Brain scans reveal how LSD affects consciousness
I&#x27;m a Ph.D student in Cognitive Science and I&#x27;m currently writing my dissertation on the topic of conscious perception.<p>I think this study is pretty damn interesting because the cingulate cortex (ACC &amp; PCC) along with the thalamus are implicated in states of consciousness (i.e. wake&#x2F;sleep&#x2F;coma&#x2F;vegetation&#x2F;etc) and also in &quot;access consciousness&quot; (i.e.:  “consciousness” in the sense of “I am conscious ​<i>of</i>​ such and such”).  Subjects dosed with psilocybin have decreased BOLD (blood-oxygen level-dependent) signals in these regions.<p>BOLD signal essentially tells you how active a brain region is (the more active the region, the more energy it needs, so the more irrigation it requires), so this tells us that the thalamic and cingulate regions are relatively suppressed by psilocybin.<p>This is congruent with a longstanding (albeit simplistic) theory on how hallucinogens work.  The idea is that hallucinogens would actually be inhibitory in their function, but they would selectively inhibit regions that are, themselves, inhibitory.<p>So in a hand-wavy way, you can think of the ACC as keeping imagination in check.  It inhibits perceptual areas (that are also activated by imagination) so that when you imagine a tiger, you don’t actually ​_see_​ a tiger.  With psilocybin &amp; LSD, this function is suppressed so you see the tiger.<p>Again, I&#x27;m simplifying to the point of risking a collective beat-down from my colleagues and lab-mates, but I thought it might help illustrate what&#x27;s groovy about this study.