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
Penn vet research identifies new target for taming Ebola
12.01.2017 | University of Pennsylvania
The strange double life of Dab2
10.01.2017 | University of Miami Miller School of Medicine
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction