form+zweck 22:
Tangibility of the Digital - Die Fühlbarkeit des Digitalen


Jörg Petruschat

Scientists have found that ...


Multisensory faculties 1
Touching is not necessarily touching

It is known even from earlier investigations that three types of sensors in the skin respond to touch. In this, the first type of sensors perceives slow and sequential contact that provides information about the surface characteristics and the form of the object being touched. The second type registers more rapid contact and delivers thus information about the movements of the object and the smoothness of its surface. Finally, the third group reacts to very rapid touch. Whether these different types of sensor information are processed also separately in the brain, was not known till now.
To investigate this, scientists simulated different types of touch on sleeping apes. During the experiments they observed the brain activity in the animals. Different ways of touching during the experiments activated different areas of the so-called primary sensory cortex. The outcome was a sort of mapping of the brain area in which different areas are found to be responsible for the perception of different ways of touch. It was possible to register all types of touch by overlapping the active areas even if they do not correspond exactly to the samples tested by the scientists.
Robert Friedman et al. (), PNAS



Multisensory faculties 2
Moving in the balance

If someone is moving in a dark room, he cannot rely on visual impressions alone. Therefore, the brain uses information from the ears, muscles and skin in order to move safely from point A to point B. But also the vestibular organ controlling the body's balance plays an important role. It registers head movements and, therefore, each movement of the body with which the head also moves. This information helps the brain to correctively influence the body movements.
For their experiment two scientists asked six volunteers to bend their torso by 10 degrees laterally. In this, they were made to wear a helmet which curtailed the vision; moreover, a rigid neck brace ensured that the head and torso could only be moved simultaneously. Now the researchers stimulated the sensory nerve of the vestibular organ so that it more or less sent nerve impulses. In this way they tricked the brain that the head was moving more or less rapidly to the side.
This had the effect that the test subjects corrected their movements: Depending on the type of signal they moved their torso either more rapidly and further or slower and less to the side. In addition, the experiment showed that the signals from the vestibular organ have actually a corrective function: If the subjects did not move, the artificially created impulses had no effect. Obviously, the body consults the body's balancing system whenever the information from the other senses is not adequate - either, because the input is too small or because the movements are so complex that additional information is needed.
Brian Day, Raymond Reynolds (University College, London), Current Biology Vol. 15, p. 1390

Multisensory faculties 3
Even without a functioning vision centre the brain can record visual information

The brain can record visual information even if the actual vision centre is not functioning. Researchers blocked the so-called visual cortex in volunteers for a few seconds while showing them lines or coloured dots on the screen. Although the test subjects reported to have seen nothing they guessed afterwards the symbols shown in more than three of four instances.

We often hear about patients with heavy damage to the vision centre in the brain being able to approximately perceive the form or position of objects although, consciously, they can see nothing at all. Researchers were able to confirm this effect in their tests on eleven subjects. The scientists paralyzed in addition the visual cortex for a few hundredths of a second with the so-called Transcranial Magnetic Stimulation (TMS). A strong magnetic field induces electric current in the nerve path, so that the brain region cannot perform its function for a brief period. At the same time the scientists showed the subjects either green or red dots or a horizontal or vertical line on the screen for a few thousandths of a second.

All the subjects reported later of having seen nothing. Since their vision centre was blocked, they were able to record with their eyes the dots or lines, but did not consciously perceive them. When the researchers requested them to guess the colour of the dots or the direction of the lines the subjects did it mostly correctly: In 75 percent of the cases they guessed the position of the lines, and with the colour of the dots the success rate was even more than 80 percent.
Even if the visual cortex was blocked the information was still captured unconsciously by the brain. How it reached the higher regions of the brain even without the cooperation of the vision centre the researchers were unable to explain as yet. The observations throw a new light on the question as to where and how consciousness occurs in the brain and what this means to unconscious perception about which controversial discussions are in vogue.
Tony Ro (Rice University, Houston) et al.: PNAS (Online advance publication, doi 10.1073/pnas.0505332102).

Multisensory faculties 4
The eye understands texts differently from the ear

It is not all the same if we listen to or read a message, information or a story. The brain activates in each case a different area of the brain.

Marcel Just, a professor of psychology, and his colleagues observed the activation of over 20,000 peppercorn-sized regions of the brain by means of functional Magnetic Resonance Imaging (fMRI) - a non-invasive imaging procedure - during reading and hearing and recorded it every three seconds. The texts presented to the test subjects were messages and informative texts. They were absolutely identical in the hearing and reading versions.
Particularly two findings surprised the researchers: During the reading activity the right half of the brain - which is responsible for imaginative power, thinking in imagery and creativity - was less active than assumed till now. While listening, the so-called pars triangularis in the left half of the brain was particularly active. This pars triangularis belongs to the Broca's area which always plays a role if it is about speech processing. This region is also responsible for keeping linguistic information active for a certain period.
This conforms to the system of hearing. Because spoken language is more time-bound than written language, each syllable stays in the air only for a fraction of a second. Humans are compelled to process the meaning of the heard information immediately or to store each part of a sentence in such a way that they can trace it back later. "In contrast to this the written language supplies an "external memory" by itself in which information can be read again, if necessary. In spoken language one needs a sort of rewinding key. This is carried out by the Broca's area", Just explains.
However, Just and his associates do not want to recommend any preference to either of the possibilities of information intake. Whether one comprehends somewhat better with the eye than with the ear depends in the long run on the routines of the individual, on the information content and on the aim of the text comprehension, the researchers claim.
Marcel Just (Carnegie Mellon University), Human Brain Mapping (20.08.2001)

Multisensory faculties 5
How ventriloquists' dolls can speak

Humans believe primarily what they see. All additional sensory impressions are then processed in such a way by the brain that they agree with the visual impression. However, if the information of the eye is not sufficiently reliable the sense of hearing takes over and the visual information is verified with the acoustic information. Italian scientists described this principle of perception on which, for example, feigned actions by ventriloquists are based.

Everyone believes that in a movie film the speech comes from the actor on the screen though, actually, the loudspeakers are located at the back or next to the viewers. Also the ventriloquist's doll seems to be actually talking even if everyone knows that it cannot. These deceptions are based on a complex cooperation between sensory perceptions. The eyesight is mostly, but not always, the leader among the other senses: If the optical impressions are too indistinct and thus not reliable enough the ears take over the rudder and dominate the perception.
In their experiments scientists showed test subjects circles which moved to the right or left in small bits on a monitor. At the same time the researchers produced a sequence of short clicking noises and asked the test subjects to determine on which side the noises were heard. The subjects always assumed the origin of the noises on the side on which the circle moved - even if the noise actually came from the other side.
This changed, however, when the circles were represented as blurred forms without a sharp outline. Under these conditions the subjects did not only have any difficulty in identifying the origin of the noises correctly but also reported that the circles moved in this direction - even though in reality they were shifted in the other direction. Obviously, the brain examines visual and acoustic impressions for their reliability and decides as to which information has the higher priority. If both the perceptions are equally good, eyesight and hearing work together to make a better judgement of a situation than when information from only one sense is basically dominating.
David Alais (Pisa), David Burr (Florence), Nature Online (04.02.2004)

Multisensory faculties 6
Gesticulating helps the brain in flights of thought

If we wave about the hands while talking, we do that not for driving a point home visually. Rather we move our hands in order to be able to think better. Women scientists observed children and young people talk, who were born blind. The researchers were surprised to find that their subjects talked also with the hands although they had never seen other humans gesticulating.
Blind people use hands even when they explained something to the other blind persons. Besides, in certain tasks the subjects made similar gestures as the researchers observed in a comparative group of visually normal children and young people. "Although we worked only with relatively small groups, the observations reveal that gestures and language go "hand in hand", explained Iverson. The hand movements are to help thinking in leaps and are not a cultural habit, maintain the women scientists.
Jana Iverson, Susan Goldin-Meadow (Indiana University, Bloomington), Nature (30.11.1998)

Multisensory faculties 7
Self-perception - information from all senses helps the brain region to differentiate between one's own body parts and the environment

The so-called premotor cortex compiles information from several senses in order to decide whether a part of the body belongs to the own body or not. The image of the body is formed by this.

Participants in a study were asked to hide their actual hand under a table while a mock-up of a human hand was placed on the table. This wrong hand was positioned in such a way that the subjects had the impression that it might be their own hand. Subsequently, the psychologists touched both the artificial and the real hand at the same time with a brush. Thus, after about 11 seconds on average the test subjects succumbed to the deceptive feeling that the artificial hand was part of their own body. During the experiment the scientists observed the brain activity of the subjects by means of so-called functional Magnetic Resonance Imaging by which the activity of different areas of the brain can be made visible.

In this, the brain activity among the participants was stronger in the premotor cortex when the hallucination was more intensive. This area coordinates, among other things, conscious movements and actions. When the subjects were asked after the experiment to point to their genuine hand most of them erred and pointed to the mock-up. The brain recognises parts of the body not with a particular sensory organ but by evaluating several senses like vision, touch and the so-called sense of location. In this, the brain believes preferably what the eyes see. This applies even if the sense of location, as the experiments have shown, gives contradictory information about the position of the hand.

The self-perception and the distinction between "oneself" and "alien" is indispensable in our daily life. Without this differentiation, for example, animals would run the risk of eating their own feet when grazing.

Incorrect perception of one's own body occurs in the case a variety of illnesses. It is not unusual, for example, in schizophrenia and after a stroke that affect the premotor cortex. Disorientation of self-perception can also occur after an amputation in the form of so-called phantom pain. In this form of ailment the patient feels pain in an extremity which is no longer present.
Henrik Ehrsson et al. (University College London), Science Online advance publication, DOI: 10.1126/science.1097011 (02.07.2004)