Psychol Res (1987) 49:209-212 Psychological Research © Springer-Verlag 1987

Some thoughts on the psychophysical representation of memories*,** (1882)

Gustav Theodor Fechner

Translated and edited by Eckart Scheerer

Institut fiir Kognitionsforschung, Universitfit Oldenburg, Postfach 2503, D-2900 Oldenburg, Federal Republic of Germany

Summary. The paper presents an annotated translation of Section 21 of Gustav Theodor Fechner's Revision der Hauptpuncte der Psychophysik (1882). The section provides an interesting illustration of what Fechner meant by inner psychophysics. Memory depends on oscillations in nerve fibers and on more or less permanent changes in the confi- guration of oscillating corpuscles. Memories are not stored in individual ganglion cells, but in neural networks per- meating the entire grey matter of the cerebral hemispheres. Memory retrieval works by the resonance principle. Fech- ner's ideas anticipate some recent developments such as the holographic theory of memory and the principle of dis- tributed representation.

Sensations and perceptions depend on processes that are mediated by sensory stimuli in our nerves and come into the consciousness by entering the general system of psy- chophysical processes that carries our entire conscious- ness. Memories depend on the aftereffects that these pro- cesses leave behind in the brain. According to the present state of our knowledge of anatomy, I assume that every fiber that conducts a sensory excitation to the brain branches out in different directions from a central place in the brain occupied by a ganglion cell; and that it encoun- ters branches and sub-branches from other sensory nerves in a network-like tissue into which the ganglion cells are inserted in the form of nodes. I believe the occurrence of memories to be localized in this tissue which pervades, and in the main constitutes, the grey mass of the brain. In fact, these ideas should, in the most general way, correspond on the one hand to the present state of our knowledge of the structure and function of the brain, and on the other to the desire to make the mental processes whereby memories meet together to generate new, higher mental products ac- cessible to psychophysical representation.

* Translation of Section 21 (pp. 290-299) in: G. T. Fechner, Revi- sion der Hauptpunkte der Psyehophysik. Leipzig: Breitkopf & Hfirtel, 1882 ** Footnotes indicated in the text by superscript numbers are translated from Fechner's original German text; those indicated by superscript lowercase letters are the translator's comments

I conceive of the physical processes underlying the sen- sations and their aftereffects - memories - in the form of oscillatory processes. In the sensory nerves, before their arrival in the centers, these processes occur in a relatively simple way. However, in the tissue formed by the branches of the nerves they meet with oscillations stemming from other sensory nerves, and thus the memories carried by these oscillations gain influence over each other. In fact, the structure of neural fibers neither permits us to think of processes other than oscillations occurring in them, nor do processes of any other kind enable the psychophysical re- presentation of memory processes.

The functions of ganglion cells should probably be re- garded from several points of view. For one thing, physio- logical facts argue that the propagation of the oscillations is slowed down by them. Thus, the oscillations of the fi- bers, among which they are inserted, will not be able to fuse with each other as quickly as would be the case if this impediment were not present, and in this way they are in some sense kept separate. On the other hand, the oscilla- tions of the different fibers discharging into the same ganglion cell will intermingle with each other, during the delayed (though not blocked) passage through the cell, and so they will emerge from it in new combinations. Thus, the ganglion cells have a separating property from one point of view and a combining property from another; more- over, they prevent mental processes from taking place too quickly. Finally, the nutritive processes that occur in them may be the main source of the psychophysical energy, though as yet we do not have any sort of clear idea about this.

In my belief, man's total consciousness depends on the oscillatory complex of his entire psychophysical system, provided that it rises above the threshold in a coherent fashion. Contrary to the opinion of some others, I see no reason why the oscillations or chemical processes in the ganglion cells only should be involved; instead, they will have the functional significance mentioned above. Every oscillation belonging to the total complex, and every oscil- latory complex entering it, whether outside or inside the ganglion cells, will contribute something towards lifting consciousness in its entirety, towards reinforcing its lucidi- ty, towards codetermining its content. In order to produce a specifically distinguishable mental phenomenon not sim- ply merged into a general phenomenon or into the entire consciousness, the specific oscillatory process characteris- tically belonging to the phenomenon in question will have

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to be greater in a certain ratio over the other oscillations accompanying it, according to the principle of the mixture threshold?

We must now ask how the long-term storage of memo- ries, or rather their long-term capacity for reproduction and their relative lack of mutual interference, may be giv- en psychophysical representation.

In itself, it is not remarkable that the oscillations pro- voked by a sensory stimulus are able to persist for a certain time in the memory fibers (to use this shorthand expres- sion) irradiating from the ganglion cells; and because of their dispersion and intermingling with oscillations com- ing from elsewhere it is easy to comprehend that they soon fall below the threshold of distinctiveness, without being immediately lost when they no longer can be distin- guished. But eventually they are bound to find their way out of the brain, l after the many combinations and per- haps reflections they incur during their propagat ion through the brain. Thus, the long-term storage and capaci- ty for reproduction of memories cannot depend on their short-term persistence in the brain; instead, it will have to be assumed that oscillatory processes once provoked in the ganglion cells and memory fibers leave behind them a more or less permanent structure facilitating the re-evoca- tion of the same oscillatory pattern - an approach which is not new and is shared by anyone at all who conceives memories to be psychophysically mediated. Nevertheless, this general thought may be elaborated in different ways, and so I continue.

First of all, some illustration may be found in the fol- lowing analogy. Within certain limits, a footpath becomes more viable the more frequently it is used. Not only do we let thoughts "run", "meet each other", etc. within our- selves; what is more, as I have been told, in Sanscrit the word "thinking" is derived from a root meaning "walk- ing". Now, in the fibers of the brain innumerable foot- paths for the psychophysical process b of representation and thought are already traced out in advance, and these form the basis of certain mental gifts. There is nothing to prevent whole complexes of these paths from becoming more viable than others through frequent use. What is more, the soft structure of the brain and the unspeakable delicacy of the fibers make for the possibility that in the course of life new connections are formed concurrently with the development of mind.

Not to rest content with a mere analogy, we increase the credibility of the existence of a principle such as that assumed here for the reproduction of oscillations in the material world by remembering that the resonance boards

a See translator's footnote d in Fechner (1987) for an explanation of what is meant by the mixture threshold (Mischungsschwelle) 1 They may also seem to vanish through friction. But this type of vanishing only means transformation into caloric oscillations. And because caloric oscillations, like light oscillations, have dif- ferent periods, I could not say why the periods of caloric oscilla- tions should not depend upon the periods of those oscillations that are transformed into them. Undoubtedly, however, the oscil- lations are dispersed in this type of conversion, and thus contri- bute to lifting the total consciousness - a frozen brain would be a dead brain - but then their contribution is only an indeterminate one b Actually, Fechner here uses the expression "Gang derpsychophy- sischen Reprdsentation', which takes up the metaphor of walking but resists literal translation

o f musical instruments become more able to reproduce their tones when they are frequently played upon. All we have to assume is that in the very pliable psychophysical system the principle will be infinitely more complex than that in solid resonance systems. In general, we shall have to assume that the various modes of oscillation with which various sensations and their memories are connected are associated with various configurations of corpuscles and of their oscillation centers (see below). Thus, if a sensory stimulus is removed, and if the memory vanishes because its psychophysical process falls below the threshold, what more or less survives is the configuration o f corpuscles adequate for it and elicited by it. Thus, the return of a sen- sation or memory of the same kind is facilitated and the evocation of different ones is rendered more difficult in the same fiber tracts, because the new excitation finds a ready-made structure adequate for certain sensations and memories. For the sensations mediated by specific sensory nerves, this can only have the effect that through training the nerve attains an ever-more suitable functioning state for the kind of sensation associated with it. But for the longer, branching fiber tracts whose oscillations subserve memories, the effect may be that while all of them were ini- tially equally fit to receive oscillations of different kinds, those that were frequently put into certain kinds of oscil- lation will settle more and more into configurations of corpuscles adequate for these kinds of oscillation.

From these premises it is easy to understand, first of all, why we do not retain memories, or distinct memories, of our first years of childhood; while in old age we retain very distinct memories of certain events in later childhood, but at the same time more recent events easily escape our memory. In the early years of life the more or less stable structures underlying the capacity for reproduction of memories have to be formed in the first place by repeated experiences in certain directions. In later years repeated experiences and the general influence of old age decrea- sing the mobility of corpuscles render the structures so stable that they are no longer adaptable to new modifica- tion.

The slow formation of structures and structural com- plexes which grow increasingly stable will be accompanied by their slow differentiation for various memories and memory complexes. As long as the structure of the fiber tracts has not become totally stable - and it will never be- come totally stable in life - the fiber tracts will have to suf- fer modifications continuously in the configuration of cor- puscles and in the oscillation modes associated with them; but to the extent that a certain structure is already estab- lished in certain memory fibers and their complexes, os- cillations of a different kind will find it easier to propagate through other branches of fibers and to establish them as their own. By means of this spatial dispersion of the struc- tures, combined with their differentiation for various memories and memory complexes, not only the occur- rence and repetition of memories of various kinds, but al- so their lack of mutual interference will be facilitated. And here I see a key viewpoint for the psychophysical mech- anism of memory.

In fact, our approach makes it easy to understand why the size of the brain and specifically that of its grey matter is so important for mental development. To be sure, given certain structures of the psychophysical system, the same fibers and cells may serve different memory complexes

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within certain limits, because the latter share, within cer- tain limits, common elements of memory, and because the different sequence and direction alone in which the memo- ry fibers are excited may cause a difference in memories even when the structure remains constant, and finally be- cause there is always the possibility of a certain structural modification of the same fiber. But all this can apply only within certain limits, and a richly developed memory sys- tem also needs a corresponding wealth of resources in a multitude of coexisting structures. Man, who is undoub- tedly able to store more memories than any other animal, accordingly also possesses more grey matter - the only place where the complex of memory tissue is to be found.

True, within certain limits there are very intelligent an- imals that have a very small brain, such as ants. But they will indeed have exceedingly few memories and these only with respect to a very circumscribed sphere of their life; and they may be structured from the beginning in such a way that they respond, both mentally and physically, with- in certain limits of purposiveness, but without any memo- ry, to external excitations not exceeding their customary life sphere. Likewise, animals in general will differ from man in this, that they are given structures in advance for their limited purposes, while man has to acquire the struc- tures in question; and consequently man has the faculty to adapt himself to more diverse purposes than animals.

These direct considerations may be assisted by mani- fold comparisons and analogies, which are interesting in that they show that the circumstances postulated for the psychophysical system are valid beyond it. What is more, one might even show (though this is not my present busi- ness) that they gain their full significance only through the mediation of corresponding circumstances in the psy- chophsical system.

In written communications, when it is important to save space, such as in letters with high postage rates, we tend to write both horizontally and vertically, sometimes even diagonally, all mixed together, and the letter is still readable if one follows the lines in different directions; and I think that the same principle may be developed to a much higher degree in brain writing, c where attention takes the place of the reader. But in letters the principle of sav- ing space in this way does not work beyond certain limits, and where there is a lot to write one starts a new page. The same my be true for brain writing.

On a harp, one can play any tune with one chord only, if the chord is tuned afresh for every new tone. But it is infinitely more practical to have many chords arranged in parallel, and to tune them for different tones. Harmony cannot be attained with a single chord; the more different- ly tuned chords, the richer and more elaborate the har- mony. Too many chords, however, would render the in- strument too unwieldy and too difficult to handle; thus, one stays within certain limits. Because of the teleology that reigns elsewhere in the organic world one may assume that it has attained a purposeful balance in this respect as well.

"Brain writing" here does not refer to "internal writing", but is an instance of Fechner's predilection for considering the relation- ship between brain and mind in terms of two language systems. It also belongs to the sphere of metaphors which later led to the term "engram" (literally: what is written in) for the neural representa- tion of memory

But let us return to more direct considerations. Notwithstanding all that has been said so far, we

should not forget that the capacity of memories to be stored, and their lack of mutual interference despite their number and the multitude o f their crossings, though it may appear admirable to us, nevertheless has its obvious limita- tions, and that even for these limited achievements an im- mensely complicated apparatus had to be developed, which if damaged will cause disturbances o f memory - a very interesting topic which would take us too far in the present context and also one which I have not sufficiently studied. Of the innumerable events occurring during our lifetime, and of all the thoughts we have had in our life, we can remember only a relatively small part, and we remem- ber it only under limited conditions and with limited dis- tinctiveness. Basically, and in general, we forget most of the specifics in life. Who can remember every path he has trodden on a particular day, every casual word he has spo- ken or heard; while he will remember the path as such, when he has trodden it frequently or when something re- markable has happened on it; or he will remember those words that he has used or heard so often, or a remarkable speech which has struck him strongly - because with re- spect to such memories the influences facilitating potential reproduction compound one another or are especially strong. Thus we can only be astonished that, given so many things forgotten, nevertheless the possibility of so many memories remains; and on the other hand we should won- der why our brain is so immensely complicated if it did not serve for very complicated achievements. Yet the principles underlying these complicated achievements may be very simple.

As long as man lives, all his brain fibers and ganglion cells are undoubtedly oscillating. The oscillations are con- tinuously maintained by the life process or are newly re- produced to the extent that previous oscillations distribute themselves across the brain - there are no completely inac- tive atoms in nature. Under the influence o f the structures left behind by the previous oscillations the newly pro- duced oscillations automatically take the form of the pre- vious ones. This entire "postlude" of memories remains unconscious insofar as it does not rise above a certain threshold; but if it does rise, it is always a repetition of the oscillatory mode caused by the structures left over by pre- vious oscillations, unless new occasions for modification occur, and so it may happen that when people who lack any incentive towards furthering their internal develop- ment remain within the customary periodic change of their external life conditions, memories of the same kind will circulate in their brains, all new excitations rediscovering the structures adequate for previous excitations and leav- ing them for reproduction in memory. On the other hand, the existing structures may also be progressively modified, either from within the feeling of spontaneous inner activity, or from outside by essentially new conditions of life; and thus a person's mental development can continue.

Considering all that has been said, an unsurmountable difficulty (and a certain difficulty is indeed to be found here) may seem to lie in the fact that occasionally, but only in peculiar circumstances, totally obsolete memories may re-emerge quite distinctly. Especially with dying people and under somnambulic d conditions, but also in ordinary

d "Somnambulism" here is an antiquated synonym for hypnosis

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dreams, according to dependab le evidence cases of this sort do indeed happen ; which has led to the opinion, not unfrequent ly voiced, that basical ly the potent ia l i ty for remember ing anything we have exper ienced is never lost, except that this potent ia l i ty may be actual ized for memo- ries that seem total ly lost only in certain specific and insuf- ficiently known circumstances.

Meanwhile , as far as psychophysics is concerned, all we have here is that we do not sufficiently know the rele- vant condit ions, while we are quite able to indicate some general points of view. First of all, we must concede that the possibi l i ty of reproduct ion is lost when nothing re- mains in the psychophysical appara tus of the structure be- longing to the reproduct ion in question, either because it has been t ransformed into other structures or because it has been included in more complex structures; and one or the other seems necessari ly to be the case for memories over which a long life, with its a t tendant repeated rework- ings of the entire psychophysica l appara tus , has elapsed. But throughout a person 's l ifetime there will always be the possibi l i ty that the new structures that have emerged in a certain sequence from the earl ier ones will lead back to earl ier structures, following the thread of the same se- quence that is now spinning off in the reverse direction.

Analogously, one may return from the final poin t of a talk that has been read forwards to some earl ier words or letters in it by fol lowing the letters or words in the reverse direction. Or we can also imagine that the complex struc- tures into which the earlier ones have been inc luded or in which they have been sublated, e as it were, are decom- posed and thus set free an earl ier structure which for a long t ime has been " impr isoned" or lost in them. Take the fol- lowing analogical case. Let us assume that we dist inctly hear the tone of some musical instrument and then other, louder instruments are int roduced. The tone of the first in- s t rument will then submerge and become indis t inguishable in the musical structure formed by the combina t ion of all these instruments. But if the other instruments are remov- ed, even after an arbi trar i ly long time, the tone of the first instrument will emerge as dist inctly as in the begin- ning. Now, it cannot be asserted a priori that circumstances o f this k ind will never obtain; though up to now we cannot tell how this may happen.

In presupposing f that not only oscil lat ions, but also structures fit for oscil lat ions may combine and decom- pose, I operate from the fol lowing conception.

General ly speaking, every corpuscle undergoes a more Complex or compl ica ted osci l lat ion when more corpuscles codetermine its osci l lat ion from elsewhere, or when the other corpuscles form more diverse configurat ions. 2 For groups of corpuscles relat ively near each other the codeter- minat ion caused by very distant corpuscles may be ne-

e "Sublated" (aufgehoben) is a technical term of Hegel's dialectics conveying the idea of being annihilated (on a lower level; here: the earlier memory structures) by being preserved (on a higher le- vel; here: the present memory structures) fThe next two paragraphs are printed in small type in the original, but they are of sufficient importance to warrant inclusion in the translation 2 Undoubtedly, the circumstances of arrangement and motion in this respect are more complicated in the organic realm than in the unorganic. In my book Some Thoughts on the Creation and Evolu- tion History of Organisms (1873) I have developed a hypothesis on this

glected. Fol lowing a wel l -known mathemat ica l pr inciple , the entire combina t ion of osci l lat ions arising from this for a given corpuscle can be b roken down into s imple oscilla- t ions with general ly different ampli tudes , per iods, and os- ci l la tory centers. In itself, the combina t ion of the oscil lato- ry centers presents a structure which belongs to the com- pl icated osci l la tory mode of every single corpuscle. This is connected, in coherent interact ion, with a pert inent , com- pl icated structure of the other corpuscles, whereby the first corpuscle is de te rmined in its own osci l latory mode, and to whose osci l latory mode it contr ibutes in turn. This re- sults in a more compl ica ted structure for the entire group of corpuscles which interact with each other to a notice- able degree. Now, if a corpuscle splits away from a group in order to direct itself towards other, more distant ones, or if a whole group splits off, then we have the case of the decompos i t ion of a complex structure leading to the de- composi t ion of the complex osci l lat ion belonging to it. Vice versa, we may unders tand the entry of s imple struc- tures and oscil lat ions into more complex ones by the addi- t ion of corpuscles from other groups or by the fusion of groups. Supposedly , this is the real state of affairs rather than a more analogy. Nevertheless, the example given above, of the musical instruments, may still serve as an il- lustrat ion for this state of affairs. Hence we might develop ideas concerning the impor tance of an active metabol i sm in the bra in for the activity of mental funct ions; and in general I bel ieve the approach taken in the present discus- sion to be very fruitful, but at present not capable of being

p u r s u e d to certain conclusions. All in all, I do not bel ieve that the preceding discus-

sions have exhausted the topic or cleared up all its obscuri- ties. For further e labora t ion of the topic, we shall have to relate the viewpoints developed above to those that have been developed on the subject of at tention in Section 19, g inasmuch as at tention may remove memory phenomena from consciousness or raise them into consciousness by disengaging itself from, or engaging itself with them; and because memories will be impr in ted more easily and more strongly when the objects to be remembered are observed more attentively. Fur thermore , it will be necessary to f ind the psychophysica l representa t ion of associative processes, which play such a great role in memory. While it is easy to indicate the general v iewpoint under which the latter are to be considered, it is not so easy to resolve the complexi- ties which entangle us when we try to e labora te our view- poin t in detail.

References

Fechner, G. T. (1873). Einige Ideen zur Sch6pfungs- und Entwick- lungsgeschiehte der Organismen. Leipzig: Breitkopf & H~irtel.

Fechner, G. T. (1882). Revision der Hauptpuncte der Psychophysik. Leipzig: Breitkopf & H~irtel.

Fechner, G.T. (1987). My own viewpoint on mental measure- ment. Psychological Research, 49, 213-219.

g"Section 19" refers to the book (Fechner, 1882) from which the present section is taken. Fechner conceives of attention as a kind of gain control entering into a multiplicative relation with the ba- sic psychophysical process