Spanish shepherds who whistle to communicate over long distance use the same region of the brains as spoken language, a finding that reflects the extraordinary flexibility of our brains, scientists say.

The shepherds work on the mountainous island of La Gomera in the Canary Islands, where they use combinations of whistles to convey phrases over rugged terrain.

The "whistle language," Silbo Gomero, is a substitute for Spanish. It's thought that Berbers from North Africa brought the language to the island.

A shepherd from La Gomera in the Canary Island whistles the language Silbo Gomero.

Proficient whistlers vary the pitch and length of whistles to represent four consonants and two vowels. By combining the whistles, they can communicate short sentences like "there is a stray sheep."

The findings add to similar research that has found the brain's language centres are active in response to sign language in deaf people, which shows the brain's versatility in adapting to different modes of communication.

In the study, researchers used brain scans called functional magnetic resonance imaging to compare brain activity in five Spanish speakers and five shepherds who spoke Spanish and Silbo.

The imaging technology showed which regions of the brain were activated as volunteers listened to sentences in both languages.

Language recognition

When whistlers listened to Silbo sentences, parts of the left side of the brain linked to language production and comprehension were activated.

A region in the right hemisphere associated with linguisitic processing was also active, the team said in Thursday's issue of the journal Nature.

The brains of people who spoke only Spanish did not show the same response, which suggests they do not recognize words in Silbo.

"Our results provide more evidence about the flexibility of human capacity for language in a variety of forms," said study co-author David Corina of the University of Washington.

"The non-Silbo speakers were not recognizing Silbo as a language. They had nothing to grab on to so multiple areas of their brains were activated," he added in a statement.

Silbo is a rare language that linguists say is in danger of dying out. Some people in Greece, Turkey, China and Mexico also use whistled languages.