11.00+ 0.m
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Copynglrt Q l99l PergamonPressplc
V i s i o nR c sV
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Pnntcd rn Grcat Bntarn. All nghts rescned
MINIREVIEW
CLASSIFYINGSIMPLE AND COMPLEX CELLS ON
THE BASISOF RESPONSEMODULATION
BsnNr C. Srorn-.rN,r RUSSTU L. De Vuos,2 Devto H. GnosOr,r J. AxrxoNv Movsttox,l
and A. B. BoNos5
Duexe G. Arnnrcrrt
rDepartmenl of Psychology and 2Department of Psychology and Physiologcal Opucs Group'
University of California, Bcrkeley,CA 94720,rCenterfor Neural Scienceand Depanment of Psychology.
'Depanmcll of Psychology,University of Tcxas,
New York University. New York, NY 10003.
5Depanmcnt
Engineenng, Vanderbilt Untversity. Nashville.
Electrical
of
78712 and
Ausrin, fi
TN 37235.U.S.A.
(ReceiuedIl July 19fl)
Abctrrct-Hubel and Wiesel (1962; Jounal of Physiology,London, I&, 106-154) introduced the
classificationof cortrcal ncurons as simple and complex on the basisof four testsof their reccplrvefield
structure.Thesetestsarc partly sub.lectivcand no onc ofthem unequivocallyplacesneuronsinto distinct
criterion basedon the form ofthe responscto dnftrng srnusoidal
classcs.A simple.objcctivcclassifica.tion
gratings has bcen uscd by scveral laboratones, although it has bcen cnticized by others. We rcview
published and unpublishcd cvidcncc which indicatcs that this simple and objcctivc ctrtcnon rchability
divldes neuronsof the striate cortcx in both cats and monkeysinto two groups that correspondclosely
simple and complex classcs.
to the classically-describcd
Complcx cells
Simplecells
lation
Linear systems
Striatc cortcx
Gratings
In their early recordingsfrom the striatecortex,
Hubel and Wiesel (1962) distinguishedtwo
main typesof cells:simpleand complex.They
describedfour characteristicsof simpie cells
( p p . 1 0 9 - ll 0 ) .
". . . the two typesof regionwithin a receptivefield were mutuall.vantagonisttc.
This was most forcefully shown by the
absenceor near absenceof a response
to simultaneousillumlnation of both
regions. . ."
(l) SpatiallyseparateON and OFF regions:
"Like retrnalganglionand geniculate
cells.
corticalcellswith simplefieldspossessec
distinct excitatory and inhibitory subdivisions.Illuminationof part or all of an
excitatoryregionincreasedthe maintained
firing of the cell. whereasa light shoneir,
the firing
the inhibitoryregionsuppressed
'off'."
and evokeda dischargeat
"A largespotconfinedto eitherareaproducedgreaterchangein rateof hring than
a smallspot.indicatingsummationwithin
eitherregion."
Responsemodu-
(3) AntagonismbetweenON and OFF subregions:
INTRODUCTION
(2) Summationwithin eachregion:
Spatial frequcncy
(4) Response
properties
from
canbe predrcted
receptivefield maps:
"From the arrangementof excitatory
and inhibitory regions it was usually
possibleto predict in a qualitativeway
to any shapeof stimulus.
the responses
stationaryor moving."
Complexcellswere definedb.vexclusionas
cellsthat faiiedto dispiaythe statedcharacteristicsof simplecells.Hubel and Wiesel(1968)
found that the cell classificationonginally
definedin cals could be used equallywell to
I 079
1080
Minireview
categorize orientation selective cells in the
monkey'sstnatecortex.
Subsequentinvestigatorshave proposeda
number of subsidiaryor supplementaryclassificationsof corticalcells(e'g.Hubel & Wiesel,
1965; Palmer & Rosenquist.1974; Gilbert'
1977;Henry, 1977),but theseare all based
on the concept of simple and complex
"families". which remainscentral to all funcof neuronsin the
tionally-basedclassifications
APPLICATION OF LINEAR SYSTEMS
ANALYSIS TO STRIATE CELIS
In recent years, investigatorshave applied
techniquesfrom linear systemsanalysisto the
stuay of cortical cells' receptivefields' Hubel
and Wiesel's original descriptionof simple
cells suggestedthat they might be well understood as having linear spatial summatlon'
while complexcells have profoundly nonlinear
behavior. Quantitative exploration of cortical
striate cortex.
broadly confirmedthis imThere are severalproblems associatedwith receptivefields has
19731Movshon'
(Maffei
Fiorentini.
&
the criteria of Hubel and Wiesel.It has proved pr.tiion
b: De Valois'
1978a.
Tolhurst.
difficult to separatecells into distinct classes Thompson &
also shown
has
1982).but
on the basis of quantitative estimatesof ON Albrecht& Thorell,
of
number
a
cells have
and OFF region overlap(Sherman,Watkins & clearly that simple
it
impossible
make
Wilson. 1976;Dean & Tolhurst,1983);invcsti- important nonlinearitiesthat
basis for classithe
as
per
se
linearity
use
to
orientation
gatorshavehad difficuttypredicting
of Hubel and Wiesel's
and directionselectivityfrom the receptivefield fication. The essence
has two components:
cells
simple
of
descnption
&
maps of simple ceils (Goodwin, Henry
by a local stimulus
evoked
response
the
Bishop,1975;Heggelund& Moors. 1983;but first.
ofcontrasusecond,
sign
preserves
the
(e.g.
a bar)
seealsoReid,Soodak& Shapley,1987;Mclean
linearly. so
roughly
combine
& Palmer,1989);and. usingthe testproposedby local responses
response
predict
the
cell's
to
possible
Hubel and Wiesel,it is difficult to distinguishthe that it is
Complex
responses.
locai
summing
iimit of spatial summationfrom saturationof by suitably
gave similar
Furthermore.the criteriaof Hubel cells,on the other hand. typically
the response.
sign of
either
of
stimuli
and Wieselare qualitativeand their application responsesto local
informatton'
polarity
dependsin part on the individualinvestigator's contrast. thereby losing
evoked
judgement.thus makingit likely that this appli- Also, complex cells sum locally
in a highly nonlinearmanner(Hubel
cation variesbetweenindividual investigators responses
et al.' 1978b:Spitzer
and laboratories.Finally. the relianceon several & Wiesel.1962:Movshon
thenotionof approxrcriteria leavesit undecidedhow to classifycells & Hochstein.1985).Thus
relatedto Hubeland
is
intimately
linearity
mate
that satify somecriteriabut not others.
classification'
simple-complex
original
Wiesel's
Some investigatorshave sought to amend
a cell
whether
to
determine
way
simple
A
the cnreria of Hubel and Wiesel by adding
gross
or
overlap
ON/OFF
substantial
or substitutingdistinguishingcharactertstics'lacks
examlne
is
to
summalion
spatial
of
Among the proposedtests are: spontaneous nonlinearity
to a sinusoidalinput: a cell lacking
Nikara& Bishop'1968: its response
activitylevel(Pettigrew.
respondsto a sinusoidalll'
Bishop.Coombs& Henry. l97l; Hammond& thosenonlinearities
(e.g.
a drifting or counter'
amplitude(Pettigrew modulatedinput
MacKay. 1977):response
sine-wavegrating) with a
field phase-modulated
et al.. 1968:Bishopet al.. l97l): receptive
slimulustemporalfresrze(Bishopet al.. l97l; Hammond& MacKay'. sinusoidaloutput at the
neuron,this
1977);lengthsummation(Bishopet al.. l97l); quency.(ln the caseof a spiking
"sharpness"of response
(Pettigrew
et al.. 1968): output is a sinusoidalmodulatronof the firing
) If a cell wereperfectlylinearin all
onentationselectivity(Hammond& MacKay, frequency.
the Fouriertransformof this response
1977):and responseto patterns of random respects.
at
all of the energyconcentrated
would
show
1989)'
dots (Hammond. Pomfretl & Ahmed.
the
even
In
realitl'.
of
stimulation.
frequency
the
on
While simple and complex cells may.
that
average.differ with respectto most. if not most iinear neurons have nonlinearities
frequenctes
at
response
the
into
terms
rntroduce
thereis reasonto believe
all. of thesemeasures.
rncludrngthe
that none of them can be usedto group cells otherthan the stimulusfrequency'.
(e.g.Enrothcomponent
or
d.c.
Moreover.thesemeasures zerofrequenc-vlnto dist.lnctclasses.
since
particular.
In
1966t.
Robson.
the receptivefield proper- Cugell&
do not acknowledge
maintained
a
have
ties addressedb1 the criteria of Hubel and most corttcal neurons
actrvirv*'hich is low or absentand cannotfire
Wiesel.
Mintrevrew
1 0 8I
finite this measurewould form an objectivetest not
at negativeratesthe responsewill have a"halfjudgementsof
dependenton the expenmenter's
d.c. component.This typically yields
wave" rectificationof the responsewaveform. responses.
but in generalthis sort of rectificationwill never
causeany responsecomponent to exceedthe
DOES CLASSIFICATION BASED ON RESPONSE
fundamentalin amplitude.We mtght thenexpect
MODULATION CORRESPOND TO
that the relatiue modulationof the response,
CLASSIFICATION BASED ON HUBEL
defined as the ratio of the responseat the
AND WIESEL'S CRITERIA?
stimulus frequencyto the d.c. response(with
Hubel and Wiesel'sclassificationschemefor
baselineactivity subtracted),would never fall
relatedto a
below 1.0 for the rectified responsesof a simpleand complexcellsis closely
(Shapley
& Lennie.
linearity
linear neuron.In the common caseof a neuron test of summadon
with
closely
correlate
whosemaintaineddischargeis zero and whose 1985). which should
"half-wave"
slne-wave
drifting
rectified. the modulation ratio from
responsesare perfectly
(1.57). gratings. Does ciassificationby these two
n,/2
be
would
the relativemodulation
Other nonlinearitiescommonly shown by differentmeasuresin fact agree?
When cells classifiedby classicalcriteria as
simple cells, such as contrast gain control,
end- and side- simple are stimulatedwith drifting sinusoidal
contrastadaptation.suppressive
modu- gratings.they respondwith a dischargethat is
relative
on
inhibition.have little effect
with the temporalfrelation. However. those nonlineanttesmost modulatedin synchrony
whereas
complexcells
quency
stimulation.
of
grossly
nonof complexcells.e-g.
characteristic
is generally
rate
that
firing
produce
elevated
an
iinear spatialsummation.have a major effect
1973:
(Maffei
Fiorentini.
&
with
dme
on relative modulation in the responseto a uniform
Wright.
&
Ikeda
1975:
Tolhurst.
grating.This reducesthe responsecomponent Movshon &
1976:
at the stimulus temporal frequency and en- 1975: Schiller, Finlay & Volman.
Pollen.
&
Andrews
b:
trans- Movshon et al.. 1978a.
at other frequenctes.
hancesresponses
1979:Dean. l98l: Holub & Morton-Gibson.
signals
input
modulated
sinusoidally
forming
dominatedby energyat even l98l: Albrecht& Hamilton. 1982:Pollen &
into responses
1982;
multiplesof the sttmulustemporalfrequency Ronner.1982:Morrone. Burr & Maffei.
(including0). In particular.thesenonlinearities Jones.Stepnoski& Palmer.1987:Hamilton.
componentat Albrecht& Geisler.1989).
weakenor abolishthe response
Movshonet al. (1978a.b)showedthat the
value of
The
itself.
rhe stimulus frequency
of responsemodulationseemedto disdegree
would
relative modulation for such neurons
simpleand complexcells'They stimutinguish
thus tend to be near0.
cellswith drifting sinusoidalgrattngs
the
lated
A useful test of linearity of summationin
analyzedthe averagedresponse
Fourier
corticalcellsmight be derivedfrom the wave- and
a measureof relativemodulation
As
waveform.
form of the cell'sresponseto a drifting sinuof the amplitudeof the first
the
ratio
the temporalluminance the;-took
soidalgrating.because
responselevel. after
mean
the
to
variatronat eachpoint in sucha gratingrs a harmonic
maintalnedrate.
average
the
advantagessubtractionof
Amongthemany'practical
sinusoid.
that when
(1978a.
reported
b)
ol usrngdrifting gratingsrather than olher Movshonet al.
were
used.
potentralsinusoidalstimuli are: r'irtuallvall gratingsof optrmalspatialfrequency
relaltve
to movingpatterns simplecellsalwaysappearedto have
striatecellsare responsive
of 1.0.whilecom(whereasman;- do not respondto flashedor modulationvaluesin excess
than 1.0. It is
were
less
values
plex
cells'
tesl
the
spots):
bars
or
sinusoidally-modulated
with gratings
when
tested
that
to
note
lmporlant
thus
is
and
few
seconds
can be carriedout tn a
they
frequency.
spatial
lower-than-optimal
position
of
reslstantto gradualchangesin eve
gave
strongly
that
cells
complex
many
be
found
can
over !ime: large and reliableresponses
elicitedb1' stimuli of moderatecontrast:the modulatedresponses.
that relattve
preciselocationand extent of ihe receptive De Valoiset al. ( 1982)suggested
grattngsof
to
response
the
of
modulation
unimportant:simultaneous
field is relativelybe used tn
could
frequencl
spatial
optimal
field elicits
stimulationof the entirereceptrve
they
neurons;
to
classifl'
tests
classical
of
that dependboth on the linearitl'of lieu
responses
whose
relattve
neurons
those
and on the wal thoseresponses termed stmple
local responses
sumspatialll.In addition.il suitabll'r'alidated. moduiationexceeded1.0. and complexthose
l 082
Minirenew
whose valueswere lower than L0. A number
of investigatorshave classifiedcells as simple
and complex using this criterion, either by
itself (De Valois & Tootell, 1983;Skottun &
Freeman,1984;Skottun,Grosof & De Valois,
1988; Bonds, l9E9) or in conjunction with
othertests(Tolhurst& Thompson,l9El; Dean,
l98l; Schumer& Movshon, 1984;Ohzawa&
Freeman, 1986a,b; Jones & Palmer, 1987;
Szulborski& Palmer, 1990).
The use of this cnterion has recently been
questioned.Hammond et al. (19E9)claimedto
find many complexcellsthat showedmodulated
finng to drifting gratings.This claim was based
on observationsmade in the course of two
studies (Hammond, Mouat & Smith, 1985,
1988) in which mainly square-wavegratings
were used.As we have noted, it is important
to determine the relative modulation using
gratingsof the optimal spatial frequency,since
a lower frequency can elicit a modulated
responsefrom many complexcells.The modulated responsesdescribedby Hammond et al.
( 1985,1988)werelikelya resultof usingtoo low
a spatialfrequency.Square-wavegratingscontain not just the fundamental frequencybut
many higherfrequencycomponents,which also
contributeto the response.
As a result.many
grating
cellsrespondoptimallyto a square-wave
whosefundamentalfrequencyis lower than the
peak spatialfrequencyas determinedby sinewave gratings(Campbell.Cooper & EnrothCugell. 1969:Pollen& Ronner. 1982:Elfar.
De Valois & De Valois. 1990).It is therefore
gratrngsto
inappropriateto use square-wave
determinea cell'soptimal spatialfrequency.
Several investigatorshave compared the
classification
of cellsby classical
criteriaand by
the relative modulatron.and have senerallv
' A b o u t t h e m e t h o d o f c a l c u i a t r n gt h e r e i a t r v em o d u l a t r o n
"The
Dean and Tolhurst *'rote:
level oi spontaneous
a c t r v r t y c o u l d b e c o r r e c t e d f o r b y s u b t r a c t r n gr t f r o m
t h c a v e r a g el e v e l o f a c t r v r t yr n t h e p r e s e n c eo f a g r a t r n g .
" (Dean
This was done for complexcelis.
& Tolhurst.
1 9 8 3 .p . 3 1 4 ) . l t t h u s a p p c a r s t h a t D e a n a n d T o l h u r s t
m a y h a v e s u b t r a c t e dt h c s p o n t a n e o u sa c t r v r t v f r o m t h e
d . c . r e s p o n s e so f c o m p l e x c e l l s b u t n o t f r o m t h e d . c .
c o m p o n e n to f t h e s r m p l ec e l i r e s p o n s e sI.f t h r s r s t h e c a s e .
r t w o u i d h a v e h a d t h e e f f e c to f d r s p i a c r n gt h e s r m p l ec e l i s
t o w a r d l o w c r v a i u e s .r . e .c i o s e r t o t h e v a l u e so f c o m o i e x
c e l l s a n d t h u s r n c r e a s r n gt h e d e g r e eo f o v e r i a p b e t w e e n
s r m p l ea n d c o m p l e rc e l ) sn n F r g . l A . B ) a n d r e d u c r n gt h e .
b r m o d a ls h a p eo i t h e d r s t r r b u r r o n
trn Frg.1A; Also. rt
m l g h t b e n o t e d t h a t t h e r ex c i u d e df r o m t h e r r s a m p l en r n e
s a m p l e c e l l s ' * r t h r e r r i a r g e m o d u l a t r o n b e c a u s et h e r r
r e i a t r v em o d u l a t r o n s a s s o l a r s e a s t o b e o f f s c a l e .
found the measuresto agree in distinguishing
simplefrom complexcells.Dean and Tolhurst
(1983)did a substandalevaluationof the two
approaches,and found generalagreementbetweenrelativemodulationand classicalcriteria,
with a high correlationbetweenresponsemodulation and a separatemeasureof the discrereness
of ON and OFF regions (r :0.87, y'{= 65.
P < 0.001).However, they also noted a sufficient number of exceptionsto state that supplementarytestswererequiredfor unambiguous
classification.
Dean and Tolhurst classified391 cells as
simpleor complexon the basisof a qualitative
receptivefield map. For the same cells the.v
also measuredthe relative modulation. The
distributionof thesevaluesis shownin Fig. lA.
Of 231 cells classifiedas simple.27oh had a
relativemodulationof lessthan 1.0. By conrast, in the caseof 160 complexcellsall but
5 (97%) had relative modulation of less than
1.0.r
For a subpopulationof 67 cells,they mapped
the receptivefield quantitatively;Fig. I B shows
the distribution of relative modulation for
thesecells.In the caseof thesequantitatively
studiedcells,thereis a much higher agreement
betweenthe relativemodulationand classical
RF mapping. Out of these 67 cells only 3
simplecellsand I complexcell (lessthan 6% of
the total population)were classifieddifferently
by use of relative modulation as opposed to
and the spatial
a combinationof discreteness
summationratio. Furtherrnore.all four of the
cellsthat weredifferentlyclassifiedhad relative
modulationscloseto 1.0. In this distribution.
all cells with relativemodulationswell below
1.0are complexaccordingto their criteria.and
cellswith relativemodulationswell above L0
are srmple.
In addition to these previouslypublished
results.we presentsomenew data. Figure lC
showsthe distributionof the relativemodulation found in 255 cellsfrom the cat's striate
cortexrecordedaccordingto the procedures
of
Schumerand Movshon(1984).The cellswere
as simpleand complex
independently
classified
basedon theoverlapof ON and OFF zonesand
on qualitativetestsof spatialsummation.No
cell with a relativemodulationof lessthan 1.0
wasindependently
classified
as simple,and only
fivecellswith relativemodulationslargerthan I
were classifiedas complexbasedon receptive
fieldmapping.yieldinga contradiction
in about
2o/oof the cases.
1083
Minirevtew
ccllsthat cannotbe unambiguouslyclassifiedby
any of the conventionalcnteria.
IS TI{EREA BMODAL DFTruBUTION
OF CELIS WTII{ REGARDTO
MODULATIOM
N,ELATIVE
We can now addressthe questionof whether
there are in fact two distinct classesof cells,
correspondingto simple and complex,classifiable on the basis of relative modulation. The
first indication that there might be a bimodal
distribution of neuronswith regardto response
modulation came from Schiller et al. (1976),
who, working in the monkey, used a measure
10
o
I
o
5
o
z
^
(A)
N
o.5
1.0
1.5
?.o
>2.?
(B)
loo
I
Retotive modu[otion
Fig. I . The distributionof relativemodulatronfor ccllsfrom
the cat's stnate cortex that werc rndepcndentlyclassified
as srmpleor complexusingclassicalcriteria.A and B are
combinationsof thc data rn panelsB. C and D of Dcan and
Tolhurst's(1983)Fig. 5 (A) The distnbutionof 391 cclls
whose receptivefields were mappcd qualitatively.Based
on thesemaps cells were classifiedas srmpleor complex
accordrngto spatial summationratio and ON and OFF
regronoverlap.ln this wav 231ccllswcreclassified
assimple
(hatchedarcastand 160as complexccllslunhatchcdareas).
(B) The distnbutronof 67 cellswhosefieldswere mappcd
wrth a quantrtatrve
technrque.
Out of 67 cells.33 were
classifiedas srmple(hatchedareas)and 34 as complexceiis
(C) Thedistributionof255ccllsfrom the
areas).
{unhatched
(methodof
stnalecortexof thecat.prevrously
unpublished
Schumer& Movshon.1984).The hatchedareasrepresenr
cellsciassrfied
as srmpleaccordrngto thc separarronof the
ON and OFF resions.
I
eol
o
60
l
c
z
I
20
I
I
?oi
I
^ i
a
We
relative
conclude
that
modulation
virtually
values
cells wrth
above L0 are
all
classified
as simpleby conventionaltests,while
wrth
cells
modulationvaluesbelow 1.0 are
classified
as complex.The few discrepantcases
involvecellswith relatrve
modularions
near1.0.
and someof thesemay represent
cellsthat could
not be classifieddecisivellwith any rest.The
introductionb1 some rnvestigarors
of rnrer(Henr1'.
mediate
classes
1977:Orban.1984).
and
our o\\'n experience.
suggesls
that thereexrst
n
I
^
t
. n
.
.
L]
2.O r2.?
Rclotive rnodu(otion
F r g . 2 . D r s t r r b u t r o no f c c l l s w r t h r c g a r d t o m o d u l a t i o n o f
t h c r e s p o n s et o d n f t i n g g r a t t n g s . ( A ) D r s t r i b u t r o n o f c c l l s
from the cat's striate accordrng to thc cltcrron of relatrve
m o d u l a t r o n a s u s c d b y D e a n a n d T o l h u r s t ( 1 9 8 3 ){ s e er e x t ; ,
redrawn from therr Fig. 5A. (As to the number of cellsin
t h r s d r s t n b u t r o n .D e a n a n d T o l h u r s t w r o t e t h a t r t c o n t a t n e d
563 ceiis.Bv ourcount there are 577 cclls.)(B) The drstnb u t r o n o f r e l a t r v em o d u l a t r o n f o u n d i n l 0 6 l c e l l s r n c a t
s t n a t e c o r t e x r e c o r d c d r n f i v e l a b o r a t o r r e s .e x c l u d r n g t h e
data of Dean and Tolhurst shown above. (C) The drstnbutron of relative modulatron rn 513 cells of monkey VI.
rccorded rn two laboratorres.
t084
Minireview
of modulation that is more accuratelycharacterizedas a measureof responsevariance
(and is therefore different from relative
modulationas we havedefinedit) (seeSchiller
et al., 1976,pp. 1335and l34l). Theseauthors
found a weakly bimodal disrribution (seetheir
Figs 8 and 16). On the other hand. using the
measureof relativemodulationdescribedabove
De Valois et al. (1982,Fig. 3), Skottun and
Freeman(1984,Fig. 2A), and Skottun et al'
(1988.Fig. l) all found pronouncedlybimodal
distributions.
Dean and Tolhurst(1983)examinedthe distribution of cells with regard Io the relative
modulation of response.and their data are
reproducedin Fig. 24. About this distribution
Dean and Tolhurst wrote:
"The degreeof modulationin the response
was continuously distributed between
low values typical of compiex cells and
high values typical of simple cells; the
distributionwas not bimodal" (Dean &
Tolhurst,1983.p. 305).
thing, the cat data are more clearl,vbimodal
than thosefrom the monkeY.
we haveexaminedthe distnTo summarize.
to the relativemodulationof
with
regard
bution
severalindependentsamplesfrom the striate
cortexof both thecat and themonkey.Notwithstandingthe statementsby Dean and Tolhurst
(1983),all samplesshow bimodaldistributions
both individually and in combination.While a
srnallnumber of cellshave ratios in the areaof
1.0,it is unclearwhetherthis is a consequence
of the method or whether thesecells are not
readilyclassifiablewith any approach'We conclude, therefore,that on the whole the relative
to drifting sinusoidal
modulationof the response
striate cortex of
thc
gratingsfrom neuronsin
two distinct
falls
into
both cats and monkeys
distributions.and that thesecorrespondto the
classicalcategoriesof simple and complex.
CONCLUSIONS
The data presentedabove indicate that in
striatecortex two differenttypesof cellscan be
Our own view of these data is that the distinguishedon the basisof the relativemodudistributionat leastshowsa bimodaltendency, lation of their responsesto drifting sinusoidal
sincethe densitydistnbutionof cellsis higher gratings.Although relative modulation is a
measureof linearity and has historically been
below0.5 and near 1.5than around 1.0.
with linearsystemstheory,adoptton
To examinethis issuewith a largecellsample associated
and to observethe consistencyof the result of thiscriteriondoesnot involvecommttmentto
acrossa wide varietyof measuringconditions, any particular theory of cortical function or
we havepooleddistributionsfrom the cat from neural circuitry. The criterion might therefore
with duecaution.to otherspecies
five laboratoriesand from the monkey from be applicable,
two laboratories.Figure 28 is a compendium or other brain areas.
of both previouslypublishedand unpubiished Using a relativemodulationof 1.0.cellsare
that correspondcloselyto
of the modulationindexin l06l dividedinto classes
measurements
of simpleand complexas definedby
cells from the cat striatecortex.Includedare the classes
in the Hubel and Wiesel(1962).There are several
cellsrecordedunderconditionsdescribed
followingpapers:Skottunand Freeman(1984). reasons for believing that classifyingcells
157 cells: Skottun et al. (1988).201 cells: according to this cntenon is more useful
( I ) thrs srngle
: o n d s( 1 9 8 9 ) . than any'previousclassification:
H a m i l t o ne t a l . ( 1 9 8 9 )3. 0 1c e l l sB
(1984).
of corttcal
great
places
ma;ontl'
the
criterion
143cells:and Schumerand Movshon
(l)
the
degreeof
ciasses:
distinct
155 cells(alsoshownin Fig. lC). In Fig. 2C cells into
quantifiable:
easily
and
is shown the drstributionof a total of 513 modulationis objective
cells from Vl of the monkel' with regard to (3) the relativemodulationts determinedwith
field
modulationindex.Includedare 343 cellsfrom stimuliwhichstimuiatethe wholereceptive
De Valoiset al. (1982).and 170cellsrecorded and typically generatesubstantialresponses:
wrth
under the conditionsdescribedbl Hamilton (4) the relativemodulationis determined
mo!'rngstimuli.and is thereforenot limltedto
et al.(1989).
patThe distributionsfrom both cat and monkel cellsthat can be activatedw'rthstationar)'
modulatton
are clearll'bimodal.Hammondet al. (1989) terns;(5) the degreeof response
quickly-often driftinga few
suggested
that relativemodulationmight be can be determined
acrossthe receptrvefield is sufficientto
usedto classifl'cellsin the monkeybut not in c-v-cles
fails determinethe cell class.once the optimal frethecat:the similarityof thesedistributrons
are known:(6) because
If anv- quencyand orientation
to lendan)'supportto thiscontention.
Minireview
r085
conex to rrsual texturc. Experincntal Brarn Research.30.
275-296.
Hammond.P.. Mouat. G. S. V. & Smrth.A. T (19E5)
Motion after<ffecs rn c:tt stnate cortex chcttcd b1
moving graunBF. Expcrtmcntal Brain Research, fi,
4l l-416.
Hammond,P.. Mouat. G. S. v. & Smith. A. T (lgEt).
Neural correlatcs of motion after'cffects ln cill stnate
conical neurones:Monocular adaptation. Expertmental
Brau Research,72, L-20.
Acknowledgemenls-Thc rescarch reported in this papcr
Hammond, P., Pomfrett. C. J. D. & Ahmed. B. (19t9).
(EY
02017'EY 03778)
was supponedby grantsfrom NIH
Neurd mouon after-cffccu in the cat's stnatc conex:
and NSF (BNS 82-169E0).DHG was supponcd by a
Orientation sclccrivity. Vision Research.?9' l 67l-l 6E3.
NEI postdoctoralfellowship.DGA wrshcsto thank the
Hcggelund,P. & Moors, J. (1983).Oncntatton sclccrivity
University of Tcxas. Martin Gizz and Robert Schumcr
and thc spatial distribution of enhancernenl and
collectedsomeof the data in Fig. 2C.
suppressionin rcceptivefields of cat striate cortex cells.
Experimenta!Brain Research,52. 235-24'1.
Henry, G. H. (1977).Reccptiveficld classcsof cclls in the
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