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48 Cards in this Set
- Front
- Back
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Behavioral Characteristics of Autism |
1. Defecits in social communication/interaction 2. Restricted and repetitive behaviors |
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Autism Diagnosis |
- Generally lifelong disorder diagnoses by age 5 - Can be diagnoses as early as 18 months - 1 in 88 prevelance - Boys are 4x more likely to get it - Associated with intellectual disability and epilepsy |
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Characteristics of Autism Spectrum Disorders |
- Accelerated brain development (larger than usual in 20%) - Smaller neuronal soma and dendritic fields = fewer synapses - Defects in neuronal connectivity |
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Synapse Formation during Development |
- Sensory --> Language --> Higher Cognitive Function - Autism appears when language and cognition should develop |
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Changes in Patterns of Brain Activity in Autism |
- Activity in autistic brains are scattered away from the normal areas |
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Social Communication/Interaction Defecits |
- Problems reciprocating social or emotional interaction - Severe problems maintaining relationships - Nonverbal communication problems |
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Defecits in Restricted and Repetitive Behaviors |
- Stereotyped or repetitive speech, motor movements, or use of objects - Excessive adherence to routines, ritualized patterns of verbal or nonverbal behavior, excessive resistance to change - Highly restricted interests that are abnormal in intensity or focus - Very high or low reaction to sensory input, unusual fixation on sensations |
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Reasons for Increased Autism Prevalence |
- Increased screening or awareness - Requirement to categorize students for Individuals with Disabilities Educational Act - Diagnostic substitution - To obtain services or treatment for kids with disabilities - Broadening of the diagnostic criteria for Autism |
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Diagnostic Substitution |
- Autism is increasing while other diseases are decreasing - Switching roles |
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Variation in Prevalence between States |
- Some states have excellent treatment options, leading to higher numbers |
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Autistic Disorder |
- Impaired social interaction characterized by averted gaze, lack of relationships, and sharing of enjoyments and interests - Impaired communication characterized by delay of language, impaired conversational ability, and repetitive language - Restricted repetitive, and stereotypical behavior interests and activities characterized by preoccupation with particular interests, inflexible adherence to specific rituals, and repetitive motor mannerisms |
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Asperger's Syndrom |
- Similar to AD - No delay in language, cognitive development, or curiosity in the environment. |
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Childhood Disintegrative Disorder (CDD) |
- Normal development for first two years followed by loss of previously acquired skills (language, social skills, bowel control, play, motor skills) - Similar characteristics to AD |
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Pervasive Development Disorder - Not Otherwise Specified (PDD-NOS) |
- Catch all category - Autism like behavior but not severe enough for AD - "Quirky" |
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Inaccurate Theories of Autism Causation |
- Vaccines - Yeast infections - Leaky gut - Gluten and casein - "Refrigerator mothers" (lack of maternal warmth) |
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Sibling Genetic Autism Risk |
- 2-6% increase in prevalence in siblings |
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Dizygotic Twins Genetic Autism Risk |
- 10% increase in prevalence |
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Monozygotic Twins Genetic Autism Risk |
- 90% increase in prevalence |
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First-Degree Relatives Genetic Autism Risk |
- 20x increase over the basal level |
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Chromosomal Abnormality Variations (CNVs) and Autism |
- ASDs exhibit high amounts of chromosomes variation in important CNS developmental proteins |
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Hot Spots |
- CNV locations that are seen in a great number of ASD cases |
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c-Met |
- Synaptic protein receptor for hepatocyte growth factor (HGF) |
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c-Met Function |
- Morphological effects - Mitogenic (division) activity - Motogenic activity - Trophic activity |
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HGF |
- Binds to c-Met - Treatment with HGF enhances synaptic size and function |
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The Neurotrophin Hypothesis |
- Growth factors are synthesized in neurons and stored in vesicles for secretion - Neural activity leads to secretion of growth factors |
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Reduced Signaling by c-Met |
- Fits neurotrophin hypothesis - Suppresses dendritic arborization |
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Synaptogenesis |
- Initiation of contact between axon and filopodia of dendrites |
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Specificity of synaptogenesis |
- Correct axon to correct target achieved by guidance cues |
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Initial Contact Phase in Synaptogenesis |
- Adhesion molecules help tether two cells together at tips of filpodia - Mutations in these proteins are linked to autism |
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Proteins in Initial Contact Phase |
- Cadherins and Protocadherins - Responsible for specificity but also bind to a wide range of proteins |
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Recruiting Phase in Synaptogenesis |
- Proteins are recruited to the active zone of the presynaptic terminal and PSD of the postsynaptic terminal - Can be translated locally or arrive in complexes |
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Maturation of Synapse |
- Size and content of synaptic machinery is modified - Ex. NR2B --> NR2A in NMDARs |
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Axonal Pruning |
- Synapses either mature or are eliminated - Development results in less synapses present |
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Neurexin (NRXN) |
- Single transmembrane domain protein in presynaptic membrane that binds to NLGN |
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Neuroligin (NLGN) |
- Single transmembrame domain protein in the postsynaptic membrane that binds to NRXN |
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α-Latrotoxin |
- Toxin released by black widows that binds to neurexin and stimulates the release of neurotransmitters |
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Neurexin Sizes |
- α-Neurexin is large - β-Neurexin is small - Determined by the alternative splicing of 3 different genes |
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NRXN Structure |
- Predominatly expressed in the brain - Short intracellular tail with a large extracellular portion
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NLGN Expression |
- 4 genes responsible for 50% of the identity |
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NLGN 1 |
- Binds to PSD-95 in excitatory synapses |
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NLGN 2 |
- Possibly binds to gephryin in inhibitory synapses |
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CASK |
- Contains PD2 domains and calcium-dependent kinase activity - Binds neurexin and voltage-gate calcium channels and actin cytoskeleton to synaptoagmin |
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NLGN 1 and Neurexin |
- Accumulation of PSD-95, NMDAR, synGAP, and other excitatory PSD proteins |
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NLGN 2 and Neurexin |
- Accumulation of gephryin, GABAR, other inhibitory PSD proteins |
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D396X |
- NLGN4 premature stop causing the loss of C-terminal tail - Tail is responsible for binding of intracellular partner proteins |
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R451C |
- NLGN3 gain of function mutation - Point mutation to cystine impaired cognition due to decrease NLGN3 migration to the plasma membrane but also increased inhibitory synaptic transmission (gain of function) |
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NLGN Overexpression |
- Control the functional balance of excitatory and inhibitory synapses in hippocampal neurons - Predominantly reduces inhibitory synaptic function |
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Neurexin Mutations in Autism |
- R8P L13F - IVS4+1 - T665I E620D - E715K |
