The mind and body are always in sync somewhat, even when under great stress like that. Anticholinergics at high doses act almost mechanistically on the PNS to create the parasthesia/formication on/under one’s skin. I think the visual perception of the insects is in that case secondary to the tactile sensation.

That is quite characteristically distinct to the “endogenous” appearance of other figures when using serotonergics, that almost certainly arise from intra CNS activity