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Dear

As a result of our discussions on 21 August 1973, I am proposing a three phase program designed to:

(1) Establish the effectiveness of electric fish in detecting foreign objects at a distance;

(2) Determine the methods used by electric fish for ranging and location; and

(3) Design equipment systems suitable for replacing electric fish in terms of targeting foreign objects.

I am enclosing a summary of this program. Phase I of the program deseribed herein will correspond to "Phase II" of the program described however the tasks have been modified somewhat to better serve the needs of the program. The remainder of the present contract will be used to assess necessary parameters of the electroreceptors system in Gymnarchus and Gnathonemus. Both of these fishes would be used in the Phase I and Phase Il of the program recommended above.

I am also enclosing a more detailed description of the experiments to be performed in Phase I of the proposed program and an example of the type of experiments that are appropriate in Phase I. Details on Phase  would depend strongly on the results of the Phase I investigation. I hope that this proposal meets with your approval. Please let me know if you can recommend any added experiments or studies which would aid in the development of a prototype hardware system.

With best wishes,

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A PROPOSED THREE PHASE PROGRAM TO DEFINE HARDWARE ANALOGUES OF ELECTRIC FISH SENSOR SYSTEM

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PHASE I

ESTIMA TING THE EFFECTIVENESS OF ELECTRIC FISH IN DETECTING FOREIGN OBJECTS AT A DISTANCE

Perform psychophysiological experiments using different kinds of electric fish in restricted water so as to estimate their ability to identify the existence of foreign objects in this water taking into account electrical discontinuities imposed by the boundaries of that water and the foreign objects placed within it. Specifically, consider the fish as a signal generator and receptor and the use of auxiliary signals which replicate the fish's signals and other signals of specific interest. Compute the expected behavior of such fish in open ocean or fresh waters given typical boundary conditions with respect to depth, topology, inhomogeneity of the water, temperature, and other applicable parameters. Summarize these findings in terms of the ability of these fish to identify foreign objects in a harbor or other natural body of water of interest... foreign objects such as small submarines, torpedoes, scuba divers, skin divers, mines, and others.

More explicitly, determine the sensory capability of individual electric fish in terms of their ability to sense the existence of foreign objects as a function of range, fundamental area, volumetric displacement, differential discontinuity, and so forth. In this regard, use a tank of water at measured temperature and electrolytic conditionts. Retain a fish near one point and insert in the water various objects, discerning the different behavior of the fish as these objects are inserted by concurrently monitoring the electrical field within the water. Specific levels of background noise will be introduced by using a noise generator and measuring the noise amplitude in the tank. Experiments will be performed under normal and extreme noise conditions. From these results,

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calculate the estimated behavior of such a fish in detecting an object in an infinite water domain and large scale waters with various boundary conditions.

PHASE II

DETERMINING THE METHODS USED BY ELECTRIC FISH FOR RANGING AND LOCATION

Perform detailed experiments wherein the particular characteristics of electric fish are related to their abilities with respect to ranging and location. Particular attention will be focused upon the use of phased arrays of receptors, the fish's ability to determine incremental time lags in the signal, the estimated spectral properties of the signal, the fish's ability to modify the transmitted signal as a reflection of knowledge gained from previous receptions, and so forth. Interpret these findings in terms of specific schematics and data analysis required to synthesize models of the fish's capability, models which when reified would provide signal advantage over the state of the art with respect to such a target as described above.

PHASE III

DESIGN OF EQUIPMENT SYSTEMS SUITABLE FOR REPLICATING ELECTRIC FISH IN TERMS OF TARGETING FOREIGN OBJECTS

Design, fabricate and test experimental apparatus suitable for replicating the above-referenced models. Perform experiments with this apparatus so as to improve its ability in various regards. Make a specific comparison of this capability to that of an electric fish and estimate the utility of such an apparatus in terms of operational situations.

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COST ESTIMATE

PHASE I- \$6 months

PHASE  - \$ 1 year

PHASE III - \$ 1 year

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I. WIIAT WE IAVE LEARNED FROM INVESTIGATION OF ELECTRK FISHES AND QUESTIONS WIIICII STILL REMAIN

Electric fishes have specialized electric organs: (1) transmitting organs which transmit eloctric siguals modulated and coded in specific ways and (2) receiving organs (electroreccptors) which are part of the lateralis system and detect either (á) discontinuities in the electric field generated by the transritäing organs when the fishes use an active detecting system; (b) changes in the electric field generated by the authorhythmic electroreceptor when the fishes use a passive detecting system and (c) electrical signals emitted by fishes of the same species or of other species, even nonelectric fish which still produce an electric field resulting from their muscular activi during swimming. All this means that electric fishes can navigate, detect, locate and identify living or nonorganic matter and can communicate underwater by means of electric signals and/or electromagnetic detection. The electric power involved is very small. Some of the electric fishes have built-in a jamming avoidance system. Most of them can extract a signal fro: a noise that is significantly higher than the signal itself.

and from the data we have from other scientists work, we concluded that unique methods of detection and communication are peculiar to some electric fishes, which could significantly improve our technology if properly applied.

In the appendices to this chapter I summarized the results of the research I have done so far on electric fishes.

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SUMARY OF WORX ACCOMPLISRED

1. Ono hundred thirty-six fresh water and marine eleetric fishes were classified; 82 fresh water fishes and 54 marine clectric fishes. Wa collected and correlated data scattered through magazines and the fow books having some chapters on electric fishes and data from our own exporiments. We Histod the loontions of specific fishes and prepared maps showing thoir habitats.

2. Some tropical diseasos of the clectric fishes were studied. We found a cure for tha ulcor-like skin disease of Electrophorus (publ. Nature, January 1964) (a cancer-type of skin disease).

S. The anatomy of the electric organs of Electrophorus, Malapterurus, Steatorecys, Sternarchus, and Cymnotus carapo was studied.

4. Histological preparations wore made of the eleotric organs (Hematoxylin-Eosin staining) and of the electroreceptors in the skia of Electrophorus (Dlsisckovsky-Gross siver ispregnetos with Cajal cousterstalaing). Photomiorographs were takon with a Nikon phase-interference microscope.

5. The type of encoding and moduiation of the electric signals emitted by sisotric fshes were studied and classified. (Elcctrophorus electricus, Ccts carapo, Sternarchus albifrons, Eigenmannia troscheli, Crsthonemus petersii, Gnathonemus curvirostris, Gymnarchus niloticus and Maiapterurus electricus.) "Informaticn Processing by Eiectric Fishes published in the Proceecings oi the i964 Rochester Conferezce on Data Acquisiton and Processing in Biology and Medicine, K. Ensiein editor, Pergamon Press, 1965.

S. Behavior experiments were performed with Sternarchus albifrons, Elactrophorus electricus, and Gymnarchus niloticus.

7. Proof was brought about the communication ability of electric fishes. Their sensitivity to electric and magnetic stimuli was checked.

8. Exact measurements were made of their discharge; and curves were traced for the Electrophorus establishing the voltage, peak power, and average power of its discharge. Curves were traced also for voltage against length of fishes and against weight of fishes.

9. Experimerts were performed, and the effect of de currents on the electric signals cf elcctric fishes has been established for Electrophorus, Sternarchus, Gymnarchus, Gnathonomus, and Malapterarus.

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10. The effeet of changes in temporature of the tail: water on the frequeacy and amplitude of the signals emitted by the eleetric fishes was investigated and curves traced for temperatures from 18°C to 28\*c.

i1. The efect of anticholinccsterase on the brain of Sternarchus was investigated. The change in its behavior and frecueney and amplitude of the signal emitted by the fish were studied. The acclimation effect at low (20°C) and high (S0°C) temperatures of the tank water on Sternarchus albifrons was studied. Comparison with the anticholineesterase is made. (Paper presented at the AAAS meeting, University of California in Berkoley; coauthor with Dr. M. Baslow, University of Hawaii. Only the expariments conducted in our laboratory are mentioned here. Dr. M. Bislow ccnducted other experiments on Kilyish and other fish at the University of Hawaii, his resuits are presented as first part of the paper. AAAS paper presented 28 December 1985.)

12. A hypothesis about the way electroreceptors of the electric fishes work was advanced, and experimests were devised to prove the hypothesis.

13. Experiments with moving eleetrostatic and magnetic fields were ccncucted. We cemonstrated thet Gymnarchus niloticus is sensitive to a potentici gradient of about 0.03 pv/em, ané Sternarchus albifrons is only half as sensitive.

14. Aiteraative explanations of some previous experiments were given in terras of this high dc sensitivity.

15. An explanation in similar terms was given of experiments in which Gymnarchus niloticus and Sternarchus albifrons were trained to detset a stationary magnet.

16. The mechanisms available for the location oi objects by electric fish . are reviewed.: It is concluded from the results of a critical experiment that Gymnarchus niloticus can detect objects by the disturbance of its owa eiectric Neid in the water.

17. Lissman's Cerivation of the approximate theory of this method of cbject location is shown. The effect of the receptors of the perturbing field due to an cbject depends on the electrical properties of the receptors. In . exireme cases, the stimulation of the receptors is proportional cither to the potential or to its second derivative. Graphs are given showing. the effect of an object on the potential and on its second derivative around the surface of the fish.

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18. Experiments are described using Gymnarchus niloticus which (a) confirm that the mechanism of object location employs the detection of the distortion of the electric field produced by discontinuities in this field, and (b) indicate the limits of the sensitivity of the fish.

19. The detection of the second derivative mode of its own emitted signals appears to be the most probable one operating in Gymnarchus. The experimentally determined limits of detection are discussed in relation to the random noise in the receptors circuit. It is concluded that both spatial and temporal integration are likely to be employed.

20. The thresholds for object location and for response to direet currents are compared. It is conciuded that the same receptors are probably oporating in both cases.

21. Exveriments were devised to find the attenuation and distortion of signals similar to the ones emitted by electric fishes in underwater wanamission. i is cloariy proved tha: sigaais are distorted and their shase is close to the derivative oi the original signal. In case we can dovise a receptor system that csn inegrats the second cerivative of the originai signal an improvement of signal-to-noise ratio to abou: 10:i is to bo expected. Experiments with electromagnetic felds, pure magnetic fields, electric integrators, and magnetic receivers are uncerwiy. The resuits of those experimeats may bring us to the recommendation of an absolute new underwater transmitting-receiving system.

23. The electric organs of Sternarchus albifrons, a South American fresh water weak electric fish, have been studied with emphasis on electroreceptors. The morphological and physiological characteristics of electroreceptors, ampullary and tuberous, were investigated. Special instrumentation required for establishing the role of these electroreceptors in object location, detection and identification has been developed.

24. We have recorded with microelectrodes the autonomous autorhythmic electrical activity of the tonic asynchronous ampullary electroreceptors of the South American weak fresh water electric fish, Sternarchus albifrons. We have also recorded the electrical activity from the asynchronous phasic tuberous electroreceptors and of the synchronous and asynchronous ampullary electroreceptors of the same electric fish, Sternarchus albifrons. Preliminary measurements have been made. The autorhythmic activity of the ampullary electroreceptors has been demonstrated.

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The electroreceptors are part of the complex lateralis line system of the electric fishes.

25. The other lateralis line system sensory receptors, like mechanical receptors and displacement receptors, have been discussed as part of a general hybrid object detection, location and identification and recognition system of the fish.

26. A study of the anesthetizing effect of tricaine-methanesulfonate (MS222= FINQUEL) on Sternarchus albifrons has been undertaken by plotting time for the anesthesia and recovery for different specimens. The anaesthetic does effect the pulse-rate and pulse-shape of the discharge of this fish. Anaesthetic other than "Finquel" which does not affect the electric fish's electric organ pulse repetition rate has been found. Also, the effect of D-tubocurarine and the counter-effect of neostigmine has been assessed for Sternarchus albifrons. Finally, some improvements in the microelectrode recording instrumentation have been made.

27. We obtained some specimens of the African weak fresh water electric fish Gymnarchus niloticus. They are supposed to be the most sensitive of all the weak electric fishes known. Together with two specimens about one foot long, we received a number of baby Gymnarchus niloticus about two inches long. The baby electric fish were iniected with a Saprolegnia fungus and could not be saved, but we fixed a number of them in buffered formaldehyde and one of them has been cut and mounted in paraffin for histological studies of the electric organs. Preliminary measurements have been made on the communication capability of adult Gymnarchus niloticus.

28. The electric discharge of Malapterurus electricus, an African fresh water strong electric fish, has been measured in and out of water. Its electric organ can discharge bursts of impulses of 100 to 350 volts and currents to about 40 mA. In general they can put an electric power of about 1000 watts per kilogram of electric tissue (1 watt electric power per gram of electric tissue). From our investigation, it can be concluded that electric fishes could use their electric organs (transmitting and receiving) for navigation and communication -in other words, underwater object detection, lccation and identification using an electromagnetic system of detection.

30. The physical analogs of tonic and phasic electroreceptors have been established. Both are represented by a generator connected to resistances and capacitances in series and in parallel. The difference

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between tonic and phasic clectroroceptors is that the first ones have one resistance in series with thc generator whereas the phasic electroreceptors have a capacitance. The tonic electroreceptors seem to be predominant, maybe like five-to-one, compared to the phasic electroreccptors. The electrorcceptors seem to act, to a certain extent, independently of the main electric transmitting organ; at least two out of three different types of electroreceptors are asynchronous and only one type of electroreceptor will synchronize with the main electric organ. It has been found that the complete denervation of the transmitting electric organ does not stop the activity of the asynchronous electroreceptors (both phasic and tonic). The fish is still capable of responding to conductive and nonconductive objects placed near the fish's body. It may affect the total capability in determining certain movements or impair, to a certain extent, its sensitivity in object recognition. Some of the synchronous tonic units are connected to one and the same nerve trunk part of the acoustico-lateralis system but connected to specialized big nuclei in the brain.

The most striking fact about fresh water weak electric fish, besides their spontaneous electric organ, is that all of them are provided with a highly developed lateralis line system. Related to this acousticolateralis system is an enlargement of the cerebellum, especially in Gymnarchus niloticus and in mormyrids. The unusual importance of the lateralis system in these fish, compared with other teleosts, is not due to an increase number of "ordinary" lateral line sensory organs, but rather to the existence of a great number of specialized sensory organs within this same system. This is supporting our hypothesis about a hybrid complex underwater object detection, location and identification system used by electric fishes in recognition of prey, predators, and navigation in general. It is recommended that the other lateralis line systems from different fresh water weak electric fishes should be studied with the aim to find out their role in object detection and navigation.

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II. CONDITIONING TECHNIQUES APPLICABLE TO THE ELECTRIC RESPONSE AND BEHAVIOR OF SELECTED ELECTRIC FISHES

Summary

A study described in this section is designed to identify the type of conditioning techniques (operant or respondent) applicable to the electric responses of selected electric fishes, with particular attention to those procedures which can be used to assess the "dynamic range"of the response with respect to major electrical parameters. Several additional behavioral studies of electric fishes are also described in some detail.

Introduction

It was mentioned in previous sections of this report that certain fish possess organs capable of generating electrical discharges; and, at least some of these, have electric receptors that are capable of detecting and discriminating among different patterns of discharge. This study is focused on determining the extent to which the electrical responses of selected specie can be brought under the control of respondent (classical, Pavlovian) and/or operant (instrumental, Thorndikian) conditioning techniques. (Skinner, 1 and Keller and Schoenfeld.)2 The results will then be examined to determine whether or not significant relationships exist between the type of conditioning operations which are applicable to a particular response and physiological data concerning the structure of the organ, the type of tissue from which it was probabiy derived, the type of neural innervation and control evidenced, its electrical characteristics, and its functioning.

These questions are of considerable interest in behavior science. Viewed as operational definitions (Feigl³ and Frank4) the two sets of conditioning operations subsumed respectively by the labels, "operant conditioning" and "respondent conditioning", are clearly different. The controversy ii the literature of the last decade or so concerning the kinds of learning which . exist has not usually been at the level of experimental procedures and results (i.e., of operational definitions) here assumed. Instead it has concerned such questions as the possibility of reducing both types of conditioning to a common, usually unobservable, intervening or mediating process; with the nature of the postulated process; or, with the type of theoretical formulation (Estes, Koch, et. al.)5 considered most promising by the particular

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o: had as his pose
W 3 Behavior, ation of the two types of 8 9 process irem and suggests follow from Es:es10 of stochast
modeis as a means desired on. Toiman, 13 15° emshasize 14 CC woy,ccsses as ons the level of operationa ras and resulis. This is : does his work.

1: tory. 2wo 2lmoa: exelusive classes of respenses can be defined, corresponding to set ci cond tons which is effoctive. That is to most responses are found to be conditionable by either respondent cr s boes further observed that responses which can be conditioned respondently typically involve autoaomically smooth muscles; whiie thcse accessible to operant procedures siways empicy striped muscles under central nervous system conirol.

The empirical relationships between the two types of conditioning procedures are quite complex. Smooth muscle ("emotional") responses are oftsa condiioned respondently in the course,or an operant conditioning program. Snere also oxists a small rumber of striped musele responses which may be aleitei respondonly by noxious stimuli (e.g., shock-leg fiexion) and which sre reirsoreed cporartly by the terminaticn of, or escape from, the noxicus stimuiatica (Skianar).1 Although the responses--fe this case, leg-flexion eloited by shock and leg-fiexion as operantly reinforced--are superficially the same, they are best regarded as two different responses with similar topography.

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Pavlovian) musclc responses and

3 re 16 17 albifrons is nervous tissue. e3 a5 Co 16). does 2 he eé 18).

i viev cf à taally the type of éor tch can be used to "ccaurol : rosponses oi several species, caraiully selected on the basis of krown structure (and availability) and to relate these findings to the relevant anatomical information.

Siace it would not be feasible to inolude in the investigation every con-Citiosiaz operation in each oi the two sets, emphasis should be placed on toso orccacures which can be used to assess the "dynamic range" of the respcase ta each case. This wil irvolve datermining, not only the moan aad cistribution, but also the maximum and minimum vaiues of major response parameters, both in the iree state and under anainable forms and degrees of enviroamental and behavioral control. Data obtained in this way can also be oorrolcted with iaformstion cbout the strueture and functioning of the pospective electrie crgans. The data will also be ralevant to the study of receptor procssses.

I is important to study the types of conditioning techniques which are cppliccble to the electric responses of selccted eloetric fishes, with some emphasis or those procedures which car be used to assess the "dynamic rarge" of the response in each case. Possible relationships between the type of conditicning operations found applicablo and the type of nouromuscular

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1 Nscussed betweon the two lasses and the two major subdivisions rot an version 1 is rather the SCLS (which are pert bahavior and a set co∴c o: behavior Data the De the knowa or readil ascertainable facts

Behavioral Research

he behavioral research should be executed in two S :e st C esうonse.

Detcwalasston of the Sind and Desree of Behavtoral Costso. which Is Attainable Co:pio Hoa7oraes cf Selootod Stesies.

Chis stage will iavolve answering the following closely related questions for cach species aad each respoase:

Doss tho cleatricai response oecur as a pafax to a discoverable end definable class of unconditioned stimuli?

Can the response be conditioned using respondent (classical, Paviovi\_n; procedures?

Can tho response be conditioned usiag operant (instrumental, Thorndikian) tochnicues?

The procadures employed to answer these questions will inelude the. folowing:

". Srsdy saoh "elaetnie resnonsa" as a "ense operart, tf

The "spontaneous" emissions of the fish have to be studied under the range of environmental conditions (temperature, light,sound, eleetromagnetic shielding, etc.) ih which the subseçuent conditioning studies will be undertaken. (Ferster, 19 Schoenield, Antonitis, , and Bersk, 20 Reed 21) The distribution of all significant response paramcters, including oceurrence in time for the non-coatinuous case,

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wil bo obtained. Since the responses of surong clectrie fish may not occur as free operants (i. e., in the absence of specific eliciting stimuli), the buik of these daia wil probably concera parametric varictions in the continuous emissions of weak clectric fish. Some of tho information gathered at this stage will bo uaciul in dotarmining the nature and degree oi experimcntal control nasossary to onsure tho Cesired prucision ia subsequent behzvioral mecsurements.

2. Reeord gross or general activity of the fisn.

"gross' or 'general" activity cf the Ksh has to be recorded on
a contiaucus basis duricg al sessions (3u) i
which movement by the fish is possible, ineluding the foregoing ree ové: Lersserve as device for this puroose.
A relationshio betwes: amissicr iree
aad stimulation has been asserted to kold for certain Gymnotidae asure parmit us to determine whether such a relationship exists and,
ii so, to spectiy its precise form. Cther uses of this measure will
be evidert as the stucy proceads.

8. Dstswwtee the effects on bokavior of selaoted stimul

The stimali to bo presemted wil be earefully selected to represest the saage of modalities and paremetric valnes kncwa or thought to be wihin the receptive capabilities of the organism or of special irterest to the investigation. Varistions in electrical response parameters, in the general acuvity measure, and in other describable bahaviors will be observed and recorded. Other technicues (Ash23 and Thorpe 24), will irolade the irvestigitior of unconcitioned raspoadents (Kuroda 25) asscciated with each stimulus and the efects of stimulus presantations on a free operant other than the alectricai respoase.

Ono of the objoctives of this step is the idontification of neutral stimuli which are suitable for use as "conditioned stimull" in respordont conditioning and as "diseriminative stimull" ark "secondary reinforeers" in operant conditioning. A sufficient number of" reinforcing stimuli" will be sought for use in manipulating the streaeth of selected opcrants.

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w are response ass

4. Condition the electrical gesponse.

3C bees).7

From. the lterature donlirg Wih eloetrie Rah, Oae would expeet to

a. That a class of eliciting stimuli exists for the strong electric response in each suecies. Pavlovian procedures are therefore Ikely to bs found applicable. Nevertheless, the possibility that these responses are accessibie to operart procecures shouid cso be checked.

b. That the continuous emissions ofthoseknifefishes whose responses kive been shown to be temnerature-correlated may not be condiionabie. It has been suggested that the control centers for these responses mcy be isolated neurologically from the necessary sensory inputs. However, Bennet and Grundiest 26 report a trarsient increase in the rate of responsc in Cymnotus carapo, one of the ssecics used in establishing the temporature-frequency rclationship, immediately following a tap on the tark. A systematic and full-scale attempt to condition this fish is therefore indicated.

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e. The weak respesscs oi those ao specles in which frequeney (and perheps cther parameters) is said to be highly variablo and depondons Lpon the cotivity and exeitation oi the Esh, are Kkely to be condkionable operamly.

The fallure of Longo and 3i -27 osistanco co en.in maercceph reinforcement --a coasistent the animal iaboratory-. lustrates the need for caution in gonert ng resuls over too wide a sogmen. etie seale and possibly over teo wido a range of ex operations, time schedules, ete.

Ca the etter 28 (359) was imprassed by the
s octopus to thoss organisms. evo vec senty of vertebrates he commenad musi be a very old and fundamertal proこCss.

Generaily speaking, it is expasted thal the resomblances amony species wil far outambor the diferenees. Nevertheless, i is ony through ressareh with she particaler spactes, responses, end experimemal prccedures of interest that clear answers to sach caestioas caa be cbsaiaed.

Doncsnladen of the "Dysemle Rarra" of Eaoh Eleettoel Roscorse

The cbjective of this stage is to "push" response parameters, singly and in selacted combinations, to their upper and lower limits.

I is at this point that the difierences between oporant and respondent conditioning bears most critically on the proposed research. Only operant procsdures provide the type and cegree of control necessary to "shapo" responses in the desired manner. The main procedure available for this parposs, namely "response cifferentiation, " consists in making reinforcement contiagent upoa the emission of responses progressively approximating the Cesirad values. (See for example, the oft-quoted study of Hays and Woodbury, initialy reported by Sul,)7. In addition, the manipuiation of reinforcenent cehedules (Ferster and Skianer 29) caa be used to "compress" two or more discrete responses in time. i

On the other hand, the control over the paramoters of those responses whiek can be conditioned only rospondontly, .is gonerally limited to those variations in magnitude and latency associated with changes in the intensity.

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30 es

The method oi exploring the dynamic range of electrical responses was seaz to dspend critically upoa the type of conditioning operations to which the respoise is accessible.

These two efforts --determining the set of conditioning operations appliecble in each case and using this information to ascertain the limits with raspcst to selaoted rosponse parametars-- are the core of the mentionedbehcviore resaarch.

In the cext part of this section certain related behavioral researoh studios are Cuseribed. These indiezte tho wide range ci questions to be answored thrsugh rasearch with respeet to the behcvicr of electric fishes. Following this, we shall turn our attention to some questions of "experimental desiga.

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Other Bohavierel Studies

ques are developed, the resources for become rescarch along 0: war and other intraspecies nunications, elcctricai roception, receptor location and certsin

Mlustrative studies in cach of these areas are described below.

Cbiact Location

chidae, Mormyridae, Gynnotidae, Eleciroie use their weak clectrical ing and navigational purposes. Studies such as the sos for direo m Cai.

32 WO De as An esse or control, of all extranecus (inc non-elcctricai) be useful to the organism in avciding the obstacies cこes 33).

The primary value of such a study would probably be as a demonstration that a particular fish actually does use its electrical system for navigational purposes. Scores obtained in the test situation could also be used to compare the porfsrmance of the same fish under different conditions, as for example, to assess performance decrements associated with experimentaliy induced impairment or isolation of the electroreceptor function. On the other hand, comparisons based on scores attained by fish differing in size, species, and perhaps other factors would be somewhat tenuous.

Directional adjustments in output. The possibility that the clectrical cutput pantern is adjusted directionally to the location of the "target" object

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Lbiirons) responses. done S points in the space around tions to preclude cxtraneous cues, and the

displaced half ance for eac Observable behavicrs also eshoic

Obiect Identification

I kes been seriously suggested that wesk cloctric fish may use the eiectricai trocess for species, perhaps even for sex, recognition. It wouid nct be difioult (thooretically) to devise exporimemts to test these hypotheses. Some minimum data bearing on specics and sex racognition could be initially colloetod as spportunities presem thomscives in the course of other studies. Afor this has bean done, the other experiments could follow.

I will be relatively simple, on the other hand, to develop an adtptation c: Kellogg's preierred food identification test.

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Varaires and Cther Imra-spesies Csmmunietions

or to whose conses to oi

38 39 29) 40) ished,

Chere exists a coicerable rumber cf techniques which can be adapted readily to the determination cf electrical thresholds for any species selocted for study. These techniques all iavoive conditiocing the crganism to respoad Eiffarantly to the presence or absence of stimulation (absclute thresholds) or to two stimuli which differ with respect to some parameter (difforence taresholds). Since thera is no restrietion on the responses which can be lirked Cisorimisctively to stimulus-prosence or to a particular parameter-difference, acy coaverient cparant or respondent may be chosen.

For this reason, the question of type or concitioring operation, which is so critieai in attempting to gaia costrolover a particular response, presonts rs problem at all for threshcld determinations. Here, it is important only to selees from the repertoire of the orgarism a response that is readily conditioned and casy to work with (record, quantize, etc), and one yhich will not contaminate the threshold determinations --e.g., by causing uacontrollabie variations in the distance between the receptor and the stimulus-object, or by cthorwise inducing significant changes in the perceived electrical fiold. Such decisions can be made best aiter one has had opportunity to observe: and conduct preliminary trials with a given specics and organism.

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The tolowiag ere aias Eve of the operane and Pospondene teehniquos which may be adapted to the task of determining absolute and differential thresholds of e\_cctrical stimulation in solocted species:

1. Oporant techniques.

Lissma: 33 trained Gymaotus Carapo to feed when a stationary magnet wes mounted just outside its aquarium. The prototype fcr for this widely used disoriminatior training prccedure may be Pepresented in the folowiag paradiga:

S4E]SR

Cho seesnd Lae popresents
feeder, ete.) in the cbsence of the magnet (S, read and sonietimes wten as "essdeka") is p: folowed by () relnforcomec (SR, i.e., food).

The first process, reinforcement in the presence of SD strengthens the response to the point where the response rate increases even in the absence of the magnet (i.e., in the S condition). This, of course, is "generalization." The second process serves to auinguish responding in the S conditicn. As a result of these two prooesses operating conourrently, the animal learns to respond in the presence of the disorimizstive stimulus,and not to respond in its absence. In a similar way, Doterkine 41 coaditioned African mouthbreeders to manipulate a lever, with the brighter of two lighis as the SD.

The following are illustrative of the numerous variations on the generai prccedure which are possible.

a. Instead of merely witholding Sk (e.g., food) for responses uader S, Lissman33 puaished such rcsponses by chasing the fish away from the food with a wire fork and, on occasions,

21

[PAGE 24]
the fish was "kaocked on the snout wih one end of this wire fork." Punishing responses msde in the absencc or the discriminative stimulus (i.e., in the S conditior) is gencrally to be avoided. It comribuies Hittlo or nothing to the learning and has undesirable, "emotional" side effects.

stimuli may be used withont prolonged amotional effects when the set of responses, [R], is reinforced by avoidance or immediate termination (Schcenfeld 40) of a us (.e., a primary negative aoxious or punishing instoad of by the procurement of a positive reinforcer.

Schiosberg 35 for cet tone or one of several …35 42 43

Che preseduros may be adapeed for the Cete é. throsholds and for decisicn-making studies by substituting two or more diffarent s picce of te nulus-prosence (S) aad the stimuius-absence (SA) pair in the paradigm.

Sutherland (e.g., Refs. 44 : and 45) trained octopi to attack one class ci geometric figures (e.g., squares) and to refrain from attacking another ciass (e.g., rectangles). He used food to roirforce "correct" responses and, in some studies, also used shook in additicn to no food for iscorreet" ressonses. Lissnie, 33 trained Gymnarchus Niloticus to diseriminate between two opaque containers of aquarium water, differing elcctrically because of the inclusicn in one container of a glass tube, 0.2 cm diamcter. The proper approach response was reinforced with food; an incorreet choice received the no-food-wire-fork-treatment, mentioned carlier.

d. The Ratliff-Blough technioue consists essentially in training an animal to make one rcsponse (e.g., dopress a lever) in the presence of the stimulus (sD) in order to obtain positive reinforcement. Each such response attenuctes the signal by some knowa

22

[PAGE 25]
amcust. When the sigsal disseppears below the crganism's throshoid, the animal shifts to aother response (e. g., a secozd lever), by means of which each response amplifies the siraai ia known izerements. When the signal reappears (i. e., reaches a suprathreshold valuc), the animal returns to the fisse Lever, vhare resporses are again reiniorced.

The prccedure is an acaptation of a standard psychophysical methed variously called the "method of limits" (originally by reeertly, for example, by Woodworth and Sohlosbarg 46), the "metod of minimal chanaes, and the "methoć of sərial exploration" (Woodworth46), it was employed by Bukesy 47 to measure auditory thresholds in humans.

As cpplied to Lower crganisms, the procedure requires careful manisulation of reinioroement scheduios and the estcblshment of ccmplex roinforeemot contingencies, making i time corsuming and serhaps beyond the capacity of some species or inorest to is proposa.

Is should be noted, howe the procedures have beer 48, 310u49), (Acler
and Dalland 51). Threskold doterminations are in torms of the
(Frick 52) aspects of changes in rate, percent occurrence, and aeney as asplied to cperant condiiozing. The feasibility ci
using this spproach should be explored whenever operant pro-.
cedures are being considared for threshold measurements.

The foregoing will suffico to fllustrate the use of operant discrimination procedures for the determination of absolute and differential thresholds.

2. Bosposdent tochaiques.

An experiment included in MeCieary's study of interocular transfer providas a recent examole of the use of rospondent technicues for threshoid measuremerts in Hish. The typicai Pavlovian (Pavlov 36). pattera for diserimination training will be recogaized in the following represontation of McCleary's procedure:

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[PAGE 26]
shock as orai ioned reilex deveioped, 53) there AS ON diagram. By sacond lure (L2) with the reguiar con trials, the conditioned response to Li inishas, and the fish comes to respond disc ninatively to the two lures.

The same basic procodure can be used to establish a responcent discrimination between two stimuli Eiffering only in some particular parameter (difference threshoids) or between stimulus-presence and stimuius-absence (absoiute throsholds). (For several exampies, sce Ash 23.)

. Uaconditioned responses to test stimuli have aiso been useç. Kurod: 25 looked for respiration changes in newts as an indication of sensitivity to such stimuli as pistol shots, tuning forks and whistles. Murphy and Harris 42 investigated the pinna reflex to sound in the rat, "with 11 at least as good repeatebility as in the normal human sudiogram.

24

[PAGE 27]
iques can bo used with constrained cues part itable for the study of clectrical receptors. They enable conespcct to test cbjects be associated

3.ottemerkveiolowedteehsiases.

As more is learned about the location and structure of the electrical Poooptors ol these Nish and cbout tho aflerent sataways iavo.vee, i. wil Beosme possible to attlise cicetrophysiologieal techniques both to verify the funetion of the suspocted receptor and to estimate arsshoids.

54 and in b2ts; 55 eye ané optie lobes in the chiek ombryo by ctors, at ai. 56 and the work of Dr. Robart Doty, Proiossor t the Corter for Brsin Rasearch at the University of Rochester, provide conemsorary examp.es.

The Locatior of Electrical Recestors

Iormation about the clsotrical receptors of these fish is disoussod elewhose ia shis repor.

Acetionri Consmcnin? Studies

Among the numarous conditioning experiments that couid be conducted, the lollowing appear to be interesting:

i. Bxperiments necessery to clarify the results of the main investigation, including those control studies mentioned in the following seetior on Experimentel Designs.

2. Experiments which repeat, with the species and responses ineluded in the main invastigation, a good-cross-section of the prototypical Suporiments corducted in the "snimal laboratory." The resuits would provide additional data on the phylogenetic generality of the conditioning operations, cata and relationships obtained with other usually higher, organisms.

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[PAGE 28]
of data related to 5 Q conclusions has to be established the best techniquos available in cach sot 5 isvclve careful analysis of the process Eon oi the relevant variables, a proper choice of the measures to bo used to repr variasios, soleotion of variables to be controlled or randomized, the removal effocis, and other experimental prccedures and techniques, Cesigned to minimize error variances and to remove bias or contamination.

se W which be used 2 C 121 and 51 52 53 64 61 snd 62 to serve 0 29
5 an Skinne anc
63 eiererce wil. course, W assi 0

Aacthes prcblom which may be enccuntered is failure to achieve any form of control over the occurrence of, cr over the parametric variatioas in, the sleotrical response of a given species. This would represent the most duflc.. outccme to interpret and wouid raise such questioss as: Were the reiniorcements, other stimuli, ete., appropriate to the organism? Was the emotionsl or physical condition of the organism such as to adversely affect learning? Was the tcsk set to the organism too diffcult --i.e., would some other choice have workac out differontly? Were the environrental conditions and other laboratory arrangements unsuitabie in any way? Were the corditiosing techniques competently applled? Etc.

Careiul observation of the orgasisms' behavicr in the course of attempting corditioriags will usually provide some relevant evidence.

In addition, it will be highiy desirable. with every species, to select a corvenient respondent (e.g., MeCleary64). and a convenient operant response (s.g.. Bonty, 65 Deterline 66 ) to serve as a kind of control. Then, if a particuiar conditioning paradigm fails to yield the expected results, as applied

Experimental Dostons

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[PAGE 29]
to the elcetrical response, the procečures used could be "checked out" usiar e appropriate alternate response. (Simiiarly, in studies of the electrical receptor, an alternate set of non-clectricai discriminative stimuli woulc bo used as a cheek on procedures when needed.)

Through thoso cnd other moans, the kind of reproducibility and preeisior in rosults that charactorizos the best sciontific resoareh ia the bokavioral setenees wil be cehieved.

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References

28

[PAGE 31]
25

[PAGE 32]
30

[PAGE 33]
31

[PAGE 34]
32

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as a Factor G4.

33

[PAGE 36]
III. PROPOSED BEIAVIORAL STUDY OF ELECTRIC FISIIES WITH EMPHASIS ON OBJECT DETECTION, LOCATION, AND IDENTIFI-CATION (PHASE I)

Three different kind of experiments are proposed with the aim to assess the ability of electric fishes to detect, locate and identify objects underwater. The first system is designed to use as a subject, a weak fresh-water African electric fish Gymnarchus niloticus. A maze has been designed (Figure 1) to be built in a water tank of 12 feet in diameter and 4 feet in height. The maze has two channels supported by bars on the tank. The fish located at C will be presented with a stimulus in the form of objects (metallic, nonmetallic, magnetic and nonmagnetic) of different sizes either moved from D to E or from E to D. The reaction of the fish and its choice of the channel will indicate how well the subject would detect different objects of different textures and sizes. The fishes are freely swimming. The second system, (Figure 2) is designed to prove the ability of electric fishes to avoid obstacles like fine aluminum wire or nylon thread. The African electric fish Gymnarchus niloticus and the South-American electric fish Sternarchus albifrons would be used. Both fishes are blind and use their electric transmitting-receiving system for navigation. Gymnarchus has a very steady frequency (around 300 Hz) and Sternarchus has a steady frequency (around 750 Hz) provided the water temperature is held constant. The fishes would be presented with stimuli (attractants and repellents) and their behavior will be monitored by filming it. The fishes are freely swimming. The third system is designed for variable rate of pulses electric fish species like the South American fish Gymnotus carapo or the African fish Gnathonemus petersii. The subject will be confined to plexiglass tube with holes and two electrodes (at the head and at the tail). The impulses emitted by these fishes will be amplified and monitored with an oscilloscope and a frequeney counter. Objects (metallic and nonmetallic) of

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different sizes would be presented from different distances and their effect on the fishes pulse rate will be recorded. Graphs will be plotted relating material, size, and distance to the pulse rate as compared with the stcadystate pulse rate. These fishes increase the pulse rate when an object disturbs their electric field generated by the transmitting organ and received by the electroreceptors in the skin of the fish.

It is hoped that these three sets of experiments will show the sensitivity and range of detection of different objects by electric fishes.

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IV. AN EXAMPLE OF HARDWARE ANALOGUE EXPERIMENT TO SIMULATEOBJECT DETECTION BY ELECTRIC FISH (PHASE II)

It is possible to simulate an equivalent sensory system of electric fishes responding to different stimuli underwater. A system with a double feedback mechanism can be envisaged: (1) one represented by a constant frequency electric field transmitting system operating on the phase-synchronous electroreceptors responding to discontinuities in the electric field or to changes in the phase relationship transmitter-receptor; and (2) another one represented by a variable frequency transmitting system responding to disturbances in the field between transmitter and receptor with a change of the frequency of the transmitting electric organ. To this we could add an independent dual autorhythmic receptor system: (a) responding with the increase or decrease of the authorhythmic frequency depending on movement direction of the disturbance in the electric field; and (b) responding with a change in the latency depending on the magnitude of the disturbance, and also distinguishing between conductive and nonconductive objects.

A simulation of the electric fish object detection system would make it possible to find out how models of the physical analogs of the sensors could be integrated in object or organism location, detection and identification. The range and sensitivity of the system could be assessed and improvements could be made. As a first step toward this simulation we present a measurement plan for an experiment in Phase II of our investigation, to build and check the first of the above mentioned mechanisms for detecting, locating, and identifying objects underwater by means of a phase detector system sensitive to changes produced by discontinuities in the electromagnetic field.

Systems and equipment for detection and location of objects in a seawater or freshwater medium have to be designed from the standpoint that the

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[PAGE 42]
medium is lossy and has a high dielectric constant. Consequent $i _ { y } ,$ the wavelength of a signal transmitted through the water medium is different that that of a signal of. the same frequency transmitted through free space. Attenuation and scattcring are also different from the values for free space.

The advantage of using a phase comparison, position determining system is evident because the precision of our measurements depend on the phase measurement precision capabilities independently of the frequency used. This gives us the possibility of using low frequency combined with a highly accurate phase measurement.

In free space we have the well-known relation between the speed of light c, the frequency of an electromagnetic wave being propagated f, and its wavelength

c = f λ (for all λ in free space)

In seawater, this formula cannot be used because the propagation velocity of an electromagnetic wave is different than the value of c in free space. Moreover, the propagation velocity in water changes with frequency and is not a constant. It is represented by the relation

$$
\mathbf { s } = \mathbf { F } ^ { \textsf { \prime } } \lambda ^ { \textsf { \prime } } \mathbf { w h e r e } \mathbf { S } = \mathbf { F u r a c t i o n } \left( \lambda ^ { 2 } \right)
$$

\*\* s = speed of propagation in water dependent on the electrolyte medium.

f = frequency (Hz)

λ' = wavelength in water (meters)

The signal travels a distance D in the time T where:

$$
\pmb { \tau } = \frac { \Delta } { \pmb { \sigma } }
$$

\* Taken from D. L. Nichols reports from the U.S. Navy Underwater Sound Laboratory, New London, Connecticut.

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[PAGE 43]
s.is depcndent of f and λ'. With respect to time zero the phase of the rated signal advances through the angle 2π fT. The received signal therefore ; behand the signal at the signal generator by 2π fT. If this phase lag could neasured, the range could be calculated. The basic equation for phasenparison distance measurement is

$$
\rho = 2 \pi \it { \{ ^ { \circ } I ^ { \circ } I ^ { \circ } = 2 \pi \it { \{ \frac { \partial D } { \partial s } } }
$$

ere P is the measured phase difference between the reference signal and the
gnal which has traversed the distance to be measured. In terms of the
stance traveled, D = sP pX' 2πf 2π

hase measurement can be based on: (1) the multiplication of two cosines or sines) and integration over one period of the function; or, (2) by determining he instants at which the reference and text signal cross zero in the same direction and measuring the time be tween the zero crossings. The phase angle is then 2πf T, where T is the time between zero crossings..

We have chosen some hypothetical parameters for a phase disturbance detection and location system. The values chosen may have to be modified according to our findings during checking, experimenting, and making measurements in a scaled model in fresh water, sea water, and mixed fresh and seawater. The parameters for our system that have to be scaled down are:

Transmitter: f = frequency = chosen between 5000 Hz and 1000 Hz

¿ = length of the antenna made of a water column in sea water = between 22 m and 50 m

p = endplates for the antenna feeding between 25 and 50 cm diam., silver silver chloride plates on Monel-metal 1/8 in. thickness; plates will be fed by coaxial cable in a coppertube 1/2 in. diam.,

I/16 in. wall thickness sprayed with a teflon coaling of minimum 1/32 in. thickness.

Transmitter power effective delivered at the endplates = 1 kW. Transmitter

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[PAGE 44]
be in a screencd roon, double copper mesh, with a good ground to an endent ground. Transmitter has to be crystal controlled. .ntenna depth = 3 to 5 m under the surface of sea level.

leceivers: Instead of dipole antennas, low-loss toroids will be used, tuned to between 5000 Hz and 1000 Hz frequency fed into matched lines and to low-noise linear amplificrs. The amplifiers have to be nonphase distort type. Phase active networks connected to the amplifier will correct for exact lSoº phase opposition of the toroids' output. The output from the phase-corrective networks will be fed into a variable high-gain (decade amplifier) differential amplifier where the output will be monitored by a scope and a null detector. Differences of 0.00l% may be possible to be detected at the highest gain.

Scaled Model: George Swain\* tried·an experimental toroidal antenna scaled to small diameters for frequencies of l.5, 2.0, 3.0, 4.0 and 7.0 MHz in a solution of NaCl of 0.285 moles per liter and a conductivity of 2.8 mhos per meter at 250 C in a tank 3.5 m in diameter and ,55 cm deep.

George R. Swain: Antennas in or at the Surface of a Conducting Medium at LF, Report EE-ll6 of the E. E. S. Univ, of New Mexico, Albaqucrque, . M. (1964).

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[PAGE 45]
t is proposed to use a plastic tank 12 ft. in diameter and 4 ft. deep for ed down experiment with fresh and seawater.

We will increase the frequency to 400 kHz corresponding to a wavelength vater of 2.25 m; also ten times smaller than one of the hypothetical values. 1 endplates of the antenna will be 8 cm in diameter (about I/10 of the surface the hypothetical plates). The power of the transmitter will be decreased l00 W at the end plates. Antenna should be submerged to a depth of from to 50 cm.

Receiver antenna will be made of corresponding toroids for the frequency 400 kHz. The ratio of the attenuation between a signal of 5000 Hz at 22 m nd 400 KHz at 2.2 m distance will be calculated and the factor applied to the esults of the measurement.

A piece of cotton filled, cotton covered, and partly isolated cotton body with a volume of one-tenth that of a human body and with similar conductance will be used to find out the phase deviation produced in the field in different positions between the transmitter and the receiver antennas at different depths.

A device for making artificial measurable waves on the water surface will be used to produce scaled down waves.

A random-noise generator will be used to simulate natural noise which will be added to the signal for different S/N ratios. Polarization and position change of the toroids will be checked to find out if it is possible to reduce the unwanted effects of water movement and noise.

The tempcrature and the salinity with respect to the conductivity of the water will be continuously monitored and recorded during experiments.

Receiver and transmitter antenna will be checked under steady positions and small movements to dctermine the effect of moving the antennas on the 1

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onse of the system. Q-factor of the toroids in air, fresh water, and ater will be measured. The ratio between deviation produced by waves or noise and the one produced by the object will be detormined inorder ecide if a full-scale experiment is warranted.

Simplified Block-Diagram of an Underwater Phase-Detector System Used to Detect and Locate Objccts

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Example of a simple ratio bridge.

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46