Research at Tel Aviv University The study examined how bats combine the sense of sight with the 'sixth sense', the sonar sense - sound waves that they send out, which are returned to them by objects in the environment * Prof. Yossi Yuval: "Understanding the combination of the senses in bats may also contribute to understanding the use of A person with multi-sensory information and even help to solve central questions regarding sensory processing and the way the brain integrates information received from different senses"
A study led by Prof. Yossi Yuval from the School of Zoology and the Sagol School of Neuroscience at Tel Aviv University revealed that in certain situations fruit bats rely on their sense of sight more than on the sonar that allows them to orientate themselves in the environment through the echoes of sound waves they transmit. More than that: they are able to translate the information received through the sonar sense into a visual image. The research was carried out by Dr. Sasha Danilovitz at the Zoological Garden of Tel Aviv University. The article was published in the journal Science Advances.
"It is a well-known fact that bats have a special sense of their kind, which allows them to find their way around even in complete darkness," says Prof. Yuval. "The sense, known as echolocation, works similar to the sonar installed in ships (to scan the underwater environment): the bats emit sound waves and process the echoes reflected from objects in the environment. This fact created among parts of the public a misconception that bats are blind. In fact, all bats see, and fruit bats of the type we studied have excellent vision, which at night is even better than that of humans. In the study, we wanted to check how they combine the two senses: the sense of sight and the sonar."
Between a cylinder and a sawmill
The study was conducted in the population of fruit bats kept in the Zoological Garden of Tel Aviv University. In the first step, the researchers taught the bats to distinguish between a smooth cube and a perforated cube in complete darkness, that is, using only the sonar. Each bat received a portion of food when it landed on the 'correct' cube, thus learning to prefer it. The researchers then reversed the situation: the cubes were exposed to light, but placed inside transparent and identical plastic boxes that could not be distinguished using the sonar because they reflect identical echoes. The bats, who actually now saw the cubes for the first time, knew how to choose the correct cube. "The meaning is that they know how to translate the information received by the sonar into a visual image, at least partially," explains Prof. Yuval.
Later, the bats learned to choose between a cylinder and a saw when both senses (sonar and vision) are active. After that they were again exposed to light to the two objects, but this time the objects were placed in transparent boxes that neutralize the use of sonar. The bats performed the task successfully using only their sense of sight. On the other hand, in the dark, when only the sonar was at their disposal, they were unable to distinguish between the objects - a finding indicating that they learned to identify the objects by sight and not by sonar. In the third part of the study, the bats flew in a corridor that splits into two tunnels - a tunnel whose end is open, and a tunnel blocked at the end. "When we blocked the tunnel with a black board, the bats always flew towards it, probably because the black board seemed to them to be the opening of a cave," says Prof. Yuval. "Only near the board did they notice, using the sonar, that the tunnel was actually blocked, and turned back. That is: the sense of sight was dominant in making the decision to fly towards the simulated 'opening', but the sonar sense prevented a collision with the barrier. This means that the bats are able to flexibly maneuver between the two senses." On the other hand, when the opening was blocked with a white board, the bats always chose the open tunnel.
"In our research, we showed with a variety of methods how the bats combine two main senses - the sense of sight and the sonar," Prof. Yuval concludes. "We discovered that in many situations they rely more on their sense of sight, and even convert the information captured by the sonar into a visual image. However, in certain situations, such as when they approach a wall, they are able to 'switch' and rely on the sonar.
Understanding the combination of the senses in bats may also contribute to understanding the use that humans make of multi-sensory information (for example, when we hear a car and see it approaching), and even help solve central questions regarding sensory processing and the way the brain integrates information received from different senses."
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