After analyzing the MRI images, the researchers found that cortical thickness was altered in eight areas of the brain in the ayahuasca test group versus the control group. The most prominent difference observed was thinning in the posterior cingulate cortex, a part of the brain posited to be a central communication hub in a special brain network involved in high-level constructs such as the ego or self. Interestingly, the researchers also detected cortical thickening in the anterior cingulate cortex of ayahuasca users, an area of the brain believed to be involved in governing attention and cognitive control. In correlation analyses, the researchers observed that a higher frequency and number of years of use of ayahuasca is associated with a thinner posterior cingulate cortex.
In line with these findings were differences in scores between the ayahuasca test group and the controls with respect to aspects of personality and neuropsychology. Ayahuasca users scored significantly lower than controls in a personality trait characterized by pessimistic worry in anticipation of future problems and scored higher in self-transcendence, a characteristic exemplified by spirituality, religiousness, and expansion beyond one’s own boundaries to consider one’s self as an integral part of the universe as a whole. These higher scores in self-transcendence were associated to a thinner posterior cingulate cortex. “Thus,” the authors of the study state, “differences in this character dimension may have a neural basis and be the result of repeated intake of [ayahuasca].”