Laterality and language

Question 1

What does our complex human language involve?

Answer 1

Associating specific and abstract meanings with arbitrary sounds and symbols, defining meanings through use of grammar

Question 2

What question do studies such as that done with Washoe the chimp raise?

Answer 2

Can animals actually LEARN a language, or are they simply imitating gestures?

Question 3

Where is Broca’s area?

Answer 3

Back of left frontal lobe, right next to region of premotor cortex responsible for fine motor control of lips, tongue and vocal cords

Question 4

What is Broca’s aphasia characterised by?

Answer 4

Slow and laboured language lacking any kind of grammatical structure, total inability to speak at the severest end of the spectrum
Often also experience ANOMIA i.e. inability to find the correct word
Automated/emotional expressions usually unaffected e.g. ouch
Patients know what they want to say and are aware that they are getting it wrong - very frustrating

Question 5

Why is Broca’s aphasia also called expressive aphasia?

Answer 5

Even ability to express language in writing is severely reduced, and sentences may be short and “telegraphic” with words like “is” missed out

Question 6

Where is Wernicke’s area?

Answer 6

Left posterior superior temporal gyrus, adjacent to the primary auditory cortex in the temporal lobe, on border with parietal and occipital lobes - damage results in deficits in language comprehension

Question 7

What are the key features of Wernicke’s aphasia?

Answer 7

Language made up of inappropriate words (paraphasia) or words that don’t even exist
Patients unaware that producing incorrect words, and while their speech is nonsensical it is fluent and connected
Usually associated deficits with reading and writing

Question 8

How can the difference between the aphasias be simply summed up?

Answer 8

Broca’s is more to do with problematic OUTPUTS while Wernicke’s is more to do with INPUTS

Question 9

What is the Wernicke-Gerschwind model?

Answer 9

Forms basis of current understanding of language, but it is an over-simplification as language regions are more widespread and less clearly defined than described by the model
Suggests info passes from Wernicke’s area to Broca’s via ARCUATE FASCICULUS - patients with damage to this show normal comprehension and normal speech production, but difficulty passing information/repeating spoken words (conduction aphasia - each area essentially operating independently)
If everything working normally, info will then pass to primary motor cortex controlling vocal cords and mouth

Question 10

What does the Wernicke-Gerschwind model suggest regarding Wernicke’s area?

Answer 10

Area where primary auditory/visual info enters for decoding

Convergence of visual and auditory language input, site of comprehension and generation of verbal responses

Question 11

What is control of language processing like in the brain?

Answer 11

In the majority of people, areas for speech production and comprehension are found in the left hemisphere
Around 0.1% of people show bilateral control in adulthood (normal in many people in childhood when language is still being learned but left hemisphere becomes progressively more dominant into adulthood)

Question 12

Which language abilities are thought to be right-sided?

Answer 12

Emotional content of speech
Emotional responding
Some lexical ability - can’t vocalise name but can often still write it/spell it out with blocks
Lexical decision-making (word vs non-word)

Question 13

How can we assess functional symmetry/asymmetry of the brain?

Answer 13

Using fMRI techniques that measure blood flow to localised brain areas - blood flow increases as activity increases, and we can pick areas up and map them to specific functions
Generally give participant a task, then switch to an entirely unrelated task that shouldn’t use the same areas - subtract the non-specific activity and be left with a clear map of activity for the initial task

Question 14

Why is the fMRI methodology limited?

Answer 14

For example, we cannot tell much about visual function or pathways - we will see activation of visual cortex in similar patterns regardless of which visual field selectively presented to because the hemispheres communicate

Question 15

What is a more helpful technique?

Answer 15

Plot the TIME COURSE of responses - when a stimulus is presented to the left visual field, for example, the right hemisphere is fastest to respond and the left comes later following the feed-through of info from the right hand side

Question 16

How does communication between the two hemispheres occur?

Answer 16

Via the CORPUS CALLOSUM, a large tract of white matter which can be severed to treat severe and intractable epilepsy (hemispheres then essentially work independently)

Question 17

How can studies using “split-brain” patients help us to understand laterality of brain function?

Answer 17

Example - word flashed to LVF only, subject asked to SAY what the word was
Only the right visual cortex is receiving the info, while the left is responsible for speech, so the patient cannot SAY what the word was but he can pick out a corresponding item with his left hand (not the right - the left hand is controlled by the right hemisphere)

Question 18

In what 4 circumstances can we see COMPETITION between hemispheres in split brain patients?

Answer 18

Block-arranging task - right hand (left cortex) tries to take over even thought the right cortex/left hand could do task while left cortex couldn’t
Reading a book in left hand - kept putting book down even though interested in it, because the right cortex controlling the hand couldn’t read
Unconscious actions of right cortex - patients often surprised by actions of left hand, same doesn’t happen for the right
Different opinions - Spoken and written opinions can be different for the same person; often the spoken answer will be more functional while the written is more personal and emotional

Question 19

What have split-brain studies indicated regarding calculation?

Answer 19

Mainly left-sided - anything beyond simple addition not possible using right hemisphere

Question 20

What are 9 key functions of the right hemisphere?

Answer 20

Arranging blocks in a specific pattern
Copy simple drawings better than right hand
Better at solving puzzles
Better at sorting items into categories according to shape, size, colour etc.
Better at mental rotation tasks
Emotional responding
Face and pattern recognition
Response to music
When damage to right parietal lobe, see deficits in spatial awareness - unaware of LVF and often of the whole left side of their body; left side of space doesn’t exist for them, even in memory

Question 21

What is the evidence that, even when separate, the left hemisphere has an “interpretor”?

Answer 21

If two different images are individually shown to each different hemisphere, see an interesting compensatory effect:
Left eye/right cortex - see snow
Right eye/left cortex - see chicken foot
When person asked to point out something connected with the original picture from an array, the left hand will choose a shovel while right hand chooses a chicken
When asked why the shovel, the answer is “to clean out the chicken house” - left cortex, speech production, no idea what image the right side saw but made educated inference based on what IT saw

Question 22

What did Roger Sperry believe?

Answer 22

Each hemisphere is its own separate brain, each possessing own conscious awareness

Question 23

What did Sir John Eccles believe?

Answer 23

right hemisphere non-conscious automaton, subservient to left hemisphere which has an interpreter that tries to bring things together