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.”
Jenny Gimpel | EurekAlert!
Further reports about: > Cognitive Neuroscience > Hollow mask illusion > Medical Wellness > Neuroscience > THC > UCL > brain area > brain disconnects > cannabis users > concave > convex > mental illness > pointing inwards > pointing outwards > schizophrenia > schizophrenia patients > tetrahydrocannabinol > three-dimensional ‘hollow mask’ illusion > visual information
Mobile phone test can reveal vision problems in time
11.02.2016 | University of Gothenburg
Proteomics and precision medicine
08.02.2016 | University of Iowa Health Care
Today, plants and microorganisms are heavily used for the production of medicinal products. The production of biopharmaceuticals in plants, also referred to as “Molecular Pharming”, represents a continuously growing field of plant biotechnology. Preferred host organisms include yeast and crop plants, such as maize and potato – plants with high demands. With the help of a special algal strain, the research team of Prof. Ralph Bock at the Max Planck Institute of Molecular Plant Physiology in Potsdam strives to develop a more efficient and resource-saving system for the production of medicines and vaccines. They tested its practicality by synthesizing a component of a potential AIDS vaccine.
The use of plants and microorganisms to produce pharmaceuticals is nothing new. In 1982, bacteria were genetically modified to produce human insulin, a drug...
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...
The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.
Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...
Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.
The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels
A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...
09.02.2016 | Event News
02.02.2016 | Event News
26.01.2016 | Event News
11.02.2016 | Life Sciences
11.02.2016 | Physics and Astronomy
11.02.2016 | Earth Sciences