Visual receptive field properties of cells in the optic tectum of the archer fish

13 Pages·2013·1.21 MB·English

Visual receptive field properties of cells in the optic
tectum of the archer fish
Mor Ben-Tov, Ivgeny Kopilevich, Opher Donchin, Ohad Ben-Shahar, Chen Giladi and
Ronen Segev
J Neurophysiol 110:748-759, 2013. First published 8 May 2013;
doi: 10.1152/jn.00094.2013
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JNeurophysiol110:748–759,2013.
FirstpublishedMay8,2013;doi:10.1152/jn.00094.2013.
Visual receptive field properties of cells in the optic tectum of the archer fish
Mor Ben-Tov,1,2 Ivgeny Kopilevich,2,3 Opher Donchin,2,3,4 Ohad Ben-Shahar,2,5 Chen Giladi,6
and Ronen Segev1,2
1DepartmentofLifeSciences,Ben-GurionUniversityoftheNegev,Be’er-Sheva,Israel;2ZlotowskiCenterforNeuroscience,
Ben-GurionUniversityoftheNegev,Be’er-Sheva,Israel;3DepartmentofBiomedicalEngineering,Ben-GurionUniversityof
theNegev,Be’er-Sheva,Israel;4DepartmentofNeuroscience,ErasmusUniversityMedicalCenter,Rotterdam,TheNetherlands;
5DepartmentofComputerScience,Ben-GurionUniversityoftheNegev,Be’er-Sheva,Israel;and6DepartmentofPhysics,
Ben-GurionUniversityoftheNegev,Be’er-Sheva,Israel
Submitted5February2013;acceptedinfinalform7May2013
D
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Ben-TovM,KopilevichI,DonchinO,Ben-ShaharO,GiladiC, Inadditiontotheadvantagesdescribedabove,thearcherfish w
SegevR.Visualreceptivefieldpropertiesofcellsintheoptictectum isaninterestinganimaltostudyasafishwithasemiterrestrial nlo
ofthearcherfish.JNeurophysiol110:748–759,2013.Firstpublished visual environment. Put differently, it is an animal that, like ad
May 8, 2013; doi:10.1152/jn.00094.2013.—The archer fish is well e
most mammals, processes a visual landscape above water d
khnanogwinngfoornivtsegeexttarteimoneavbiosuvaelwbaethearv.iTohriisnfisshhoiostiangprwomatiesrinjgetsmaotdeplreiny level,whileasafish,itdoessowithabrainwhosestructureis fro
m
the study of visual system function because it can be trained to verydifferentfromthatofmammals.Thusstudiesofthevisual h
respondtoartificialtargetsandthustoprovidevaluablepsychophys- processinginthearcherfishcanleadtobroaderperspectiveon ttp
iocvaelrdathtae.Apaltshtoutwghomduecchadbeesh,alviitotlrealidsatkanhoawvneianbdoeuetdtbheeenfucnocllteiocnteadl twhiethfusnuccthioennavlirpornompeerntite.s of visual systems that have to cope ://jn.p
organization of the main visual area supporting this visual behavior, The central unit of the fish visual information processing is hy
namely,thefishoptictectum.Inthisarticlewefocusonafundamen- s
the optic tectum. The information from each eye travels di- io
tal aspect of this functional organization and provide a detailed rectlytothetectallobeontheoppositesideofthebrain,where lo
analysis of receptive field properties of cells in the archer fish optic g
tectum.Usingextracellularmeasurementstorecordactivitiesofsingle information processing work flow is believed to occur (Ki- y.o
cells,wefirstmeasuretheirretinotectalmapping.Wethendetermine noshita and Ito 2006; Kinoshita et al. 2002; Vanegas and Ito rg
their receptive field properties such as size, selectivity for stimulus 1983).Informationprocessinginthemammalianvisualcortex a/
directionandorientation,tuningforspatialfrequency,andtuningfor appears to progress hierarchically, where the visual stream t M
a
temporal frequency. Finally, on the basis of all these measurements, ascends from one cortical region to another with progressive rin
we demonstrate that optic tectum cells can be classified into three representationandprocessingofvisualinformation.Theoptic e
categories: orientation-tuned cells, direction-tuned cells, and direc- tectum of fish, however, appears to be much more uniform Bio
tion-agnostic cells. Our results provide an essential basis for future acrossthetectumsurfaceintermsoffunctionalunits(Nevinet lo
investigations of information processing in the archer fish visual g
al. 2010); i.e., the cells in the optic tectum are diverse in their ic
system. a
responsetodifferentfeaturesofthevisualstimuli,andtheyare l L
archer fish; optic tectum; early visual processing; retinotectal map- not arranged in columnar organization. Furthermore, next to a
b
ping;orientationanddirectionselectivity visualsignalsfromtheretina,inputfromothersensorymodal- o
n
ities such as auditory, lateral line, and somatosensory are also A
u
mapped topographically over the tectum (Bodznick 1990; g
INRECENTYEARS,THEARCHERFISHhasprovedtobeaveryproduc- u
Catania et al. 2010; Knudsen 1982). Anatomically, it was s
tivemodelinthestudyofmanyaspectsofvisualbehavior,from found in other teleosts that the most important distinction is t 1
retinalencoding(Tsvillingetal.2012;Vassermanetal.2010),eye betweenthesuperficiallayers,whicharemainlyvisual,andthe , 2
movements(Ben-Simonetal.2009),animalcompetition(Schus- deep layers, which are multimodal and motor (Bastian 1982; 013
ter2011),andvisualacuity(Ben-Simonetal.2012a;Templeetal.
Bodznick 1990). Focusing on vision, we have therefore se-
2010, 2013) to tracking of moving targets (Ben-Simon et al.
lected the superficial layers of the archer fish optic tectum as
2012b; Schlegel and Schuster 2008; Schuster et al. 2006; Tim-
our target of research.
mermans2000,2001)andvisualsearch(Mokeichevetal.2010).
Studies have described the retinotectal maps in fish by re-
The productivity of the model can be explained, in part, by the
cording from the superficial tectum using single electrodes (Ja-
ability of the archer fish to overtly report its visual decisions by
cobson and Gaze 1964; Schwassmann and Kruger 1965). These
employing a squirt of water from its mouth aimed at selected
studies showed that there is correspondence between dorsal and
targets. The archer fish can be trained to shoot at a variety of
rostral points within the visual field of the eye and points in the
artificialtargetsfromsmallfoodpelletstoprintedtargetsonpaper
contralateraltectum.Inaddition,researchwasdevotedtofindthe
andeventargetspresentedoncomputermonitors.Thuscomplex
sizeofthereceptivefields.Itwasfoundthatthesmallestsizeof
experimentsofrecognitionanddecisionmakingcanbeconducted
the receptive field was 7.7° and 1.8° for zebra fish and goldfish,
withcarefulexperimentalsettingstoexplorevariousaspectsofvisual
respectively (Damjanovic´ et al. 2009b; Sajovic and Levinthal
informationprocessinginapsychophysicallyrigorousmanner.
1982). Knowledge about spatial mapping between the primary
visual area of the fish and the visual field and the sizes of the
Addressforreprintrequestsandothercorrespondence:R.Segev,Dept.of
receptivefieldscanprovidetheopportunityforfurtherinvestiga-
Life Sciences, Ben-Gurion Univ. of the Negev, Be’er-Sheva 84105, Israel
(e-mail:[email protected]). tionofspatialdiscriminationandvisualacuity.
748 0022-3077/13Copyright©2013theAmericanPhysiologicalSociety www.jn.org
VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM 749
Seekingtostudytheoverallfunctionalorganizationoftheoptic and were in accordance with government regulations of the State of
tectumofarcherfish,thespecificpurposeofourpresentworkis Israel. Twenty-eight archer fish (Toxotes chatareus; Fig. 1A), 6–13
twofold: 1) to reveal the retinotectal mapping of the archer fish cminlength,10–15gbodyweight,wereusedinthisstudy.Thefish
werenormallykeptinawatertank50(cid:1)70(cid:1)30cminsize((cid:2)100
optic tectum, and 2) to describe the functional properties of the
liters)filledwithbrackishwater(2–2.5gofredseasaltmixfor1liter
receptivefieldofoptictectumcells.Ourresultswillthusprovide
ofwater)at26–28°C.Theroomwasilluminatedwithartificiallight
afoundationforfuturestudiesofvisualprocessinginthearcher
witha16:8-hday-nightcycle.
fish and of the mapping between its visual behavior and neural
visualprocessing.
Surgery
Fish were anesthetized with MS-222 (100 mg per liter of tank
MATERIAL AND METHODS
water;A-5040,Sigma).ThepHlevelwasadjustedtocompensatefor
Animals MS-222 acidity. After the fish lost its buoyancy balance and flipped
onto its back, it was restrained in a special device and its gills were
All experiments with fish were approved by the Ben-Gurion Uni- watered continuously with tank water containing MS-222. The wa-
versity of the Negev Institutional Animal Care and Use Committee tering of the gills was essential due to a possible respiratory failure D
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A B Stimulus Recording lo
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Water Fig. 1. The archer fish and the experimental .o
with air setup.A:anarcherfishshootsataninsectabove rg
pump waterlevel.B:aschematicviewoftheexperi- a/
mental setup, which consists of a monitor to t M
presentthestimuli,arecordingsetupof1ex- a
C D tracellularelectrode,andalifesupportsystem rin
forthefish.Thefish’sgillswerecontinuously e
On-Off Diffuse Flash Static Bar wateredthroughatubeinsertedintoitsmouth. Bio
Thewaterreservoirisequippedwithairpump lo
thathelpsinsufflateairinthewatertanksothat g
oxygenisavailabletothefish.Astreambreaker ica
deviceisusedtopreventanelectricalcurrent l L
from passing through the water molecules. a
b
C–F:the4typesofvisualstimuliusedinthe o
experiment.C:on-offdiffuseflash,arepeating n
A
loopconsistingof1sofwhitescreenfollowed u
by1sofblackscreen. D:staticbar,astationary g
u
barin8differentorientations(orientationsvar- s
iedby22.5°).E:movingbar,abarmovingin8 t 1
differentdirections(directionsvariedby45°). , 2
Thedirectionofmotionwasorthogonaltothe 01
bar’sorientation.F:sinusoidalgratings,drifting 3
in different spatial and temporal frequencies.
Spatialfrequencyvariedbetween0.03and0.7
E F cycles/deg(6logarithmicsteps),andtemporal
Moving Bar Sinusoidal Grating frequency varied between 1.5 and 9 cycles/s
(6linearsteps).
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org
750 VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM
causedbyexposuretoMS-222.Anincisionwasmadeovertheoptic ofthereceptivefield.Inasimilarway,thebarwasmovedindifferent
tectum,theskinandfattytissuewereremoved,andlidocaine(L-7757, directionstodeterminethebordersofthereceptivefield.Thismethod
Sigma)wasappliedtotheboundariesoftheincision.Atthispointwe enables us to mark the receptive field boundary fast enough that
injectedthefishwith5–15(cid:1)lofthenondepolarizingmusclerelaxant mapping of many cells from each animal was possible. The error in
gallaminetriethiodide(17g/l;G8134,Sigma)toitsspine,towardits determiningtheexactlocationoftheedgesis(cid:2)1.5°.
tail,topreventmusclemovementduringtheexperiment.Specifically,
weconfirmedthattheeyemovementsofthefishwereeliminated,and VisualStimuliandDataAnalysis
onlythendidwecontinuewiththerestoftheprocedure.Adentaldrill
(Fine Science Tools micro drill, no. 097883, with a 2.7-mm tip Four types of stimuli were presented on the screen, and they are
diameter; stainless steel trephines, no. 18004-27) was then used to demonstratedinFig.1,C–F.Allstimuliweregeneratedusingeither
open the skull and meninges over the optic tectum. A silver wire thePsychophysicstoolboxinMatlabordirectlyinC(cid:4)(cid:4).
(76.2-(cid:1)mdiameter,tipcoatedwithsilverchloride)wasplacedinthe ON-OFFstimulus.TheON-OFFstimulusconsistedof1sofwhite
cerebrospinal fluid near the optic tectum to use as a reference elec- screenfollowedby1sofblackscreen(lightintensityvaluesof2.66
trode. The tectum was then covered with a thin layer of Vaseline to and0.41(cid:1)W/cm2,respectively)in20–30repeatingloops(Fig.1C).
preventitsdehydration. Foreachcondition,wecalculatedtheresponseasthemeannumberof
spikes in a time window of 50 ms around the peak response time. D
InVivoElectrophysiology Afterobtainingtheseresponses,wecomputedtheresponseratio(R) ow
asfollows: n
lo
smTalhleerwfisahterantadnkth(elenrgesthtra2i5nicnmg,wdeivditche6wcmer,ehepilgahcte6dctmog)efithlleerdwinitha R(cid:2)RON(cid:3)ROFF, ade
b(nraocMkisSh-2w2a2teart(trheids ssteaagesa;lst,ee2–F2i.g5.g1/Bl)).uTphteofi0s.5h’csmgilalbsowveereeyceolnetvine-l RON(cid:4)ROFF d fro
where R is the response to the onset of the flash and R is the m
uouslywateredthroughatubeinsertedintoitsmouthtocompensate responseOtNotheoffsetoftheflash. OFF h
for possible respiratory degradation. The fish was placed so that its Stationary bar. The stimulus consisted of a bar (white over black ttp
roifghthteeyfieshw)aisn0t.h3eccmenftreormofththeegltaasnsk.wTahllis(pgalraaslslewltaollthweassahgiigtthaelrptlhanane background) in eight different orientations (orientations step 22.5°; ://jn
seeFig.1D).Thelengthandwidthofthebarwereadjustedtomatch .p
theotherwalls(12-cmheight)andthusallowedthefishawidevisual h
thereceptivefieldsize,asestimatedbytheinitialstimulationproce- y
field (about 110° in both the vertical and horizontal axes). Using a s
single electrode (tungsten, glass coated, 250-(cid:1)m diameter, 2-M(cid:3) dscurreee(ns,eteoaabvoovied).aEnaychadbaaprtaptrieosnenetfafteicotns,wians7f–o1ll2owreepdebaytin0g.5losoopfsb.lFacokr iolo
impedance, 60-mm length; no. 366-060620-11, Alpha-Omega, Naz- g
eachorientation,wecalculatedtheresponseastheaveragefiringrate y
areth,Israel)mountedonacalibratedmanipulator(Narishige,Tokyo, .o
Japan), recordings were made from the superficial layers (up to 500 in a time window of 200 ms around the peak response time. To rg
(cid:1)m deep) of the optic tectum. The signal obtained was magnified determinewhetherthecellisorientationtunedornot,wecalculated a/
((cid:1)104)andfiltered(band-passboxfilter,300Hz–10kHzrange)byan theorientationindexasfollows: t M
kacmhHazpn,lniafienlesdr:2(1D))tAthhMeessi5igg0nn,aaWllwwPeaIn)stastnahmdroptuhlgeehdnaatnrnadannsremacloiotgrtedndeodtthctorhoaufiglcthoermtw(pHouutepmraraBatlul2ge0l, OrientationIndex(cid:2)RRpp(cid:4)(cid:3)RRoo, arine B
Q(AuMes9t,SGcriaesnstiIfincs)t,rurmemenotvsi)nagnd50anHozs,ciallnodscothpeen(TtoDSan21a0u,dTioekmtroonniitxo)r. whereRpistheresponserateatthepreferredorientationandRoisthe iolog
response rate at the orthogonal orientation. According to previous ic
Inthiswaytheneuralresponsecouldbebothheardandseeninreal studies(Baronetal.2007;Wangetal.2010),weusedthevalueof0.5 a
ti3in0mg–es4ed0susrmiioninng.wthaese(cid:2)xp5erhim, aenndt.Twheewavereeraagbeledutroathioonldosfiangtylepiucnailtsreucoprdto- tooriednistatitniognu-iashgnboesttwiceecnelltsw.oCceelllsl cwlaitshseso:rioenriteantitoantioinn-dtuenxed(cid:5)c0e.5llswaenrde l Lab o
consideredorientation-tunedcells.Wethenfittedparametriccurvesto n
responsesasafunctionoftheorientationofthebar,todeterminethe A
u
SpikeSorting width of the orientation tuning. The fit was based on the probability g
u
density function of the von Mises distribution (Fisher 1995) as s
Spikesortingwasdoneofflineusinganin-houseMatlabprogram. describedinEq.1: t 1
First, the signal was filtered with a band-pass filter with additional , 2
noisereductionat50-Hzfrequency.Potentialspikesweredetectedin p.e(cid:6)cos(cid:1)x-(cid:1)(cid:2) 01
M(x)(cid:2) , (1) 3
events where the filtered signal crossed a threshold of 4.5 times the 2(cid:7)I ((cid:6))
0
standard deviation of the signal. The peak in every segment was
determined,and1.5msofsignalwaskeptbeforeandafterthepeak. where I (x) is the modified Bessel function of order 0 and the fitted
0
Usingagraphicaluserinterface,wemanuallyremovedeventsthatdid parametersarep,peakresponse;(cid:1),centerorientationatthepeak;and
nothavetheshapeofaspike.Wethenclusteredthespikesintoone (cid:6),concentrationfactor.
ormoregroupsbasedonspikeamplitudeandwidth. Weexploredtheparameter(cid:6)tofindtheorientationtuningwidth.
TheadvantageinfittingavonMisesdistributiontothiskindofdata
EstimationoftheLocationoftheReceptiveField isthatitenablesusnotonlytofindthepreferredorientation,butalso
tofacilitatetheextractionofdatasuchasthetuningwidth.
We stimulated the visual system using a hand-held flashlight to Moving bar. A circle 120% of the receptive field size was drawn
determine whether each single cell could produce a high-quality around the estimated receptive field location, and a bar, with length
neural response. In well-isolated cells with a high-quality neural andwidthadjustedtomatchthereceptivefieldsize,wasmovedfrom
response,thestimulatingcomputerscreenwaspositioned20cmfrom onesideofthecircletotheoppositeside(1cycleper1.5s,followed
theanimal’seye.Toestimatethelocationofthecell’sreceptivefield, by 0.5 s of black screen, to avoid any adaptation effects, in 7–12
a white bar was moved interactively by the experimenter across the repeating loops) with direction of motion orthogonal to the bar’s
screen in different orientations and moving directions to detect the orientation(8differentdirections;seeFig.1E).Foreachdirection,we
limitsofthereceptivefield.Thebarwasmovedacrossthescreenuntil calculated the response as the mean number of spikes in a time
astrongreactionwasheard;thispointwasmarkedasoneoftheedges window of 200 ms around the peak response time. To determine
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org
VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM 751
whetherthecellisdirectiontunedornot,wecalculatedthedirection EstimationofConfidenceIntervalsonCellTypeRatiointhe
indexasfollows: Population
DirectionIndex(cid:2)Rp(cid:3)Ro, For each cell type ratio, we determined the 95% confidence
R (cid:4)R intervalsusingtheClopper-Pearsonmethod.Inaddition,weestimated
p o
the confidence interval of the event that there is an additional cell
whereR istheresponserateatthepreferreddirectionandR isthe groupwedidnotobserveinthedataset.
p o
response rate at the opposite direction. Cells with direction index
(cid:5)0.5 were considered direction-tuned cells. For cells with direction
index(cid:5)0.5,wecalculatedtheorientationindex(asdescribedabove). RESULTS
Cells with orientation index (cid:5)0.5 were considered orientation-tuned
We measured the receptive field location and functional
cells. We then fitted parametric curves to responses as a function of
the direction of the bar to the cells with direction index (cid:5)0.5, to properties of cells in the optic tectum of the archer fish using
extracellular electrodes. The fish was immobilized during ex-
determinethewidthofthedirectiontuning.Thefitwasbasedonavon
MisesfunctionsasdescribedinEq.1. periments, and respiration was reduced by perfusing the gills.
For comparison, and for ensuring our results are robust, we also Overall, we measured from a total of 166 cells in 28 different
D
fitted the response of the cell to the different directions with a animals in different stimulus conditions. o
w
second-orderharmonicfunction(HF)assuggestedbyMaximovetal.
n
(2005): lo
Retinotectal Map of Archer Fish Optic Tectum a
d
HF(x)(cid:2)a (cid:4)a cos(x(cid:3)(cid:1))(cid:4)a cos(2x(cid:3)2(cid:1)), (2) e
0 1 1 2 2 Torevealtheretinotectalmappingofreceptivefieldsofcells d
where a are the amplitude and (cid:1) are the phases of the different in the optic tectum, we mapped the location of 35 cells in 5 fro
i i m
harmonics. The amplitudes of the harmonics (a0, a1, and a2) were different animals by using an interactively moving bar in h
usedtoclassifythecellsintothreedifferentgroups:direction-tuned, different orientations. For each location on the optic tectum ttp
oclraiesnsitfiateidona-studnireedc,tiaonnd-tduinreecdtiiofnth-aegirnfiosrstitchcaerlmlso.nSipcehcaifidcdailsltyi,nccetlrleslawtievree surface (see MATERIALS AND METHODS), we found several cells ://jn
atahme(cid:6)iprlis0teu.c5doaen,,dia.hen.ad,rmaa1sod(cid:6)niirceahc2taiadonndd-iasagti1nnoc(cid:6)sttri0ec.l5aoatni0ve,seaiasfmtohpreliiertneutldaaettii,ovin.ee-a.t,umanp2el(cid:6)dituoadn1eesasnoidff fteiraoocnmhaldnoidcfafedtirioemnnetonansnitoihmnesa.olspTtahincedtaemvceteuraamsguesruelrdofcatachteeiowrneecareenpdtthivdeeinmficeaenllcsdiuollonatceoad-f .physio
2 0 torevealthemapbetweenthespecificplaceintheoptictectum lo
both their first and second harmonics were small (Maximov et al. g
2005). and the location in the visual field (Fig. 2, A and B). y.o
Sinusoidal gratings. The stimulus consisted of drifting sinusoidal We found that the dorsal visual field projects to the lateral rg
gratings (maximum and minimum light intensity values of 2.66 and part of the optic tectum and the ventral visual field projects to a/
0.41(cid:1)W/cm2,respectively)indifferentspatialandtemporalfrequen- themedialpartoftheoptictectum.Thevisualfieldinthenasal t M
cfoiellsow(Feidg.by1F0)..5Esaocfhbplarceksesnctraeteionn,toofavaogidraatinnygaadpappetaatrieodnefoffrec1t.s5,isn, dteimrepctoiroanl dpirroejcetcitosntoprothjeectrsosttoratlhepacratuadnadl pvaisrutaolffitehledtienctuthme arine
7–12 repeating loops. The direction of the grating was chosen to be B
thepreferreddirectionobtainedfromthemovingbarstimulus.Spatial (Fig. 2, A and B). io
Inaddition,wefoundthatthereceptivefieldscanbedivided lo
frequency varied between 0.03 and 0.7 cycles/deg (6 logarithmic g
steps), and temporal frequency varied between 1.5 and 9 cycles/s (6 into two groups according to their location, size, and shape. ica
linearsteps),resultinginatotalof36gratingconditions.Firingrates Thefirstgroupconsistsofcellswithreceptivefieldsinfrontof l L
foreachgratingwereobtainedbyaveragingthenumberofspikesover thefish’seyeinthedorsal-ventralplane,i.e.,atthesameheight ab
the1.5-sstimulusdurationacrossalltrialsandsubtractingthefirst50 as the fish eye. The second group consists of cells with o
n
ms, to avoid the onset response. Collecting these responses for all receptive fields located more dorsally (Fig. 2B). A
stimulus conditions, we then determined the preferred spatial and Exploringtheshapeofthereceptivefields,wefoundthatthe ug
temporal frequency combination for each cell. Finally, we evaluated majority of receptive fields that were located in front of the us
the spatial frequency tuning at the preferred temporal frequency and fish’s eye in the dorsal-ventral plane were elongated in their t 1
the temporal frequency tuning at the preferred spatial frequency by verticaldimension(Fig.2C,red,yellow,andgreencircles).In , 2
0
fittingthemwithaGaussianfunction. cells with receptive fields located more dorsally, the receptive 13
fields were slightly more elongated in their horizontal dimen-
RetinotectalMappingoftheOpticTectum sion than in their vertical dimension (Fig. 2C, blue and cyan
circles). A closer examination of the width and height of the
To determine the gross mapping between the visual field to the
optictectumsurface,wefirsttookaphotooftheoptictectumandaligned receptive fields shows that the receptive fields of cells with
ittoagridconsistingofsmallregionsalongtheanterior-posteriorand receptive fields located in front of the fish’s eye in the dorsal-
the medial-lateral axes. This procedure divided the optic tectum ventralplanearesignificantlynarrowerandlongerthanrecep-
surfacetosmallregionsofinterest(Fig.2A).Onceawell-isolatedcell tive fields of cells with receptive fields located more dorsally,
with a high-quality neural response was found, we marked the loca- which were wider and shorter.
tionofthepenetrationtotheoptictectumonthephotowepreviously Wedeterminedthesizeofthereceptivefieldasthegeomet-
took.Theaccuracyofthedeterminingtheexactpenetrationpointwas
ricalmeanofitstwoedges(Fig.2D).Wefoundthattherewas
(cid:2)0.4 mm. At the end, we grouped single units to those regions by
a significant difference in the size distribution of the two
their tectal location. For each unit, we estimated the receptive field
groups (Kolmogorov-Smirnov test, P (cid:5) 0.001). Specifically,
dimension and location as described in above. We then assigned an
small receptive fields (range: 3.12°–9.48°, mean: 5.32°) were
averagereceptivefieldlocationanddimensionforeachgridregionby
averagingthosepropertiesofallcellsthatcorrespondedtothatregion. locatedabovethetemporal-nasalline.Largereceptivefieldsof
This procedure was done in different animals and allowed us to cells(range:5.45°–17.69°,mean:10.14°)werelocatedinfront
combinedatafromdifferentexperiments. of the fish eye.
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org
752 VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM
A B
DORSAL
L
LATERAL A
R N
O A
P S
Fig.2.Spaceandsizeorganizationofreceptive R M A
fieldsinthearcherfishoptictectum.A:aphotoof AL OS TE L
the archer fish brain with the left optic tectum D T
delineated(top)andtheelectrodepositionsonthe U R
left optic tectum (bottom). B: topographical ar- A A D
C L o
rangementofreceptivefieldsintherightvisual w
n
fieldofthearcherfish.Theblackcirclerepresents 10° lo
thefisheye.Eachcolorcorrespondstotheelec- a
MEDIAL d
trodepositionshowninA.Solidrectanglesrep- VENTRAL ed
rdeismeenntstihoen,aavnedracgoentroeucreprteicvteanfigeleldsrleopcraetisoenntatnhde fro
m
areaintowhichallthereceptivefieldsbelonging C D
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Widt Cell 5 ysio
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Receptive Field Height (deg) Receptive Field Size (deg) io
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ic
Inaddition,weexaminedtheareainwhichallthereceptive We found that most cells respond to both ON and OFF a
fieldsbelongingtothesamegridfall(Fig.2B,contourrectan- stimulus and that there is a continuum in the response of cells l La
b
gles). We found that there is no significant difference in the to this kind of stimulus, since the ON/OFF response ratio of o
widths of the circumscribed receptive field areas (permutation different cells spans continuously the interval (cid:7)1 to 1 (Fig. n A
test, P (cid:6) 0.05). However, there is a significant difference 3D). In addition, there is a slight preference for the OFF u
g
between the two groups in the variability in the dorsal-ventral stimulus, since the peak of the response histogram is negative us
axis (permutation test, P (cid:5) 0.01). The height of the circum- ((cid:7)0.14 (cid:8) 0.05, mean (cid:8) SE). t 1
scribedareaofthereceptivefieldsclosertothefisheyeissmaller , 2
0
than the height of the circumscribed area of the receptive fields 1
Orientation Selectivity in Archer Fish Optic Tectum 3
locatedmoredorsally.
The orientation selectivity of cells was tested by flashing a
ArcherFishOpticTectumCellsRespondtoanON/OFFStimulus
bar on the receptive field center. This was done first by
Wetestedtheresponseofthecellstotheonsetandoffsetof detecting the receptive field boundaries (see MATERIALS AND
alightbypresentingafull-fieldflashstimulus.Werecordeda METHODS) and then by flashing a bar with a matched size in
total of 83 cells from 15 animals using this type of stimulus. eight different orientations. We recorded 38 cells from 8
Severalcellswithdifferentresponsepropertiesaredepicted animalsusingthistypeofstimulus.Wequantifiedtheresponse
in Fig. 3, A–C. Generally, cells responded to the onset and of different cells to orientation by calculating the orientation
offset of light in various degrees. To quantify the response index and determined the width of the orientation tuning by
profiles,foreachcellwedeterminedtheONresponseleveland fitting a von Mises function only to the cells with high
theOFFresponseandcalculatedtheON/OFFresponseratioR, orientation index (for additional details, see MATERIALS AND
which quantifies the ON/OFF polarity of the cell. Cells that METHODS).
exhibitastrongONresponse(Fig.3A)willhaveresponseratio Wefoundthattheresponseofcellscanbeclassifiedintotwo
close to 1, whereas cells that exhibit a strong OFF response types. The first is a strong response to specific orientation,
(Fig. 3B) will have response ratios close to (cid:7)1. The response where the response to the preferred orientation could be up to
ratio of an ON-OFF cell (Fig. 3C) will be close to 0. 20 times higher than the response to the null orientation, and
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org
VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM 753
Response to a Diffuse Flash
A B
ON Cell OFF Cell
# #
at at
e e
p p
e e
R R
Fig.3.CellresponsestoON-OFFstimulus.
A:exampleofanONcell,acellthatresponds
totheonsetofaflash.B:exampleofanOFF
cell, a cell that responds to the offset of a D
o
0 1000 2000 0 1000 2000 flash.C:exampleofanON-OFFcell,acell w
Time (ms) Time (ms) thatrespondstoboththeonsetandoffsetof nlo
aflash.D:adistributionoftheresponseratio a
d
C D of ON and OFF responses shows that the e
ON-OFF Cell cbeeltlwsefeanlloOnNacaonndtinOuuFmFocflaresssepso.nsTehpeattmeronsst d fro
12 abundant pattern is a symmetrical ON-OFF m
response. h
10 ttp
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Time (ms) -1 -0.R5 e s p o n 0s e R a t i 0o.5 1 rine
B
therefore the orientation index is (cid:6)0.5 (Fig. 4, A and B). In cellsinthearcherfishoptictectumhaverelativelysharporienta- iolo
addition,wefoundcellswithveryweakdependenceonorien- tiontuningprofiles. gic
tation,wherethedifferencebetweenthemaximalandminimal a
l L
orientation spike count is marginal, for which the orientation Direction and Orientation Selectivity of Tectal Neurons in a
index is (cid:5)0.5 (Fig. 4, C and D). We define cells with such Response to Moving Bars b o
weak dependence on orientation as orientation-agnostic neu- n A
rons. Thedirectionselectivityofcellsinresponsetomovingbarswas u
g
Using this analysis, we found that 58% of the cells were testedbyfirstlocatingthereceptivefieldcenterandthenmovingabar u
s
orientation tuned (Fig. 4E). We tested the sensitivity of these acrossthereceptivefield(seeMATERIALSANDMETHODS).Werecorded t 1
numbers to the threshold between cell types and found that 36cellsfrom8animalsusingthisstimulus.Toclassifycellsinto , 2
0
10% change in the threshold results with only 1 cell moving different response groups, we first calculated the spike count in 1
3
between groups. Moreover, the preferred orientation had a response to specific direction (see MATERIALS AND METHODS) and
strong bias for the vertical orientation with 59% of the orien- thencalculatedthedirectionindexandtheorientationindex.We
tation-tuned cells having a preference for the vertical orienta-
then fitted a von Mises function to the response to measure the
tion or its neighboring orientations ((cid:8)22.5°), 13.6% of the
directiontuningwidth.Forcomparison,wealsofittedaharmonic
orientation-tuned cells having a preference for the horizontal
function to the response to determine whether our results are
orientationoritsneighboringorientations((cid:8)22.5°),and27.2%
robust(seeMATERIALSANDMETHODSformoredetails).
oftheorientation-tunedcellshavingapreferencefortheother
diagonal orientations or its neighboring orientations ((cid:8)22.5°) Wefoundthreetypesofcellsaccordingtotheirresponsetoa
moving bar: 1) an orientation-tuned response, where the cell
(Fig. 4F).
respondswithhighfiringratetomovementsalongaspecificaxis
WefittedvonMisesfunctiontotheorientation-tunedcellsand
explored the parameter (cid:6)to find their orientation tuning width. in space (Fig. 5A); 2) a direction-tuned response, where the cell
Wefoundthat45%ofthecellshadasharptuningwidthbetween respondswithhighratetomovementinaspecificdirection(Fig.
15°and30°,41%ofthecellshadamediumtuningwidthbetween 5B); and 3) an agnostic response, where the cell responds with
30°and45°,and14%ofthecellshadatuningwidthof45°to60°. marginaldifferencesbetweendirections(Fig.5C).
Onaverage,meanorientationtuningwidthwas33.26°(SE2.36°; Onthebasisofthequantitativeanalysisdescribedabove,we
Fig.4G);i.e.,themostprevalentwidthwas(cid:5)34°,indicatingthat found that 11% of the cells were direction tuned, 39% were
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org
754 VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM
Response to a Flashing Bar
A B
Orientation-Tuned Cell
60
nt
u
n o
o C
ati e 40
ent pik
Ori e S
ar ag 20
B er
v
A
0
Fig.4.Orientationselectivityprofilesassessed 0 1000 2000
usingthestaticbarstimulus.A:rasterplotsof Time (ms) Bar Orientation D
the responses to the 8 oriented bars for an ow
orientation-tunedcell.Blacklinesrepresentthe C D n
startandendtimeofthebardisplay.B:orien- Orientation Agnostic Cell lo
a
tation tuning profile for the orientation-tuned 20 de
cell from A. The dashed black line repre- nt d
sentsthefittedvonMissesdistributionfunction. n ou fro
C:rasterplotsoftheresponsestothe8oriented o C 15 m
barsforanorientation-agnosticcell.D:orien- ati e h
tc9ae5tli%lofnrcotoumnnfiiCndg.enEpcr:eodfiiinlsettrefirbovurattlih)oenfooorrifoesnreitelaentcitoatintvi-oiatnyg-nt(uownsitetihdc Orient e Spik 10 ttp://jn
andorientation-agnosticcells.F:distributionof ar ag 5 .ph
preferredorientation(with95%confidencein- B er ys
terval).Themajorityofcellspreferredthever- Av io
ticalorientation.G:distributionoftuningwidth 0 log
fortheorientation-tunedcells. 0 1000 2000 y
Time (ms) Bar Orientation .org
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ells 70 n=38 ells 70 n=22 ells 40 n=22 rine
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Pe 0 Agnostic OSreielenctatitvioen Pe P0referred Orientation Pe 0 10-2T0 u 2n0i-3n0g 3W0-4id0 t h40 -(5d0 e g50)-60 on A
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orientation tuned, and 50% were classified as direction agnos- Using the second method, fitting of a harmonic function, to t 1
tic(Fig.5D).Wetestedthesensitivityofthesenumberstothe determine the selectivity of the cell in response to a moving , 2
thresholdbetweencelltypesandfoundthat10%changeinthe bar, we found similar results with a few exceptions. All the 01
3
threshold results with 5 cells moving between groups. cells that were classified as direction-tuned cells with the first
Of the orientation-tuned cells, 86% preferred the vertical ori- method were also classified as direction-tuned cells with the
entation (as shown in Fig. 5A) and 14% preferred the diagonal second method. The second method classified an additional
orientation. We calculated the confidence interval for the possi- cellasadirection-tunedcell.Asfortheorientationtuning,the
second method missed two cells that were classified as orien-
bilityoftheexistenceofanadditionalcelltypethatwehavenot
tation-tunedwiththefirstmethodandaddedanadditionalcell
observedinourdataset(seeMATERIALSANDMETHODS),orientation-
asorientation-tuned.Overall,itseemsthatuseofthedirection
selectivecellswithapreferenceforthehorizontalorientation.We
and orientation indexes and the von Mises distribution gives
found that with 95% of certainty, the proportion of this possible
robust results, and moreover, it adds the ability to determine
missinggroupisbetween0and0.1.
the tuning width, compared with the second method.
Wefoundthathalfofthedirection-tunedcellshadthegreatest
response to a moving bar in the temporal-nasal direction, as
Spatial and Temporal Frequency Tuning
determined by exploring the fitted parameter (cid:1) in Eq. 1 and
shown in Fig. 5B. The other direction-tuned cells preferred the The spatial and temporal tuning of cells was evaluated by
diagonaldirection,onefromnasal-ventraltocaudal-dorsaldirec- analyzingtheresponseofcellstosinusoidalgratingdriftingalong
tion and the other from nasal-dorsal to caudal-ventral direction. thecell’spreferreddirection.Oncethecellpreferreddirectionwas
Thewidthsofthedirectiontuningvariedbetween60°and90°. detected, we stimulated it with all combinations of six spatial
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org
VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM 755
Response to a Moving Bar
A B
Orientation-Tuned Cell Direction-Tuned Cell
Dorsal
Nasal Temporal
D
o
w
Fig.5.Directionselectivityprofilesassessed n
usingthemovingbarstimulus.A:orientation- lo
1 s tunedcellprofile.B:direction-tunedcellpro- ad
Ventral file.C:direction-agnosticcellprofile.D:dis- ed
tirnitbeurvtiaoln) ofofrsealgencotisvtiicty, o(wriietnhta9t5io%n-ctuonnefidd,eanncde from
C D direction-tunedcells. h
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Agnostic OSreielenctatitvioen SDeirleeccttiiovne iolo
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frequencies(rangingfrom0.03to0.7cycles/deg)andsixtemporal that we have not observed in our data (see MATERIALS AND ab
frequencies (ranging from 1.5 to 9 Hz). For this stimulus, we METHODS).Wefoundthatwith95%ofcertainty,theproportion on
recordedatotalof30cellsfrom6animals. of a possible missing group is between 0 and 0.12. A
u
For each cell, we found the combination of spatial and In a similar way, to analyze the spatial tuning of a cell, we g
u
temporal frequencies that elicited the maximal response. The tookitsbesttemporalfrequencyandfittedaGaussianfunction s
cells had a higher response to a unique combination of spatial totheresponseatallcorrespondingspatialfrequencies(i.e.,to t 1
and temporal frequencies (Fig. 6, A and B). 1columnoftheresponsematrix).Wefoundtwogeneraltypes , 2
0
We analyzed the cell response to obtain further frequency oftuningprofiles:lowpassandbandpass.Figure6Fshowsa 13
tuningproperties.Toanalyzethetemporalfrequencytuningof low-pass tuning profile. The maximal response of this cell to
a cell, we took the best spatial frequency and analyzed the the sinusoidal grating is at the lowest spatial frequency tested
cellular response for all the different temporal frequencies at (0.03 cycles/deg), and at higher spatial frequencies the re-
that spatial frequency (i.e., 1 row of the response matrix). sponse gradually decreases. Figure 6G shows a band-pass
Fitting a Gaussian function to these responses, we obtained tuning profile. The response of this cell to the sinusoidal
three types of temporal frequency tuning profiles: a low-pass gratingatthelowestspatialfrequencytested(0.03cycles/deg)
tuningprofile,inwhichcellselicitthemaximalresponsetothe andatthehighestspatialfrequencytest(0.7cycles/deg)islow,
lowertemporalfrequenciestested(Fig.6C);ahigh-passtuning and the maximal response is for a spatial frequency in the
profile, in which cells elicit the maximal response to the middle of the range (0.09–0.18 cycles/deg). We found that
highest temporal frequencies tested (Fig. 6D); and an all-pass 57%ofthecellshadalow-passtuningprofileand43%ofthe
tuning profile, in which there was almost no difference in the cells had a band-pass tuning profile (Fig. 6H). We calculated
response to the different temporal frequencies (Fig. 6E). We theconfidenceintervalforthepossibilityoftheexistenceofan
foundthat23%ofthecellshadalow-passtuningprofile,54% additional tuning profile group that we have not observed in
hadahigh-passtuningprofile,and23%hadanall-passtuning ourdata(seeMATERIALSANDMETHODS).Wefoundthatwith95%
profile(Fig.6H).Wecalculatedtheconfidenceintervalforthe of certainty, the proportion of a possible missing group is
possibilityoftheexistenceofanadditionaltuningprofilegroup between 0 and 0.12.
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org
756 VISUAL RECEPTIVE FIELDS IN THE ARCHER FISH OPTIC TECTUM
Response to a Sinusoidal Grating
A B
1 1
g) 0.7 g) 0.7
e 0.9 e 0.9
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atial Fr 0.05 00..23 e Coun atial Fr 0.05 00..23 e Coun Down
p t p t lo
S 0.03 0.1 S 0.03 0.1 a
d
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Te1.m5por3al Fre4.q5uen6cy (c7y.c5le/s9) Te1.m5por3al Fre4.q5uen6cy (c7y.c5le/s)9 from
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Low High All Low Band
Pass Pass Pass Pass Pass
Spatial Frequency (cycle/deg) Spatial Frequency (cycle/deg)
Temporal Tuning Spatial Tuning
Fig.6.Responsestospatialandtemporalfrequenciesandtuningprofilesassessedusingsinusoidalgratings.A:exampleofacellforwhichthemaximalresponse
rate is at the lowest spatial and temporal frequencies tested. B: example of a cell for which the maximal response rate is at one of the central spa-
tialandthehighesttemporalfrequenciestested.C:low-passtemporalfrequencytuningprofileshowingthehighestresponserateatthelowesttemporalfre-
quencytested.D:high-passtemporalfrequencytuningprofileshowingthehighestresponserateatthehighesttemporalfrequencytested.E:all-passtemporal
frequencytuningprofile.F:low-passspatialfrequencytuningprofileshowingthehighestresponserateatthelowestspatialfrequencytested.G:band-passspatial
frequencytuningprofile.H:distributionoftuningprofiles(with95%confidenceinterval).Lightgray,temporalfrequencytuning;darkgray,spatialfrequency
tuning.Wecalculatedtheconfidenceintervalforthepossibilityoftheexistenceofanadditionaltuningprofilegroupthatwehavenotobservedinourdata(see
MATERIALSANDMETHODS).Forboththespatialfrequencyandtemporalfrequencytuning,wefoundthatwith95%ofcertainty,theproportionofapossiblemissing
groupisbetween0and0.12.
JNeurophysiol•doi:10.1152/jn.00094.2013•www.jn.org