Psych 351B: Midterm 2 Review (Semantic Memory)

Hub and Spoke Model (HSM)

A model to describe how cognition, consists of spokes and a hub

What are the spokes representing

HINT: 6 features

1. Visual features

2. Verbal descriptors

3. Sounds

4. Olfaction

5. Praxis 

6. Somatasensory

What does the hub represent

The anterior temporal lobe (ATL)

T or F: If the ATL is damaged all of the other spokes will damaged

T, will impair the spokes as well

What would Wernicke say regarding blindness and colour understanding

His model would argue that the only way we understand colour is through vision, that verbal descriptors are not enough and thus congenitally blind individuals would know nothing of colour

What would the HSM say with regard to blind people’s view of colour

That they would be able to define colours based on semantic knowledge relating to colour

How was the colour disagreement between the HSM and Wernicke’s model tested

Gathered congenitally blind patients and controls and asked them to compare two colours on how dissimilar they are (0 being the same, 9 being opposite). The patients were only asked each pairing once and and never asked to judge the dissimilarity between the same two colours

What did the colour-blindness experiment find

That controls and blind individuals did almost equally on the test, same findings will be found if one asked to compare the colours of fruits/vegetables

How was blindness and colour relations tested at a neural level

Patients underwent fMRI and asked about 3 categories of words, brain activation was recorded

What were the 3 types of word categories used in the fMRI colour vision experiment

1. Visually dominant - words only explained visually

2. Words without sensory features - words that represent abstract concepts

3. Non-visual sensorily accessible concepts - words that can be experience with sensory modalities other than vision

What was found when the word pair Rainbow vs Rain was presented

Rainbow (visually-dominant word) would generate stronger activation than words like rain (Non-visual sensorily accessible concept word) in the ATL, the difference is bigger for blind individuals

Occipital cortex activation during fMRI test

Activated by colours in sighted individuals but not activated by blind individuals

What will happen if the occipital cortex is damaged

Colour agnosia - inability to recognize colours

From the fMRI colour experiment what can we conclude the ATL actually does

Involved in recognizing semantic or abstract meaning of words, this is why its activation is stronger in blind individuals as sighted individuals can rely on the occipital cortex

T or F: the ATL’s activation is more sensitive to non-sensory, language derived knowledge representations that are not specific to visual knowledge

T, as this knowledge is semantic information

T or F: Neuropsychology can explain how words enter our language and how they are transformed over time

F, we have no explicit answer to this question

Semantic dementia

Individual loses their semantic memory

T or F: Those with semantic dementia are very bad at naming objects despite no problems with working memory, langauge or verbal reasoning

T, impaired naming is due to one no longer having access to the meaning of an object or word

Patients AB and EM

Both had semantic dementia, tested on several different brain areas against controls

What was found when AB and EM were tested on their phonological loop

Equivalent to controls

What was found when EM was tested regarding concrete and abstract words

Impaired on defining abstract words, but sufficient at concrete words. Also better at words in their native language

What was found when AB was tested regarding concrete and abstract words

Impaired on defining concrete words, but sufficient on abstract words, likely because the hub was intact and spokes damaged

Peabody Picture Vocabulary Test (PPVT)

Individual is shown four pictures and asked what picture includes the target (e.g. what image shows a person laughing)

What is found regarding familiarity, typicality and specificity with regard to performance on the peabody vocab test in a patient with semantic dementia

Familiarity - higher familiarity leads to better performance

Typicality - typical items are associated with better performance

Specificity - highly specific knowledge decreases performance

In the PPVT what are error rates a function of

Semantic differences, or the specificity of knowledge

Semantic storage impairment

Individual’s conceptual representation of some objects is consistently impaired while others are impaired (greater damage leads to more objects impaired), same results as semantic dementia

Semantic access impairment

One’s comprehension of individual items is variably impaired due to failure to access full semantic specification

What can you expect if one with semantic access impairment takes the PPVT

They will get worse as task gets more difficult, however do much better if information is presented more slowly.

If one is presented with familiar words they will start very good but get worse as trials commence

T or F: The HSM can explain the difference regarding semantic storage and semantic access

F, therefore we must bring in the executive system as an extra part of the HSM

Executive system

Generally engaged in allowing access to the HSM

System has two parts, the internal task representation and integration layer, located in the pars triangularis (frontal lobe) and the postmedial temporal gyrus (pMTG) respectively

With the inclusion of the executive system, how can we explain semantic access impairment

Says that the integration layer is damaged but still accessible, leads to the system getting fatigued quickly (why patients do worse as trials increase)

What is found regarding the pars triangularis with regard to hard and easy association tasks

Will be highly activated for hard association tasks, but hardly activated for easy tasks

What is found regarding the pMTG with regard to hard and easy association tasks

Will be highly activated for hard association tasks but not activated for the easy one

Why is there differing levels of activation with regard to hard/easy association tasks and the pars triangularis and pMTG

Because the simple task does not lead to activation for normal people as there is an immediate and unconscious association between like words, one must think about words to distinguish them on the hard task

Semantic Aphasia (SA)

One cannot properly access the meaning of words, ability highly affected by task demands, another name for semantic access impairment

What is the major difference between semantic aphasia and semantic dementia

Semantic dementia involves a degraded knowledge store and semantic aphasia involves difficulty accessing or controlling existing semantic knowledge

What are the 7 characteristics of SA

1. Inconsistent performance across tests

2. Insensitivity to the frequency/familiarity of stimuli

3. Strong influence of the ambiguity or semantic diversity of word meanings

4. Strong effects of cueing and miscueing on task performance

5. Poor inhibition of strong competitors and associated items (e.g. falsely selecting a jar of marmalade when intending to make cheese on toast)

6. Associative as well as coordinate and superordinate semantic errors in naming

7. Tendency in category and letter fluency to produce strong associates of prior responses that fall outside target category

Why must the hub and spoke model must be further modified to have two hubs

Because of modality-specific semantic access impairment

Modality-specific Semantic Access Impairment (MSSAI)

Cognitive condition where a person loses the ability to access meaning (semantics) for certain types of information (will do fine for some pictures in word-picture matching even after a number of trials)

What are the two hubs in our modified HPS

Verbal features - strong bidirectional connection between the left ATL demi-hub and right ATL (more reliant on left)

Visual features - strong bidirectional connection between left ATL and right ATL (more reliant on right)

Patient ELM

Had bilateral temporal lobe damage, impaired on shape features in memory

What would happen if ELM was presented with a picture of a fruit

He would be able to describe all uses and facts of the object fine but could not describe shape or colour (he does not know what objects look like)

T or F: ELM will mix up fruit/vegetables when he is shown a photo

T, he can distinguish the shape, and that they are different but is unable to access imagery from meaning

What would happen if ELM were asked to draw a fruit

He would be unable to do it, will draw a concept of what he expects a fruit to look like

What area is ELM damaged

He is damaged on his access to visual features, not visual features itself

(he can still recognize visual features from what he sees, but cannot access visual features from memory)

Why can ELM know the difference between words and not between pictures of the same item(s)

Because for words he can ignore shape features by relying on his stored visual form of the word to access the HSM so he can recall other semantic features

T or F: There is a dissociation between being impaired on living things but sufficient on man-made objects or vice versa

T, as demonstrated JBR and YOT

Patient JBR

Lost ability to comprehend animals as they are known by sensory properties, but preserved knowledge of body parts and things known by function

Patient YOT

Impaired on comprehending man-made objects and body parts (based on functions) but her comprehension of inanimate things defined by sensory properties (e.g. musical instruments) was spared

What conclusions can be drawn from patients JBR and YOT with respect to the neurological basis of the HSM

Degradation of the ATL transmodal hub in patients with SD will generate a category specific pattern, whereas selective damage to the spokes leads to category specific deficits

What is the difference between praxis and function spokes

Praxis - how to use an object

Function - what an object can be used for

What happens if TMS is applied to the area where the spoke of praxis is neurologically located

One will be impaired on naming objects, specifically objects that are based on function

Why are the TMS results regarding praxis not fully accurate

Because patients with damage to the same region (known as ideomotor apraxia) can name tools and are impaired on the function of tools

How can one “solve“ the paradox present between TMS on the praxis area of the brain and a lesion on the praxis area of the brain

Have two separate modes of naming:

1. Hybrid semantic/pragmatic mode (dorsal and ventral stream)

2. Purely semantic stream (ventral stream)

How can ideomotor apraxia be explained by the two modes of naming

One is impaired on the hybrid semantic/pragmatic mode but the purely semantic mode is intact

Iconic gestures

Gestures that help guide us into finding a word when in the tip of the tongue (TOT) state, have to do with the shape or function of an object

T or F: Damage to the parietal lobe cause one to be unable to retrieve the name of a tool/utensil when in a tip of the tongue state

T

T or F: Preventing the ability to gesture will not affect the ability to retrieve the name of a tool/utensil when in a tip of the tongue state

F, it will effect it greatly