The brain and the mind are the final frontier (...)

There were no evidence of toxic manifestation of these 
substanses (...) We conducted pretty careful 
neuropsychological asessments on our ayahuasca subjects, 
and a light number of matched controls who had never 
taken ayahuasca, and we found that the ayahuasca subjects 
had, on certain peramieters, had a significantly better 
neuropsychological function.

With eyes closed they often have well-formed images, 
often of thematic content.