Biological Explanations ASD Flashcards
Szamatari (1991) family study sibling concordance rate findings
With siblings - 2.2%
Without siblings - 0.11%
-20x greater risk of developing ASD if you have a sibling with ASD
Bailey et al. (1995) twin study findings
After widening definition:
MZ - 92%
DZ - 10%
Definition of multiplex family
More than 1 family member has ASD
Definition of simplex family
Only 1 person in family has ASD/characteristics
How is ASD caused in simplex families?
De novo mutation (a variant that arises in fertilised egg itself during early embryogenesis)
Role of the amygdala
Part of the limbic system involved with fear and emotional processing, also associated with memory and connections to the prefrontal cortex
What does the amygdala dysfunction explanation suggest?
Amygdala has faulty emotional processing in those with ASD
What did Nordhal et al. (2012) find?
At two years of age children of 2 have larger amygdala growth than normal (6-9%), but there is no growth difference in late adolescence/early adulthood.
How does abnormal amygdala overgrowth damage functioning?
Overgrowth results in growth of other connected areas being obstructed, impairing their functioning too
How does Baren-Cohen (2000) link amygdala overgrowth to ASD?
Since there are neural connections to the frontal cortex (decision and behaviour), abnormal development is a causal factor in social/behavioural deficits, linking to difficulty in understanding the emotional expression of others
Supporting Example - Baren-Cohen (2000) - eye task
Adults with ASD matched with control group.
Presented with photos that only showed the eyes of a person making different facial expressions.
Pps asked to identify the expression shown.
Brain activity measured in an MRI scanner.
ASD group performed significantly worse, and the left amygdala was not activated at all in ASD but strongly in controls.