Epilepsy and autism spectrum disorders, or ASD, present a remarkable degree of comorbidity and may share similar pathological mechanisms. But how are epilepsy and autism related? Does autism cause an increase in epilepsy? Or does epilepsy alter the brain circuit, which then promotes the development of autism? Scientists at the University of California, Riverside, and Rutgers University (New Jersey) are providing the first answers to these questions, with this study conducted in animals.
“One hypothesis is that during brain development inhibitory neurons, which regulate brain rhythms, develop abnormally, the way in which the brain circuit sets in is then abnormal, which can lead to both autism and epilepsy, ”suggests lead author Dr. Viji Santhakumar, associate professor of molecular, cellular and systems biology at the University of California at Riverside.
The key role of inhibitory neurons
The researchers focused on the function of inhibitory neurons in mice. These inhibitory neurons function as a brake by suppressing and regulating the activity of downstream neurons. The researchers generated mice with an overall mutation in all cells that prevents inhibitory neurons from migrating to their normal location in mature brain circuitry. The researchers find:
- unsurprisingly, a reduction in inhibitory currents in the hippocampus, which plays a key role in memory;
- these mice experience a high incidence of behavioral traits associated with ASD and seizures;
- fewer inhibitory neurons in brain circuits seem to induce an abnormality in the development of inhibitory neural circuits.
In summary, the study suggests that a common underlying defect in the formation of inhibitory circuits could contribute to both ASD and epilepsy and provide a basis for further research. The objective would therefore be to identify the mutations underlying the abnormalities of inhibitory neuronal migration and the maintenance of neuronal connections, in the development of ASDs and epilepsy.