Research by Weizmann Institute scientists shows that sensory perception is based on a dynamic sampling process
Intuition tells us that "active sensing" should provide the brain with completely different information compared to that obtained by "passive sensing" (for example, touch performed without movement of the fingers). But nevertheless, most of the experiments carried out today in the laboratory with the aim of investigating the sensory input reaching the brain are based on signals coming from sensory organs that are not in motion, that is, on passive sensing. Prof. Ehud Ahisher, from the Department of Neurobiology at the Weizmann Institute of Science, hopes that researching the sensory input that reaches the brain from sensory organs that are in motion will help us better understand our senses, and will enable the development of more effective aids for the deaf and blind.
The constantly vibrating whisker hairs of rats serve as an effective tool for exploring and locating objects that are near them. Prof. Ahishar, Dr. Kanarik Baghdasarian, and research student Marcin Shved investigate the movements of these whisker hairs to learn about the role played by the movement of the sensory organ in forming the animal's perception of space.
The scientists recorded the transmissions of the nerve cells that transmit the information collected by the vibrating hairs of the mustache to the brain. In this way they were able to examine the neural coding of the sensory information collected by these hypotheses. The scientists noticed two types of nerve cells: the cells of the first type were called "fluttering neurons". These cells respond to the waving movement only, regardless of contact. The cells of the second type, which the scientists called "touch neurons", transmit information to the brain about objects found in the field. Some of these cells react immediately at the moment of contact; others convey information about prolonged contact with some bone (these signals may be related to the structure and texture of the surface); And a third group of neurons transmit signals for a short time only when the whisker hairs break contact with the bone.
Later, the researchers examined the way in which these nerve cells encode the position of an object in space, and discovered that the different axes of space (vertical, frontal horizontal, and perpendicular horizontal) are encoded using different neural variables: spatial arrangement of the nerve cells, the time of their action, and the intensity of their action. These discoveries, published in the scientific journal Neuron, indicate that sensory perception does not arise from a simple series of stimulus-response events in which the sense organs quietly await stimuli. In fact, it appears to be more akin to a dynamic sampling process in which the hands, eyes, whisker hairs, and possibly other sensory organs, are constantly moving in order to collect and transmit comprehensive information about the environment to the brain.
Exit the maze
Israeli research on the vibrating Schafman of the rats will help in the development of measures for the blind and deaf
Alex Doron
The vibrating whisker hairs of rats are used for probing, locating and examining the objects in their vicinity. Israeli research on these hypotheses may lead to the development of more effective aids than the existing ones, for deaf and blind people.
The neurobiologists Prof. Ehud Ahisher and Dr. Kenrik Baghdsarian, and their assistants from the Weizmann Institute, study the movement of the whisker hairs to learn about the role this movement plays in the formation of the rat's spatial perception. Several discoveries were made in the study.
The researchers recorded the transmissions of the information collected by the vibrating hairs and transmitted from the nerve cells to the brain. It was discovered that 3 types of neurons are involved in the process: one, the "flutter neurons", responds only to the fluttering movement, regardless of the contact between the hairs and any object. The second type, "touch neurons", transmits information to the brain only about the objects found in the area where the rat moves. Some of these neurons react immediately when contact is made, and the others convey to the brain the information about prolonged contact that the animal maintains with the object it encounters. The researchers believe that these signals are related to the structure and texture of the objects in the field.
The third type of nerve cell transmits signals to the brain for only a short time, when the vibrating whisker hairs break contact with the bone the rat encountered.
The research also examined the way in which the nerve cells encode the information regarding the location of an object in space, and it was discovered that the different axes of space - vertical, horizontal-frontal and horizontal-perpendicular - are encoded using different neural variables, which include the spatial arrangement of the nerve cells, the time of their action and the intensity of the action.
In an article published by the researchers in the scientific journal Neuron, which deals with nervous system research, it was emphasized that it turns out that sensory perception does not result from a simple series of stimulus-response events. The sensory organs do not wait patiently for stimuli to reach them. The entire process is dynamic, and strives to constantly sample and examine the area.
