CINXE.COM

<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "royalsocietypublishing.org",cType: 'managed',cRay: '8e83812f1c985f54',cH: 'F5U17Q.NzOiArQO8QKljSvoDTjxTQRdPT5FdnPJcAMQ-1732557273-1.2.1.1-vAaaN7U8irD4T9Pas5xM4YA7_SQ1YglAYy7iMDWOiLb5NShKcjou0Qgls8Gd9oWQ',cUPMDTk: "\/doi\/10.1098\/rsnr.1992.0003?__cf_chl_tk=XGOILdKmZJJ0i_94L3yK72CgIixO8b0TI5i92wq5b0Y-1732557273-1.0.1.1-yp2BN7T9CHe1gMq8rxrwZi2rlExYJm0JOi6MlW6Hq6g",cFPWv: 'b',cITimeS: '1732557273',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/doi\/10.1098\/rsnr.1992.0003?__cf_chl_f_tk=XGOILdKmZJJ0i_94L3yK72CgIixO8b0TI5i92wq5b0Y-1732557273-1.0.1.1-yp2BN7T9CHe1gMq8rxrwZi2rlExYJm0JOi6MlW6Hq6g",md: "E_EV5dJ.KjleTuOYfpzNeeS2CB1D5HnFZr_bsB5Ojd4-1732557273-1.2.1.1-J2Ms9tkA9eQIlUTWCtegY18ahr6uhfnoc.v8lb1g5z1pMwqdJzNUN7oS.O6QTiAA9nqmiUnmoMaYUefw6bohW4x06LGOpefOhAZUUBo4l27KJgBlft27apAa4WAhO12w7mvFYgDmyq.DfIXGnHq67Gvvg_hcO2KOb3GmSkQM.lL7__PGBtalxxbHDbL7MHHwDa1RCL_6GoqBXb3mn1fwKiyCQ4OPaUZyRpCP.z4.oh1wWqrpMJvDg0LWoltpMgTKhXL3G_FnSEJbabCHhWKtbY5DtREChtvMbcS6KpKQ556lrK0qkuZs8akP79L2htNUlVvPudPZ.xNkIFHe31SeME5IIIt2sNXNmz1R8I_r2AdPVND4NJLc2Pxi4yPi.lCR9Lru8vBu04afcxycTn_0rVSs4AVvkJbwZUm1HGbw9oOJJdqP7ncW0GHwhTgPxlWHyTuM4IjhGO4.ulDar_2wF4ZnU88skK7UVy1u3sSA0_ve0VDm34wPgNugrvgSVY7sc22RIwMWb2RJfVO0pAU7cGKQ97Bi_Bqt3mAktBRzxFLu9.f2pbXBIcSDaKQoUJmPA3k4CZgHiPmE0qZK61AZix_UBVvsY8APykAsdqTJCEaP9YTKImMnHL3CUtOGmXizMLf6D3K1zD_uoSPti_GA02QihNFDQkTuQkGLTJsjoE3L7yeL2kMj71snAVeP1GYzLJ0GGUWqjGWVWMlZwAWeQXkM1sLDYLsv9YuiJ.g3rPFZdg0nyS1ymD4MVZC4Aa_KQ_N451Vgv7b5lbAHIC6TaChNDgAHh2M8HY.3HldQFFd359HWIf_uaN6ejnYWIyf6bYJk970s615uCIMXtF1LVO61hz2XmLZ5WcA5FLWh2OP4QOs69.4wSGAo8jtpETW6PHfWZLNfQq2U6ygVBLevNvHn39S3nKfCUUU3NMeQWVymkYQ5d4qLK9adSxqGbODapAfWJT7.9.5q9vXaFhtm8mCyUyjxKTnufbGyMwrdoQ4rK_Yvt2VvypAOkYD2zBNKvVZB8.pWF39tgTB4E90sZQsGHs91CSbOU13U6q8xBV5O4fHp1fLJ.0m24YIaEvoicgYRn8GNSh7mq7_Uz4efVZXEcMWLSYWzh133joJCVfCeBoCSfY74zXkNouwV6_X2vXZ7jfCUN2C_SISCeH85IVPvz23BeFUtw76DJVhLJcKmAbJwt7vqVwXKMnLbHtsgPDWMsKVGBHh.sBQEIXvmMeAWBn6el3eJMu0WzHqJFpNn2IDl9vdDB3ntUhL_gxZke09rafK5aIx90GTzgYErrpEtyeFjiPDmIYM12r4JODALqdkF6LRC2hm5eUv929l1P7c742Cro41Nd9k_1YrpODu3Xwnx.NOS0oJ_0AYGCC5QQPAY1ZdRIuggaqjyMlkyRB74j9vDB8Q1gEaTSFEoOx57OtRQkMFDuK4ej7rFlh01ptETTD8NU4k.C8PfT5ayBf9YhITCKUA4sTw2rjS6DjV4ng_uodRVLrCpTytUVIi3sV_icC6HdzK8FX_9R8R0McoIgTKVIuGNlgSQsoMs4DY.sRkHLW2bipf8K9O6JL6uC4au7Zxod8RUOQiOT.0Icl27AIzgl1ukERXswFDj_i060XXX4lDT0iR7PX0PIfmZ3oubG1ldglLZ7MZ6NrQvhMJ8gidOe6C.wVB.VS4iiHjV3hXarHazxYyS2bZ72Lcjdzs5tOEZTRguewIeCSqnoDQ_gjxrJYa4UJ7lUuL33Gy_v5TEwuRiRYGiXObTAl_XLeyvAHw0JdVb.tnpnlJo1XbCZUwHs_H5u4xXMVMqdj0KsZjEo92inzgUQUeE0kv0WDY7UHFXZAjxy1S0QQbRQAKCMPVSJtHTD0ZdR1dFnZCEdhmpxus4NkR8xZZCqT.cjj0kfAsCR7xYWBUvxHEfLTZikfSoQGrsOZy3QORNR8GfT_YFuPETfabZNteEh_OimMV24hO1rU8Aa.k6SPShwgjNjuRX5iKifXjXH4jow1ycGHZtkIYv44RgPXOwxXXejeviNanQetYNeTPXZItpYcAynPjdlfiZEaH5Mli0G_rD6ZOAn1jaUh5mexJo.6zdeoRjYhSIHBcdX1u0uSYYlezJJYV9Wf0w_KAgXB5vis9qtH3rGYcAPU5IKfpqZ9ss5VErdLuPywORWAm9Z5nGivyhIYGWR9mqhIhEjf3FgZzkeydrYSJYKwdvWTA.2DGleOSQuGTQ8XIiFZaFl1DaXoWUgpLFHRvwqMW8XlHYi94zYROo4LPZYfnqnreHYLF3k7716OP.8Va_TUpShsplCn37ULiPF64T6U3XWRvB1K60fSSclyB_SxLgLLyr_yusiP_a5uubqzX1lh6J9Ye7F2yVdxgqJ5ukWOphPZBwybDLUtksfokrQK0qdJ91S_wZbzOYL6IMXsaXDHyBKGEkSe4YxLNUndsJRZGO9NTQtEEcB5peqXEMy0X4cOn4gdQoxcU7DMPLSIZGmeQJUmi8sBtqwANRFgOwqIlplP2OYia4RcjM1s1p.1ayS183peVLKsStCPsOpsKuiiA29IVxjCsCE6zl5EAUQ623cufVLyBPgP3_vbfCL.tbkW97Rs41fi8p_LgMY34bSHEF8f8kUatAiIlTI7cLIikzLFxGua9WmEJBdObNVriogKK8RDMiFMjYRd3xN7PcY_uywShgH19eNC9H.MDnCujrXP4i39fpQ6UdGmmCp.T1.Vuc8mhQQMT63TMp3paX2Mbwjvf9rVmQiS8AnIkS6LU42H.0cHjPBlmCYR26tAzrvjg8sO6mqXbwKaTJmRBW52UdoAdP4imSoIqr7XnK_e1AP3CJKidCVb_D5YDAGnWjIahAvn9uGYd.f3pIuIANhmv4loPFTZ3w70GCo80YYLqmbTOyINRoMC2BvjzvjzA_0NMB3N.jsGlFQXJqhIhSUVvX3I7zNoN6y3lskAli79Hk1QsgoWHj0YSVfuPJm5i1HAOKQmwNowXIPfeEZoyQPw7FKttH",mdrd: "uYCpJRx0A.EXnpOWgjH2LVT62TXAXpMs3FlULTzu.Uk-1732557273-1.2.1.1-dRuTasjri_rak1NxJtjkVtqoyXJNc9gwNuyBukANd.NlvVbk0uBi5KGWeJUO8z_jKe_loTqbdNMamI_xGpc0WG3dQqh4m247hBnYZyOx2tWzIUXzVnZVrI4JBXE_uC9JCKwHth_H_QI153ER6YftQt3KleVt9k7SP2Ge_M8Z_aE8zkrnN9wjon7B9pJGCgECwZ_JonYqs.6Itgh_axKp1M6edGQk3RfUAfblbGmy4alQyLuiQ8qtE1ekaP7zKcO.uNxTdMzjJRYOAwqzPEaonVa9Eop.NmX35k6Bsjcc4y79XkM0tw1KnCzIOU.zrglmv5tq6xZjk3L.P3sQCSEYdb9nrjrSZGsHVDhYDvJ5ybBAGxMb0ZfxjOQimdkURdJbiFDg6nlixJ4y8ANy0pFhVgYyJjbFtX_SjqDscg__.F9VFBBNmNo.xno5qjb1dqNmV77suSpSdqkPewcNzbstUFBiZJpd0EdiPpJZjE4frK3IKfuWyp8Qk9gYV651RKJ0JawfFrvi8w7aKGkbt7Mk9q8TL5Q6Wtn34Vxl4a4Z5SAQrRNvPZsnvu2PflSnVQ4fEyJ2LLVrQtvqzPn6lRZUh98Oi5LWKgtnsUcC5XTJf.kkSJqtzStDXmVC3B2S35xh9_jiWCBHgB6xhL8fxqiKwRuBhoG.i_InpH66nn96TagSy6VQZsCLumMxWC43WM9oFTIoT8Kv4Dckg_G702aw7.a0qp0pwP_VMvxwG6GiUh4aQhCYxYtCUL6tAftdU5A6c5PT9hyx.S.GmDxIWFC5MJjdqZhaFEtXp8NJUI_GMHqPvM2sysAx0dmtIj7yL4qZRZXQCgSjN2pKzUNLIJ8lYKEZOGz6qN4TeiaLqM6sEMQ.kSmjfkCh54aV7k0le7Tzl5EC5D3CguUSgTu76rbic9fopwUMgm7Z5bQ9m55FAIlIQWT6gX0p.qHt5wyRjuwFVhqDcUezT06UheeD5AoGHRlj1ra7ZsEOuspkLiR9NpP6uEauv8kr7DotuwsXS3iSz5iFY.dYl.UqYOKB8H1s.F4ozP71BOrDfSyDYiLJRqDXNiivMHxM4ZUQcjn3lIBC0WjmR1FDG0fvOznQMzwUCwhje3NjjUn1CoOAoDQ4DSmWrKznxtGEkPeBUU8F2DaOYa.br4oDBvGH9H1kHQaq8U9H7grt0HB3vl4ih_qrtAahu9YHdxp1on2.7GjLTyuo1zDJo8p107amQa5HGFNT5VC9TjQiKATSoFq5_zIQf1I187UFqM2Mj1zdL0Bi7oisnb.dB.QwqcH3a0_uB2dbCKyjxlPDiMR1II9mn_ynipNNURjunrZld.f5QpTRGyEkfn0H85xany27wl1rSfPDQpsaKqEEi_Mqj6ToyjDv5Bw0p1wFUQCY8sc5it_UI92RaIzmj7.jBZV_S3NHx9yfgU2uSq0EjJlgHdM9ifrki_w7N3Zb2Br9gkh0kaR8m0BaF0EHv2nztuYzxdTYQr2ft091ebVVt9cR75h5nw8qvODW5_4E3DSuq0e7YXjj8Aj7elDwFs0WpY_u9NnNWGone2qu07pzfo4zMEfzdDG7nTpNuETlM_F_16kQmwmfu0E5PKcPG5YnaJA.u8arqBzgucmciyTuDNCEHx221fsiwxBuyzYbw92mWC6J2J._mO1bFVr4uoG3XuWMd_yrj9ReIj9iZNuzmmXiuhvBrAP7ObULTxPet3iOxaAWJ5ifuWLHK8fUAlMLTj_v6cNKnjUVKJ9L0rjz8z7ZFZ7wPpDnHYy39FGpBwrXcDF.5jTpa1faF6mwyCa9d1GWFi7p0r1Q15pv7Drt1QllrB8ynhi.zQCA4f5YgeQGjn8q86lwJuq5KQuEb5qkZ2Z4OIdt5u2P6y.FvXufkx8o7jnTX_mXfWyVvaIbppOOBDmBvuiz_JBlit1PavfEPiGWN92X25ltGQifJLfjuz_4t2XvROjhHkdTE9XUqq7a7y7gfxjY5LmbP8nmcfGrjmPE5r0DLTTsW.N0IbL9zU1R.r.7JMUdeos"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=8e83812f1c985f54';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/doi\/10.1098\/rsnr.1992.0003?__cf_chl_rt_tk=XGOILdKmZJJ0i_94L3yK72CgIixO8b0TI5i92wq5b0Y-1732557273-1.0.1.1-yp2BN7T9CHe1gMq8rxrwZi2rlExYJm0JOi6MlW6Hq6g" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>