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Dolphins Can 'See' Underwater By Using 'Echolocation' Technique, Scientists Find

Experts trace auditory signals in the cerebellum cortex of a dolphin and gain meaningful insights about echolocation that facilitates it.

BY SOMDATTA MAITY

PUBLISHED 5 HOURS AGO

Bottlenosed dolphins at the water's surface. (Representative Cover Image Source: Getty Images | Stuart Westmorland)

A team of researchers has managed to delve deeper into the minds of dolphins. They are hopeful that it will aid them in understanding an intriguing process called "echolocation," which stimulates mammals, like dolphins, orcas, and beluga whales, in traversing dark and murky habitats, according to Earth. For the first time, a study published in PLOS ONE showcases how this process is facilitated in the brains of these marine beings. Scientists define echolocation as a biological sonar system used by beings like dolphins to find their way underwater, hunt their prey, and communicate with other members of their kind.

Bottle-nosed dolphins (Tursiops truncatus) Honduras,underwater view - stock photo (Representative Image Source: Getty Images | Photo by Stuart Westmorland)

In this process, they send a series of high-frequency clicks, which then travel through water and reflect off objects in their way. These reflections are echoes, which are processed by echolocators to determine the distance, pace, size, shape, as well as the internal structure of the objects. These objects could be the targets they want to hunt or things they possibly encounter. Humans can't use this process because the clicks are too high-pitched for them to understand, according to Cosmos Magazine. Researchers know this about humans as they have mapped their brains. However, the same has not been done with as much detail for dolphins. For a long time, experts have been in pursuit of understanding the aspects of dolphin brains that allow echolocation to happen.

Inferior Colliculi and Cerebellum ROIs. (Image Source: PLOS ONE)

In this study, researchers attempted to understand the facilitation of this process by comparing the brains of echolocating dolphins with non-echolocating baleen whales. The subjects used for the examination were deceased or stranded. Experts focused on the differences in the auditory pathways of an echolocating mammal and a non-echolocating one. For the analysis, experts also utilized already available information on how humans process auditory signals. They essentially traced the path taken by sound in the subjects to the cerebral cortex. Before the examination, this part of a dolphin's brain had not undergone much analysis.

Dolphin using echo location - stock illustration (Representative Image Source: Getty Images | Photo by VICTOR HABBICK VISIONS) — Dolphin using echo location. (Representative Image Source: Getty Images | VICTOR HABBICK VISIONS)

The team zoomed in on a portion called the "inferior colliculus" in dolphins and baleen whales using a high-resolution brain imaging technique. The inferior colliculus is also present in humans. This part is the stage where sound signals pass on to more complex zones for processing. They chose this bilateral structure for examination due to it being a common factor across species, which also features a considerable point of difference between the two subjects examined for the study, according to Eco Magazine. For dolphins, the portion is larger when contrasted with their total brain size compared to other terrestrial species. Based on the difference, experts concluded that the pathway of auditory information through this part must contain the secret of echolocation. The tracing led to surprising results for researchers.

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Both dolphins and non-echolocating baleen whales, like the sei whale, depend on sensitive hearing while communicating. However, only dolphins perform echolocation, suggesting they must have stronger auditory projections compared to the sei whales. But this was not the case. Analysis showcased that dolphins had more projection sites but not stronger projections. The only area where the projections were stronger in dolphins, compared to the sei whales, was in descending pathways extending from the inferior colliculi to the cerebellum. The finding provided researchers with the breakthrough they needed to understand how echolocation translates in the brains of dolphins.

Peter Tyack, Emeritus research scholar in Biology at the Woods Hole Oceanographic Institution (WHOI) and a co-author of the study, believes that the stronger projections imply that the cerebellum is an integration center where sensory and motor information are combined for processing. Furthermore, the part could also serve as a rapid prediction center, where the body's future actions based on the situation in front of them are decided. Based on the findings, researchers claimed that dolphins point their heads toward the objects they want to perceive and release a narrow-beam echolocation click. According to Tyack, echolocation is "part hearing and part vocalization." Here, they are producing the energy, which eventually returns to their projections.

The energy and direction of the clicks are distinct for different objects, and the "perception" of this energy aids the dolphins in detecting the difference between the target objects. This calculation of how much energy needs to be emitted and in which direction it is pointed is possibly done with the help of stronger projections present in the descending pathways extending from the inferior colliculi to the cerebellum. This function is facilitated by integrating sensory and motor information. However, researchers are ecstatic that they have taken one step forward in resolving the mystery of echolocation and want to continue their trajectory by analyzing more dolphin and mammal brains.