Binge eat­ing trig­ger point lo­cated deep inside brain SCI­EN­TISTS

Pakistan Observer - - KARACHI CITY -

be­lieve they have lo­cated a point deep in the brain that links an ex ter­nal trig­ger to binge-eat­ing or drugseek­ing be­hav­iour. They found when they switched off cer­tain brain cells in that lo­ca­tion, rats that had once re­sponded ex­cit­edly and speed­ily to cues for sugar - much like binge-eat­ing - re­sponded with less mo­ti­va­tion and ur­gency. The find­ing could lead to new ways to help peo­ple re­duce ad­dic­tive be­hav­iour, they sug­gest.

The re­searchers re­port their find­ings in the jour­nal Neu­ron. Lead au­thor Dr. Jo­ce­lyn M. Richard, who re­searches psy­cho­log­i­cal and brain sci­ences at Johns Hop­kins Univer­sity in Bal­ti­more, MD, says: “Ex­ter­nal cues - any­thing from a glimpse of pow­der that looks like co­caine or the jingle of an ice cream truck - can trig­ger a re­lapse or binge eat­ing. Our find­ings show where in the brain this con­nec­tion be­tween en­vi­ron­men­tal stim­uli and the seek­ing of food or drugs is oc­cur­ring.”

The area of the brain that the study fo­cuses on is called the ven­tral pal­lidum (VP), a struc­ture within the basal gan­glia - a col­lec­tion of brain cell clus­ters lo­cated deep be­neath the cere­bral cor­tex, the outer layer of the brain that is often re­ferred to as gray mat­ter. While it is thought that the VP is in­volved in re­ward seek­ing, note the authors, very lit­tle is known about its role in trig­ger­ing be­hav­iour in re­sponse to in­cen­tive cues.

To in­ves­ti­gate this fur­ther, the team trained rats to learn that if they pushed a lever when they heard a par­tic­u­lar sound - such as a siren or se­ries of sharp beeps - they would be re­warded with a drink of sugar wa­ter. The re­searchers then got the trained rats to re­spond to the trig­gers while they mon­i­tored neu­ron ac­tiv­ity within their VP ar­eas.

The team saw that many more neu­rons than ex­pected be­came ac­tive - and quite vig­or­ously so - as the rats heard the cues they had been trained to re­spond to. The re­searchers also noted that the stronger the neu­ron ac­tiv­ity, the more rapidly the rats re­sponded and sought their re­ward. The team could even pre­dict how fast the rats would move to­ward their re­ward just from ob­serv­ing the size of the neu­ron re­sponse to the cue, as Dr. Richard ex­plains:

“We were sur­prised to see such a high num­ber of neu­rons show­ing such a big in­crease in ac­tiv­ity as soon as the sound played.” In an­other part of the study, Dr. Richards and col­leagues used op­to­ge­net­ics to tem­po­rar­ily turn off the VP neu­rons when the rats were ex­posed to the sound cues. Op­to­ge­net­ics is a method where an­i­mals like rats and mice are ge­net­i­cally en­gi­neered to have brain cells that can be se­lec­tively switched on or off us­ing light pulses.

When they switched the trained rats’ VP neu­rons off, the re­searchers found they were less likely to pull the levers to get the sugar wa­ter. Also, when the rats did pull the levers, they did so much more slowly.

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