Low registration?

Florak8

On DS' EI eval, the OT stated that he has low registration, and they showed us again how to press on his shoulders, hips etc. to help him have better body awareness. I had always thought that was done to help stimulate his muscles to support his body (he has low tone). But when I googled it, I am seeing a lot of stuff about autism and SPD.

His highest score on the HELP eval was his socialization (10-12 months) and he is very good at connecting with people via sounds, expressions, and gestures.

Can low registration be solely a function of low tone? Or should I be preparing myself for a possible dx of autism? 

TIA