[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/7237\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EThe science of tickling: why the brain won\u2019t let us tickle ourselves\u003C\/h2\u003E\u003Cp\u003EThe first thing to understand about our inability to self-tickle is that it\u2019s just one example of a widespread phenomenon: humans respond differently to touch depending on whether the sensation was created by ourselves or something else.\u003C\/p\u003E\u003Cp\u003EIf you clap your hands, then have someone else clap one of your hands with theirs, you will generally perceive the latter as more intense. This difference in how we perceive ourselves and other things in the environment isn\u2019t limited to humans, or to touch. In 2003, a study showed that \u003Ca href=\u0022https:\/\/www.jneurosci.org\/content\/23\/11\/4717\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Ecrickets perceive their own chirps as quieter than those of other crickets\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003EHaving this ability makes sense in evolutionary terms, says Dr \u003Ca href=\u0022http:\/\/www.ehrssonlab.se\/kilteni.php\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EKonstantina Kilteni\u003C\/a\u003E at the Karolinska Institute in Stockholm, Sweden. It\u2019s useful to know if a sensation is worth paying attention to or not. \u2018If you have a bug crawling up your arm, you want to be sure you notice that,\u2019 she said.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EBody ownership\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EA prerequisite to this is that our brains have a sense of body ownership, so that we know whether a touch comes from our own moving fingers, say, or some foreign object. Understanding how this works is probably a crucial part of getting to grips with tickling. Dr Kilteni says that a raft of studies began to probe this in the late 1990s, but while they established a link between the intensity of touch and where it originates, they didn\u2019t explore the precise conditions for this. She began the \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/704438\/es\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003ETickle Me project\u003C\/a\u003E in 2017 to go deeper.\u003C\/p\u003E\u003Cp\u003EOne of her key experiments involved looking at the way people perceived touches on their fingers using a clever set up of levers. In the first part of the experiment, people touched a lever with their left forefinger, which instantly triggered a second lever to touch their right forefinger.\u003C\/p\u003E\u003Cp\u003EDr Kilteni then compared this with two variations. In the first, people let their left finger rest on a plate above the first lever, then the plate was removed letting the finger fall onto the lever. This triggered the second lever to touch the right finger, but crucially this was now involuntary. In a final variation, the right finger was touched by the lever without any input from the person at all. It turned out that people \u003Ca href=\u0022https:\/\/www.cell.com\/iscience\/fulltext\/S2589-0042(20)30026-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2589004220300262%3Fshowall%3Dtrue\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Eperceived the touches generated by these three methods as successively more intense, even though they were all made with the same force\u003C\/a\u003E. This suggests that if the brain knows a touch is coming, it feels it as less intense. This confirms that one of the reasons we cannot tickle ourselves is because our brain has already planned it, says Dr Kilteni.\u003C\/p\u003E\u003Cp\u003EIn a separate experiment that used the same lever equipment, Dr Kilteni also introduced a sneaky twist so that when the participants touched the first lever with one finger, there was a delay of a fraction of a second before the second lever touched their other finger. It turned out that this element of surprise was important; the \u003Ca href=\u0022https:\/\/elifesciences.org\/articles\/42888\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Edelay made the sensation more intense\u003C\/a\u003E. All this gives us another hint as to why self-tickling is so hard: when you tickle yourself it is hard to be caught unaware.\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018You have to get kind of rough with the rats to get them to laugh; it\u2019s rough play they like.\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EMarlies Oostland, Princeton University, US \u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003EDr Kilteni conducted a raft of experiments like this during her project, but perhaps the most telling paper she has produced \u003Ca href=\u0022https:\/\/www.jneurosci.org\/content\/40\/4\/894\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Ecame out just a few months ago\u003C\/a\u003E and concerns an area of the brain called the somatosensory cortex, a part of the brain that receives sensory information from the body.\u003C\/p\u003E\u003Cp\u003EIn one experiment she had 30 volunteers touch their index fingers together, and then separately have their fingers touched by a robot, while she scanned their brains using an fMRI machine. Some people seemed to perceive the self-touch as less intense than others, and Dr Kilteni could see that these individuals tended to have stronger connections between the somatosensory cortex and another area of the brain called the cerebellum.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ELittle brain\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThe cerebellum, or \u2018little brain\u2019, is found at the nape of the neck. It is central to the control of our bodies\u2019 movements but it is also thought to play a crucial role overseeing cognitive processing. Think of the brain like a factory with different parts processing different information and the cerebellum is the quality control supervisor. Neuroscientists suspect that the cerebellum sends signals to dial down the perception of tickling in the somatosensory cortex when it is our own fingers, not someone else\u2019s, at work. Dr Kilteni\u2019s fMRI studies lend weight to that hypothesis.\u003C\/p\u003E\u003Cp\u003EOver in New Jersey, US, Dr\u0026nbsp;\u003Ca href=\u0022https:\/\/scholar.princeton.edu\/marliesoostland\/home\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EMarlies Oostland\u003C\/a\u003E is planning to further probe this connection through her \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/844318\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003ENeuroTick\u003C\/a\u003E project. One of Dr Oostland\u2019s project supervisors, Professor Michael Brecht, at the Bernstein Center for Computational Neuroscience at Humboldt University of Berlin, Germany, was the scientist who along with his colleague Dr Shimpei Ishiyama, \u003Ca href=\u0022https:\/\/www.nytimes.com\/2016\/11\/11\/science\/tickling-rats-neuroscience.html\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Ediscovered that rats are ticklish\u003C\/a\u003E in 2016. They showed that when tickled, rats emit ultrasonic \u2018laughs\u2019 and that their somatosensory cortex lights up like a Christmas tree at the same time.\u003C\/p\u003E\u003Cp\u003ETickling the rats didn\u2019t come entirely naturally to Oostland when she had a go on a visit to Berlin. \u2018I\u2019m used to working with mice, so I was too gentle,\u2019 she said. \u2018You have to get kind of rough with the rats to get them to laugh; it\u2019s rough play they like.\u2019\u003C\/p\u003E\u003Cp\u003EDr Oostland is beginning her project at Princeton University by making fundamental studies of how the cerebellum in mice predicts the animals\u2019 movements. She is using probes to measure the activity of individual cells in the cerebellum of a mouse to understand what\u2019s going on in its brain as she puffs air at their whiskers (which isn\u2019t unpleasant but should be surprising).\u003C\/p\u003E\u003Cp\u003EArmed with this understanding, the plan is for her to then move to Prof. Brecht\u2019s lab in Germany in two year\u2019s time to study the connection between the cerebellum and somatosensory cortex and try to confirm whether and how the signals pass between the two.\u003C\/p\u003E\u003Cp\u003EAs well as helping us build a better fundamental understanding of the most sophisticated object in the universe, the human brain, Dr Oostland says work like this could help us understand autism spectrum disorder better too. People who have an injury to the cerebellum soon after birth have a 36 times higher chance of developing autism later in life. We don\u2019t fully understand why, but Dr Oostaland says fundamental studies like this could help.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research in this article was funded by the EU. If you liked this article, please consider sharing it on social media.\u003C\/em\u003E\u003C\/p\u003E\u003C\/textarea\u003E\n\u003C\/div\u003E\n\n \u003Cdiv id=\u0022edit-body-content--description\u0022 class=\u0022ecl-help-block description\u0022\u003E\n Please copy the above code and embed it onto your website to republish.\n \u003C\/div\u003E\n \u003C\/div\u003E\n\u003Cinput autocomplete=\u0022off\u0022 data-drupal-selector=\u0022form-rmsovjtudmtx-r4hu-ntkmsm9nnjdki1kbk1ro9wwzc\u0022 type=\u0022hidden\u0022 name=\u0022form_build_id\u0022 value=\u0022form-rmsoVJTUdmTx_R4hU_nTkmsm9nnjDKi1kbk1ro9WWZc\u0022 \/\u003E\n\u003Cinput data-drupal-selector=\u0022edit-modal-form-example-modal-form\u0022 type=\u0022hidden\u0022 name=\u0022form_id\u0022 value=\u0022modal_form_example_modal_form\u0022 \/\u003E\n\u003C\/form\u003E\n\u003C\/div\u003E","dialogOptions":{"width":"800","modal":true,"title":"Republish this content"}}]