Number of posts: 5647
Location: Amsterdam, the Netherlands
Registration date: 2007-07-21
|Subject: Schizophrenic Brains Not Fooled by Optical Illusion Wed Apr 08, 2009 8:11 am|| |
|Schizophrenia sufferers aren't fooled by an optical illusion known as the “hollow mask” that the rest of us fall for because connections between the sensory and conceptual areas of their brains might be on the fritz.|
In the hollow mask illusion, viewers perceive a concave face (like the back side of a hollow mask) as a normal convex face. The illusion exploits our brain's strategy for making sense of the visual world: uniting what it actually sees — known as bottom-up processing — with what it expects to see based on prior experience — known as top-down processing.
"Our top-down processing holds memories, like stock models," explains Danai Dima of Hannover Medical University, in Germany, co-author of a study in NeuroImage. "All the models in our head have a face coming out, so whenever we see a face, of course if has to come out."
This powerful expectation overrides visual cues, like shadows and depth information, that indicate anything to the contrary.
But patients with schizophrenia are undeterred by implausibility: They see the hollow face for what it is. About seven out of 1000 Americans suffer from the disease, which is characterized by hallucinations, delusions, and poor planning. Some psychologists believe this dissociation from reality may result from an imbalance between bottom-up and top-down processing — a hypothesis ripe for testing using the hollow mask illusion.
In healthy viewers, the illusion is so powerful that even when aware of the illusion (see video below), they are unable to see the concave face — the mind just flips it back. Though the illusion is strong for faces, it doesn't work well with other objects, or even with upside-down faces. This bias is likely due to the special relationship we humans have with faces. Many neuroscientists believe we have brain regions dedicated to processing faces, and some brain injuries can leave patients unable to recognize faces, even though their vision and other memories remain intact.
Dima and Jonathan Roiser of University College London wanted to understand why people with schizophrenia aren't fooled. They put 13 schizophrenia patients and 16 healthy control subjects in an fMRI scanner that measures brain activity, and showed them 3D images of concave or convex faces. As expected, all of the schizophrenic patients reported seeing the concave faces, while none of the control subjects did.
Dima and Roiser analyzed the fMRI data using a relatively new technique called dynamic causal modeling, which allowed them to measure how different brain regions were interacting during the task. When healthy subjects looked at the concave faces, connections strengthened between the frontoparietal network, which is involved in top-down processing, and the visual areas of the brain that receive information from the eyes. In patients with schizophrenia, no such strengthening occurred.
Dima thinks when healthy subjects see the illusion, which is somewhat ambiguous, their brains strengthen this connection such that what they expect — a normal face — becomes more influential, overpowering the actual, though unlikely, visual information. Schizophrenia patients, meanwhile, may be unable to modulate this pathway, accepting the concave face as reality.
Schizophrenics aren't the only ones who see the concave face — people who are drunk or high can also 'beat' the illusion. A similar disconnect between what the brain sees and what it expects to see may be occurring during these drug-induced states.
Citation: "Understanding why patients with schizophrenia do not perceive the hollow-mask illusion using dynamic causal modelling" by Danai Dima, Jonathan P. Roiser, Detlef E. Dietrich, Catharina Bonnemann, Heinrich Lanfermann, Hinderk M. Emrich, Wolfgang Dillo, NeuroImage, In Press, Available online 24 March 2009.
Number of posts: 979
Registration date: 2007-12-29
|Subject: Re: Schizophrenic Brains Not Fooled by Optical Illusion Wed Apr 08, 2009 8:39 am|| |
That is seriously creepy. Check out the video in this article
, too. I stared at the two faces for like 10 minutes and honestly can't tell how someone could possibly know the difference. Wtf.
Number of posts: 144
Registration date: 2007-07-21
|Subject: Re: Schizophrenic Brains Not Fooled by Optical Illusion Wed Apr 08, 2009 8:45 am|| |
so much for Stef's theory that taking drugs or being schizophrenic makes one not experience reality as it is.
cheap shot, I know, but still
I second the thing about the two faces and not being able to see the difference. Freaky indeed
though I never considered that the pic on the right of the page could be the back of the mask. I only saw it as the front. Should I worry? - No, you shouldn't. Of course you should. -but you'd be mad then? Doesn't matter, who is this talking anyway?
worst joke ever? quite possibly yeah
Number of posts: 979
Registration date: 2007-12-29
|Subject: Re: Schizophrenic Brains Not Fooled by Optical Illusion Wed Apr 08, 2009 8:58 am|| |
I know he's not schizophrenic...but he clearly isn't experiencing reality well enough to realize how badly that joke ought never to have been made...he must be on drugs?
Number of posts: 215
Registration date: 2007-08-18
|Subject: Re: Schizophrenic Brains Not Fooled by Optical Illusion Wed Apr 08, 2009 1:22 pm|| |
The logical/anaylizing side(most commonly referred to as the left hemisphere) of your brain is an highly ordered neural network and it lives in its own world without regards to anything but the very analysis itself, turning inside-out of every petty detail no matter where the stimuli originates from(either the outside world or from your own thinking). The analyzing network is a very introspective process and this is where your sense of self is rooted. This neural network of the brain also shows most activity cause it takes a whole lot to analyze everything down to the last detail.
The other neural network takes the stimuli and aimlessly queries for patterns and associations without regards to relevancy, it has no sense of self but rather lives as one with all the information you have obtained about the whole universe you experienced. This network while not showing as much activity has a more homogeneous levels of activity as it is constantly querying for associations and patterns.
Schizophrenia is a symptom of an hyperactivity of the analyzing neural network which will then dominate the personality and worldview by suppressing the other neural network. The reason you come to experience hallucination and become paranoid is because the analyzing neural network do not discriminate stimuli coming from your own thoughts and stimuli coming from outside, it merely analyzes it all without regards to patterns and association and the two realities(the outside world and your inner thinking) will meld together without the information provided from the other side of the brain in the other neural network.
No one experiences the real world, we can simply not. We all make models of the world some more accurate than others. It is a result of an evolutionary advantage to perceive the world most beneficial to your survival, you simply have no use and in many cases would be catastrophic to your survival if you could perceive every single molecule in detail, the whole electromagnetic spectra and so on. A schizophrenic personality just have a different model of the world. I do not see how one could objectively call one or another model of how one perceives the world as more or less wrong. It simply is another kind of model. A schizophrenic world incorporates a different set of stimuli in the model, nothing inherently wrong with that, just different.
A person that has a fairly well balance, between the neural networks do of course have a hard time seeing any difference because the non-logical side is feeding associations and patterns into the model, while a schizophrenic personality merely analyzes the object and models it without much associations nor patterns attached.
|Subject: Re: Schizophrenic Brains Not Fooled by Optical Illusion Wed Apr 08, 2009 9:31 pm|| |
|Danny Shahar wrote:|
That is seriously creepy. Check out the video in this article, too. I stared at the two faces for like 10 minutes and honestly can't tell how someone could possibly know the difference. Wtf.
can tell the difference. Which is interesting to me because my visio-spatial perception isn't that great. I suck at action games.