cortex sends information to the angular gyrus
2. the Angular gyrus sends information to Wernicke’s area
3. Wernicke’s area transmits information via the arcuate fasciculus.
4. The arcuate fasciculus sends information to Broca’s area
5. Broca’s area forms a speech plan and sends that to the motor cortex
6. The motor cortex produces speech.

Question 21

What is the Motor theory of language?

Answer 21

Speech is perceived using the same left hemisphere mechanisms that are used to produce the complex movements that go into speech. Essentially, when we listen to speech, we analyze the sounds according to the underlying movements of the throat and mouth to create them. We do this using the same neural system we would use to make these movements.

Question 22

About how many human languages exist that we are aware of?

Answer 22

between ~6000-7000

Question 23

What does it mean to say that language has both learned and unlearned components?

Answer 23

Infants are born being able to babble using all existing phonemes but lose those that are not used in the language(s) they are exposed to (unlearned and learned components).

We have a critical period that we must learn a language in order for the skills to develop normally (during which our development can be permanently altered by an experience or treatment) (unlearned and learned components)

Language disorders can have genetic (unlearned) components. e.g. the FOXP2 gene is associated with stuttering disorders.

Question 24

What is Williams syndrome and what does it tell us about the genetic component of language?

Answer 24

Williams syndrome is a disorder characterized by impairment in spatial cognition and IQ but superior linguistic abilities.

It is caused by the deletion of 28 genes on chromosome 7. Possession of extra copies of these genes is associated with significant impairment of language (opposite of Williams syndrome). This not only tells us that language has a genetic component but it also tells us which collection of genes are likely involved.

Question 25

What are similarities and differences in the neurological aspects of language/communication between humans and non-humans?

Answer 25

While primates are capable of elaborate communication systems, they use subcortical systems (like the limbic system) for communication unlike humans who use their cortex.

The FOXP2 gene is implicated in communication across many species including humans, birds, rats, and mice.

Question 26

What is dyslexia and what neurological differences are associated with it?

Answer 26

Dyslexia is a reading disorder with neurological causes. Essentially, the brain uses two systems during reading: one to focus on the sounds of the letters and one to focus on the meaning of the words. People with Dyslexia appear to a disconnection between these two systems which impairs their coordination of the sounds with meaning.

Dyslexia is associated with, atypical layering of neurons in the cerebral cortex, excessive cortical folding, and atypical clusters of neurons, all particularly centred in the frontal and temporal lobes.