"Long before it's in the papers"
August 24, 2015


Researchers make people indecisive by tweaking brain waves

Aug. 24, 2015
Courtesy of the University of Zurich
and World Science staff

Some peo­ple find it hard to de­cide things. Now, re­search­ers say they have found that the in­tens­ity of the com­mu­nica­t­ion be­tween dif­fer­ent re­gions of the brain dic­tates wheth­er we’re in­de­ci­sive.

It’s the same old sto­ry: You’re in a res­tau­rant and can’t make up your mind what to or­der. Af­ter stu­dy­ing the men­u for some time and many dis­cus­sions, you even­tu­ally choose the steak. But you can’t re­lax dur­ing the meal and keep won­der­ing wheth­er you should have gone for the veal. 

This sketch high­lights the two brain regions—pa­ri­e­tal cor­tex (blue) and pre­fron­tal cor­tex (or­ange). (Cour­tesy of U. of Zurich)

Such dif­fi­cul­ties crop up in all as­pects of life. But they mainly af­fect pref­er­ence-based de­ci­sions, ques­tions like “what do I prefer­—melon or cher­ries?” ac­cord­ing to sci­en­tists. Purely sen­so­ry de­ci­sions, like “what is big­ger—melon or cher­ry?” are less prone to in­de­ci­siveness.

So how come some peo­ple are so un­cer­tain while oth­ers know ex­actly what they like and want? 

The researchers behind the study found that the key for sta­ble pref­er­ence choices is the in­tens­ity of com­mu­nica­t­ion be­tween two brain ar­eas that rep­re­sent our pref­er­ences or are in­volved in spa­tial ori­enta­t­ion and ac­tion plan­ning.

The investigators used a non-invasive brain stimula­t­ion meth­od that leads to co­or­di­nated os­cilla­t­ions in the ac­ti­vity of spe­cif­ic brain re­gions. The test sub­jects, who did­n’t know they were be­ing stim­u­lat­ed, had to make pref­er­ence-based or purely sen­so­ry de­ci­sions about food.

Us­ing the tech­nique, called tran­scra­nial al­ter­nat­ing cur­rent stimula­t­ion, the re­search­ers in­tensified or re­duced the in­forma­t­ion flow be­tween the pre­fron­tal cor­tex, just be­hind the fore­head, and the pa­ri­e­tal cor­tex just above both ears.

“Preference-based de­ci­sions were less sta­ble if the in­forma­t­ion flow be­tween the two brain re­gions was dis­rupted. Our test sub­jects were there­fore more in­de­ci­sive. For the purely sen­so­ry de­ci­sions, how­ev­er, there was no such ef­fec­t,” said Chris­tian Ruff, a neu­roe­conomist from the Un­ivers­ity of Zu­rich in Switz­er­land who led the study.

So “the com­mu­nica­t­ion be­tween the two brain re­gions is only rel­e­vant if we have to de­cide wheth­er we like some­thing and not when we make de­ci­sions based on ob­jec­tive facts.” There was no ev­i­dence of any gender-spe­cif­ic ef­fect, he added.

The re­search­ers weren’t able to make de­ci­sions more sta­ble by in­tensifying the in­forma­t­ion flow, they said, but they not­ed that the par­ti­ci­pants were young and healthy with well-de­vel­oped decision-making skills. On the oth­er hand, they re­marked, the find­ings could be used for ther­a­peu­tic meas­ures in the fu­ture—such as in pa­tients who suf­fer from high im­pul­sive­ness or in­de­ci­siveness af­ter brain disor­ders.

The research was reported Aug. 20 in the journal Nature Communications.

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Some people find it hard to decide things. Now, researchers say they have found that the intensity of the communication between different regions of the brain dictates whether we’re indecisive. It’s the same old story: You’re in a restaurant and can’t make up your mind what to order. After studying the menu for some time and many discussions, you eventually choose the steak. But you can’t relax during the meal and keep wondering whether you should have gone for the veal. Such difficulties crop up in all aspects of life. But they mainly affect preference-based decisions, questions like “what do I prefer—melon or cherries?” according to scientists. Purely sensory decisions, like “what is bigger—melon or cherry?” are less prone to indecisiveness. So how come some people are so uncertain while others know exactly what they like and want? A team headed by Christian Ruff, a neuroeconomist from the University of Zurich in Switzerland, found that the key for stable preference choices is the intensity of the communication between two brain areas that represent our preferences or are involved in spatial orientation and action planning. The researchers used a non-invasive brain stimulation method that leads to coordinated oscillations in the activity of specific brain regions. The test subjects, who didn’t know they were being stimulated, had to make preference-based or purely sensory decisions about food. Using the technique, called transcranial alternating current stimulation, the researchers intensified or reduced the information flow between the prefrontal cortex, located just behind the forehead and the parietal cortex just above both ears. “Preference-based decisions were less stable if the information flow between the two brain regions was disrupted. Our test subjects were therefore more indecisive. For the purely sensory decisions, however, there was no such effect,” said Ruff. So “the communication between the two brain regions is only relevant if we have to decide whether we like something and not when we make decisions based on objective facts.” There was no evidence of any gender-specific effect, he added. The researchers weren’t able to make decisions more stable by intensifying the information flow, they said, but they noted that the participants were young and healthy with well-developed decision-making skills. On the other hand, they remarked, the findings could be used for therapeutic measures in the future—such as in patients who suffer from high impulsiveness or indecisiveness after brain disorders.