Navigation Links
Hollow mask illusion fails to fool schizophrenia patients
Date:4/6/2009

Patients with schizophrenia are able to correctly see through an illusion known as the 'hollow mask' illusion, probably because their brain disconnects 'what the eyes see' from what 'the brain thinks it is seeing', according to a joint UK and German study published in the journal NeuroImage. The findings shed light on why cannabis users may also be less deceived by the illusion whilst on the drug.

People with schizophrenia, a mental illness affecting about one per cent of the population, are known to be immune to certain vision illusions. The latest study confirms that patients with schizophrenia are not fooled by the 'hollow mask' illusion, and that this may relate to a difference in the way two parts of their brains communicate with each other the 'bottom-up' process of collecting incoming visual information from the eyes, and the 'top-down' process of interpreting this information.

Illusions occur when the brain interprets incoming sensory information on the basis of its context and a person's previous experience, so called top-down processing. Sometimes this process can mean that people's perception of an object is quite different to reality a phenomenon often exploited by magicians. The new study, by scientists at the Hannover Medical School in Germany and UCL Institute of Cognitive Neuroscience in the UK, suggests that patients with schizophrenia rely considerably less on top-down processing during perception.

The study used a variation on the three-dimensional 'hollow mask' illusion. In this illusion, a hollow mask of a face (pointing inwards, or concave) appears as a normal face (pointing outwards, or convex). During the experiment, 3D normal faces and hollow faces were shown to patients with schizophrenia and control volunteers while they lay inside an fMRI brain scanner, which monitored their brain responses.

As expected, all 16 control volunteers perceived the hollow mask as a normal face mis-categorising the illusion faces 99 percent of the time. By contrast, all 13 patients with schizophrenia could routinely distinguish between hollow and normal faces, with an average of only six percent mis-categorisation errors for illusion faces.

The results of the brain imaging analysis suggested that in the healthy volunteers, connectivity between two parts of the brain, the parietal cortex involved in top-down control, particularly spatial attention, and the lateral occipital cortex involved in bottom-up processing of visual information, increased when the hollow faces were presented. In the patients with schizophrenia, this connectivity change did not occur. These results suggest that patients with schizophrenia have difficulty coordinating responses between different brain areas, also known as 'dysconnectivity', and that this may contribute to their immunity to visual illusions. The research group is now investigating dysconnectivity in schizophrenia further, which will hopefully advance our understanding of this disorder.

Danai Dima, Hannover Medical School, says: "The term 'schizophrenia' was coined almost a century ago to mean the splitting of different mental domains, but the idea has now shifted more towards connectivity between brain areas. The prevailing theory is that perception principally comprises three components: firstly, sensory input (bottom-up); secondly, the internal production of concepts (top-down); and thirdly, a control (a 'censor' component), which covers interaction between the two first components. Our study provides further evidence of 'dysconnectivity' between these components in the brains of people with schizophrenia."

Dr Jonathan Roiser, UCL Institute of Cognitive Neuroscience, says: "Our findings also shed light on studies of visual illusions which have used psychomimetics drugs that mimic the symptoms of psychosis. Studies using natural or synthetic tetrahydrocannabinol (THC), the ingredient of cannabis resin responsible for its psychotic-like effects, have found that people under the influence of cannabis are also less deceived by the hollow mask illusion. It may be that THC causes a temporary "disconnection" between brain areas, similar to that seen in patients with schizophrenia, though this hypothesis needs to be tested in further research."


'/>"/>

Contact: Jenny Gimpel
j.gimpel@ucl.ac.uk
44-207-679-9726
University College London
Source:Eurekalert

Related medicine news :

1. Hollow gold nanospheres show promise for biomedical and other applications
2. ev3 and FoxHollow Technologies Announce Completion of Merger
3. Optical illusions: Variety makes us perceive smaller quantities
4. Drug Fails to Slow Progression of Atherosclerosis
5. Collagen injections can help some incontinence patients when surgery fails, researcher finds
6. FDA Fails to Protect Public: Remains Silent About Lead in Lipstick
7. Imaging of Low Back Pain Fails to Change Outcomes
8. Virginia Leaders Should Reject Flawed Smoke-Free Legislation That Fails to Protect Everyones Right to Breathe Clean Air
9. HIPAA privacy rule fails to adequately protect patient privacy and hampers health research
10. Sepsis Therapy in Preemies Fails to Boost Survival
11. Common treatment for chronic prostatitis fails to reduce symptoms
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:8/19/2017)... ... 19, 2017 , ... DMG Productions, producers of the award ... an upcoming episode, slated to air fourth quarter 2017. Check your local listings ... a company committed to supporting dentistry using the most technologically advanced restorative materials ...
(Date:8/19/2017)... (PRWEB) , ... August 19, 2017 , ... Curl Keeper® ... of NaturallyCurly.com® The Curl Leaders, Editors’ Choice 2017 Award for the second year in ... for hair stylists and curlies alike was voted Best Moisturizer for Type 2 Wavies ...
(Date:8/19/2017)... ... August 19, 2017 , ... “Congratulations! It's A Boy! God’s Gift: ... both their parents and God. “Congratulations! It's A Boy! God’s Gift: A Story of ... from Long Island, New York. , Published by Christian Faith Publishing, Dale Anthony and ...
(Date:8/18/2017)... NY (PRWEB) , ... August 18, 2017 , ... ... of “Vision & Hearing” campaign, advocating for active, healthy lifestyles and highlighting the ... available for individuals with hearing impairments and shares the latest innovations in hearing ...
(Date:8/18/2017)... VA (PRWEB) , ... August 18, 2017 , ... ... asset protection services and financial consultations to communities throughout the greater DC region, ... K9 with the goal of rescuing local animals and training them to be ...
Breaking Medicine News(10 mins):
(Date:8/2/2017)... Aug. 2, 2017 CaryRx, a next-generation full-service pharmacy, ... service for patients in the Washington D.C. ... pharmacy by providing delivery of medications through the convenience of ... delivery or delivered within one hour to any location in ... to bring this invaluable service to Washington D.C. ...
(Date:7/28/2017)... July 28, 2017 Hill-Rom Holdings, Inc. ("Hill-Rom") ... third quarter ended June 30, 2017, and updated its ... For the fiscal third quarter, Hill-Rom ... $0.68 per diluted share in the prior-year period. These ... $0.39 per diluted share primarily related to the non-cash ...
(Date:7/26/2017)... 2017  Radium Medical Aesthetics, a leading medical aesthetic clinic in ... by effectively addressing several skin conditions from the inside. ... and more fragile. The skin becomes more transparent due to the ... harmful UV rays from the sun contributes to aging skin, causing ... ...
Breaking Medicine Technology: