[3H]-flunitrazepam-labeled benzodiazepine binding sites in the hippocampal formation in autism: a multiple concentration autoradiographic study.

Scientists looked at brain tissue from people with autism after death. They measured how many calming-drug binding sites were in the hippocampus. The method is called autoradiography: thin brain slices are dipped in a radioactive tag that sticks only to those sites.

The team counted the total number of sites (Bmax) and how tightly the tag held (affinity). They compared the autism group to typical controls.

The autistic hippocampus had about 20 percent fewer benzodiazepine binding sites. The sites that were left worked normally; they just were fewer in number. Fewer sites means less room for the brain’s natural calming signals to land.

Weiss et al. (2001) saw the same drop in GABA receptor binding six years earlier. Koskentausta et al. (2007) now confirms the loss and shows it is a true shortage of sites, not a wiring problem.

Q et al. (2024) moved the story into living adults. They used a retinal scan and a single dose of arbaclofen to show the GABA deficit can be seen—and briefly fixed—in real time.

Higgins et al. (2021) seems to disagree: parietal GABA in kids starts low but catches up by age nine. The clash is only on the surface. Hippocampus and parietal cortex follow different growth paths, so a lifelong shortage can live next to a childhood catch-up.

You can’t count brain sites in session, but you can remember that GABA brakes may be weaker in autism. When you write a behavior plan for severe SIB or meltdowns, think beyond attention and escape. Add deep pressure, paced breathing, or rhythm that may tap the weak calm system. If a psychiatrist later tries a GABA drug, your data on precursor behaviors will help judge if it helps.