Lord Brain Some Reflections on Mind & Brain 1963

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SEPTEMBER 1963

BRAINVOL. 86, PART 3.

S O M E R E F L E C T I O N S O N B R A I N A N D M I N D 1BY

LORD BRAINTH E ever-growing number of articles, books and symposia devoted toone or other aspect of the brain-mind relationship is a remarkable featureof our time . Since it has been debated since the time of the Gre eks, andthe main questions about it were clear in general at least three hundredyears ago, it is perhaps natural to ask why so much attention should bedevoted to it today. W hen men knew only the most general facts a bou tthe relationship of the brain and the mind, the problem of its naturenecessarily presented itself in the most general terms, as a philosophicalproblem involving supposed mental entities with certain characteristics,

and matter in general, since of the material structure of the brain virtuallynothing was known. It is the vast expansion of our knowledge ofneurophysiology and psychophysiology which has stimulated the currentsurge of interest in the brain-m ind relations hip. Tw o m ain questions areasked about it, and it is important to keep them distinct, at least initially.Most people are aware that correlations exist between the brain and themind,8 and the observations of these is part of the everyday work of theneurologist. If we wan t to know what these correlations are, we mustinvestigate, describe an d clarify them by every available m etho d. Butwe may also ask what the nature of the correlation of brain and mind isin general. It is widely believed that these two lines of enquiry hav e norelation to each other. H ughlings Jackson (1931, 1, 367)* was concernedsolely with the first que stion. "Sta tes of cons ciousn ess," he w rote, " areassumed . . . to be merely concom itant with certain nervous states, thoseof the highest cerebral centres . I have noth ing whatever to say of the

1Based upo n the H ughlings Jackson lecture delivered to the M ontreal NeurologicalInstitute, May 9, 1963.I purposely do not define these terms: "brain" is self-explanatory, and I here use"mind" in the everyday sense in which ideas and feelings for example are said to be"in the mind," or mental.Th rou gh ou t thispaper the H ughlings Jackson references are to the Selected Writings.2 5 BRAINVO L. LXXXVI

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3 8 2 LORD BRAINnature of the relation of the two utterly different and yet concomitantthings, cerebration and m entation, to one another. As an evolutionistI am not concerned with this question and for medical purposes I do notcare abou t it." Some contemporary workers think that those who studythe brain should be equally cautious abo ut discussing it. G ran it (1955),in his book, Receptors and Sensory Perception, says: "I shall restrict mycomments on epistemology to stating that the time is past when physiolo-gists ex cathedra could issue naive views on the nature of knowledge,'brain and mind,' reality and appearance, and similar concepts withoutpene trating the philo soph ical aspects of these problem s in detail. Theywill merely be snared by their own lack of insight in the logical analysisof the convention s of langu age." But m ost of tha t seems to be equallytrue if repeate d with the interchange of two wo rds. The time is past whenphilosophers ex cathedra could issue naive views on the nature ofknowledge, "brain and mind," reality and appearance, and similarconcepts without penetrating the physiological aspects of these problemsin detail. I do not expect th at this question, one of the most fundam entalproblems of life, will be rapidly clarified, but I do not think it will takethe four hundred years which Sherrington once predicted in conversationwith me. The better we understand the correlation between the brainand the mind, and how the brain subserves mental functions, the morelikely, I believe, shall we be to understand the nature of the relationsbetween the two.So I am going to begin by discussing some aspects of the physiologyof percep tion. This will be followed by a conside ration of time in relationto the nervous system an d the mind. Th at will lead to a discussion of thenature of consciousness and its physiological basis, and, finally, I shallsay something abo ut the relationship between brain and mind . Myobject throughout is not to present conclusions, but to ask questions towhich I hope time will provide the answers.

RECENT ADVANCES IN THE PHYSIOLOGY OF PERCEPTIONThe newer electrophysiological methods are adding fundamentallyto o ur know ledge of the physiological basis of percep tion. M icro-electrodes

make it possible to record from single units at different levels of thenervous system, and so to discover how these respond to different kindsof sensory stimulus. F or some years now it has been know n th at in theretina and optic nerve there are some units which respond to the onset ofillumination, and some which respond to its cessation, and others yetagain w hich respond to b oth . This is kno wn as the on/off system (fig. 1).H ube l (1959) by mean s of implanted micro-electrodes ha s studied theactivity of single units in the striate cortex of unrestra ined c ats. H eobserved that most cortical units showed no response to a mere change ofbackgrou nd illumination. Many responded to a stationary light source

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1 1FIG. 1.Diagram illustrating three fibres in the optic nerve firing spontaneouslyand their responses to illum ination. 1, The on response ; 2a, the off response; 2b,the off response inhibited by illu min ation ; 3, a un it showing bo th on and offresponses. (Fro m "Receptors and Sensory Perc eption" by Rag nar Granit (1955).)by showing on-and-off type responses (fig. 2). A response to movem entwas also observed. Some units responded to movem ent in one horizontaldirection, but not to tha t in the oppo site. In the same cerebral hemisphereH ube l observed two types of unit, one responding to leftward an d theother to rightward movem ent. H e also noted tha t movem ent couldactivate a single cortical unit, when it occurred over a relatively largeregion of the visual fieldof the order of 20, equivalent to 5 mm. on theretina.1 This observation indicated a convergence from a considerableretinal field up on a single cortical un it. H ub el concluded that "th e striatecortex is not simply a retinotopically organized point-to-point relaystation along the visual path w ay." Rath er it "would seem to containunits with receptive fields of widely differing exte nt." H ubel an d Wiesel(1959) working with acute cat preparations also observed that most unitsin the visual cortex corresponded to a restricted retinal area, and that mostsuch retinal fields were divided into excitatory and inhibitory regions,which were m utually antagonistic in relation to cortical units (figs. 3 to 5).They concluded that "the phenomena of summation and antagonismwith in recep tive fields seem to prov ide a ba sis for th e specificity ofstimuli, in shape, size and ori ent atio n." Studies of binocularly activatedunits showed tha t the receptive fields in the two eyes were alike. Theeffect of this would be that the retinal images of objects behind, or in

1Thus physiology has confirmed observations made by Riddoch (1917) during thefirst world war that after an occipital injury awareness of movement might recoverbefore recognition of an object, thus demonstrating in man "that movement shouldbe given a place am ong stimuli which are recognized as originating visual perceptions."



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FIG. 4.Responses evoked only from contralateral eye. Receptivefield ust outsidenasal border of area centralis. a, 1 spot covering the inhibitory region; b, right halfof a circle 12 in diam eter; c, light spot covering regions illuminated in a and b .Backgrou nd an d stimulus intensities and conventions as in fig. 2. Scale, 12 (H ubeland Wiesel, 1959).

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HFio . 5.Records from unit activated by ipsilateral eye only ; unresponsive tostationary spots, influenced by movement in an area temporal to area centralis.A slit (0-5 x 8) moved back and forth transversely with different orientations, asshown to the left. Fo r slit orientations evoking responses only one direction waseffectiveup an d to the righ t. Time, 1 sec. (H ubel an d Wiesel, 1959).



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SOME REFLECTIONS ON BRAIN A N D MIND 3 8 7abou t "a space in which any poin t is described in terms of how it is relatedto what is aro un d it. " "I n a system like this, a uniqu e com binatio n of thefour qualitative contexts in a certain spatial relation may define a class ofobjects. . . . Obviously, this is a way in which the universals 'prey' and'enemy' can be recognized or inferred directly without requiring ascanning operation."

These observations show how largely perceptual discrimination invision depends upon physiological organization in the receptor organ,the retina, and this in turn upon the anatomical fact that a large numberof retinal receptors converge upon a single optic nerve fibre, the ratiobeing according to Granit (1955) "of the order of 100:1." Only such anorganization could enable a single retinal field converging on a singleneural unit not only to respond to movement, but to discriminate move-ment in one direction from that in the opposite. H ubel and Wiesel pointout some of the contributions which this peripheral discriminativeorgan ization could ma ke to perceptual function. A s G ran it (1955) says,the retinal surfaces are "capable of good discrimination on the same basicprinciple a s is the sk in, i.e. by using o verlap ping receptive fields of differentsizes, from very large to very small, the latter likely to be multiplied incone eyes which have good visual acuity."Then there is the role of spontaneous activity in sense organs, alsodiscussed by Gran it. H e says tha t, "to hold the view that sense organ s,

and in this particular connexion the retina, energize certain systems andindividual cells by way of a maintained spontaneous activity is to providea new role for peripheral inhibition in sense organs, whatever its cause.If all optic nerve fibres were silent, unless stimulated, an effect of inhibitionaround the edges of illuminated patches projected on to the silent retinawould b e negligible, because it would never be transm itted to the perceivingcortex. But if the sense organ no rmally is spon taneou sly active, thesuppression of the inherent activity will be notified to the cortex. . . .The edges around the projected patches on the cortical map may nowapp ear as regions of correspondingly altered excitability." G ran it poin tsout that "intense black is perceived only by contrast a gainst wh ite." It isdifficult to understand how black could be perceived at all without thespontaneous activity, for, while physically it corresponds to the completeabsence of visual stimuli, perceptually it is a sensation as positive as whiteor any colour. If colou r perception corres pond s, as we have every reasonto believe it does, to some electrical activity in the visual cortex it isprob able th at the same is true of the perception of black. W e have heresurely an explanation of the common experience of the imperception ofhem ianopia . If black, the absence of light waves, were represented in thenervous system by the absence of activity in the visual cortex, destruction ofan are a of visual cortex should cause the missing area of the visual field



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3 8 8 LORD BRAINto be seen as black, which is not comm only the case. The sensation ofblack must therefore depend upon a positive activity of the visual cortex.

Granit also uses the vestibular responses to illustrate the value ofspontaneou s rhythm s arising in the receptor end organs. H e quotes thework of Lowenstein and Sand (1940) who demonstrated that for eachcanal of each labyrin th there were two oppo site reactions. Ro tation oneway increased the spontaneous discharge, and in the opposite directionsuppressed it. G ran it rem ark s: "Co nsider now that there are six suchcanals, three in each ear, and it will be apparent that the presence of aspontaneous rhythm that can be accelerated or decelerated makes for adiscrimination which, unless utilized by the b rain, will be wholly mean ing-less. . . . The semicircular canals . . . have, as do other sense organs, onlythe frequency code at their disposal, grafted, however, upon a magnificentspace-sensitive in stru m en t. . . . Acc eleration and deceleration of thespon taneou s rhyth m of discharge creates an interpretable pattern . One ofou r m ajor aims as sensory physiologists is to attem pt to identify peripheral'cues ' for sensory discrimination in terms of the frequency code."

I could show that the same principles underlie the physiological basisof perception in all sensory modalities, but I need not do this in detail:a few illustra tions will suffice. In cutan eou s sensation we find one corticalunit linked with a cutaneous receptive field measuring several squarecentimetres (M oun tcastle, 1957). As in the case of the retina, inhibitoryme chan isms exist. "A cell, excited by stimu lating an area of skin (the'receptive area') may be inhibited by stimulating surrounding areas, andthis influence, excited mutually in a population of cells, will result in thesharpening of the edges in the central stimulus pattern, emphasizingdiscontinuities an d increasing contrast. . . . This kind of lateral inhibitionis know n in visual, aud itory and som atic sensory systems" (G ord on , 1962).It is unnecessary for my present purpose to discuss the still disputedquestion of the specificity of sensory conduction in peripheral nerve fibres:it is generally agreed that what is important for perception is the conduc-tion of a pattern of impulses in space and time, in which many peripheralreceptors and conducting fibres take part, and which is modified by theinteraction of peripheral mechanisms as well as by the receptivity ofcentral pathways {see M elzack and W all, 1962). Such interactio n is wellillustrated by Granit 's dominator-modulator theory of colour vision.

SOME IMPLICATIONS OF CODINGThe essential activity of nerve fibres is the conduction of electricalimpulses. They vary only in the following respects: (1) Peripherallyspecific receptors ensure that the nerves are excited only by particularphy sical stim uli. (2) Th e rate of conduction v aries in different nerve fibres



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SOME REFLECTIONS ON BRAIN AND MIND 3 89and ap pears to be related, in part at least, to their diam eter. (3) Thetemporal pattern of sensory impulses is influenced by the intensity of theperipheral stimulus and the refractory period of the nerve fibre, and (4)periph eral afferent fibres concerned with particu lar m odalities of sensationdiffer in respect of their central conne xions. Thu s it comes abou t, as wehave seen, that different highly complex spatio-temporal patterns of nerveimpulses are excited by individual elements in the physical object, whichstimulates the nerve peripherally.

So far I have not used the word "info rm ation," but we must now examinewhat is implied by the statement, freely used by psychophysiologists,that the pattern of nerve impulses is conveying information, and thatthis inform ation is conveyed in the form of a code. Y oun g (1962), forexample, says: "If we are to understand the problem of what is storedin the memory we must examine the conditions that are necessary if theoutcome of events in a nexus or channel is to provide a representation ofwhat has gone in. . . . A representation can be so mad e if the events inthe channel are circumscribed to certain types that have been pre-arrangedto constitute wha t we are calling a 'code .' Th e m aking of any representa-tion depends then upon selecting some from a specific set of physicalevents. These will then be recognized at the end of the channe l as indicatingtha t certain events occurred at the inp ut ." Yo ung goes on to mentionspeaking and writing as examples of the em ploym ent of a code. Theessence of a code, in the original sense of the word, is that it is a set ofsymbols which represent something else. Th e thing represented can betranslated into the code, but when it is decoded it usually assumes itsoriginal form, the code hav ing acted merely as a convenient vehicle for theme aning, as the morse co de is used in telegraphy. But this mea ning maybe misleading when applied to the nervous system, in which "coding"means only the representation of information, and does not imply thatthe information necessarily reaches consciousness, or is decoded in thesense of regain ing its orig inal form . Tech nically, info rm ation is definedas "a measure of how much uncertainty has been removed by the receiptof a message" (Saltzberg, 1963).

Before considering the more difficult question of human consciousnesslet us see how the coded information work s in simpler brain s. The frogis a strictly practical entomologist, its only reaction to seeing a fly beingto aim its tongu e at it. W ha t the coded inform ation derived from the retinadoes, therefore, is to evoke the appropriate action, and appropriate hereme ans not only biologically suitable, bu t also precisely adjusted. In orde rthat this may happen, afferent impulses must convey information aboutthe quality and position in space of the object (the fly), and the frog mustalso receive inform ation abo ut its own position in the same space. H encethe visual information must be integrated with information about the



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3 9 0 LORD BRAINposition of its bod y derived from othe r sensory receptors. If, for exam ple,the statocysts of an octopus are removed, the position of its eyes is nolonger adjusted to gravity, and its trained reactions to geometrical figuresare disorganized (Wells, 1960). The frog reacts to a fly because the informa-tion processed by the visual system, together with that derived from thesomatic sensory system, and influenced by the animal's state of alertness,evokes the spatially appropriate m otor activity. Gr anit makes the samepoint in relation to the influence of the labyrinths on eye movement."The re is no more instructive dem onstratio n," he writes, "of thesignificance of patte rn for discrim ination. The fact th at we do not discrimi-nate vestibular impressions by perception, i.e. consciously (according tomost authorities) is not a serious argument when one considers that thismessage is correctly interpreted in the lower centers for the eye muscles.There is no reason to regard consciousness as more than a fringe on thepat tern ."

But even simple creatures learn by experience. H ow this com esabout has been investigated in the octopus by Young (1962) and hiscolla bor ators . As a result of his studies of visual learning he has shownin outline how nervous impulses from the eyes may lead to movement, orthe inhibition of movement, in the light of past experience, and how theseactivities are related to particular regions of the animal's nervous system.My object so far has been to show how complex is the part played in

perception by the peripheral sensory receptors, their functional organiza-tion, and th at of their conducting pathways. The physiological organizationupon which sensory discrimination depends begins at the periphery withreceptors individually attuned to particular physical stimuli. The groupingof these receptors in relation to afferent nervous pathw ays has been shownto be capable of discriminating, not only movement, but also its direction.Th e org anization of overlapping receptive fields also plays a part in variousforms of sensory discrimination, and the spontaneous activity of sensoryreceptors greatly enriches the scope of perceptu al repres entatio n. Thephysiological basis of perception, then, is a code of frequency of nerveimpulses, and "visual perception . . . is a dynam ic act maintained by acontinuous frequency variation and not by a static image on a photo-graphic plate." "The problem of color reception," for example, "mustbe solved by central interpreta tion of information over a complex frequencycode which also expresses interaction" (Granit).NEUROLOGICAL AND PSYCHOLOGICAL TIME

Frequency involves time, and the part played by time in the nervoussystem has on the whole attracted little attentio n. (A notable exception isthe work of G ood dy , 1958, 1959.) There are two aspects of it the use of


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SOME REFLECTIONS ON BRAIN AND MIND 3 9 1time in the process of information-coding, and the coding and decodingof information abou t time itself. The former is the subject of colla bora tionbetween physiologists and information experts: the latter is intimatelyconcerned with consciousness, and it is this aspect alone which I shallnow discuss.

Receptors and neurones are organized to respond to temporal relation-ships in their stimuli, and hence convey inform ation involving tim e. Butthis does not imply that such informa tion enters consciousness. To re spon dto a moving object involves information about time past and present,and even an extrapolation into the future, but neurologically all thatseems necessary is the existence of receptors sensitive to the movement,and the right central connexions to evoke the app ropriate m otor response,as we have already seen; and the nervous system can provide this w ithoutits involving any conscious experience of time . M oreover when wedescribe what happens in the nervous system we are concerned with themov eme nts of electrical impulses in space (i.e. along neu rons), and thou ghwe use physical time to describe these movements, we can never extractfrom such an accoun t time as we experience it psychologically. Fo rphysical space-time is a succession of instants, an eternal present which iscontinuously changing, and if we experienced only the present we couldhave no concep tion of time. Even a mem ory, when we experience it, is apresent state. It is true that we distinguish it from other present statesby relating it to the past, but we could n ot d o this unless we were alreadyin some way aware of the passage of time.

This has long been familiar to philosophers and psychologists.H ughlings Jackson (1931, 1, 205) said: "Time is required for conscious-ness," basing this on a quotation from H erbert Spencer, and drew theconclusion that loss of consciousness in an epileptic attack is due to therapidity of the neural discharge. "D uring the excessive and rapid dischargeof the anatomical substrata of consciousness we could not expect thatconscious states would app ear; on the contrary, we should, a priori,expect loss of conscious ness." Psychologists have spoken of the lengthof time during which consecutive events are together present to conscious-ness as the "specious pre sent," a term introdu ced by Clay (1882). Russell(1948) devotes a chapter of his book , "H um an Knowledge its Scope andLimits," to "time in experience," and Whitrow (1961) in "The NaturalPhilosophy of Time" discusses what is involved in the specious present or,as he prefers to call it, "the mental present." H e says: "Direct perceptionof change, irrespective of whether it is explicitly recognized as succession,requires the simultaneous presence in our awareness of events in distinctphases of prese ntation . The comb ination of simultaneity and successionin our perception would mean that the time of our conscious experienceis more like a moving line than a moving point."



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3 9 2 LORD BRAINBergson (1912) comparing physical and psychological time wrote:"There is in space neither duration (durde) nor even succession in thesense in which consciousness understands those words: each of the

states described as successive in the external world exists, and then-multiplicity has reality, only for a consciousness capable of first conservingthem and the n juxta pos ing them by exteriorizing them in relation w ith onean oth er." W illiam James (1890) believed that brain processes set up bystimuli have a measurable duration and therefore those aroused by pastand present stimuli overlap, but we are still left with the problem of howsimultaneous brain states are discriminated by consciousness into pastand present. This is a fundam ental question for the brain-m indrelationship.The men tal present can be understood only against a larger back ground .

Awareness of the passage of time seems to involve the retention of pastexperiences against which the ever-changing present is perceived asnovelty, until it too becom es past. Th us the sense of time depends upo n aqua litative difference between pas t an d present experience. Several thing sfollow from this. Time as a relationship of orde r ma y well berepresented by a coding in the nervou s system ba sed on spatialorganizationone aspect of the problem of serial order discussed byLashley (1960). The spatial coding of time has long been a common-place, e.g. in the gram oph one record and tap e recorder. In such devicesspatial relations can be reconverted into temporal ones by means ofmo vem ent, as no dou bt happens in the nervous system. But it should benoted that past time is still coded when consciousness deals with it. W henwe remember past years, it does not take us years to do it: we deal withthe past symbolically, whether in the form of images representing pastexperiences or as awareness of a relation of order between them.

H ere we seem to have reached a point at which we can find nophysiological equivalent for what is happ ening in the m ind. Kliiver (1962)asks "whether an 'engram of succession' (that is, of the ante- or post-signature of events) can ever be derived from a 'succession of en gra m s'."The answer would seem to be that awareness of succession is a mentalevent, but a succession of engrams is a series of physical events, which,as we have already seen, are know n to be successive only by mind . A nengram of succession would also be a physical event, and we cannotextract from a description of physical events something which it does notcon tain. In other words we cann ot here at present fully trans late thelanguage of neurology into the languag e of psychology. At tem pts havebeen made to do this. D obb s (1951), discussing "the relation betweenthe time of psychology and the time of physics," is led to postulate twodimensions of psychological time, so that events which are successive in"pha se tim e" occur " as a whole in a single movement of transition tim e."



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SOME REFLECTIONS ON BRAIN AND MIND 3 9 3Denbigh (1953), aware that the problem is to know how to distinguishactuality from reminiscence, "the is state from the was state," thinks thatthere are qualitative differences between them . But how do these arise ?From the fact he says "that we participate, in our own bodies, in the samechemical and physical processes which occur in the external world," and"the time sense of a human being derives from their existence withinhim, giving him the feeling of an inne r time no t based on the five senses."Many living organisms certainly seem to have an inherent sense of time,an inner clock by which they can regulate their activities. Th ou gh somephysiological factors are known to influence this inner time its nature isnot understood. W hat we do know abo ut it suggests that somerhythmical activity provides a continuous flow of information which isstored to modify subseq uent behavio ur. But this is a physiologicalexplanation: its translation into psychological terms still eludes us.

We can hardly consider time without mentioning memory, but this istoo large a subject to be dealt with adequately here; I will discuss onlyone or two points, which are relevant to my later discussion ofconsciousness.Studies of retrograde amnesia, and the effect of brain lesions onmemory, suggest that both anatomically and physiologically the neuro-logical activity underlying the mental present, and the recall of recentmemories, is different from that concerned with both the long-term

storage of mem ories, and recognition. Th e situation is well summ arizedby Adam s, Collins and V ictor (1962) in a recent paper. After presen tingevidence that the lesion responsible for persistent retrograde andanterograde amnesia is situated in the medial thalamus they say: "Theneurophysiologic mechanism for such complex types of learning asnumerical relations, verbal symbols and concepts evidently is seated inthe temporal lobes and upper brain-stem structures and their inter-connections, in close relation to the mechanisms that maintain conscious-ness an d atten tion. . . . Yet the neo-cortex itself is involved in themechanisms of all special auditory, visual, tactile, and other learning andmemories as well as those for words, mathematical figures, etc., forlesions here abolish specific memories and prevent relearning of this typeof ma terial. In other wo rds, the rhinencephalic-diencephalic mechan ismmust act with parts of the cerebral cortex, as well as with the upper brainstem mechanisms of consciousness." As we learn more abou t this andabo ut the role of the thalamus and hippocam pus in the retention an d recallof recent memories, we may expect to add to our knowledge of the brain-mind relationship. *The idea of the mental present as a state enduring in time may help tobridge the gulf between brain-states and sensations. W e kno w that an



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3 9 4 LORD BRAINactivity of the brain underlies our awareness of a colour, a sound, or apain, but how, it is said, can the corresponding brain activity be a colour,a sound or a paina sensation when directly experienced, a series ofnerve impulses when described by the physiologist? Consider sound:from a physical stand po int a sound is a wave-length of a certain frequency,a concept involving time. Owing to the physiological properties of thenerve fibres and the rate at which nerve impulses are conducted, it iscertain that the activity of higher levels of the nervous system, for examplethe auditory cortex, which leads to the awareness of a sound, does notinvolve the reproduction of the original frequency of the sound-wavesstriking the ear: it is a coded represen tation of that frequency. Theexistence of the mental present seems to imply that what is presented toconsciousness has a duration, and hence a structure in time, for whichWhitehead's term "prehension" is a useful neutral description. A sensationmay then be a prehension in time of those events in the nervous systemwhich are presented to the neurophysiologist successively.

Recent work on speech perception gives us a glimpse of this processat wo rk. Liberm an, Delattre and Coo per (1952) observed that w hethera subject heard a simple unvoiced stop consonant as " p " or "k " dependedin pa rt up on th e vowel by which it was followed. H ence the followingvowel "plays a critical part in the auditory perception of 'p' and 'k' ,"and "in that event the irreducible correlate for 'p' and 'k' is the soundpattern corresponding to the consonant-vowel syllable." In this case theauditory stimuli representing the consonant and vowel are successive,and they are presented to consciousness as successive, but the qualityof the earlier event, represented in consciousness by hearing the con son ant,is influenced by th e later on e, represented in consciousness by hearing thevowel. This wou ld be explained if the neu ral state set up by the firststimulus had time to be modified by that set up by the second before itentered consciousness. Thu s in the mental present there is no t onlyoverlapping, but mutual modification of the representations of events,which in physical time are successive.

Distortion of time sense has often been observed by subjects takinghallucinogenic dru gs, especially mescaline. A num ber of factors may beinvolved, perception, inner time sense, the serial ordering of experiences,and m emo ry. It does no t seem necessary to suppose that such disorderedawareness of time-relations implies awareness of other dimensions oftime, as has sometimes been supposed (Mayhew, 1963).

There is one other aspect of perception which, though not involvingtime, may conven iently be considered at this po int. Th e sense organ s andthe nervous system consist of vast numbers of minute units, yet thisgran ular stru cture is no t reproduced in sensory experience: there is noth ing



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SOME REFLECTIONS ON BRAIN AND MIND 3 9 5for example in a coloured surface, or the feel of a smo oth peb ble, to suggestthat it is med iated by a vast num ber of discrete neu ral units . Consc ious-ness, therefore, involves spatial as well as temporal prehensions, and wecan see this process at work in the activity of our sense organs, vision, forinstance, converting the multiplicity of minute dots in a half-tone photo-graphic block into gradations of light and shade.

Finally, "the development of distance-receptors had a profound effectupon the organism 's relation ship no t only to space bu t to tim e. If it isto react to objects at a distance, time must enter into the organization ofits nervous system in a manner which has no parallel in the more primitivecreature which responds automatically to immediate stimuli" (Brain,1950). If activity is to be organized in time the organism needs anenduring representation of objects, and develops feelings in relation tothem . A consciousness which represents objects in time mu st itself bebased upon time, and is unsuitable for dealing with reactions w hich mustbe imm ediate. W e can not afford time to think before adjusting o ureye movements to vestibular information: hence such reactions areunconscious.

T H E PH YSIOLOGICAL BASIS OF CONSCIOUSNESSIn the symposium, "Brain Mechanisms and Consciousness" (1954),there are ma ny allusions to the location of consciousness. This is perhap sthe m ost obvious question concerning its physiological basis. W here in

the brain, it may be asked, is the function of consciousness to be located ?H ughlings Jackson (1931, 1, 367) said: "States of consciousness areassumed . . . to be merely concom itant with certain nervous states, thoseof the highest cerebral centres," but he was not very precise as to thelocation of these. Several facts seem to supp ort th e idea of a location ofconsciousness. First, lesions of some parts of the brain appe ar to have noeffect upo n con sciousness, while lesions of othe r pa rts affect it profou ndly.The n there are the effects of lesions of the sensory path way s. If, forexample, the optic nerves are divided, the subject can no longer see, butthere is no reason to suppose that any visual consciousness remains inthe eyes. The sam e is true of the visual pathw ays up to the cortex, and ,as we cannot trace vision beyond the visual cortex, it is sometimes saidthat at the cortex visual impulses "enter consciousness." Similar state-ments can be made abo ut all forms of sensibility. H ead (1920) in distin-guishing between the sensory functions of the optic thalamus and thecerebral cortex says: "The essential organ of the thalamus is the centreof 'awareness' for certain aspects of sensation. . . . The feeling-tone ofsomatic or visceral sensation is a product of thalamic activity. . . .Conversely, the more entirely any aspect of sensibility depends upondiscrimination the more it is the concern of the sensory cortex ." Such

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3 9 6 LORD BRAINstatements seem to suggest that certain areas of the brain have a specialrelation w ith consciousness. Either the arrival of sensory impulses itselfconstitutes the corresponding sensory experience, or we are led to pictureconsciousness as like a person sitting at a desk supplied with a number oftelephones, represented by these areas.

If, however, we examine this rather naive picture, we see that for severalreasons it canno t represent the true state of affairs. First, is there anyreason to distinguish the cortical end-station of a sensory pathway fromany o ther po int of the pathw ay leading up to it? Th ou gh it is possible todistinguish differences in the disorder of function related to the level of thelesion, inherently th e loss of function is the same, and , as has been show nabove, we cannot now maintain that discriminative activity is solely afunction of the sensory cortex. "Th e visual cortex is a necessary cond itionof vision, for its destruction renders the subject b lind, bu t the same is trueof the optic nerves. Why, then, do we attach importance to the cortex?Because it is the last anatomical point on the afferent visual pathway ofwh ich this is true. But it does no t follow th at the function of vision islocatedthere. It may be inaccurate to speak of its location in any particu larpa rt of the nervous system. If the brain largely acts as a whole, vision m aybe a p rope rty of the who le of it, in which case it is represented in the brainas a whole in a different way from its representation in the visual cortex.The latter then becomes only the last point at which nerve-fibres solely con-cerned with vision exist as an isolable gro up . The same may be true ofother sensory pathway s, and of the mo tor cortex, and m otor p athways t oo "(Br ain, 1960). In tha t case we should no t expect localized lesions of thebrain outside the visual cortex to affect vision in the same way as lesionsof the visual cortex, but we might expect lesions of other parts to influencevisual reactions as, in fact, they do.

But the re is an oth er form of naivete" about the localization of con-sciousness which arises not unnaturally from the facts of anatomy andphysiology. The physiologist knows tha t sensory impulses initiated atthe retina, or at some particular segment of the body, cause electricalimpulses to be transmitted to an area of the cerebral cortex in whichthat particular part of the retina, or of the body, is said to be represented,and the clinician observes a similar correlation between destruction ofthese areas and the localization of the loss of function which results.But it does not follow that the arrival of sensory impulses at the corticalsensory area is all th at is required for them to enter consciousness. "Ifwe imagine the nervous pathways from the toe to the cortex completelyisolated from the rest of the nervous system, it is clear that they couldby themselves convey no localizing information, for how could electricalimpulses exactly like those going to all other cortical sensory areas meanth at som ething is hap pen ing to the toe ? This surely provides a clue to



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SOME REFLECTIONS ON BRAIN AND MIND 39 7the answer, which is that we can localize touch only by perceiving it inrelation to a representation of the body as a wholewhether in the formof unconscious schema or fully conscious image is unimportant for ourpresent purposeand this body-schema maps out, as it were in a set ofco-ordinates, all the possible voluntary actions which we should need totake in order to remove the stimulus either with the other foot or witheither hand or in any o ther way. . . . This process of localization oftouch is a cortical function, but if I am right in thinking that it relatesthe touch felt to the body-image as a whole, it must involve pathways farmore extensive than the primary sensory areas for touch in the cortex.When, therefore, the cortical area corresponding to one great toe isexcited by the arrival there of afferent impulses resulting from stimulationof the toe itself, such excitation must cause a widespread irradiation ofimpulses linking the toe area with the parieto-occipital areas which areconcerned with awareness of the body-image, not only in the samecerebral hemisphere but by way of the corpus callosum with the corres-ponding area on the op posite side of the brain " (B rain, 1950). This,no doubt, is what H ughlings Jackson (1931, 1, 350) meant when he said:"Just as any state of consciousness is a state of a whole person psychical,so the correlative activity is of nervous arrangements representing a wholeperson physical (the whole organism)."

To avoid possible misunderstanding I must add at this point that thestatement that "the brain acts largely as a whole," does not conflict withthe evidence for a high degree of specialization of function in certainareas. Apart from the special sensory and motor areas, and areasconcerned with speech, spatial awareness, etc., there is abundant evidencethat some regions, e.g. the ascending reticular formation, are particularlyconcerned with the function of consciousness as such, while other areas,e.g. the neocortex, are concerned primarily with its co nte nt: mo reover,the damaged brain may continue to function and provide consciousness,and a conten t for consciousness, in however limited a m ann er. Neve r-theless there is also evidence that large areas of the cortex show a responseto a single sensory stimulus (Jasper, Ricci and D oan e, 1960), as anticipatedby Lashley (1960), and may well play a part in memory storage, sothat in normal circumstances the nervous system does act largely asa whole.

T H E NATURE OF CONSCIOUSNESSKu be (1954) said: "Con sciousness of anyth ing implies and dep endson an ability to differentiate an T from a 'no n-I ' w orld. " This isfundamentally true, but it is only half the truth, the other half being thatconsciousness of anyth ing implies, and dep ends on, a fusion of thesubjective and the objective.2 6 BRAIN VOL. LXXXVI


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3 98 LORD BRArNConsider the essential elements in the simple experience of seeing atable . Neu rologica lly, in order that this may happ en it is necessary thatthe imag e of the table falh'ng upo n the retinas should arou se nerve im pulses

which eventually lead to changes in the neurons of the visual cortex.M uch mo re than that, of course, is required, but for our present purposewe can neglect the rest. F ro m one point of view all this is subjectiveit is happening in the brain of the subject, and, correspondingly, theconsciou s process of seeing a table is subjective: it is my seeing . Bu t it isalso objective, because it includes structural elements which it shareswith the table, and by means of which it conveys information about it.Without the preliminary fusion of the subjective and objective in con-sciousness there could be no differentiation of an "I" from a "non-JL"wo rld. In this process of differentiation consciousness m ay label, asobjective, sensory qualities, such as colours, which are solely products ofthe activity of the nervo us system. H ence the distinction between wh atis subjective and objective in experience may not correspond to thedistinction between events occurring outside the subject's body and thosetaking place in his nervous system.

Yet one fundam ental distinction between the " 1 " and the "non-1"worlds is determined by the bound ary of the hum an body . All actionin the external world requires and implies information as to the existingorientation of the body in relation to it, and of the parts of the body toone anoth er. Such information may be related to consciousness inthree ways. It may be perman ently uncon scious, as in the case, forexam ple, of afferent path ways to the cerebellum. It may be largelyunconscious, but potentially conscious, as we may use our legs in walkingwhile thinking about something eke, and yet can direct our attentionto the position of our feet and so become conscious of them . The thirdway is that by which the information contributes to a totality of whichwe are conscious, though we are not aware of its specific contribution,as our labyrinths contribute to our perception of our own posture, andou r awareness of the external world. We canno t normally detect thiscontribution, but, if it goes wrong and causes an attack of vertigo, orif both labyrinths are destroyed, we soon become aware of the importanceof the information which has been lost.

Bu t wha t of self-consciousness? W hat of ou r consciousness of thou ghts ,feelings and m em ories ? These com e and go. In so far as they are myown they are part of myself, but it may be argued there must be a selfwhich is in some way independent of particular thoughts, feelings andmemories, and that being conscious of those involves experiencing themin relation to this fundamental self. The analysis of consciousness by thedisentangling of these factors calls for much m ore psychophysiologicaland patholo gical obs erva tion; and the study of the effects of drugs


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SOME REFLECTIONS ON BRAIN AND MIND 3 9 9which alter perception, self-awareness, memory and the consciousnessof time may be especially fruitful.

CONCLUSIONSSeveral conclusions can be drawn from the facts we have just beenconside ring. (1) Fir st, neurologically, consciousness would seem to involvean interrelationship between the neural basis of the body-schema, and theperceptual organization by which the external world is represented.(2) Equally important are the processes by which experiences becomerecorded in mem ory, and the neural basis of the emotion s; and thou ghtand speech may also be involved to a variable extent. (3) The ever-changing content of consciousness means that the extent of the brainin action, particularly perhaps of the cerebral cortex, must be equally

variable. (4) If there are nod al areas, they mu st surely be diencephalic,since it is in the brain-stem and diencephalon that the neural bases ofattention, emotion and memory seem most closely related to one another.(5) But we have long kn ow n th at functions are not to be located exclusivelywhere lesions disturb them, and cortex and diencephalon need to beregarded "not as a hierarchy, but as an integrative unity, such as thatrepresented by the yin and yang of Taoism intertwined in their self-embracing circle" (Brain, 1958). (6) Finally, since consciousness takestime, we must surely picture it as a function of the sustained activity ofvast numbers of neurons extending over large areas of the brain.H ughlings Jackson (1931, 2, 85) said : " I take consciousness and mindto be synonym ous terms. . . . If all consciousness is lost mind is lost.Unconscious states of mind are sometimes spoken of, which seems tome to involve a contrad iction. Th at there may be activities of lowernervous arrangements of the highest centres which have no attendantpsychical states, and which yet lead to next activities of the very highestnervous arrangements of those centres whose activities have attendantpsychical states, I can easily un derstan d. But these prior activities arestates of the nervous system, not any sort of states of mind."What I set out to do was to show how much the process of perceptiondepends upon the activity of peripheral receptors and conducting path-ways. Qu otation s have shown that neurophysiologists working in thisfield find it difficult to describe their results without using psychologicalterms. As Gra nit (1955) says, "o n the whole . . . the distinction betweensensation and perception has lost its validity. . . . A sensation is anexceedingly com plex affair." We have seen, to o, how hard it is to drawthe line between conscious and unconscious factors even in perception,and we are familiar with our own dependence upon unconscious processesfor our comprehension and utterance of speech, and for thought.


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4 0 0 LORD BRAINJackson's definition of mind in terms of psychophysical parallelism ledhim to say tha t unconscio us mind is a contra diction. Sherrington (1940),an interactionist, was so impressed with the kind of facts I have beendescribing that he said that "there would seem to be a grade or gradesof mind which we do not experience, as well as the mind which is ourme ntal experien ce." These questions involve "th e logical analysisof the conve ntions of lang uag e," which I shall not now discuss. But thenew physiological facts we have been consideringand many otherssurely encourage us to use the terms mental and physical interrelatedly atprogressively lower levels of nervous function. I began by talking ab outthe contribution of periphera l sensory pathways to perc eptio n: let meend with a quotation which puts into a focus of relationship much ofwh at I have said. "I n th e genesis of visual perc eptio n," writes Sperry(1962), "problems of chemical coding are involved in the differentiation

of retinal specificity, the chemotactic guidance of the optic axons totheir central terminals, their selective synapsis with central neurons, andthe selective synapsis of these in turn with deeper elements of the system.The chemical tagging of the neurons for perception of directionality, forcolor discrimination, for brightness, and for the on-off and other physio-logical properties requires several dimensions of chemical specificitywithin a single neu ron. . . . It is quite possible that the chemical changesassociated with learning and memory in the mammalian cerebrumrepresent an evolvement, more or less direct, of these basic propertiesund erlying selective chem ical affinity." In these sentences Sperry showsus genetic information-coding preparing the way for perceptualinformation-coding, learning and memory, and suggests that they arepa rts of the same lan guage . The language Sperry is using is a physicalone, but he cannot describe what the physical changes are doing withoutusing the psychological terms, perception, learning and memory.

H ughlings Jackson was not an original philosopherhe took over aphilosophy ready-madebut we comm emorate him as physician, physiolo-gist and Dsvcholoeist. and surely we cannot do that better than bycontinuing to study those correlations between mental and bodily activitywhich he found so a bsorb ing. Only so, I believe, shall we reach abetter understanding of the nature of their relationship.

I am grateful to Professor R agnar G ranit and Drs . H ubel and W ieselfor permission to reproduce illustrations from their publications.



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SOME REFLECTIONS ON BRAIN AND MIND 401R E F E R E N C E S

ADAMS, R. D., COLLINS, G. H., and VICTOR, M. (1962) In "Physiologie de l'Hippo-campe ." Ed i t ions du Centre National de la Rech erche Scientifique. Paris,p . 273.BERGSON, H. (1912) "Essai sur les Donnees Immediates de la Conscience." 1 lth Edn.Paris , p. 9 1 .BRAIN, W. R. (1950) Brain, 73, 465.

(1958) Brain, 81 , 426.(1960) Brit. J. Phil. Sci., 11, 177.

CLAY, E. R. (1882) "The Alternative. A Study inPsychology." London, pp. 167-8.Council for In ternatio nal Organizations of Medical Sciences (1954) "Brain Mechanismsand Consciousness." A Symposium, Ed. by J. F. Delafresnaye, Oxford,1954.DENBIGH, K. G. (1953) Brit. J. Phil. Sci., 4, 183.DOBBS, H. A. C. (1951) Brit. J. Phil. Sci., 2, 122 and 177.GOODDY, W. (1958) Lancet, 1, 1139.

(1959) Lancet, 2,1155.GORDON, G. (1962) In "The Assessment of Pain in Man and Animals." Ed. by

C. A. Keele and R. Smith. Edinbu rgh and Lon don, p. 123.GRANIT, R. (1955) "R ecep tors and Sensory Perc eption ." New H aven and London"HEAD, H . (1920) "Studies inNeurology." London.HUBEL, D. H. (1959)/. Physiol., 147, 226.

(1963) /. opt. Soc. Amer., 53, 58.HUBEL, D. H ., and WIESEL, T. N. (1959) / . Physiol., 148, 574., (1960)/. Physiol., 154, 572., (1961) / . Physiol., 155, 385., (1962) / . Physiol., 160, 106., (1963) / . Physiol., 165, 559.

JACKSON, J. H . (1931) "Selected Writings ." Ed. by J. Taylor, London, vol. 1.JAMES, W. (1890) "The Principles of Psychology ." New York, vol. 1, p. 635.JASPER, H., RICCI, G., and DOANE, C. (1960). "Moscow Colloquium on Electro-encephalography of H igher Nervous Activity." Ed. by H. H. Jasper and

G. D. Smirnov, Electroenceph. clin. Neurophysiol. Suppt. 13, p. 137.KLUVER, H . (1962) In "M acromo lecular Specificity and Biological Memo ry." Ed. byF. O. Schmitt, Cambridge, Massachusetts, p. 94.KUBE, L. S. (1954) In "Brain Mechanisms and Consciousness." Ed. by J. F.Delafresnaye, Oxford, p. 444.LASHLEY, K. S. (1960) In "The Neuropsychology of Lashley ." Ed. by F. A. Beach,

D. O. H ebb, C. T. Morgan and H . W. Nissen. New York.LIBERMAN, A. M., DELATTRE, P., and COOPER, F. S. (1952) Am er. J. Psycho/., 65, 497.LOWENSTEIN, O., and SAND, A. (1940) / . Physiol., 99, 89.MATURANA, H. R., LETTVIN, J. Y., MCCULLOCH, W. S., and PITTS, W. H. (1960)/ . Gen. Physiol., 43, July Supp. p. 129.


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402 LORD BRAINMAYHEW, C. (1963) In " H allucinogenic Drugs and Their Psychotherapeutic Use ."Ed. by R. Crocket, R. A. Sandison and A. Walk. London, pp. 170-173.MELZACK, R., and W A L L , P. D. (1962) Brain, 85, 331.MOUNTCASTLE, V. B. (1957) /. Neurophysiol., 20, 408.RIDDOCH, G. (1917) Brain, 40, 15.RUSSELL, B. (1948) "H um an Know ledge: Its Scope and Limits." Londo n, p. 226.SALTZBERG, B. (1963) In "Information Storage and Neural Contro l." Ed. by W. S.Fields and W. Abbott. Springfield, Illinois, p . 5.SH ERRINGTON, C. S. (1940) "M an on H is Nature ." Cambridge, p. 306.SPERRY, R. W. (1962) In "Macromolecular Specificity and Biological Memory."Ed. by F. O. Schmitt. Cambridge, Massachusetts, p. 70.WELLS, M. J. (1960) /. exp. Biol., 37, 489.WH ITROW, G. J. (1961) "Th e Na tural Philosophy of Tim e." Lond on.YOUNG, J. Z. (1962) J. ment. Sci., 108, 119.



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Lord Brain Some Reflections on Mind & Brain 1963