Autism Flashcards
Neurobiological underpinnings of ASD
Not a consistent explanation
-Morphological and connectivity differences
Disturbance of excitation/inhibition balance
Layered and columnar organisation of the cortex
Neuronal and synaptic density increases in the cortex during early postnatal development.
In sensory cortex, neurons are arranged in columns, with a layered structure.
These columns are 500um wide and can also be divided into microcolumns around 50um wide.
Layered and columnar organisation is important for information processing
Increased neuronal density in ASD
Studies in postmortem cortical brain samples of ASD and neurotypical controls show increased density of neurons in cortical layers
These data suggest that the cortical microcolumn is smaller in ASD.
The functional consequences of this anatomical change is unknown: it could suggest greater connectivity between neurons locally.
Decreased long-range connectivity in ASD
High-functioning ASD subjects and age-matched controls were scanned using fMRI during rest and specific tasks.
Researchers calculated connectivity scores for activation between different brain regions, including many frontal cortical areas.
ASD subjects had lower connectivity scores between regions than controls, suggesting decreased long-range activity between these regions.
Excitation/inhibition balance
Nerontransmitter glutamate is the chemical responsible for excitatory signalling in the brain. Too much of this leads to overactivity
The neurotransmitter GABA is the primary chemical responsible for inhibitory signalling. Too much of this leads to underactivity
Studies show that in ASD there are reduced levels of GABA along with elevated glutamate levels
Evidence for disturbed EI balance in ASD
High comorbidity with epilepsy
Single cell RNA sequencing shows enriched expression of ASD risk genes in inhibitory neurons
Altered EI balance in animal models for autism
