It requires the brain to align the tactile sensation on the skin with spatial information about our surroundings and our posture. For the first time, a study done by the Cognitive Neuroscience Research Group (GRNC), attached to the Barcelona Science Park, has shown how this process unfolds over time, examining the conflicts posed by the coexistence of differing spatial maps in the brain.
GRNC researchers Salvador Soto-Faraco (ICREA research professor) and Elena Azañón conducted the study forthcoming in the 22 July issue of the journal Current Biology, available online on 10th July (doi:10.1016/j.cub.2008.06.045).
“The main finding of the study is that it has enabled us to confirm that tactile sensations are initially located unconsciously in anatomical coordinates, but they reach our awareness only when the brain has formed an image of their origin in the spatial coordinates, external to the body,” explained Salvador Soto-Faraco. The coexistence of different spatial reference frames in the brain has been known for some time. So has the fact that confusions between them may result in some cases, such as when we invert the usual anatomical position of some body parts (e.g. when crossing our arms over the body midline). “The brain sorts out problems of this kind rapidly, in a matter of tenths of a second. To do so, however, it has to integrate information arriving in formats that are quite disparate”, Sotoa-Faraco added. “Our research has helped us understand how this process works and how the brain manages spatial realignment when faced with conflict”, he concluded.
A simple example serves to illustrate the confusion that can occur when different spatial reference frames are set in conflict: cross one of your arms over the other, then interleave the fingers of both hands together, palms touching, and turn your hands towards your body so that the left hand is on the right side and vice versa. While holding this position, if you receive an instruction but no direct physical contact that you are to move one of your fingers, you will most likely move the equivalent finger of the opposite hand.
In order to determine how long it takes for the brain to realign these conflicting spatial reference frames, the GRNC researchers devised a specific methodology that enabled indirect measurement of the location of a tactile sensation on the skin. To do this, they measured response times to a brief flash (produced with an LED light emitting diode) appearing near one of the observer’s hands. The researchers then compared the reaction times to the flash when it had appeared near a hand that had previously received a tactile stimulus, versus when the flash had appeared near the opposite hand. In the main study, the participants (a group of 32 university students) were asked to cross their arms so that their right hand lay in their left-hand visual field and vice versa. The purpose of this procedure was to ensure that the actual external position of the hands was in conflict with their anatomical location.
Each participant underwent roughly 600 essays of this sort. The time between the tactile sensation and the appearance of the target visual stimulus, as well as their realtive locations, were varied at random. It was observed that the participants’ responses to the flash changed dramatically as a function of the time elapsed between receiving the tactile sensation and the presentation of the visual stimulus. In the initial phase (60 ms or earlier), the brain tended to locate the tactile sensation in anatomical terms, i.e. if it received the sensation on the left hand, even though it was crossed over to the right- visual field, the sensation was processed as though it had happened on the left-hand side of the body. However, only a few tenths of a second later (roughly 200 ms), compensation occurred and the tactile sensation was determined to arise from the right-hand side. Curiously, when participants in the study were asked to locate the tactile stimulus explicitly, they always referred their response to its external source. This reveals that, although a transition occurs from an initial anatomically-based reference frame towards a visually or externally-based reference frame, we apparently become aware of the tactile sensation in the latter phase.
“The study’s results have allowed us to deepen our understanding of how tactile information is located, suggesting that our brain avoids confusions among the various spatial reference frames by keeping the initial part of the process below the threshold of awareness”, explained Soto-Faraco. “Put simply, it could be said that this system of spatial transformation works much as when we hastily jot down some rough notes and later copy them out into final form, discard the original draft,” he concluded.Reference:
Carme Pérez | alfa
A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg
Urbanization to convert 300,000 km2 of prime croplands
27.12.2016 | Mercator Research Institute on Global Commons and Climate Change (MCC) gGmbH
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...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering