As I suspected it appears they tortured the snails somehow (my guess is electric shock) to create traumatic memories. This has been done with caterpillars I think to see if they retain memories after turning into butterflies and they do, despite basically turning into primordial goop in the cocoon. They do, and it's tested by seeing if they retain aversions to certain areas of their cages that are electrified.
Then something about enzymes created which associate memory with pain and being able to target them.
Pretty cool, and I for one definitely have a few traumas I'd like erased.
There is debate about how the therapy works and whether it is more effective than other established treatments.[1][5] The eye movements have been criticized as having no scientific basis.[6] The founder promoted the therapy for the treatment of PTSD, and proponents employed untestable hypotheses to explain negative results in controlled studies.[7] EMDR has been characterized as a pseudoscientific purple hat therapy (i.e., only as effective as its underlying therapeutic methods without any contribution from its distinctive add-ons).[8]
I read about that fifteen years ago and dismissed it as pseudoscience. Wikipedia confirms. Pass (thanks though, don't mean to be rude)