The present results can be interpreted from a Bayesian
[Doya et al., 2011] and free-energy minimization [CarhartHarris
and Friston, 2010; Friston, 2010] perspectives.
According to this view, the brain is seen as an inference
machine making predictions about the world [von Helmholtz,
1866] and updating them based on experience and
more specifically “surprise” [Friston, 2010; Friston et al.,
2013]. From this perspective, any mental act, including
perception, is analogous to a scientific experiment: an
inference is made based on prior knowledge and then
modified or updated based on what is experienced
[Fletcher and Frith, 2009]. According to our observations,
psychedelics alter these core functions of the brain with
the effect of diminishing confidence or “certainty” about
perceived phenomena. It is intriguing to speculate about
the mechanics underlying this phenomenon and the present
results implicate a role for decreased PHC-neocortex
communication and/or decreased salience network integrity.