Sensory substitution
Sensory substitution is the conversion of sensory stimuli from one particular sensory modality into another in order to be able to compensate (substitute) for the loss of the relevant sensory modality (e.g. due to disability or illness).
It is hoped that such systems will be able to help disabled people by replacing a defective sense with another sense.
A sensory substitution system consists of three parts:
- sensor
- Coupling system
- Stimulator
The sensor records stimuli and forwards them to the coupling system, which interprets the signals and transmits them to the stimulator. If the sensor receives signals that were not previously available to the wearer of the system, this is called perception expansion (“ sensory augmentation ”).
Sensory substitution, on the other hand, affects human perception and the plasticity of the brain and therefore allows these aspects of neuroscience to be studied more through neuroradiology .
history
Paul Bach-y-Rita is usually seen as the father of sensory substitution , who already in the early 1960s enabled blind people to find their way around the room by transmitting image information in pressure stimuli on the skin. For this purpose, the image of a video camera is imaged on part of the skin of the blind by means of pressure . Because this sensory substitution is embedded in the sensorimotor loop , i.e. the direct change in sensory perception through active movement of the blind, the brain soon learns to use these stimuli and so after a few weeks the skin sensation disappears and a spatial sensation takes its place.
This historic invention was followed by many studies on sensory substitution in the field of perceptual and cognitive neuroscience.
Physiology of sensory substitution
Generally, when someone becomes blind or deaf, they do not lose their ability to see or hear. All that is lost is the ability to transmit sensory signals from the periphery ( retina for vision and cochlea for hearing) to the brain. Since the pathways that transmit visual impressions are still intact, someone who has lost their ability to receive data via the retina can still see subjective images if this data is collected through other sensory modalities, such as the sense of touch or Listen.
In a regular visual system, the data collected by the retina is converted into electrical stimuli in the optic nerve and passed on to the brain, which recreates and perceives the image. Since the brain is responsible for the final perception, sensory substitution is possible. During such a substitution, an intact sensory modality forwards information to the areas of the brain that are responsible for visual perception, so that the person perceives seeing. In the case of sensory substitution, information obtained through one sensory modality can reach brain structures that are physiologically related to other sensory modalities. Sensory substitution of keys-to-See ( English touch-to-visual ) transferred information from touch receptors to the visual cortex to local interpretation and perception. For example, fMRI can be used to determine those parts of the brain that are activated during sensory perception. In the case of blind people, while they are merely receiving tactile information, their visual cortex is also activated when they perceive objects to "see".
There is also touch-to-touch sensory substitution , where information from touch receptors in one region can be used to perceive touch in another region. For example, in an experiment by Bach-y-Rita, tactile perception was restored in a patient who had lost his peripheral sense of touch due to leprosy .
Technological support
In order to preserve sensory substitution and to stimulate the brain without intact sensory organs that transmit the information, one can also develop machines that take over the transmission of signals. This brain-computer interface is located where the external ones are collected and converted into electrical signals for the purpose of interpretation by the brain. Generally, a camera or microphone is used for this to collect the visual or auditory stimuli that are used to replace the lost sensory information. The visual or auditory data collected by the sensors are then converted into tactile stimuli, which in turn are passed through to the brain for the purpose of visual and auditory perception / perception. This kind of sensory substitution is only possible thanks to the plasticity of the brain.
Brain plasticity
Brain plasticity is the brain's ability to adapt to the complete absence or deterioration of a sense. Sensory substitution can therefore most likely be explained by studying brain plasticity. To cortical mapping (English cortical re-mapping ) or reorganization occurs when the brain undergoes a kind of deterioration. It is an evolutionary mechanism that allows people with a loss of senses to adapt to it and to compensate for the loss by using other senses. Functional imaging of patients who have been blind since birth showed cross-modal recruitment of the occipital cortex while performing perceptual tasks such as: B. Reading Braille , tactile perception, object recognition using keys, sound localization and sound differentiation. This proves that blind people can use their occipital lobe , which is mainly used for vision, to perceive objects through the use of other sensory modalities, which would explain their common tendency to amplify the remaining senses.
Perception versus sensation
While sensory aspects of the physiological substitution speaks, it is essential (English between sensation sensing ) and perception (English perception to distinguish). The main question posed by this differentiation is: Are blind people able to see or perceive seeing by combining different sensory data? While the sensation arrives via a particular modality - visual, auditory, tactile, etc. - perception due to sensory substitution does not only include one modality, but is the result of cross-modal interactions. Hence, it can be said that while sensory substitution of vision induces vision-like perception in sighted people, it induces auditory or tactile perception in blind people. In short: blind people perceive seeing through touch / touch and hearing through sensory substitution.
Sensory augmentation / expansion
Based on the research on sensory substitution, investigations into the possibility of expanding (augmenting) the body's sensory perception began. The intention behind this is to expand the body's ability to sense aspects of the environment to areas that are normally imperceptible.
Active work in this direction is being promoted by the e-sense project of the Open University and Edinburgh University and the feelSpace project of the University of Osnabrück .
The results of the relevant investigations (as well as with regard to sensory substitution in general), which the emergence of perceptual experience ( qualia ) from neuron activity, have implications for the understanding of consciousness .
Magnetic perception (orientation to the earth's magnetic field)
In 2005 the feelSpace group carried out a study on sensory augmentation, in which a vibrotactile magnetic compass belt was worn around the waist. In this study, participants were given the direction of the magnetic north pole as a vibration at the waist (the part of the belt that vibrated that was pointing north).
Significant improvements in the implementation of navigation tests were observed, which exceeded the performance of those from the control group in the same period with the same training. At the same time, the perception of belt vibrations underwent a fundamental change in half of the participants: from simple tactile innervation to real and immediate sensory perception of allocentric orientation. In other words, they could perceive 'north' as an entity that had nothing to do with the vibratory transmitter around the waist, much like a glass on a table would be perceived as an entity that was more than the reflection of photons on the retina. In addition, tests regarding the influence of the belt information on the rotational nystagmus effect suggest that - after training - the processing of the belt information had become subcognitive.
See also
literature
Individual evidence
- ^ Paul Bach-y-Rita, CC Collins, F. Saunders, B. White, L. Scadden: Vision substitution by tactile image projection . In: Nature . tape 221 , 1969, p. 963-964 .
- ^ Nicholas Humphrey , A History of the Mind: Evolution and the Birth of Consciousness . Springer, 1999, ISBN 0-387-98719-3 ( limited preview in Google book search).
- ^ Paul Bach-y-Rita: Tactile sensory substitution studies . In: Annals of New York Academic Sciences . tape 1013 , 2004, pp. 83-91 .
- ↑ a b L. Renier, AG De Volder: Cognitive and brain mechanisms in sensory substitution of vision. A contribution to the study of human perception . In: Journal of Integrative Neuroscience . tape 4 , no. 4 , 2005, p. 489-503 .
- ↑ Paul Bach-y-Rita, SW Kercel: Sensory substitution and the human-machine interface . In: Trends in Cognitive Neuroscience . tape 7 , no. 12 , 2003, p. 541-546 .
- ↑ a b JK O'Regan, A. Noe: A sensorimotor account of vision and visual consciousness . In: Behavioral and Brain Sciences . tape 24 , no. 5 , 2001, p. 939-973 .
- ^ Paul Bach-y-Rita: Brain Mechanisms in Sensory Substitution . Academic Press New York, 1972.
- ^ A b Paul Bach-y-Rita: Nonsynaptic Diffusion Neurotransmission and Late Brain Reorganization . Demos-Vermande, New York 1995.
- ↑ C. Poirier, AG De Volder, C. Scheiber: What neuroimaging tells us about sensory substitution . In: Neuroscience and Behavioral Reviews . tape 31 , 2007, p. 1064-1070 .
- ↑ e-sense project ( Memento of the original from December 8, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b feelSpace
- ^ SK Nagel, C. Carl, T. Kringe, R. Märtin, P. König: Beyond sensory substitution - learning the sixth sense . In: Journal of neural engineering . tape 2 , no. 4 , 2005, p. R13-26 ( online ).
