ASD (Autism Spectrum Disorder) Flashcards
What are core symptoms of ASD?
- deficits in social communication and social interaction (non-verbal and verbal domains)
- restricted repetitive behaviors, interests, or thoughts (rigid thinking, routines, and fixed interests)
What is savant syndrome and what is an example?
Savant syndrome is the display of extraordinary ability in some domain such as music, art, and mathematics (Not always correlated with superior IQ)
Example: daniel Tammet: extraordinary mathematical ability
Example: Derek Paravicini, musical savant
What is Reduced theory of Mind?
The ability to interpret the thoughts, beliefs, and feelings of others to predict behavior
Social deficits in ASD are thought to arise from an impaired ToM
Researchers found evidence of symptom severity based on ToM level
The lower the ToM the greater the social deficits/communication problems
What is reduced social motivation?
Atypical processing of facial stimuli in the Fusiform area (FFA)
FFA in neurotypical populations is responsive to faces
Faces did NOT cause more activity than objects in ASD participants
Faces are just as stimulating as normal objects
Therefore, there are deficits in the processing of social stimuli
What is developmental influence?
Altered social/other experiences during sensitive periods can change developmental trajectories
Can drive differences as the neural and behavioral levels
Two perspectives (neonatal genes vs. environment)
1. Ignores 1st year experiences, children are “predestined” to develop ASD due to genetics; predicts form of ASD is inevitable
2. Emphasizes 1st year experiences in contributing towards development of ASD; predicts ASD trajectory may be influenced
How do individuals with ASD process facial stimuli?
Research implicates differences in the eye gaze patterns in individuals with ASD
A meta-analysis revealed a consistent decrease in fixation on eyes in ASD individuals compared to healthy ones
Eyes are often processed as an isolated feature from the rest of the face
What do findings of human studies with ASD tell us about circuitry/behavior?
Some important aspects of ASD symptoms can be observed through dysregulated striatal activity
Dorsal striatum is important in goal-directed learning
Dysregulation can impair flexible actions
Ventral striatum is important for learning about rewards
Dysregulation can impair responsiveness to social rewards
How is reward circuitry involved in altered behavioral responses in ASD? How does behavioral flexibility change in ASD?
Research conducted a study in which children responded to rewarding stimuli
Methods
Feedback was positive when they earned money and was paired with a picture of money
Feedback was negative when they didn’t earn money and the picture of money was crossed out
For the social version ,the outcomes were a smiling face or frowning face
Results
Ventral striatal activity was found to be reduced for social rewards in the ASD group compared to TD controls
What is the genetic basis of ASD?
Copy number variants (CNVs):
Refers to a situation where the number of copies of specific segments of DNA differ among individuals’ genomes
This includes deletions and duplications
In a large amount of cases, the exact cause is unknown
ASD is highly heritable
An increase in shared genome with person with ASD increases the risk of developing ASD
Highly likely in monozygotic twins who share the same genetic information
Female Protective Effect from ASD
Males are diagnosed at four times the rate of females
Female ASD cases have more mutations than the average male case
Increased genetic risk is needed for females to develop ASD
Male Vulnerability to ASD
Males could be more genetically variable than females, which confers greater risk
Overrepresentation
What is 16p11.2 hemi deletion and its consequences?
Hemideletion is a CNV associated with the diagnosis of neurodevelopmental disorders like ADHD and ASD
ASD is reported in 16-25% of hemi deletion carriers
Trait deficits such as in the domains of communication and sociality
How are genetic animal modesl used to learn more about neurodevelopmental disorders
ASD is highly genetic and thus many models have been developed in different organisms to try to capture specific mechanisms
These are powerful methods to model certain aspects of ASD, but important to note no model captures perfectly the human condition
What findings were there in the mouse model of hemideletion?
Hemi Deletion mice
Generated a genetic model for hemi deletion in mice by deleting the conserved region in mice
Research shows evidence for differences in basal ganglia volume between wildtypes and hemi deletion mice
Reinforcement learning in hemi deletion mice
Research trained mice to nose poke on a FR1 schedule for sweet rewards
Male hemi deletion mice showed delayed reinforcement learning, females do not
No effect of reward preference, mice enjoyed the sugar reward equally
Females may be at higher risk for developing a heightened anxiety phenotype
After fear conditioning, female hemi deletion mice stay in closed arms more in an elevated plus maze (correlate of anxiety)
Do Hemi Deletion mice have ASD?
No, deletion syndrome does not always result in ASD
ASD is diagnosed condition in humans
The best we can do is study the behaviors and related circuits in non-human animals
