What does it all mean?

May 3, 2012 9:20 AM

Can askmefi break down my experience with psilocybin mushrooms?

I had two supposedly common things that I'm rather curious about from my "trip":

1. There was a constant auditory hallucination that was very similar to the "revving" type sound represented here throughout this video http://www.youtube.com/watch?v=PKdfYmej7Uw. What causes this? And what, if any, is the popular interpretation of this experience?

2. There was a strong visual hallucination in which whatever was the focus of my vision became, in part, the entirety of my vision. For instance, if I was looking at someone's eyes, my field of vision would be somewhat overcast by dozens of eyes. If I was looking at a tree branch, my vision would replicate that into a somewhat cathedral effect. What causes this alteration of vision?

posted by Philipschall to science & nature (5 answers total)

Here's some awesome math that models what we see in the medicine space. If you take that notion and mix it with the idea that human vision is only a little bit optics and a whole lot of pattern recognition based on your life experience and you can see how visual effects are just not explainable in a generalized way.
posted by chairface at 9:59 AM on May 3, 2012 [9 favorites]

1. The buzzing is common, and is often called a 'carrier wave'. I don't know what causes it.

2. One of the things that hallucinogens do is kind of short circuit your brain's ability to identify objects based on sensory input. Ordinarily, your brain kind of constructs a virtual 'scene' where it places objects around you. That's why you can close your eyes and still imagine where everything is around you, and why you normally kind of have a picture in your head of a much larger area than you are directly looking at with your eyes. When you're tripping, that whole process gets disrupted and your brain just has a really hard time creating that scene. So you can't tell if it's a tree branch or a cloud or an eye that you're looking at unless you concentrate on it and think about it.
posted by empath at 10:16 AM on May 3, 2012

It has been known to increase blood pressure a bit, so that might be the origin of what you're hearing. Sometimes blood pressure increases can cause weird auditory effects.

The rest is, yeah, we don't actually understand a lot about exactly how the prefrontal cortex works. And psilocybin gets in there and stirs that pot around.
posted by lumpenprole at 10:16 AM on May 3, 2012 [1 favorite]

Disclaimer: undergraduate who took a course on visual processing last fall. Grain of salt time.

The eye thing has to do with the physiology of the eye-brain system, no doubt. The receptors in the retina record the basic contrast and some very primary color/line information from one 'focus area' per cell. The cells then communicate with each other and integrate in the ganglion nerve cell layer, which then passes the information onward using the optic nerve, to go to the two levels of visual processing in the brain (the M and P systems), which in turn have to communicate with each other to form the final 'image' (which is really a reconstruction of the basic parts your eyes provide you with and the memories and identifications your P system can access).

There are multiple steps in the reconstruction process it can go wrong in the brain and disrupt the basic 'image' of what we see, because the retinal receptors don't provide the visual centers with an 'image' but a fragmentary and possibly jumbled collection of facts about stimuli. One of the most delicate aspects of the reconstruction process involves unifying the multiplicity of 'views' from the receptor/ganglion cells into a single coherent panorama. It is quite a sturdy system, of course, which doesn't require conscious control or even 'consciousness' (say, sleep-walkers can see), but if you chemically short-circuit your messenger soup, the nerves get confused and communication breaks down.


As a guess, I think the replication of one 'focus area' into a false panorama implies that only some-- the strongest-- of the retinal signals were being reconstructed properly, while the rest of the signal got lost into noise. As it happens, the focus-point of our retina at the fovea has the greatest concentration of receptor cells. That is the maximum acuity of vision and the literal focus-point of the gaze, since it lies directly in the line of light focused by the cornea. As I said, those extra cells are dedicated to providing maximum sharpness and resolution to the dead center of the focus area, and it sounds like this strong signal was the only one being received properly by the visual processing centers at V1, V4 and other areas Possibly irrelevant but interesting, the receptor cells in the retina naturally specialize and divide into 'on-center' and 'off-center' perception, so that some see the bulls-eye and some see the surrounding circle. Bulls-eye-only would also imply chemical interference-based filtering of the signal being received from the retinal ganglions.
posted by reenka at 10:34 AM on May 3, 2012 [2 favorites]

Having experienced countless trips with 'magic mushrooms', I can only say its a property of the drug and its interaction with neurotransmitters.

I'd look at erowid and MAPS for a more detailed and research oriented explanation for your experience.
posted by handbanana at 12:55 PM on May 3, 2012