Brain has a noise-can­cel­ing cir­cuit, team says

Tehran Times - - SCIENCE -

A team of sci­en­tists has un­cov­ered the neu­ral pro­cesses mice use to ig­nore their own foot­steps, a dis­cov­ery that of­fers new in­sights into how we learn to speak and play mu­sic.

The “abil­ity to ig­nore one’s own foot­steps re­quires the brain to store and re­call mem­o­ries and to make some pretty stel­lar com­pu­ta­tions,” ex­plains David Sch­nei­der, an as­sis­tant pro­fes­sor at New York Univer­sity’s Cen­ter for Neu­ral Sci­ence and one of the pa­per’s lead au­thors. “Th­ese are the build­ing blocks for other, more im­por­tant sound-gen­er­at­ing be­hav­iors, like rec­og­niz­ing the sounds you make when learn­ing how to speak or to play a mu­si­cal in­stru­ment.”

The re­search, con­ducted at Duke Univer­sity’s School of Medicine, cen­tered on an in­tu­ition -- that we are usu­ally un­aware of the sound of our own foot­steps -- as a ve­hi­cle for un­der­stand­ing larger neu­ral phe­nom­ena: how this be­hav­ior re­veals the abil­ity to mon­i­tor, rec­og­nize, and re­mem­ber the sound of one’s own move­ments in re­la­tion to those of their larger en­vi­ron­ments.

The “ca­pac­ity to an­tic­i­pate and dis­crim­i­nate th­ese move­ment-re­lated sounds from en­vi­ron­men­tal sounds is crit­i­cal to nor­mal hear­ing,” Sch­nei­der ex­plains. “But how the brain learns to an­tic­i­pate the sounds re­sult­ing from our move­ments re­mains largely un­known.”

To ex­plore this, Sch­nei­der and his col­leagues, Janani Sun­darara­jan and Richard Mooney at Duke’s School of Medicine, de­signed an “acous­tic vir­tual re­al­ity sys­tem” for the mice. Here, the sci­en­tists con­trolled the sounds the mice made walk­ing on a tread­mill while mon­i­tor­ing the an­i­mals’ neu­ral ac­tiv­ity, al­low­ing them to iden­tify the neu­ral cir­cuit mech­a­nisms that learn to sup­press move­ment-re­lated sounds.

Over­all, they found a flex­i­bil­ity in neu­ral func­tion -- the mice de­vel­oped an ad­justable “sen­sory fil­ter” that al­lowed them to ig­nore the sounds of their own foot­steps. In turn, this al­lowed them to bet­ter de­tect other sounds aris­ing from their sur­round­ings.

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