WEEK 4 Flashcards
In a study using fMRI, Kelly and his colleagues discovered different peaks of activity in the two hemispheres of the frontal cortex depending on the specific type of stimuli being encoded.
Which side did; unfamiliar faces, familiar objects and words appear?
words: left hemisphere
familiar objects: both hemispheres
unfamiliar faces: right hemisphere
familiar faces: both hemispheres
What was the difference in activity of the brain hemispheres when participants were asked to encode (remember) vs just passively view the words/objects/faces?
All round greater activation in the encoding trails:
Greater left activation during intentional encoding than passive viewing of words, greater right activation
during intentional encoding than passive viewing of faces, and greater bilateral activation during intentional encoding than passive viewing of
objects.
What is Paivio’s Dual-Coding Theory and how did he arrive to this conclusion?
- Words stored in verbal code
- Pictures stored in verbal and visual code
Hence better recall for pictures as 2 codes are better than 1 code (words)
- Automatic naming of pictures no automatic picturing of words
What regions of the brain have been said to be associated with high levels of memory performance and what kind of memories?
frontal regions more active –> verbal materials
In a follow-up study, Kelly and his colleagues used the “Wada test” to determine what the effects
of anesthetizing either the right or the left frontal cortex would have on participants’ memory for
words and unfamiliar faces. What did they find regarding memory for words when the left
frontal cortex was anesthetized?
When the left side was anesthetized memory performance was worse for words. Similarly when the right side of the PFC was anesthetized memory for faces was worse, but not words. vice versa
What did Kelly and colleagues achieve suing Wada testing and fMRI
By integrating results across both
techniques (fMRI & Wada), a richer understanding of
the neural architecture of memory formation was achieved.
What is a mental representation?
• Mental representations may be very
specific to a stimulus (perceived object or
event), or very abstract (broad category).
• Mental representations can reflect different
levels of categorization.
e.g. types of birds, animals, list of random things
What is Hierarchical network theory? Collins & Quillian
Proposed that people store information about various
categories in a network structure
– hierarchical network
– cognitive economy
• properties stored at highest node to which they
apply
– questions activate concepts
– activation traverses nodes and links to enable decisions
– predict RT based on distance in network
In the Hierarchical network theory what is an intersection?
When two concepts are questioned (e.g. is a canary an animal) activation at two nodes occur (canary and animal) until they intersect at “bird” at which people can answer “yes” ==> if no intersection then “no”
What would take longer to respond to and why:
is a canary a bird?
is a canary an animal?
is a canary an animal?
- as there is a longer distance to travel in the network
- -> greater distance = longer RT
What are some problems for Hierarchical Network Model?
Strict hierarchy questioned:
- is a dog a mammal –> should be faster than: is a dog an animal –> but mammal is actually slower
Cognitive economy questioned
Typicality effects - how many links separate:
- A canary is a bird?
- A robin is a bird?
- A chicken is a bird?
- An ostrich is a bird?
RT varied – the less typical birds took longer than the more typical
What are some difference with Collins & Loftus (1975) Spreading Activation Model?
- Got rid of hierarchy
- Got rid of cognitive economy
• Allowed links to vary in length to account for
typicality effects
• Spreading activation
– Activation is the arousal level of a node
– Spreads down links
– Used to extract information from network
What is spread of activation?
Nodes connected to the accessed node are also activated. Nodes connected to these nodes are then activated. As the activation spreads out from the accessed node it grows weaker
What is spread of activation theorized to do?
Collins and Loftus proposed that
it is spread of activation that allows us to access semantic information about concepts.
What are some of the key points of Collins & Loftus (1975) Spreading Activation Model?
• Abandons strict hierarchy, cognitive
economy.
• Any categories and properties can be
associated.
• Associations vary in strength.
• Activation “spreads” to associated concepts,
including indirect associations (e.g. lion –
stripes).
• Reaction time depends on both strength and
proximity of associations.
