Mice with microglia missing receptors for the neurotransmitter serotonin since birth have too many synapses and show social difficulties in adulthood.

Mice and rats, for example, gravitate toward their mother’s bedding over bedding that is clean or smells of a different dam.

A researcher’s existential crisis led to a scientific breakthrough.

Drugs such as LSD act primarily on the serotonin system, which is implicated in autism — and some autistic people who experiment with psychoactive compounds report enhanced social connections, among other benefits. But researchers have more questions than answers.

Social memory, which may be altered in autism, depends on serotonin-sensitive neurons that send signals from the medial septum to the hippocampus.

Octopuses can solve some of the same problems as people but do so in unusual ways.

The finding that MDMA and an experimental serotonin agonist increase sociability across six different model mice suggests that disparate autism-linked mutations converge on the same underlying pathways.

The high levels of serotonin seen in the blood of some autistic people have confounded scientists for more than half a century. Despite so little progress, some researchers refuse to give up.

A glowing protein tracks serotonin levels and location in the brains of living mice and could yield clues to the neurotransmitter’s role in autism.

A class of medications used to treat obsessive-compulsive disorder seems to ease compulsive behaviors in adults with autism. Why can’t we tell if these medications work similarly in children with the condition?