How our brains op­er­ate like GPS

Sci­en­tists pin­point cells that in­te­grate in­for­ma­tion from the senses and help us de­cide which way to go

Sunday Times (Sri Lanka) - - INTERNATIONAL - By Shivali Best

You may think that nav­i­gat­ing your way around a city is as easy as see­ing where you are, and then step­ping in a cer­tain di­rec­tion. But a new study has re­vealed that in or­der to find your way around, your brain must per­form com­plex cal­cu­la­tions that work in a sim­i­lar way to GPS. The find­ings could shed light on why peo­ple with Alzheimer's dis­ease and other neu­ro­log­i­cal dis­or­ders of­ten find it dif­fi­cult to nav­i­gate un­aided.

Re­searchers from Florida State Univer­sity have dis­cov­ered new in­sights into how the brain is or­ga­nized to help a per­son nav­i­gate through life. Dr. Aaron Wil­ber, lead au­thor of the study, said: 'We have not had a clear un­der­stand­ing of what hap­pens when you step out of a sub­way tun­nel, take in your sur­round­ings and have that mo­ment where you in­stantly know where you are. Now we're get­ting closer to un­der­stand­ing that.'

Dr. Wil­ber wanted to get a clearer pic­ture of how a per­son makes the tran­si­tion from see­ing a scene, and then trans­lat­ing the im­age into a plan for nav­i­ga­tion. He dis­cov­ered that a re­gion of the brain called the pari­etal cor­tex helps make that hap­pen, by in­te­grat­ing in­for­ma­tion from var­i­ous senses and help­ing a per­son un­der­stand what ac­tion to take as a re­sult.

The re­sponse gets recorded as a mem­ory with help from other parts of the brain, cre­at­ing a 'map' of the lo­ca­tion that a per­son can re­call to help get around from place to place. This means that in the fu­ture a per­son can link that same view to the brain's map and know what ac­tion to take.

The re­searchers dis­cov­ered how the pari­etal cor­tex al­lows us to per­form the ap­pro­pri­ate ac­tion for a par­tic­u­lar lo­ca­tion. Sin­gle cells in that re­gion take in streams of sen­sory in­for­ma­tion to help a per­son get ori­ented, but those in­di­vid­ual cells also clus­ter, and work to­gether as a 'mod­ule'. Those mod­ules in the pari­etal cor­tex gen­er­ate a phys­i­cal re­sponse and, at the same time, are able to re­con­fig­ure them­selves as a per­son learns and makes mem­o­ries.

Dr. Wiber said: 'These dif­fer­ent mod­ules are talk­ing to each other and seem to be chang­ing their con­nec­tions just like sin­gle cells change their con­nec­tions. But now we're talk­ing about large groups of cells be­com­ing wired up in dif­fer­ent ways as you learn and re­mem­ber how to make a series of ac­tions as you go about your day-to-day business.'

To un­der­stand the brain mech­a­nism, the re­searchers recorded var­i­ous areas in a rat's brain, and plot­ted the ac­tiv­ity pat­terns in a vis­ual model. Every time the an­i­mal per­formed a series of ac­tions, the team then doc­u­mented an iden­ti­cal se­quence of pat­terns. While the rat slept, the re­searchers con­tin­ued to make record­ings, and dis­cov­ered that the an­i­mal re­played the same ac­tions in the brain dur­ing dream­ing at a rate about four times faster than real-life speed. Dr. Wil­ber said: 'We think these fast-for­ward "dreams" we ob­serve in rats could ex­plain why in hu­mans when you dream and wake up, you think a lot more time passed than ac­tu­ally has be­cause your dreams hap­pen at high speed or fast for­ward. Maybe dreams hap­pen in fast for­ward be­cause that would make it eas­ier to cre­ate new con­nec­tions in your brain as you sleep.'

The re­searchers hope their find­ings will help to un­der­stand how the cre­ation of new con­nec­tions breaks down in peo­ple with neu­ro­log­i­cal dis­or­ders, such as Alzheimer's dis­ease.

A study re­veals that to find your way around, your brain per­forms com­plex cal­cu­la­tions sim­i­lar to GPS.

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