Task 2 Flashcards
(19 cards)
What are the 4 pathways from Johnson’s model for visually guided behaviours?
SC Pathway
MT Pathway
FEF Pathway
Inhibitory Pathway
What is the SC Pathway and when does it develop?
It is a subcortical pathway present from birth. Visual information from the retina are sent to the SC
What is the MT Pathway and when does it become activated?
SC Pathway + V1 to MT to SC.
It is activated when the infant is 2 months
What is the FEF Pathway?
V4 to FEF & MT to FEF
Activated from 3 months
What is the inhibitory pathway and when is it activated?
V1 to BG to SN to SC
activated at 1 month
Which pathway is activated at birth?
SC pathway
Which pathways are activated at 1 month?
SC & Inhibitory
Which pathways are activated at 2 months?
SC, Inhibitory & MT pathway
Which pathways are activated at 3 months?
SC, Inhibitory, MT & FEF pathway
What is obligatory attention?
Infants are compelled to attend to certain features (e.g. red over green) and cannot disengage
When does obligatory attention occur and why does it occur?
1 month. It is due to the weak inhibition of SC. While the inhibitory pathway allows them to have control over orientation to periphery field, they have difficulty to disengage from a stimulus.
How can Johnson’s model explain the observations made in habituation paradigms?
Johnson proposes that habituation in newborns are mediated by the weakly functioning inhibitory pathway to SC.
More development of this pathway in 1 month old results in a stronger inhibition of SC activities; thus there is an inhibition of specific preferential tracking of faces & difficulty in disengaging from a stimulus (obligatory attention).
at 2 months+ = decrease in looking time due to excitatory control over SC & brainstem by cortical attention pathways via MT & FEF.
When is the onset of smooth pursuit?
2 months
How do the three eye movements develop?
- Saccades present from birth to 2 months lags behind moving stimuli– influenced by SC
- Anticipatory saccades appear from 3-6 months due to involvement of FEF pathway
- Smooth pursuit onsets at 2 months & greatly improved by 6 months.
When and why does the switch from subcortical to cortical involvement happen?
The switch occurs at 2 months when there is more cortical involvement due to the layers being extended to deeper parts of the brain
Both TDC and those with ASD prefer direct gaze when they are born. However, at 2 months TDC increase their eye fixations while those ASD decline their eye fixations.
Explain why does this happen
Decline in eye fixation is due to a delayed cortical involvement.
What is the neural underpinning of face processing
Cingulate cortex
What are some evidence for Johnson’s model?
Functional subcortical visual pathway at birth, but immature primary visual cortex; little influence on visually guided behaviour
Myelination of subcortical visual pathway begins 2 months prenatally & completed by 3 months after birth. Myelination for cortical visual pathway starts at birth & ends at 4 months
Subcortical structures (E.g. LGN) have finished most of their dev. Before birth. V1 = increased synaptogenesis in 1st two months.
Retinocortical pathways = fully functional at 2 months after birth
Cortical specialization for face processing at 2-3 months shown by PET & ERP
Different EEG patterns in familiar vs. unfamiliar face processing & show that 3 months old can visually recognize their mother.
What is the avian/visual imprinting model?
Chick model system of visual imprinting (avian model system):
Studying the development of birds show that they have some predisposed genes that enable them to cling to their mothers when they are hatched (filial imprinting). Over time, as they are exposed to the environment, they are able to recognize their mothers based on her specific characteristics. This experience can affect the bond.
2 phases of avian model:
* Early dispositions (reflexive) to orient to certain stimuli in environment – survival value
* Learning processes (cortical involvement) where the organism identifies characteristics in parent & is reinforced to bond to it.
