Brain in Perception - From Kohler's Fields to Gabor's Quanta of Information T-188

8/13/2019 Brain in Perception - From Kohler's Fields to Gabor's Quanta of Information T-188

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R ~ I B R AM H (1995) Brain in Perception: From Kohler's Fields to Gabor's Quanta ofInformation, Proceeding of the 39th Congress of German Society for Psychology, pp. 53-69.4

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BRAIN K PERCEPTION: FROM KOHLER S FIELDS TO GABOR S QUANTA OFINFORMATION

Karl H PribramRadJord Univcrsiry Virginia USA

lust as now, at the time Wolfgang Kohler developed his theory regarding brain function inthe received 'view of the operation of the nervous system dealt mainly with the

of nerve impulses and their transmission across connections between nerves. B yKijhler based his Gestalt mechanism on the existence of neuroelectrical fields. I believe

h e time is ripe for a reconsideration of field theory as it applies to brain function. especiallyprocessing in the cerebral cortex. The da& to be presented will support a view of neuroelectricfields considerably different from that presented by Kohl er, so mewha t more like that held by Karl~ ~ ~ h l e ~ . ' b u tased on the issues that deeply concerned them both.

1was fortunate to be able to partake in Kohler's explorations which attempted to demonstrateexistence of generalized direct current (DC) electrical fields in the brain. The experimental3tuck proved successful (Kohler, 1958). Such fields are restricted to the approp riate corticalregion when an organism is s timulated through one or another sensory portal (Gumnit. 1961).Further studies in my laboratory sho wed 'the se fields to be correl ated with the speed with whichlcarning occurs (Stamm Knight. 1963; Stamm Pribram, 1961; Stamm Warren , 1961). andthe imposition of direct currents onto h e cortex can retard or speed learning depending on thepolariry of the imposed potential (Stamm. 1961). But Kohler was seriously disappointed when Iexpressed my uneasiness about the connection between the these fields and perception. Later.when 1 had finished exper iment s (reviewed by Pribr am. 197 1, pp. 110-114) in which I hadimplanted aluminum hydroxide cream over the primary visual cortical surface of monkeys. wewere once m ore in agreement. T he experiments showed that discrimination of fine visual patternsrcmains intact despite marked disruption of recorded brain electrical activity. Kohler had neveraccepted experiments performed by Lashley (Lashley, Ch ow , and skmm es. 1951) in which goldroil was used to short circuit neuroelectric fields as evidence against his theory, nor did he yieldto Sperry's crosshatches (Sperry, Miner, and Meyers, 1955) into which insulating mica strips had

placed.'But when faced with the evidence from the aluminum hydroxide cream implantationshc exclaimed: that ruins not onl y y D C ield but every other current neurological theory ofperception.

me briefly indicate the evidence which has accrued since that conversation to dispel forme this dismal view of a field theoretical approach to the neurolo gy of percepti on. Ne rve impulsegeneration and transmission in neuronal circuits is but one of the important electrical cha rac-te r is t icsof neural tissue. Ano ther characteristic is the production of patterns of pre- and post-s yn3~t i c o l a r i z a t ionsn axonal and dendritic arborizations. Though these polarizations are akin'o Kohler's fields. they differ importantly in that they are nor diffuse but sharply localized at thejun tions between neurons or in dendrites where they may even be miniature spikes. However.such mini more often than not, immediately attenuate completely, precluding their ability' propag ate. These Pre- and post-synaptic patterns of polarization are produced everyw here inr a in when nerve impulses arrive at synapses as a result of the fact that the impulses

hccome a t tenuateddue to decreased fiber size resulting from the branching of axons. BranchingI s o assures lh t the consequent presynaplic polarizarions are never solitary but constitute an

pat ter n. When polarizations are then ind uced postsynaptically in dendritic arboriza tionsa re insuficiently large to immediately influence the pattern of nerve impulse


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generation which occurs at (or near) the axon hillock. Thus. the patterns of post-synaptic polari;[ions develop a design which resembles a wave front and ca n be described a s a population vect,This design of polarizations is not some esoteric field. an epiphenomenal mirag e sup erimpos edknown neural function it results from the arrivals of nerve impulses "awaiting" axonic departu

Arrival and dep arture patterns thus conceived become a third alternative to the neural circversus "floating" field argument about the neurological process coordinate with awareness. Tneed for such. an alter native was recognized by Lashley who w as profoundly troubled by Iproblem:Herc is thc dilcmma. Nerve impulses arc transmitted ovcr dcfinitc, rcstrictcd paths in thc sensory and motor ncrvcs ; ...in the central ncrvous system from ccll to ccll through dcfinire intcrccllular conneclions. Yct all behavior seems todaerrninc d by masses of cxc iution. by the form or relatiom or proponions of cxc iution wilhin general fields of activwi th ou ~ egard to particula r ncrvc cclls . It is Lhc psttcrn and no1 thc clcment Ihst cou nu . What s o n of ncrvous orgmiz;rrmight be capable of rcsponding lo a patlcrn of cxciulion without limitcd, spccializcd paths of conduction? f h c prob.is almost univcrssl in rhc sctivilic s of [he nenf ous system and some hypothesis is nccdcd 10 direct funhcr rcscar[Larhlcy. 1942. p. 3 61 .

Subsequently. he suggested that an interference pattern model would acc ount for the phen om e~When Lashley and I discussed these issues wi~h ohler. none of us had, as yet. conceived of Iobvious: that classical pre- and post-synaptic and dendritic polarizations could serve our purpoThis lefr Lashley's patterns both too much tied to the neuronal circuitry he found unsatisfactorand at the same time too disembodied as were Kohler 's geometric fields. Nonetheless, bnKohler 's and Las hley's insights have proved to be most incisive as will try to sh ow here.

Issuesrojection

Let me hegin at the heginning: The study of behavior has provided indispensable tools for Istudy of psychological processes. However. if the concern of psychologists is to include awalness. the conscious mentali ty that we experience, inferences must be made from observbehavio r. Kijhler's interest. as was that of all of Gestalt psychologists. was in the operationsmind rather than the organization of behavjor whereas classical behaviorists focussed on behavit(for a clear statement of this issue see Pribram, 1962 and the Epilogue in Miller. Galanter 31Pribram. 1960 .

But the relation hetween mind and behavior concerns not only psychologists. Whether he iphilosopher. humanist. politician. psychiatrist. neurologist or neurophysiologist. the minibehavior relation becomes an issue for him sooner or later. Basically, we all must deal with esotller by constructing a sharable world out of the variety of private experiences. Constructitdemands that we behave verbally and nonverbally. Behavior organizes this sharable world. bin order to have this organization reflect inner experience. that experience must become projectinto the sharable world.

Georg \*on Bike sy performed a series of crit ical experiments that s howed how such projectitoccurs .Using touch. which is not ordinarily interpreted as distant. he creates conditions under whirthis "disranr" interpretation is made:


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~ ~ n ~ c u dight from an cxtcrnal object Products an imagc on the retina. Thc scnsations cxist only within our body. yet welocaji21: h e imagc ouuidc the Cyc. cvcn when we use only a single cyc and look at a n object far away. This ' lool iwti onbeyond our pcrccptual sYs[cm is of great importa nc~ or suneival bc au sc it cmblcs us to a pp ru ia v impending dangcr oro b j a f g r u t necessity. This cxtcrnaliwtion is achicvcd without thc siightcst recognition of h c optic imagc iuclf or therljmulaion on thc r ~ l i ~ .

same conditions hold for hearing. The scnsai ons arc produced by the action of stimuli on h e basilar mcmbranc ofhc co ch ~ u . h c cochlca i s deeply imbcddcd in bont, but uec do not localize auditory scnsations lhcrc but usually rcfcrto a source somcu Shcrc n the cnvironmcnt. H owcvcr, as uf c havc seen. this cxtcrnal rcfcrencc docs not scc m lo bc

m c for hur i ng with carphones.This cxurml projcction has probably been Icarncd early in life: certainly this is true for huring and vision. But we havcnot aqu irc d this kind of cxtcrnal projection for skin scnsaions . and s o we havc an opponunity to discover how stimuluspmjcction in spacc is Icarncd.For hi s s tudy a pair of vibrarors stimulate tufa fingcnips Each vibrmor is aauatcd by thc samc s t r i a of clicks. andheir applied currcnis arc varicd lo givc equal magnitudes of scnsaiion on each fingmip whcn the stimuli arc prcsentcdscparacly. Al so thc sctup includes a means of va ci ng the dclay timc baw ct n thc clicks of the two st ri a . 11 click isdclaycd for onc finger morc than or milliseconds, a pcrson feels scpa ralt scnsations in thc two fingcnips. as alrwdydacr ibcd . If. howcv cr. the timc bc~ wc cn licks is rcduccd to about 1 mill isecond h e W O click scrics will fusc into onc.md h e vibratory scnsation will bc localized in thc fingcr that rcccivcs u c h click he carlicr. If the time dclay is furdrcrdccrcascd thc scns a~i on or a traincd obscrvcr will movc into thc rcgion be tur cn t wo fingcrs. m d if then thc timc rclationbcrwccn the two click scrics is rcvcrscd thc click will movc to the opposite sidc

The intcrating point in this cxpcrimcnt is that for the condition in which thcrc is no timc dclay thc vibrations arclwlizal bctuecen thc two fingcrs whcrc no skin is prescnt. If the fingcrs arc sprcad apan the samc cfftct is found. andwhen the amount of timc dclay is varied thc sensation will movc correspondingly in thc frce space bcrwccn thc fingcrs.

Evcn morc dramatic than this cxpcrimcnt is thc one in which tw o vibraton arc placed on lhc thighs, onc abovc tac hkncc. Hcrc thc vibrators can stimulate large skin surfaces and produce strongvibra tory scnsations. By :raining an obscrvcrfint lo notc thc localiwtion of the vibration whcn the knccs arc together he w n bc madc to pcrccivc a scnsation thatmoves continuously from one knct to thc othcr. If thc obscrvcr now spre ads thc knces ap an hc will againcxpcricncc at firsta jumping of the scnsation from onc knce lo the othcr. In timc. howcvcr. thc obscrvcr will becom c convinccd that thcvibratory scnsation o n be localizcd in the frcc s pacc bctu8cen the k n m . and hc will be able to cxpcricncc a displaccmcntof h c scnsation in this frc t spacc when an approprislc timc dclay b cturccnonc stimulus and thc othcr is introduced. Thiscxpcricncc is a vcry peculiar oneThis maltcr of thc cxtcrnal projcction of vibra tory scnsations s cem s to be strange and hard to believe. yct it is well knownin many ficlds. Evcry well-traincd machinist projccu his scnsaio ns of prcssurc to thc tip of screwdri ver, and it is thisprojection that cmbles him 10 work rapidly and correctly. For most pm plc this projection is so commonthat thcy arcunaware of b cxistcncc. Thc sam c typc of projection occurs in cutting with a knifc. and our ad justmenu of thc bladcd c se of sc nsations projccrcd to u cdgc.

found thc localiwtion of sc nsai ons in free spacc to bc a vcry imponan t fw turc of behavior. T o study thc matter furthcrI wo rt two hcaring aids that wcrc propcrly damped so that thc sounds could bc pickcd up by m a n s of two microphoneson thc chat and thcn transmitted to thc tw o cars changc in prcssurc amplitudc. Stcrcophonic hcaring was wella ~ l i s h c d . ut a pcrc cp~i on f thc disunc c of sound sourccs was lost. 1 shall not forgct my frustration in trying to cross

U m during rush hour traffic while wearing this transmission system. Almost all thc cars sccmcd to jump suddcnlyinlo consciousness. and I was unable to put them in ordcr according to thcir immediacy. should probably have rcquircdWaks of cxpcrirncc lo bccomc adjusted to this ncw rypc of projtction. A small changc in thc amplification of one sidcWas cnough to cancel thc wholc lcarncd adjustmcnt. (Btktsy. 1967. pp. 220-261

Dual ProcessBCkesy further observes that both his experience and behavior are organized by processesoccurring in the sensory systems his monograph is entit led "Sensory Inhibition". To grneralizet is observation. a claim can be made that both awareness and behavior are organized by neuralProcesses. However. only some of these processes lead to awareness: there are others thatorganize behavior of which we a re not aware. In fact, instrumental (often automatized) be haviornd awarene ss are ro a large extent opposed the more efficient a performa nce. the less aware w e


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become. Sherrington (19061191 1) noted this antagonism, stating that between reflex action andmind there seems to beactual opposition. Thus, for the neuroscientist, the question becomes: What kinds of neuralactiviry allow awareness to be inversely related to automatized action?

Patterns of synaptodendritic polarizations and nerve impulses are two kinds of processes thatfunctio n reciprocally. simple hypothesis states that the more or less persistent designs ofdendritic field polarization paaerns are coordinate with awareness (Pribram. 1971, Chapter 6).Thi s view carries the corollary that circuit s of nerve impulses per se and the behavio r they gene-rate are unavailable to immediate awa rene ss. Eve n the production of speech is unconsc ious atthe moment the words are spoken.

Nerve impulses arriving at synaptic junctions generate patterns of dendritic polarizationswhich compose a structured (that is, vector) field. The design of this structured field interacuwith that already present by virtue of the spontaneous activity of the nervous system and iuprevious 'experience. The se interactions thus act as cross-correlation devices to produce newfigures from which the patterns of nerve impulses are initiated. The rapidity of changes inawareness would reflect the duration of the correlation process.

What evidence suggests that the junctional electrical activities of the central nervous systemare involved in awareness? Joseph Kamiya (1968) and others (Ga lbra i~h. t al. , 1970; Engstrom,Lond on, and Hart. 1971) have shown . using instrumental-conditioning techniques. that people canbe taught to discriminate whether or not their brains are producing certain wave forms whichrepeat approximately 10 times per second . the so-called alpha rhythms. even thoug h they havedifficulty in labeling the difference in the states of awareness they perceive. Subjects who havebeen able to label the alpha rhythm state claim that i t is one of pleasantly relaxed awareness.Mo re experiments of this kind.are now being carried out in my laboratory.

Equally irnpomnt are some of Ben Libet's experiments (1966: 1994) that have explored awell-known phenomenon. Since the demonstrations in the 1880s by Guswv F ri~ sch nd EduardHitzig (1969) that electrical stimulation of certain parrs of man's brain results in movement,neurosurgeons have explored irs entire surface to determine what reactions such stimulationsproduce. For instance, Ottfried Foerster (1936) mapped regions in the post-central gyrus whichgive rise to awareness of one or another part of the body. Thus sensations of tingling or ofpositioning can be produced in the absence of any observable changes in the body part experien-ced by the patient. Libet has shown that the awareness produced by stimulation is not immediate:a minimum of a half second and maximum of five seconds elapses before the patient experiencesanything. t appears that the electrical stimulation must set up some state in the brain tissue. andonly when that sure has been attained does [he parienr become aware.

Th e evidenc e for electr ical f ieldsThe ieldISpike ual

In a comprehensive and critical examination of the evidence. D.S. Faber and H . Korn concludedin an article in Physiological Reviews (1989):-[ha[ rhc major conditions that favor the gcncrati on of clccrrical field cfr ecu . (ar c] an incrcascd cxtraccllula r resistivity[andl a rcgular pal tcrn of ncuronal oricnlalion such as b a t found in lamlnar structures. [Thus]. wc u p r c d i c ~ h fwhcncvcr the (cx~racellularly ccordcd potcnuals] ar c more than a fcw mill ivolu in ampli tude b e y should rcflc uc l c c t r ~ ca l i cl d c ff c c u . O b v i ou s c ~ n d ~ d a t c sould includc conical cvokcd potentials, which arc associated with potential


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Pribram,jcnu in Ihe n n gc o f 4 to 30 rnvimm . In those conditions. as more cxciratory inpuu 10 a syst em are ~ c ~ i v c .hcgmwing cxtracellular fields and synaptic potcnlials ugould su mm tc to recruit more posuynaptic ncurons. (pp. 839-8401.

~onvcrscly, undling of conical cell dendrites might [also] facilitate electrical intcraaions. In [such] regions largeE wp r of ncurons do not tend to fire synchronously. wilh thc possible e xccpiio n of ccna in slccp stag cs or in seizurc condi-Thus Ihc background conditions may not be favorable for producing large widespread field cff cc u. Rather. it may

such inter ctions . . . arc highly localized and will only be rcvcaled in conditions whcrc small clusrcrs of cellsugtiv c synchronously. (p. 848).These localizing conditions obuin when extracellular recordings show bursts of spikes (actionpolentials) created by adjacent clusters of neuro ns. Und er these conditions we c an -separately'record the bursts of spikes (as well as individual action potentials) with a high pass filter ands i m u l ~ & ~ ~ s l yecord,the electrical field effects through a low pass filter. This procedure allowsus lo compare the time course of the ~e co rdi ng s rovided we h ave adjusted for the relative delayproduced by the low pass filter. In our recording apparatus this delay amounts to 8-10 msec.Figures 1 and 2 show that the onsel of the field effect precedes that of the initiation of spikes.Spike generation becomes most active just prior to the occurrence of the maximum amplitude ofthe depolarizing field and c eases as rhe field deca ys (Figure 3). O ut of 2,369 record ings 1.573 or61% showed his relalionship; during sensory stimulation the rario went to 7 5 % . The remainingcases were made up of 796 instances where the field effect was recorded without any simultane-ous spike activin; and where spikes were recorded independently of field potentials. 1.573 times

To summarize the import of these finding s: just a s depolarization of axon m emb ran es is anecessary precursor of the generation of action potentials, so also is the local build up of syn-aptodendriric f ie ld potcntials a precursor to the recruitment of action potentials in post synapticneurons.

Receptive ields in ensov ProcessingFor a half century, neurophysiologists have used extra cellular rec ording s in extensive explorationso f h e functions of single neurons in sensory processing. Th e wealth of d a ~ a btained in theseexplorations has focussed on the properties the features of a sensory s~ im ul us hat wouldincrease (or decrease) the number of action potentials (spikes) that was recorded in the presenceof the inciting stimulus prope rty.

However, axonal spike trains recorded from single electrodes reflect three separable proces-seS: 1) those due to the sensory inpur per se , as is usual in feature analytic studies: 2) tho se thatdirectly modulate the output of h e axon hillock a s determin ed by intracellular recordin g (Pri-bram, et al, 1981; Berge r and Pribram. 1992) ; and 3 those that ma p the intrinsic respo nse o f thesYnaplodendritic field; and as shown when ex~ rac ell ula r ecord ings are used to demons trate the

configuration of the dendrit ic field of the neuron as i t responds to sensory Slim~lati~n.This method of mapping the Functional geometry of dendritic receptive fields was initiated byKuf fler (1953) and developed by Hubel and Wiesel (1959 ; 1 968) for the visual syste m. Kuffler

that he could map h e geometry o f the dend ritic field of a retinal ganglio n cell byfrom its axon in the optic nerve. Kuffler s is a simple technique for making receptive

fie'd maps, which is now standard in neurophysiology. By activating a receptor or a Set ofreceplors with a variety of stimulus dimensions and using the density of unit responses recordedfrom axons, a map of the geometric organization of the synaptodentritic receptive field of thataxon can be obtained. (See e g revlews by Bekesy, 1967 and Conn or and Johnson . 1992 for


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igure 1 An example of the relationship between spikes and bursts of spikes to coincident s lowpotentials

Spikes, envelope of spikes, and slow potential

somesthesis: and by Enroth-Kugel and Robson. 1966: and Rodiek and Stone. 1965 for vision).Exper imen ts by Barlow 1986) and by Gilbe n and Wiesel 1990) have shown that sensorystimulation beyond the reach of a particular neuron receptive field can. under ce r~ ai n onditions.change that neuron s axonal response. Synaptodendritic polarizations are thus subject to fieldeffects produced in a more exten ded field of potentials occurring in neighboring synaptodendriticfields.

The Kuffler technique maps these relations among local field potentials occurring in extendedoverlapping dendritic arbo rs. The axon s) fro m which the records are being made. sam ple alimited patch o f this extended domain. As s how n in the previous section, we can readily demo n-strate the correlation between burst activiry recorded from an axon and the local field potentialsoccurring in the synaptodendritic receptive field of that axon.

In the following study. we aimed to explore the relations among local field potentials bymapping recep tive field organization using the Kuffler technique. The rat soma tosens ory systemwas chosen for convenience and because the relation between whisker s timulation and central

time ms)


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Spikes, envelope of spikes, and slow potential6r I IEnvelope of spikes I

-41200 205 210 215 220 225 230 235 240 245 250time ms)igure 2. Enlargement of one example of the relationship shown in Figure 1.

neural pathways has been extensively studied (see review by Gustafson and Felbain-Keramidas,1977 . Whiskers were stimulated by a se t of rout ing cylinders, each grooved with equally spacedsteps, the step width and adjacent grooves subtending equal angles. Three cylinders were usedwith their steps measuring 3 deg. , 15 deg.. and 7.5 deg. , respectively. The cylinders wererotated at 8 different speeds , varyin g from 22.5 deg.lsec. to 360 deg.lsec. (The rotating cylinderswere meant to mimic the drifting of gratings across the retinal receptors in vision.)

In most of our experiments an entire array of whiskers was subjected to contact with therotating cylinders. This was d one in ord er to bring the results of these somatosensory experim entsinto register with those performed in the visual system where an entire array of receptors isstimulated by the drifting grating.

In our experiments, sensory input is generated by the frequency with w hich the whisk ers arestimulated. This frequency is a function of the stimulus as modulated by the spacings of thegrooves on the cylinders and the speed with which the cylinders are rotated. The number ofbursts or spikes generate d at eac h rec ord ing location is thus deter mine d by the spatial and


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average of ursts spikes) at each latency prior to and atler peak of slow potential50 I

O 40 30 20 10 0 10 20 30 40 50Latency msec)igure 3 Thi s t igure demonstrates the aver age thirry data sets which include 1.715 burstslspikes

opuined under a variety of st imulations. Note that the peak of the slow potential is marked zero.

temporal p aram eters of the sensory input as they influence the frequency o f st imulation Figures4a-f).

The activity abov e or below baseline which resulted from whisk er st inwlation is plotted a s amanifold describing to ul numb er of bursts or spikes) per 100 secs. of st imulation. Spatialfrequencies are scaled in terms of grooves per revolution. while temporal frequencies are scaledin terms of revolutions per second. Th e density or pure frequen cy) of st imulation of a whiskeror set of whiskers) is a function of both the spacings of the cylinder g roov es and the speed with

which the cylinder rotates. I t is this density of st imulation per se which generates the map ormanifold, the geometry of the receptive field. As this map is constructed in terms of purefrequency, i t reflects processing in the spectral domain.

imulation

Acco rding to signal process ing theo ry, the general sha pe of a receptive field manifold is Lhe samefor each combination of spatial and temporal frequencies. However, a central peak, reflecting thedensity of response for that spectral location in the manifold. will be shifted within the fieldaccording to the part icular spatial and temporal st imulation values.


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Figures 4a f. Examples of receptive field manifolds and heir associated contour maps derived by an inter-polation (spline) procedure from recorded whisker stimularion. hc contour map was abstracted from thmanifold by plotting con tours in tcrms of equal numbers of bursts per recording interval 100 sets. . Eachfigurn shows baseline activiry (no whisker stimulation) at a given electrode location as a gr-plane located interms of number of bursts per 100 sccs.

In o rde r to d isce rn whe th e r . indeed , o ur da ta fi t the requ irements o f s igna l p rocess ing theory ,a s imula t ion o f the p roce dur e wa s execu te d . Th e f i rs t s tage o f the s imula t ion was to cons truc t aPu tat ive recep t ive f ie ld manif o ld . A ny ex ten t o f manifo ld genera ted by t he f requ ency char ac -te r is t ic ~ f the s t imulus is best desc r ibed fo rmal ly by a t runca ted spec tra l func t ion such a s ac on s tr ai ne d F o ur i er r e p r es e n w t io n . ~ a b o r1946 p.431) defined such a func t ion as fo l lows: Le tUs I Iow ten ta tive ly adop t b e v iew tha t both t ime and frequency a re leg i t ima te re fe rences fo rdescribing a signal and illustrate this by taking them as orthogo nal coor din ates . Its freq uenc yS exactly defined [only] while its epoch is entirely undefined. A su d d e n su rg e o r d e lt a fu n c t io n


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(also called a unit impulse function ) has a sharply defined epoch. but its energy is distributedover the whole frequency spec trum. Daugman (1990), ~ a c ~ e n n a n1993) and Pribram andCarlton (1986). have extended this il lustration to include, in addition to the time parameter, twospatial dimensions.

W e chose a recrangular wind ow in the spatiotemporal domain to constra in the two dimensio-nal s inusoidal s ignal. T he reasons fo r this choice are: First, that the resulting sp ectrum generatesa num ber of s ide lobes surrounding a central peak. In the visual system a number of s ide lobeshas been observed at the lateral geniculate nucleus, (Hammond, 1972: Pribram, personal observa-t ion, 1974) and a t the conex (Pollen and Feldon 1979; Pollen and Pribram, personal observation1972). The second reason for the choice of a rectangular window is that it reflects the spatial andtemporal constraints on the extent of the distribution of the signal: the spatial constraint reflectsthe limits on spacing s of the grooves on ou r cylinders: i ts temporal constrai nt, the limits on theirrotation speed.

In addition, the rectangular window allows for maximum resolution o f frequencies (see Zeeviand Daugm an 1981: and Oppenheim and Shafer 1989 esp. Chapter 11. for review). The use ofsuch a window genera tes a sinc function in the spectral domain.

figure 5 12 and b 53 presen u a stimulated manifold (mcxican hat function) representing a specrn l distributioninduced y single external stimulus (spatial and remponl frequen y combination) across the conicalsynaprodendritic field. 5b presenu the second srage of the stimulation as a probe consisting of a band-passfilter formed by a Gaussian (exponential) function.

In our s imulations (Figure 5a) each plot is a manifold of a spectral density function of arectangular win dowed con tinuou s two-dimensional s inusoidal s ignal. Wh en. in other experimenrs.only a s ingle frequency of s timulation is used. a spatiotemporal connection matrix can be con-structed from recordings made with multiple electrode arrays to represent the da ta (Barcala.Nicolelis and Chapin 1993). Our version of such a matrix represents the variety of spatially andtemporally constrained spectral data gathered in our experiments as a s inc function. centered atthe frequency of each stimulation pair. i .e .


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where is a scalin g Constant. w , and w2 are spatial and temporal frequen cies o f the spectru m. anduO nd U are the Spatial and temporal frequencies of the stimulation. The function sinc(w) isdefined as:

The second stage of the simulation u ses as a probe , a Gaussian (exponential) function (Figure 5b).Whell this probe represents a single neuron it is limited by the spatial extent of the local fieldpot,=ntials fluctuating am ong that neuro n s dendrites. W hen a bu rst manifold is modelled. thespatial constraint is 'assu med to po rtray a greater reach and is limited by the barrel (columnar)arrangement of the somatosensory cortex. Sampling is performed by the generative activity of theaxon hillock, which, due to the upper and lower temporal limits of spike generation, functions as

bandpass filter of the response of the sensory system. This filter is multiplied with the sincfunction to yield a display of the manifold.

Figures 6a-f depict manifolds and contours derived from these simulations. Note the close fit1 the experimentally derived manifolds and contours shown in Figures 6a-f. A total of 48 mani-folds were experimentally g enera ted. Of those, three were essentially flat. Of the remaining 45.we simulated six; all but two of the remaining 39 have a sha pe that can be seen to be su ccessfullysirnulatable with the technique described.

The similarity of these manifolds obtained by recordings made from the somatosensory cortexlo the receptive field characteristics demonstrated in the primary visual cortex (DeValois andDeValois. 1988: Pollen and Taylor, 1974; Pribram and Carlton. 1986: Daugman. 1990) suggeststhat this process is ubiquitous in the cortical synaprodendritic network.

The manifolds derived from our data are constructed of two orthogonal dimensions: onedimension reflects the spatial frequency of the stimulus and the other iti temporal frequency.Because spatial and temporal va riabl es constrain the spectral density response, a Gabor-like rathe rthan a simple Fourier representation describes our results. Thus the results of our exp eriments canbe interpreted in terms of an information field composed of Gabor-like eleme ntary functions. thatis. of truncated two dimensional sinusoids.An unconstrained spectral representation is globally holographic: the constrained spectraldomain. as in patch or multiplex holography, is termed holonomic. (For the derivation of this no-menclarure, originated by He rtz, see Pribram, 1991, p. 27.) Holonomic constraints quantize anessentially spectral proce ss. G abo r called the rlern en~ ary unction described by the intersection ofhis spectral and time parameters a quan tum of information. His reason was that he couldaddress the problem o f the efficiency of communicatio n acro ss the Atlantic cable in terms of thef~rmu lation f Heisenberg s principle of indeterminacy in 1927 . This discovery led to a greatslm~l ificat ion n the mathematical appa ratus of quantum theory which was recast in a form ofwhich use will be made in the present paper (1946, p. 432).

quantum information f ie ld theory of dendr i t ic process ing?The formal. fnarhematical fou ndat ions of the computation s which contribu te to cont empo rary fieldIhcoretical conc epts regardi ng brain fun ction rest on generalization of the application of the

of a Spectral domain: not only colors and tones can be analyzed into their componentof oscillation. Pr ocess ing o f all exteroceptive sensations including those dependent on

spa tio tem ~or al onfigurations (such as the shapes of surfaces and forms) can be understood as


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igure 6. Examples of stimulated receptive field manifolds and their associated contour maps tobe compared with the empirically derived maps presented in Figures 2a-f. Axes are normalizedfrom 0amplitude modulations of these oscillations. In fact, due to the Fourier transformation, spectraenfold the ordinary conception of both space and time.

The mapping of dendritic receptive fields is based on the Fourier relationship. s noted.Fouri er's theorem states that a pattern ca n be decom posed into components representing the rela-tionships amon g sets of regula r (i.e.. perio dic) oscillations each of which has been furtherdecomposed into oscillations 90 out of phase. Components encode frequency. amplitude andphase (the relations between oscillations). These components are quantified as Fourier coeffi-cients. T he ensemble of such coefficients. w hen emb odied in physical form , becomes palpable asan optical hologram. When coefficients of identical value are connected as in a contour m ap , theresulting schema is what in the hoionornic brain theory is called a holosc ape. Th e conto urs


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formingsuch a holoscape are embodied in the microp rocess of polarizations occurri ng in dendriticnelwortsu s constituting a sub- and transneuronal manifold.~ ~ d ~ ~he Fourier theorem states that the original pattern can be reconstituted. recon-

s,mcted. by performing the inverse transform. It is this simplicity, its invenibility and linearit)'i n analysis and (re-)synthesis, which is one of the attractive features of the Fourier theorem.ncre is, therefore , a computational gain leading to better understanding were brain processes tool low h e rules of the Fourier relationship. Actuality is somewhat more complex.

per eived patterns are ordinarily described in space and time. When the Fourier analyticalprocedure decomposes a spacetime pattern into an ensemble of components representing the fre-qucncie s of oscillations from which the pattern can be recon structe d. the decomposition isdescribed as harmonic and the result, the spectrum of the pattern. Thus 1) spacelime. and 2spcclrum are differentiated by the Fourie r procedure.An additional concept der ives -fro m plotting spectral and sp acetim e values within the sam eframe. It rums out that when this is done there is a limit with which both frequency and space-lime can be concurrently determined in any measurement. As noted. this is the uncertaintyrclalion was used by Gabor (1946 ) to describ e a Fundamental unit. a quantu m of information.This unit differs from the unit of information defined by Shannon. usually taken as a bit. (ahinary digit) i.e., a binary (Boolean) choice among alternatives (Shannon and Weaver 1949).Ilowev er. Shanno n also defined information as a reduction of uncertainry. This unc erui nryrrlationship provides a link between Gabor's anil Shannon's definitions and allows for an explicitconver gence of 'information processin_e heories . Furth ermor e. the distinction between Gabor 'sand Shannon's formulations provide the basis of the distinction between configural and thecognitive aspects of percepiion (see Pribram. 1991).

Gabor bec ame interested in describing a joint spacetime-spectral domain because he notedLhal here is a limit on the precision to which simultaneous measurement of spectral componentsand Ispacelrime can be made. It is this limit. defined by residual bandwidth of freq uencies and theprobability of an occurrence within a range of spacetime. that proscribes the efficiency withwhich the system can operate. In effect. therefore, the Gabor relation describes the compositiono a sensory channel, and the residual uncertainty defines the limits of channel processing span.

Processing efficiency was handled by Gabor in terms of a measure he termed the Log on .Today we ofren refer to these Logons as Gabor elemen ray functions. In Gabor 's two dimensio-nal scheme the Logon was a unitary minimum. This minimum describes an area surrounding theintersection of frequency and a temporal impulse function.

Gabor's mathematics paralleled that used by Heisenberg to describe experimental findings inh e field of quantum physics. In essence. therefore. the mathematics found so useful in under-~ u n d i n g elationships in quantum physics was generalized to deal with issues in psychoph ysicsand Gabor termed the Logon a quantum of information. An ensemble of such quanta, pro cessingchanne ls, is dealt with by what m athematicians call a Hilbert spac e. as Hilbert originally devised

mathematics used by Heisenberg and Gabor.In our experimental results, Gabor elemenwry functions are composed in dendritic arboriza-

receptive fields of the neuro ns from which we are record ing. Pollen and Ronner (1 980)found adjacent neurons in the visual cortex to respond'best to gratings 90 out of phase . Theseneurons make up a couplet, a quadriture pair. Thus in the visual system a module of receptive

encodes the quadriture relation (essentially sine and cosine components that make upcOeficients). Each logon. i . e each such receptive field module. is a channel. AccordingGabor. the ensemble of such channels is a measure of the degrees of freedom. the number ofdistinguishable dimensions or features (e.g. . spatial and temporal frequency, degrees of orienta-


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l ions. prefe rred direction. color). Th e minimum uncertainry relation ex pr ess ed~ by abor elemen. 1tary func tions sets the lim iu on the information processing competence of each of these channels , jC o d a

Given that an aspect of dendritic processing in the sensory cortex can be described in terms ofquantum-like fields made up of Gabor channels . we are faced with a discrepancy: Such fields,comp osed of arrival and d ep am re patterns of synapto-dendritic polarizations. ar e considered tobe coord inate with perceptual awa reness, which occurs within spacetime coordinates. Kohler did , . ,not have this problem with his more generalized fields which were deemed geometricallyisomorphic not only with the physical sensory input but also with subjective experience.

Resolution of this discrepancy is beyond the scope of this address but has been dealt with indetail in Pribram and Carlton (1986) and in Lecrure 6 of rain and Percepfion (Pribram. 1991). \.~ o l l o w i n ~he lead given by Poincare, Helmholtz and Lie (see Pribram Epilogue. 1991). move-ment is given the critical role of organizing an inverse transform to produce our experience ofentities such as ob jects in a spacetime frame. In visual processing. this organization is imposedby the peri- and prestriate conical systems operating back (top-down) on the primary geniculos-triate visual input.

Mu ch ha s been made recently of the modular composition of mental (Minsky. 1986) andbrain processes (Gazzaniga, 1985). This emphasis on neural systems which localize separatebrain-behavioral relationships is vitally important to understanding such processes as memoryretrieval (a nd has constituted the bulk of my laboratory research). Howe ver. equally important isthe fact that these various systems not only relate to one another in a hierarchical manner but thatthe higher o rd er systems operate on lower order systems by interpenetration. Th us , we ordinarily,immediately perceive named and categorized objects , not just sets of images (though we arecapabl e of imagi ng by suspending the higher order processes). There is abundant evidence ofsuch top-down penetration in the visual. auditory and somatosensory neural systems.

Mathe matica lly, conformal (Lie) group procedures (Hoffman. 1966) are show n to describethis process. Fra me effects are accounted for (Palmer 1988) as is the fact. in Poincare 's terms,that objects ar e relations . Move ment, whether acrual or imaged follows a least action (or actionintegral) geodesic (Carlton and Shepard, 1990 IBLII) described by. vectors in the Gabor informa-t ion process ing domain.

final question needs to be addressed. Why should the brain process go through a spectraltransf ormat ion only to have to inverse transform in order to allow the organism to behave appro-priately in a spacetirne object(ive) world? Th e answer is that correlations are achieved mu ch moreparsimoniously when such transformations are employed. In statis tical manipulations. the T(Fast F our ier Trans form) has provided an incredibly useful tool to facilitate the comput3tion ofcorrelations. Medical applications of image processing such as computerized tomography (CTscans) a nd magnetic reson ance imaging (MRT) have at their basis spectral domain transformations.

T he eviden ce that brain processes partake of this computational s implification was not soughtfor but has ac crued over the past two and a half decades serendipitously in various laboratories.The evidence is . at present. overwhelming that some such transformational brain process under-lies perception: that Gabor-like synaptodendritic receptive fiel s are critical. fields that aresensitive to a multitude of chemical modulations but sufficiently robust to allow our experienceof the world to be stable and predictive. The step in the process that needs more experimentaleviden ce in various sensory modes is how the invers e transformation from field to action path


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Brain in Perception - From Kohler's Fields to Gabor's Quanta of Information T-188

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