Guru Magazine - - IN THE NEWS - Ross Harper

Any­one who saw the 1997 block­buster, Men

In Black, will be aware that one day – thanks to a pen torch and some strate­gi­cally-placed sun­glasses – trou­bling mem­o­ries will be a thing of the past. Well we may not be there yet, but if Merel Kindt and her col­leagues are cor­rect, we’re not that far off. The re­sults from their Am­s­ter­dam Univer­sity labs showed that tak­ing the old-fash­ioned blood pres­sure medicine, pro­pra­nolol, can fully erase fear mem­o­ries. Sixty vol­un­teers were trained to as­so­ciate a spi­der pic­ture with fear by giv­ing them small elec­tric shocks. Th­ese vol­un­teers demon­strated that their brains had learned to make the as­so­ci­a­tion by show­ing an ex­ag­ger­ated

star­tle re­sponse when­ever they were sub­se­quently shown a spi­der photo. How­ever, Kindt showed that, when in­di­vid­u­als took pro­pra­nolol and were then shown the spi­der pic­ture days later, their ex­pres­sion of fear was com­pletely abol­ished – un­like those who did not re­ceive the tablet, whose star­tle re­sponse re­mained un­changed. This new mem­ory-wip­ing tech­nique is based on the prin­ci­ple of mem­ory re­con­sol­i­da­tion: when we re­mem­ber some­thing, the in­voked mem­ory is re­trieved from its long-term stor­age lo­ca­tion (in a part of the brain called the neo­cor­tex) – at which point it be­comes vul­ner­a­ble to dis­rup­tion. (It’s a bit like retriev­ing a file from a fil­ing cabi­net. Once the file is re­moved, the pa­pers stored in the file could get jum­bled up in a way that’s not pos­si­ble while the file is safely stored away.) The mem­ory is then ‘resta­bi­lized’ by be­ing stored back into the neo­cor­tex – where it be­comes re­sis­tant to change once again. It is thought that this process may un­der­lie our abil­ity to strengthen and weaken in­di­vid­ual mem­o­ries based on new ex­pe­ri­ences. In her ex­per­i­ment, Kindt man­aged to block resta­bi­liza­tion of the fear mem­ory, caus­ing it to be lost for­ever: once re­trieved from the ‘fil­ing cabi­net’ of our neo­cor­tex, the mem­ory ‘file’ was ba­si­cally shred­ded by the pro­pra­nolol be­fore it could be safely re-filed. Un­for­tu­nately for the sci-fi fans among us, tak­ing pro­pra­nolol did not cause in­di­vid­u­als com­pletely to for­get the whole ex­pe­ri­ence of be­ing tested: they ex­pected to re­ceive a shock when pre­sented with the pic­ture of a spi­der, but didn’t seem to care any­more. This high­lights a lim­i­ta­tion of the mem­o­ry­wip­ing tech­nique – the drug seemed only to tar­get the fear-mem­ory link, and noth­ing else. While it may seem pos­i­tively ‘James Bond’ that mem­o­ries can be se­lec­tively erased, the idea of block­ing resta­bi­liza­tion is not a new one. Count­less ex­per­i­ments car­ried out on an­i­mals have pro­duced sim­i­lar re­sults. But Kindt’s work is spe­cial be­cause she has shown that tak­ing a drug, which is al­ready well es­tab­lished in the med­i­cal com­mu­nity, can se­lec­tively erase fear mem­o­ries in hu­mans. This could prove to be a land­mark dis­cov­ery in the treat­ment of psy­cho­log­i­cal trauma (in par­tic­u­lar, post-trau­matic stress dis­or­der) and could even be ex­tended to ther­a­pies for drug ad­dic­tion. So what next? Well, as with all new treat­ments, rig­or­ous test­ing will have to be car­ried out: his­tory is lit­tered with the empty pack­ets of in­no­va­tive new medicines, which never made it through clin­i­cal tri­als. In­deed, three years af­ter the ini­tial ex­per­i­ment, we are still wait­ing for any key de­vel­op­ments. So, for now, psy­chol­o­gists and neu­ro­sci­en­tists sit with crossed fin­gers – the hope be­ing that the treat­ment of un­pleas­ant mem­o­ries will soon be read­ily achiev­able through a sim­ple process of ‘ther­a­peu­tic for­get­ting’.

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