Feature-based attention influences motion processing gain in macaque visual cortex

Transcription

1 7N 6N 4N 3N N 7N 6N 4N 3N N X 2PC ( ) - Control (189-69) A P B C Q M D 9W 6W 3W GHG (89-99) - Control (189-69) 9W 6W 3W Y N 14. Gent, P. & MWillims, J. C. Isopynl mixing in oen irultion models. J. Phys. Oenogr., (199).. Roerts, M. J. & Wood, R. A. Topgrphi sensitivity studies with Bryn-Cox type oen model. J. Phys. Oenogr. 27, (1997). 16. Gordon, C. et l. The simultion of SST, se ie extents nd oen het trnsports in version of the Hdley Centre oupled model without flux djustments. Clim. Dyn. (in the press). 17. Levitus, S. & Boyer, T. P. World Oen Atls 1994 (NOAA/NESDIS E/OC21, US Dept of Commere, Wshington DC, 1994). 18. Houghton, J. T. et l. (eds) Climte Chnge 1992: the Supplementry Report to the IPCC Sientifi Assessment (eds Houghton, J. T., Meir Filho, L. G., Cllnder, B. A., Hrris, N., Kttenerg, A. & Mskell, K.) (Cmridge Univ. Press, 1996). 19. Wever, A. J. & Hughes, T. M. C. On the inomptiilityof oennd tmosphere modelsnd the need for flux djustments. Clim. Dyn. 12, (1996).. Bryn, F. O. Climte drift in multi-entury integrtion of the NCAR Climte System Model. J. Clim. 11, (1998). 21. Bon, S. Dedl vriility in the outflow from the Nordi ses to the deep Atlnti Oen. Nture 394, (1998). 22. Clrke, R. A. Trnsport through the Cpe Frewell Flemish Cp setion. Rpp. P.-v. Réun. Cons. Int. Explor. Mer. 18, 1 13 (1984). 23. Rhmstorf, S. & Gnopolski, A. Long-term glol wrming senrios omputed with n effiient oupled limte model. Clim. Chnge (in the press). 24. IPCC Workshop Report on Rpid Non-liner Climte Chnge (Intergovernmentl Pnel on Climte Chnge, Brknell, 1998). 2. Dikson, R., Lzier, J., Meinke, J., Rhines, P. & Swift, J. Long-term oordinted hnges in the onvetive tivity of the North Atlnti. Prog. Oenogr. 38, (1996). 26. Stoker, T. F. & Shmittner, A. Influene of CO2 emission rtes on the stility of the thermohline irultion. Nture 388, (1997). 27. Wdley, M. R. & Bigg, G. R. Ayssl hnnelflow in oen generl irultion models with pplition to the Vem Chnnel. J. Phys. Oenogr. 26, (1996). 28. Doesher, R. & Redler, R. The reltive importne of northern overflow nd supolr deep onvetion for the North Atlnti thermohline irultion. J. Phys. Oenogr. 27, (1997). 29. Prill, G., Lvin, A., Bryden, H. L., Gri, M. & Millrd, R. Rising tempertures in the sutropil North Atlnti Oen over the pst 3 yers. Nture 369, 48 1 (1994). 3. Lzier, J. R. N. in Nturl Climte Vriility on Dede-to-entury Timesles (eds Mrtinson, D. G. et l.) (Nt. Ademy Press, Wshington DC, 199). Aknowledgements. We thnk H. Cttle, G. Jenkins, J. Murphy, S. Rhmstorf, R. Stouffer, R. Thorpe nd A. Wever for omments. This workws supported y the UK Deprtment of the Environment, Trnsport nd the Regions. Correspondene nd requests for mterils should e ddressed to R.A.W. (e-mil: rwood@meto.gov.uk) Figure 4 Chnges in dedl men se surfe temperture ( C)., Differene etween 2PC run nd ontrol ;, differene etween GHG run nd ontrol In re lso shown the pproximte pths of the setions used in Fig. 1 (the GIS ridge (MN), Cpe Frewell (PQ), 24 N (XY)) nd Fig. 3 (ABCD). for the response of the oen thermohline irultion to CO 2 foring. If this pttern is roust, monitoring system sed on repeted hydrogrphi setions in the Lrdor Se nd t 24 N, nd urrent-meter mesurements of the GIS overflows nd the Cpe Frewell oundry urrent, ould provide mens of detetion of hnges in thermohline irultion resulting from inresed greenhouse-gs foring. Muh of this would uild on the existing historil dtse 11,21,22,29,3. The extent to whih suh signl ould e deteted t present depends on the nturl vriility in these elements of the irultion, whih hs not yet een fully quntified from oservtions. Reeived 6 Novemer 1998; epted 26 Mrh Mne, S. & Stouffer, R. J. Two stle equilir of oupled oen-tmosphere model. J. Clim. 1, (1988). 2. Hll, M. M. & Bryden, H. L. Diret estimtes of oen het trnsport. Deep Se Res. 29, (1982). 3. Roemmih, D. & Wunsh, C. Two trnstlnti setions: meridionl irultion nd het flux in the sutropil North Atlnti Oen. Deep Se Res. 32, (198). 4. Mne, S. & Stouffer, R. J. Century-sle effets of inresed tmospheri CO 2 on the oen tmosphere system. Nture 364, (1993).. Murphy, J. M. & Mithell, J. F. B. Trnsient responseof the Hdley Centreoupled model to inresing ron dioxide. Prt II. Temporl nd sptil evolution of ptterns. J. Clim. 8, 7 8 (199). 6. Cush, U. et l. Time-dependent greenhouse wrming omputtions with oupled oentmosphere model. Clim. Dyn. 8, 69 (1993). 7. Rhmstorf, S. Risk of se-hnge in the Atlnti. Nture 388, (1997). 8. Houghton, J. T. et l. (eds) Climte Chnge 199: the Siene of Climte Chnge (Cmridge Univ. Press, 1996). 9. Mrotzke, J. & Stone, P. H. Atmospheri trnsports, the thermohline irultion, nd flux djustments in simple oupled model. J. Phys. Oenogr. 2, (199). 1. Rhmstorf, S. Bifurtions of the Atlnti thermohline irultion in response to hnges in the hydrologil yle. Nture 378, (199). 11. Dikson, R. R. & Brown, J. Theprodution of North Atlnti Deep Wter: soures, rtes nd pthwys. J. Geophys. Res. 99, (1994). 12. Johns, T. C. et l. The seond Hdley Centre oupled oen-tmosphere GCM: model desription, spinup nd vlidtion. Clim. Dyn. 13, (1997). 13. Roether, W., Roussenov, V. M. & Well, R. in Oen Proesses in Climte Dynmis: Glol nd Mediterrnen Exmples (eds Mlnotte-Rizzoli, P. & Roinson, A. R.) (Kluwer, Dordreht, 1994). Feture-sed ttention influenes motion proessing gin in mque visul ortex Stefn Treue & Julio C. Mrtı nez Trujillo Cognitive Neurosiene Lortory, Deprtment of Neurology, University of Tüingen, Auf der Morgenstelle, 776 Tüingen, Germny Chnges in neurl responses sed on sptil ttention hve een demonstrted in mny res of visul ortex 1 4, inditing tht the neurl orrelte of ttention is n enhned response to stimuli t n ttended lotion nd redued responses to stimuli elsewhere. Here we demonstrte non-sptil, feture-sed ttentionl modultion of visul motion proessing, nd show tht ttention inreses the gin of diretion-seletive neurons in visul ortil re MT without nrrowing the diretion-tuning urves. These findings ple importnt onstrints on the neurl mehnisms of ttention nd we propose to unify the effets of sptil lotion, diretion of motion nd other fetures of the ttended stimuli in feture similrity gin model of ttention. We studied the influene of ttention on the sensory seletivity of neurons in visul ortex, nmely diretion-seletive neurons in the middle temporl visul re (MT), whih is importnt in the pereption of visul motion nd for motor plnning,6. MT neurons hve een linked diretly to psyhophysil performne in motion tsks 7 nd they hrteristilly show diretion tuning urves (ell-shped response profiles s funtion of stimulus diretion; Fig. 1), whih ount well for psyhophysil thresholds of motion pereption 8. We reorded from neurons in re MT of two mque monkeys while using displys of oherently moving rndom dot ptterns (RDP) to determine wht effet ttention might hve on these diretion tuning urves. Attention might enhne the sensory gin of the neuron, tht is, inrese the response to ll ttended stimuli y the sme proportion ( multiplitive modultion ), leving the NATURE VOL JUNE

2 width of the tuning urve unhnged 9. Alterntively, ttention might inrese the response of neuron only for stimuli moving in the preferred diretion, thus inresing the shrpness of the neuron s tuning urve ( shrpening modultion ) 1. Experiment 1 ws designed to isolte the influene of sptil ttention on tuning urves. One RDP ws pled inside the reeptive field of the neuron eing reorded nd the other one, moving in the sme diretion, ws pled in the opposite visul hemifield (Fig. 1). On given tril, using sptil ue, the niml s ttention ws direted to either one or the other stimulus, the trget. In oth the ttend-in nd the ttend-out onditions, we derived the neuron s tuning urve y rndomly interleving trils with one of 12 possile diretions of movement (Fig. 1). Figure 1 shows histogrm of the hnges in the height nd width of the tuning urve etween these two ttentionl onditions ross ll the ells we studied. On verge, the height of the tuning urves ws out 1% lrger when the trget ws the stimulus inside the reeptive field, ut the tuning urves were not shrpened; insted, there ws slight, non-signifint widening. The inrese in the height of the tuning urve in the sene of nrrowing indites tht ttention hs the sme effet on ll stimuli, tht is it inreses the responses y multiplitive modultion. This modultion reflets purely sptil ttentionl mehnism, euse the pirs of onditions ompred in Fig. 1 differed only in the ttended lotion, with the ttended diretion remining the sme. Psyhophysil studies suggest tht ttention n lso e seletively lloted to stimuli tht mth prtiulr feture, without shifts in the ttended lotion (see for exmple refs 11 13). To test for suh effets of non-sptil, feture-sed ttention, we introdued vrition into Experiment 1 (Fig. 2). While the stimulus inside the reeptive field now lwys moved in given neuron s preferred diretion, the other stimulus moved in either the sme (s in the previous experiment, Fig. 2, rrow B) or the opposite diretion (Fig. 2, rrow A). This llowed the ttended diretion to e swithed without hnging the ttended lotion nd without hnging the stimulus inside the reeptive field. We ompred the responses when ttention ws direted to the stimulus outside the reeptive field, moving either in the preferred or nti-preferred diretion. Chnging the stimulus diretion outside the reeptive field hd no effet on the responses when tht stimulus ws ehviourlly irrelevnt, tht is when the niml ws ttending inside the reeptive field or simply fixting. Figure 2 shows histogrm of the resulting ttentionl modultion ross ll neurons studied. Attending to the preferred motion outside the reeptive field inresed the response y, on verge, out 13% ove the response evoked when ttending nulldiretion stimulus outside the reeptive field. This is not n effet of sptil ttention, s the lotion of ttention ws unhnged etween the two onditions. Rther, it represents neurl orrelte of ttention to stimulus feture. Compring the responses ginst those evoked in trils in whih none of the moving stimuli ws ehviourlly signifint shows tht this non-sptil ttentionl modultion is omintion of enhnement (preferred diretion trget, men enhnement of %) nd suppression (nti-preferred diretion trget, men suppression of 6%). Thus, ttending to given diretion enhnes the responses of neurons whose preferred diretion ligns with the ttended diretion nd redues the responses of those neurons preferring the opposite diretion. tt out tt in tt in diretionl gin 1 1 tt out ell jfe Stimulus diretion inside nd outside the reeptive field Response (spikes per s) Numer of ells Diretionl gin Width Rtio (%) Rtio (%) Geometri tt vs. tt. tt vs. tt. men: 11% in out in out > Attentionl index Figure 1 Experiment 1: Effet of direting ttention inside versus outside the reeptive field on the diretionl tuning urve., Sketh of the stimulus lyout on the sreen. One rndom dot pttern (RDP) ws presented inside the lssil reeptive field (dshed irle) while the other ws presented out the sme distne from the fixtion point in the opposite hemifield. In given tril, oth RDPs moved in the sme of 12 possile diretions., Exmples of tuning urves. The upper urve shows the response when the monkey ws ttending to the stimulus inside the reeptive field (mrked tt in in ), nd the lower urve plots the responses when the monkey ws ttending to the stimulus outside the reeptive field (mrked tt out ). These tuning urves show n inrese in diretionl gin nd width when ttention is swithed from outside to inside the reeptive field. Attentionl index, Histogrms showing the influene of ttention on the diretionl gin nd width of the tuning urves for 131 ells. Binning is ording to the ttentionl index AI ¼ðX in X out Þ=ðX in þ X out Þ, where X is the gin or width in the orresponding ttentionl ondition. The top sle shows the orresponding rtios. The left histogrm shows shift to the right, with n verge AI of. (mrked y the ross, where the horizontl rms spn the 9% onfidene intervl of the men), inditing tht ttention inreses the height of the tuning urves on verge (geometri men) y out 1%. The right histogrm shows no shift to the left, demonstrting tht ttention does not shrpen the tuning urves. Rther we find smll, non-signifint inrese in the width of the tuning urves (verge inrese: 4%, P : in pired t-test). 76 NATURE VOL JUNE

3 This influene is fr rehing; our stimuli were s muh s prt nd in opposite visul hemifields. Hving demonstrted ttentionl modultion of out equl size with shifts in the sptil lotion of ttention nd with feture-sed effets in the sene of shift of the ttended lotion we plot the omined effet of the two modultions. Figure 2 ompres responses when the niml ws ttending the nti-preferred stimulus outside the reeptive field with those trils when ttention ws direted into the reeptive field to the stimulus moving in the preferred diretion (Fig. 2, rrows A nd C). The ttentionl modultion (2% on verge) is the sum of the shifts shown in Figs 1 nd 2, emphsizing tht feture-sed ttentionl effets n e dditively omined with modultions sed on the sptil lotion of ttention. Compring the two ttentionl onditions ginst responses when neither of the stimuli ws ehviourlly signifint shows tht the ttentionl modultion is omintion of the suppressive effet of swithing ttention to the null diretion outside the reeptive field ( 6% suppression) nd the enhning effet of direting ttention into the reeptive field onto the preferred diretion ( % enhnement). Previous studies demonstrted strong response modultion when ttention ws swithed etween stimuli tht were oth inside the reeptive field 1 4. In our third experiment we tested whether the sene of ttentionl shrpening of the tuning urves persists under these irumstnes y pling two stimuli side-y-side inside the reeptive field. Pttern A lwys moved in the ntipreferred diretion of the ell. To generte tuning urve, pttern B moved in one of twelve diretions of motion. Agin, in given tril, either one of the ptterns ws designted s the trget. By plotting the response of the neuron s funtion of the diretion of motion of pttern B, tuning urve ould e determined for eh of the two ttentionl onditions. Figure 3 shows n exmple of these tuning urves for one ell together with the sensory tuning urve, reorded when neither of the two ptterns inside the reeptive field ws ehviourlly relevnt. The lower pnels of Fig. 3 show histogrms of the ttentionl modultion of the diretionl gin nd tuning width. As in Experiment 1, ttention inreses the diretionl gin of the neuron, lthough now with men effet of out 6%. Even with these very strong response modultions, no shrpening of the tuning ws oserved. Our results demonstrte physiologil orrelte of non-sptil, feture-sed ttention y showing response modultions in the sene of sptil shifts of ttention. We further show tht sptil nd feture-sed ttention represent summle proesses tht hve multiplitive effet on the responses of neurons. Suh ttentionl modultions resemle hnges to neuron s sensory gin nd thus n e mimiked y sensory effets, suh s reduing the luminne ontrst of stimulus, whih similrly does not hnge the tuning width of diretion-seletive neurons 14,, suggesting tht response modultion sed on ttentionl nd sensory spets employ ommon mehnisms. Non-sptil, feture-sed modultion of sensory responses hs een oserved in imging studies 16,17 nd using psyhophysil prdigms However, previous studies did not show n unmiguous single-ell orrelte of this effet, euse they investigted ttentionl seletion sed on stimulus fetures, leving open the possiility tht the modultion itself is sed on stimulus lotion 18,19, or onfounded hnge in the ttended feture with simultneous hnge in ttended lotion 9. Although the sene of shrpening of the tuning urves is in ontrst to one report from res in the ventrl visul pthwy 1,it losely mthes nother 9, inditing tht ttention my work in similr wys in the dorsl nd ventrl visul pthwys. A reent study ttempting to model psyhophysil orienttion disrimintion performne in dul-tsk ttentionl prdigms hs indited tht the oserved performne n only e ounted for y models tht implement shrpening of tuning urves with ttention.aswe hve found no indition for suh shrpening, further studies will e neessry to understnd the resons for this disrepny. The A B C Feturl ttentionl modultion Sptil + feturl ttentionl modultion Numer of ells Geometri men: 113% vs. A B Numer of ells Geometri men: 12% vs. A C Figure 2 Experiment 2: Non-sptil effets of ttention nd the summing of sptil nd feturl ttentionl modultion., Stimulus onditions used. The stimulus inside the reeptive field lwys moved in the ell s preferred diretion (upwrd pointing rrow); the stimulus outside moved in either the sme (B) or the opposite diretion (A). Trils in whih the niml ws instruted to ttend to A, B nd C were presented in n interleved fshion., Histogrm ompring responses of 131 ells when ttention ws on the preferred (B) or nti-preferred (A) diretion outside the reeptive field. The histogrm is shifted to the right (men shift 13%) inditing n inresed response when the stimulus moved in the ell s preferred diretion., Histogrm ompring responses when ttention ws on ntipreferred motion outside (A) or the stimulus inside the reeptive field (C). The histogrm is shifted to the right, inditing n inresed response when the trget ws inside the reeptive field. NATURE VOL JUNE

4 Pttern A Pttern B ttention on pttern B 'sensory' response ttention on ell jme pttern A Response (spikes per s) Stimulus diretion of pttern B Numer of ells 1 Diretionl gin Width Rtio (%) Rtio (%) Geometri men: 6% Attentionl index Attentionl index Figure 3 Experiment 3: Effet of direting ttention to one of two stimuli inside the Histogrms of the ttentionl modultion of the tuning urve ross 6 ells. The reeptive field., Stimulus onfigurtions. Both ptterns were presented inside men inrese in diretionl gin is out 6% (whih is omintion of the reeptive field. Pttern A lwys moved in the ell s nti-preferred diretion, response enhnement when swithing ttention from the sensory ondition to pttern B in one of 12 possile diretions., Tuning urves when pttern B ws pttern B nd of suppression when swithing to pttern A). Agin there is no the trget (upper urve), when pttern A ws the trget (lower urve) nd when nrrowing of the tuning width. On verge, width is inresed y 8% (nonsignifint, neither pttern ws ehviourlly relevnt (entrl urve) euse the niml P :1). ws instruted to respond to luminne hnge t the fixtion point., ttentionl enhnement we oserve does support etter stimulus disriminility even without tuning shrpening, y inresing the slope of the tuning urve 21,22. A ised ompetition model hs een proposed 23, whih supposes tht ttention influenes the ompetition etween two stimuli for ess to given ell in fvour of the ttended stimulus. This is hieved y inresing the strength of the signl oming from the popultion of input ells tivted y the ttended stimulus 24. The ttentionl modultion we oserved when ttention ws swithed etween two stimuli inside the reeptive field (Experiment 3) onforms to the preditions of this model. Given the model s emphsis on ompetition within the reeptive field, our findings in Experiment 2 (ttentionl effets outside the reeptive field nd the dditivity of sptil nd non-sptil effets when ttention is swithed into the reeptive field) do not seem to e predited y the model. We propose tht sptil nd non-sptil ttentionl effets n e unified in feture similrity gin model, in whih the upor downregultion of the gin of sensory neuron reflets the similrity of the fetures of the urrently ehviourlly relevnt trget nd the sensory seletivity of the neuron long ll trget dimensions. Thus this up- or downregultion will lso ffet neurons whose reeptive fields do not inlude the ttended stimulus lotion. The relevnt trget fetures inlude the sptil lotion, diretion of motion nd presumly others. Correspondingly, the sensory seletivity of the neuron inludes the lotion of its reeptive field (or of the smller reeptive fields of its input neurons), its preferred diretion of motion nd presumly other preferred fetures. This model not only provides good ount of other physiologil studies of ttention tht inluded onditions without ompeting stimuli inside the reeptive field 2,9, ut lso inorportes the ide, from psyhophysil nd imging studies s well s other modelling ttempts, tht non-sptil stimulus fetures n e the sis of ttentionl effets. Methods Cells nd reording. Our reording methods hve een desried elsewhere 3,2. All niml proedures omplied with the NIH Guide for Cre nd Use of Lortory Animls nd were pproved y the lol niml re ommittee. Cells were determined to e from MT y their physiologil hrteristis (diretionlity nd reeptive field position nd size) s well s y the position of the eletrode in the ortex. We lso reorded from MST ells, finding similr ut lrger ttentionl modultions to those reported here. Stimuli. Rndom dot ptterns were reted y plotting right dots t density of dots per deg squre within irulr sttionry virtul perture on drk omputer monitor. Dots moved oherently t the preferred speed of the neurons nd were re-plotted to the opposite side when they rossed the order of the perture. The size of the perture ws hosen so tht the stimulus did not exeed the oundries of the lssil reeptive field. Trils. Every tril strted with the pperne of the fixtion ross. After it ws foveted, sttionry RDP (the ue) signlled the lotion of the trget. The monkey then depressed lever. 3 ms lter the ue disppered (Experiments 1 nd 2) or moved for 4 ms (Experiment 3). After lnk intervl of 6 ms (Experiments 1 nd 2) or 27 ms (Experiment 3) two moving RDPs ppered, one (the trget ) t the lotion of the ue nd one (the distrtor ) t nother lotion. The monkey s tsk ws to relese the level when the trget hnged speed or diretion (whih ourred t rndom point 78 NATURE VOL JUNE

5 etween 27 nd 4, ms fter trget onset) nd to ignore hnges in the distrtor. Filure to respond within retion-time window, responding to hnge in the distrtor or deviting the gze (monitored with slerl serh oil) y more thn 1 from the fixtion point used the tril to e orted without rewrd. The hnge in the trget nd distrtors ws seleted so s to e hllenging for the niml. In experiments 1 nd 2 the niml orretly ompleted, on verge, 79% of the trils, roke fixtion in 11%, might hve responded to the distrtor stimulus in 6% nd responded too erly or not t ll in % of the trils. In Experiment 3 the orresponding vlues re 78, 13%, 8% nd 2%. In none of the three experiments ws there differene etween the performnes for the two possile trgets. Differenes etween verge eye positions during trils where one or the other stimulus ws the trget were very smll, with only n verge shift of.2 in the diretion of the shift of position etween the stimuli. Only orretly ompleted trils were onsidered. Firing rtes were determined y omputing the verge neuronl response ross trils for 1, ms strting ms fter the eginning of the trget stimulus movement. Tuning urves. Tuning urves were derived y fitting the responses to the 12 diretions presented with gussin funtions: r null þ dirgin exp ð : ðdir prefdirþ2 =width 2 Þ. The four prmeters of gussin urve pture the four fetures of diretion-seletive ell: preferred diretion ( prefdir), response to the nti-preferred diretion (r null ), the diretionl gin (dirgin; the mximl response modultion) nd the seletivity or tuning width (width; the rnge of diretions the neuron responds to). Reeived 14 Deemer 1998; epted 14 April Morn, J. & Desimone, R. Seletive ttention gtes visul proessing in the extrstrite ortex. Siene 229, (198). 2. Motter, B. C. Folttention produes sptilly seletiveproessing invisul ortil resv1, V2, nd V4 in the presene of ompeting stimuli. J. Neurophysiol. 7, (1993). 3. Treue, S. & Munsell, J. H. R. Attentionl modultion of visul motion proessing in ortil resmt nd MST. Nture 382, (1996). 4. Luk, S. J., Chelzzi, L., Hillyrd, S. A. & Desimone, R. Neurl mehnisms of sptil seletive ttention in res V1, V2, nd V4 of mque visul ortex. J. Neurophysiol. 77, (1997).. Newsome, W. T., Wurtz, R. H., Dürsteler, M. R. & Mikmi, A. Defiits in visul motion proessing following ioteni id lesions of the middle temporl visul re of the mque monkey. J. Neurosi., (198). 6. Newsome, W. T. & Pré, E. B. A seletive impirment of motion pereption following lesions of the middle temporl visul re (MT). J. Neurosi. 8, (1988). 7. Britten, K. H., Newsome, W. T., Shdlen, M. N., Celerini, S. & Movshon, J. A. A reltionship etween ehviorl hoie nd the visul responses of neurons in mque MT. Vis. Neurosi. 13, 87 1 (1996). 8. Snowden, R. J., Treue, S. & Andersen, R. A. The response of neurons in res V1 nd MTof the lert rhesus monkey to moving rndom dot ptterns. Exp. Brin Res. 88, (1992). 9. MAdms, C. J. & Munsell, J. H. R. 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Attention does not shrpen diretion-tuning urves in mque monkey MT/ MST neurons. So. Neurosi. Astr. 24, 649 (1998). 23. Desimone, R. & Dunn, J. Neurl mehnisms of seletive visul ttention. Annu. Rev. Neurosi. 18, (199). 24. Reynolds, J. H., Chelzzi, L. & Desimone, R. Competitive mehnisms suserve ttention in mque res V2 nd V4. J. Neurosi. 19, (1999). 2. Treue, S. & Munsell, J. H. R. Effets of ttention on the proessing of motion in mque visul ortil res MT nd MST. J. Neurosi. sumitted. Aknowledgements. This work ws supported y the MWF-Württemerg. J.C.M. is fellow of the Grduiertenkolleg Neuroiologie, Tüingen. Polewrd shifts in geogrphil rnges of utterfly speies ssoited with regionl wrming Cmille Prmesn*, Nils Ryrholm, Constntı Stefnesu, Jne K. Hillk, Chris D. Thoms, Henri Desimon#, Brin Huntleyk, Luri Kil, Jkko Kullerg, Tooms Tmmru**, W. John Tennent, Jeremy A. Thoms & Mrtin Wrren * Ntionl Center for Eologil Anlysis nd Synthesis, 73 Stte Street, Suite 3, Snt Brr, Cliforni 9311, USA Evolutionry Biology Centre, Setion of Zoologil Eology, Uppsl University, Noryvägen 18 D, S Uppsl, Sweden Butterfly Monitoring Sheme, Cn Liro, 848 Snt Pere de Vilmjor, Brelon, Spin k Environmentl Reserh Centre, Deprtment of Biologil Sienes, University of Durhm, Durhm DH1 3LE, UK Centre for Biodiversity nd Conservtion, Shool of Biology, University of Leeds, Leeds LS2 9JT, UK # Lortoire de Systémtique Évolutive, Université de Provene, 3 ple Vitor Hugo, Mrseille, Cedex 3, Frne Finnish Museum of Nturl History, Division of Entomology, University of Helsinki, P.O. Box 17, Helsinki FIN-14, Finlnd ** Institute of Zoology nd Botny, Estonin Agriulturl University, Rii 181, EE-114 Trtu, Estoni Biogeogrphy nd Conservtion Lortory, The Nturl History Museum (BMNH), London SW7 BD, UK Furzerook Reserh Sttion, Institute of Terrestril Eology, Wrehm, Dorset BH AS, UK Butterfly Conservtion, P.O. Box 444, Wrehm, Dorset BH YA, UK Men glol tempertures hve risen this entury, nd further wrming is predited to ontinue for the next 1 yers 1 3. Some migrtory speies n respond rpidly to yerly limte vrition y ltering the timing or destintion of migrtion 4, ut most wildlife is sedentry nd so is inple of suh rpid response. For these speies, responses to the wrming trend should e slower, refleted in polewrd shifts of the rnge. Suh hnges in distriution would our t the level of the popultion, stemming not from hnges in the pttern of individuls movements, ut from hnges in the rtios of extintions to oloniztions t the northern nd southern oundries of the rnge. A northwrd rnge shift therefore ours when there is net extintion t the southern oundry or net oloniztion t the northern oundry. However, previous evidene hs een limited to single speies or to only portion of the speies rnge 6,7.Hereweprovide the first lrge-sle evidene of polewrd shifts in entire speies rnges. In smple of 3 non-migrtory Europen utterflies, 63% hve rnges tht hve shifted to the north y 3 24 km during this entury, nd only 3% hve shifted to the south. We nlysed distriutionl hnges rodly spred over the pst entury for non-migrtory speies of utterfly whose northern oundries were in northern Europe nd whose southern oundries were in southern Europe or northern Afri. We exluded some dt where irumstnes suggested tht rnge oundries were ontrolled or ltered y non-limti ftors. This yielded suset of suffiient qulity for us to detet distriutionl hnges predited y models of glol wrming, yet is unised with respet to suh hnges. However, euse dt for some speies were exluded t either their northern or southern oundries, we Present ddress: Integrtive Biology, Ptterson Lortories, University of Texs, Austin, Texs 78712, USA. NATURE VOL JUNE