wk3: ND - Agnosia, Neglect, Dyslexia

Question 1

When are the 3 parallel pathways no longer segregated?

Answer 1

at the striate cortex

Question 2

What does damage to the dorsal visual pathway lead to? (symptom)

Answer 2

impaired goal-directed “action” (dorsal is “where” pathway)

Question 3

What does damage to the ventral visual pathway lead to? (symptom)

Answer 3

Agnosia (inability to perceive)

Question 4

Can patients with visual agnosia see objects? Explain

Answer 4

yes, however even though they see the object, they don’t understand what it is

Question 5

Can patients with visual agnosia copy drawings?

Answer 5

No, however they can draw from memory

Question 6

Define optic ataxia

Answer 6

a high order deficit in reaching (i.e. reaching with their arms) visual goals that occurs with posterior parietal cortex (PPC) lesions. Is a problem with dorsal pathway

Question 7

What is a classic test you can use to test for problems with dorsal stream (optic ataxia)?

Answer 7

Hold out an oval with a rectangular slit in it at arms length from the subject and ask them to extend their arm and match the orientation of the slit with their hand and spatially have their arm in the same spatial plane as the slit

Question 8

How do patients with optic ataxia fair with orientation matching?

Answer 8

Generally not too much worse than normal. Not too many errors

Question 9

How do patients with optic ataxia fare with spatial matching or “posting”?

Answer 9

Much worse. People with optic ataxia make more spatial errors

Question 10

What is “posting”? in the context of the dorsal test in this lecture

Answer 10

posting = putting the card in the rectangular slit

Question 11

How are parallel channels integrated into visual processing?

Answer 11

carry visual signals from retina into thalamus and thence into cortex (Magno-, parvo- and konio- cellular pathways)

Question 12

Describe top-down feedback

Answer 12

modulation of afferent signals by processes such as attention

Question 13

What is Functional Localisation?

Answer 13

Different attributes of each object being processed in different cortical areas; different modalities (e.g. sensory, cognitive) processed independently

Question 14

What are the 3 parallel pathways from retina to primary visual cortex

Answer 14

Magnocellular
Parvocellular
Koniocellular

Question 15

Name 4 other functions of the posterior parietal cortex

Answer 15

Central role in directing attention to spatial locations
Helps bind different attributes of an object together
Gating inputs into ventral stream
Important for reading? (dyslexia)

Question 16

How can visual neglect occur?

Answer 16

via primary cortex damage. If this occurs, visual neglect will affect the contralateral visual field

Question 17

True/False: Visual neglect leads to the same type of constructional disability

Answer 17

False

Question 18

Which visual hemifield is visual neglect most common in? Why?

Answer 18

Left hemifield. This is because the right parietal cortex controls attention in both hemifields while the left parietal cortex controls attention in only the right hemifield. So if the right parietal cortex is damaged, the other side can’t compensate for the left hemifield.

Question 19

Is there an association between pre-reading phonological skills and reading ability?

Answer 19

Yes. Pre-reading phonological skills can predict later reading failure (Goswamy & Bryant, 1990; Richardson et al. 2003)

Question 20

What did Ahissar, Temple, and Breier (2000, 2000, 2002) find dyslexic patients have trouble with?

Answer 20

difficulties in discriminating syllables and rapid acoustic stimuli

Question 21

What are the 2 routes in the dual-route model of reading

Answer 21

Route A: direct lexical

Route B: phonological

Question 22

What is “Dysphoneidesia” and what proportion of dyslexics have it/are it?

Answer 22

Phonological dyslexia. 28%.

Question 23

What did (Castles & Coltheart, 1993, 2004) find in relation to dyslexia and phonology?

Answer 23

In some dyslexics, the errors are for irregular words and in others, the impairment is not matched by deficits in phonological awareness

Question 24

What did (Ramus &Szenkovits, 2008; Boets et al., 2013) find in relation to dyslexia and phonology?

Answer 24

Phonological representations themselves are normal in dyslexics; it is access to them that is defective

Question 25

What did (Stuart, 1990) find in relation to dyslexia and phonology?

Answer 25

Reading affects auditory perception (e.g., r-i-ch, p-i-t-ch)

Question 26

What did (Ehri, 1989; Castro-Caldas et al., 1998; Mann & Wimmer, 2002) find in relation to dyslexia and phonology?

Answer 26

Orthographic training (reading) improves phonemic awareness

Question 27

What is MEG?

Answer 27

Magnetoencephalography: a functional neuroimaging technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers.

Question 28

Where does activation occur in MEG during reading? (3)

Answer 28

Starts in occipital poles at the back on both sides/(visual cortex)
(By 170ms) it extends to the left occipito-temporal region
Then it goes to other areas

Question 29

What is the role of the occipito-temporal region of the brain

Answer 29

is the brain’s “letterbox” that extracts word forms from the visual scene

Question 30

Name 4 potential biological deficits in dyslexia

Answer 30

Gene translocation on chromosome 6 in the HLA region
Abnormal hemispheric symmetry of the planum temporale?
Neuronal ectopias and architectonic dysplasias located mainly in perisylvian regions and affecting predominantly the left hemisphere
Abnormal magnocellular pathway

Question 31

List 4 magnocellular defects that have been shown in dyslexics

Answer 31

Poorer contrast sensitivity at lower spatial frequencies (Lovegrove et al., 1980)
Low contrast stimuli elicit poorer visual evoked potentials (Livingstone et al., 1991)
Magnocellular layers in the LGN are abnormal (Livingstone et al., 1991)

Impaired visual motion sensitivity both psychophysically and in fMRI (Eden et al., 1996).

Question 32

In what contrast would dylexics have poorer visual evoked potentials? Why?

Answer 32

Lower contrasts. Low contrast gratings activate only M cells, and the magnocellular pathway is messed with in dyslexics

Question 33

How would you describe learning to read? (as a process)

Answer 33

probably a process of training the attentional spotlight to move sequentially along the visual scene.

Question 34

True or False: Visual search mechanisms are random and have memory

Answer 34

False. Visual search mechanisms ARE random BUT DON’T have memory

Question 35

On the integrity of what visual pathway does the attentional spotlight depend on?

Answer 35

M pathway and dorsal stream. Therefore, any impairment of the M pathway or the parietal cortex can lead to reading problems

Question 36

How well do we expect dyslexics to perform in visual search tasks?

Answer 36

poorly

Both attentional engagement and disengagement are poorer in dyslexic children. (Facoetti et al., 2008).

Question 37

What have FMRI studies found in terms of brain activation when reading? (2.5) What does this suggest? (1)

Answer 37

poorer activation in temporal lobe and posterior cortical areas concerned with grapheme-phoneme correspondence and phonological processing. – this provides evidence for the classic phonological theory of dyslexia

Question 38

What might FMRI brain activation results for subjects reading be due to? (other than what was concluded) (2)

Answer 38

the poorer activation of these areas may be downstream effects due to lack of a fluent temporal sequence of graphemes being shunted into the “letterbox” areas for word recognition and further grapheme-phoneme correspondence.

Question 39

Does reading influence brain structure?

Answer 39

There is a correlation that suggests that Left superior longitudinal
fasciculus and the left arcutae fasciculus show correlation of their
size (fractional anisotropy) with reading scores.

Question 40

What is the main role of the Left superior longitudinal

fasciculus and the left arcutae fasciculus?

Answer 40

are the two main pathways connecting brain regions involved in reading.

Question 41

Does language exposure change Left superior longitudinal

fasciculus and the left arcutae fasciculus?

Answer 41

Yes. Makes profound changes to these tracts [Romeo et al., J.
Neuroscience (2018) ].

Question 42

Define Synesthesia

Answer 42

stimulus in one sensory modality (or submodality) causing perception in another sensory modality (or submodality) - e.g. hearing music accompanied by seeing colours

Question 43

What might synaesthesia be due to?

Answer 43

may be due to lack of pruning during development between cortical areas processing different modalities or submodalities