Doc 0000022023

- . ~ Tflt SENSITIVITY AND RESPONSE ,· OF WEAKLY EUCTR.IC FISH TO STATIC AND PULSED MAGNETIC FIELDS .. June 1, 1970 I. It-t'TRODUCTION. The study of bioelectrogenesis, particularly in the various species of electric fish, has been of increasing scientific concern in recent years. This interest stems primarily from the potential usefulness of research in this area in contributing to our understanding of a number of fundamental and significant problems. By defining the electric fish's unique sensitiv• ity to and magnetic fields, and how it codes and utilizes such sens elect~ic ory information in its detection and navigation behavior, current evidence is providing a more complete concept of such basic'questions as migration and territoriality, and is leading toward the of various bionic deve~opment devices in the form of underwater sensors and power sources. In addition, knowledge of the effects of magnetic and electric fields on physiological behavioral processes has assumed great importance in view of man's ex an~ posure to drastic changes in such stimuli during space travel. Living things produce a changingelectric field at and near the surface of their bodies; all fish, being sheathed in a conductive substance and living in a conductive medium, produce an electric field that may be detect ed at relatively great distances. However, there are certain fi~h which produce electric fields exceeding the norm by hundreds or thousands of degrees of magnitude. The electric eels of the Amazon can produce bursts in excess of 600 volts. Other electric fish, i.e., weakly electric fish, produce continuous fields measured only in millivolts, but by means of in• terpreting distortions in t:hese fields are able to sense and navigate through their environment to a degree comparable to that of other species in which vision used for these purposes. The weakly electric fish, ~s having very poorly developed visual abilities, must depend on information acquired thr::>ugh their e lec:.tric fields in order to survive. The magnetic field is a form of energy to which all plants and ani mals- are exposed.. Its influence on living systems, however, is subtle and not well understood. One approach to studying the effects of magnetic fields upon ·:>ehavior is through the use of an organism which produces an electric field and uses it as a detection and navigation mechanism. The electric fish is just such an organism, and this report will review a one• year study of two of these This page displays the title "THE BLACK VAULT" in large, stylized white text against a dark background with a blue glow. To the left, a detailed illustration of a bank vault door suggests security and the idea of hidden information. The majority of the page is filled with text explaining that the document was obtained from "The Black Vault," an online database of declassified government documents, specifically referencing the MKULTRA/Mind Control Collection. The text also provides a URL for the collection. The image is a declassified document page with dark gray text on a white background. The text is centered on the page and reads "THE SENSITIVITY AND RESPONSE OF WEAKLY ELECTRIC FISH TO STATIC AND PULSED MAGNETIC FIELDS". Below this, also centered, is the date "June 1, 1970". The page is covered in small, scattered dark specks, typical of older scanned documents. There are no photographs, stamps, handwritten annotations, or diagrams present on this page. studying the effects of magnetic fields upon ·:>ehavior is through the use of an organism which produces an electric field and uses it as a detection and navigation mechanism. The electric fish is just such an organism, and this report will review a one• year study of two of these species (Sternarchus albifrons and leotor• ~· hynchus; see Figure 1) which has just been completed .. · · • .f In these fish, impulses are dis- charged fr'om the tail and' received by the head which becomes positive in J regard to the tail. This potential difference creates an electric field about the fish's body, permitting it to detect objects through distortions in the field. Several studies h-1ve shown that these fish can perceive a static (constant strength) m.1g netic field, but only when either the orga nism or the field is in motion, thus generating a current in the Hsh. It was thought that the fish was responding to the current generated in itself by the magnet. However, in these experiments the magnetic field was presented as a static field, and the sensitivity of the fish to a pulsed field presented at various frequencies, particularly the frequency at 1 ·.:.. which the fish discharges its own electric field (500-1500 cps), was not investigated. Other investigators have shown dramatic increase in sensi• tivity to approximating the frequency of the fish's discharge. applied~.£. In addition, the strength of the field was not systematically varied in terms of the gauss level in the fish's proximity. Therefore, there are c.onsiderable gaps in our knowledge of the degree of sensitivity of the fish to magnetic fields at various frequencies and strengths. The present study was undertaken clarify some of these problems regarding the perception ~o of and response to a magnetic field which is systematically varied along several continua • . ' Figure 1. St~~hus albifro~ (top) and Sternarchus ~torhvnchus (bottom) II. BACKGROUND. Comparatively little work has been done on the sensitivity of weakly electric fish to various types of electrical and magnetic fields, although the evidence that is available indicates that these fish have an extremely low threshold for such stimuli. Lissmann(l958) and Lissmann and Machin (1958), for example, have shown that Gvmnarchus niloticus will perceive an the movement of a magnet or electrified insulator when either is moved outside its tank or aquarium.* A small bar magnet was held against the *Szabo The page is a scanned document, likely from a report, with dense black-and-white text. There are no images, diagrams, handwritten annotations, or stamps visible. There are no redactions or signs of experimental procedures. The page appears to be a standard academic or scientific text, with the only visual elements being the text itself and a small black ink circle near the top center of the page, possibly indicating a printing artifact or a placeholder. have an extremely low threshold for such stimuli. Lissmann(l958) and Lissmann and Machin (1958), for example, have shown that Gvmnarchus niloticus will perceive an the movement of a magnet or electrified insulator when either is moved outside its tank or aquarium.* A small bar magnet was held against the *Szabo et al. (1969) write that the electroreptors respond to both the presence and movement of an object or !ield. 2 wall of the aquarium and moved in a vertical direction, with the result that a "single downward sweep produced a response in the fish if the movement was sufficiently rapid and the distance between the fish and the magnet su.ffi· ciently small. With the particular magnet used a response could be elic.ited at a velocity of about 3 m/sec when the fish was about 50 em from the m.agnet11 (Lissmann and }fachin, p.451). When an electrostatic charge* was moved hori• zontally in front of the tank, the fish was seen to respond to a voltage of 60 kV when the distance from the fish was 50 em and the charge was moved at 3 m/sec. The authors conclude that Gvrnnarchus is able to detect potential gradients of about O.JO~v/cm in the surrounding water. Table 1 shows the remarkable sensitivity of this species as compared to other fish. It is apparent that the perceptive ability of Gymnarchus is of a different order Table 1. The sensitivity of six species of fish to direct current. (After , Lissmann and Machin 1958.) Cunent density 2 Species (,uA./cm. ) Phoxinus phoxinus (minnow) 10 Cyprinus carnio (carp) 60 £. ~r~ ,(goldfish) 16 Parasilurus asotus (catfish) 8 aculeatus (stickleback) 110 Ga~erosteus Gymnarchus niloticus 2 x 1o-s £/. .... of magnitude than other fish. Since it can detect a direct current of about • 15 microvolt per centimeter, an individual sense organ in Gymnarchus should be sensitive to a current c.hange as small as .003 micromicroampere. :~----· Lissmann (1958) has observed that Gvmnotus carano can be conditioned to feed in response to a stationary permanent magnet mounted outside its tank and to inhibit feeding responses when the magnet is absent. He notes that although there is no s:peeifically relevant data, it would seem that this fish should be able to perceive a field of about 10 oersted when moving at a rate of 10 em/sec. ln a subsequent paper by Machin and Lissmann (1960), it was shown magnet is absent. He notes that although there is no s:peeifically relevant data, it would seem that this fish should be able to perceive a field of about 10 oersted when moving at a rate of 10 em/sec. ln a subsequent paper by Machin and Lissmann (1960), it was shown that the receptors responding to small direct currents were also used in the fish's object detection and locatl.on. That is, "the sensitivity of the fish to ex ternally applied currents gives information about the electric receptors for object location 11 (Machin and Lissmann, p.802). *A small aluminum cylinder on an insulated handle and charged from a Wimshurst machine was used. 3 A. }iagnetic field effects. The effects of various types of magnetic :ields on living organisms has been a subject of increasing interest in recent years for both theo• retical and practical reasons. "Basically, the magnetic field, being a form of energy, just as are light, heat and sound, impinges upon all liv• ing organisms ~hether plant ~r animal. The question as to its effect on living matter is what we are seeking to learn. Is it an active or passive process? How will an organism react to an environment that is devoid of a magnetic field? Further, what will happen if the field is altered or distorted?" (Caldwell and Russo, 1968, p.233). Caldwell and Russo studied the effects of an A.C. magnetic field upon the behavior of the Italian honeybee mellifica), and found (~ that the bee would respond to the magnetic energy field a stereo• ~-lith typed nodal reaction, i.e., three of the four subjects would situate and become rigidly fixated over one of the magnetic nodes themsel~es when the magnet was on. Gottlieb and Caldwell (1967) investigated the magnetic field effects on the compass mechanism and activity level of the snail Helisoma durz! endiscus. Using a bar magnet with a weak field (1.5 gauss), they obtained significant effects on the activity level of the subjects. Since astronauts have and will continue to be exposed to magnetic fields are much less intense than the Earth's magnetic field while ~hich exploring the surfaces of neighboring celestial bodies, "the question arises as to whether the human body has during its evolution become de pendent on the presence of the Earth's magnetic field for the maintenan~e of its normal functional integrity. Accordingly, it has become most i~ portant: to ascertain "1hether The page contains a black and white illustration of two fish, identified in the caption as *Sternarchus albifrons* (top) and *Sternarchus leptorhynchus* (bottom). The illustration is detailed, showing the body shape and fin structure of both fish. Below the illustration, there is a section titled "II. BACKGROUND." with text discussing the sensitivity of electric fish to electrical and magnetic fields. There is also a footnote marked with an asterisk referring to "Szabo et al. (1969)". At the bottom of the page, the number "2" is printed, likely indicating the page number. There are no photographs, stamps, handwritten annotations, or redactions visible on this page. ~hich exploring the surfaces of neighboring celestial bodies, "the question arises as to whether the human body has during its evolution become de pendent on the presence of the Earth's magnetic field for the maintenan~e of its normal functional integrity. Accordingly, it has become most i~ portant: to ascertain "1hether a low-intensity oagnetic field exposure could pos~ibly lead to an impairment of health or performance of an in dividual" (Busby, 1967, p. 7). However, there is also the possibility that astronauts could be exposed to intermittently high-intensity mag• netic fields up to 1,000 gauss for varying pe=iods during space travel~ Beischer (1963, 1969) and Beischer et al. (1957) have studied the ef fects of both low- and high-intensity fields on man and animals. Their results show that man does not seem to be affected by a two-week exposure to 50-gamma fields; mice survive a one-hour exposure to 120,000 gauss; and in a low-intensity magnetic field, there is a significant gradual decrease of the scotop.i c flicker fusion threshold in man • Agalides has recently completed a series of studies on weakly electric fish, including some work on their sensitivity to moving magnetic fields. Using Gymnarchus and Sternarchus as subjects, he observed that they responded to a permanent bar magnet of 930 gauss. The magnet was moved at 3 m/sec and was perceived by the fish at a distance of 120 em. This was very close to the fish's sensitivi~ to static electric fields, and corresponds to a gradient of 3 emu, or 0.031~V/cm. 4 B. Electrosensitivity Granath et al. (1967) worked with Stcrnarchus albifrons in their ef fort to determine its sensitivity to imposed electric fields. To study the frequency response continuum, the authors used a conditioning prob• lem in ~hi:h both uniform and nonuniform alternating current (A.C.) fields were employed as signals for the subjects to leave a porous cylinder and swim to a vertical plastic tube for a food reward·. After the conditioned response was establi.shed with high stimulus values, the signal was re• duced to deternine the threshold of the fish. The results indicated that Sternarchus is most sensitive at its own discharge frequency at toom temp .. erature, i.e., in the area of 1,000 cps, with a maximum sensitivity of 0.2 microvolts per em. However, a secondary maximum was observed at the second harmonic of the discharge frequency. Watanabe and Takeda (1963) employed the South American The document page contains a table presenting data on the sensitivity of fish species to direct current. The table includes columns for "Species" and "Current density (µA./cm.²)". Two rows are visible for Gymnarchus niloticus, with a value of "2 x 10-5" in the current density column. The page also includes explanatory text discussing the findings presented in the table and referencing specific studies. There are no photographs, handwritten annotations, official stamps, forms, diagrams, or visual evidence of experimental procedures on this page. The document page contains only text. There are no photographs, handwritten annotations, official stamps, forms, diagrams, schematics, organizational charts, or tables. There are also no redactions or visible evidence of experimental procedures, equipment, or facilities. The page is solely composed of typed text and a page number "4" at the bottom center. most sensitive at its own discharge frequency at toom temp .. erature, i.e., in the area of 1,000 cps, with a maximum sensitivity of 0.2 microvolts per em. However, a secondary maximum was observed at the second harmonic of the discharge frequency. Watanabe and Takeda (1963) employed the South American gymnatid, Eigenmania, in their study of the effects of externally applied electric current. Like Granath et al., they found that the effective stimulus was an alternating current presented at a frequency very close to that of the fish's own discharge. In this case, Eigenmania has a discharge rate of about 300 cps at 25°C, Their -results showed that "when a sinusoidal (or a square pulse) electric signal with a frequency similar to that of the fish's own discharge is applied to the fish, the latter's discharge frequency changes a9 if to escape from the applied signal frequency. The of effectiveness the stimulus depends on the difference beween the two frequencies S); when is more thanlO cps the response is barely rec• (~ ~S The smallerhS, the mo-re effective the stimulus, except when ognizable~ AS is very small, whe-re the response again fails to occur" (Watanabe and Takeda, p.65) Dewsbury (l966b) believes that stimuli* differ and interact in the kind and/or amount of change they induce in the discharge frequency of weakly elect-ric fish. R1a observed several different species, but not Sternarchus albifrons, which does not appear to behave in this way. Dewsbury attempts to relate his data to a concept of arousal, wher~in discharge frequency changes with arousal level. In another study (1966a), he confirmed the hypothesis that electric organ discharge frequency in gymnotids is higher in darkness than in light. This would normally be expected, although we have not found such evidence albifrons. in~· The effect of temperature on discharge frequency is a particularly important problem in that 'the exact nature of this relationship must be knc~n in order to establish baseline data for further study on the fish's discharge behavior. Gallon et al. (1967) and Enger and Szabo (1968) have found that the rate of discharge varies with temperature in mormyrids and *For example, light-darkness, shock, aeration, metallic objects, and a buzzer (Dewsbury, 1966c). 5 gymnotids. Their results are summarized in Figures 2 and 3. 1 ~ A Gl 030/ZO=Z OS /V. 6 .... o c~~----~----~- u , 6 GZ • / OJOI2o • z.a/ ·.· ~ 4 temperature in mormyrids and *For example, light-darkness, shock, aeration, metallic objects, and a buzzer (Dewsbury, 1966c). 5 gymnotids. Their results are summarized in Figures 2 and 3. 1 ~ A Gl 030/ZO=Z OS /V. 6 .... o c~~----~----~- u , 6 GZ • / OJOI2o • z.a/ ·.· ~ 4 0 . :X: (1 Q u 2 ., c;/ Vl E 12 10 :;~·" I 6 ( 0 20 25 30 TEMP. "c Figure 2. Discharge rate as a function of temperature. Open circles, as• ·cending series; filled circles, return to temperature; triangle, lo~er second ascending measurement. (After Gallon et al., 1967.) .. Str~~~ 2000 rltrncii<JS ~ ~.......,SitrfWJrc;/lus ~Sttr~s 1000 ~~- ... • • Eit;ffiiTII:II'IIIio . --···· a,.a ll ~ 500 ••••- ···.· ··· .•• 0 a15 . . . . ~~ 10 •••- ·--· . -· 0111·17 Q, .:~·.......... ,.""'~,_·#~ • . .. I ... .. ~ • : #i,;""'~ . 1 ,.,y.. . ,.~, #~ E ••••. ........ ~ St•moPyg<~s ... lOO ~ SltoiOIJMfS ~ · o lncrusing trmp. ...... /o . . 0 . .N ~ • • .. ,.~''"~ lfl'l'lp. ;~0. .~ 2~5~~lO~~l~S~~~ Figure 3. Relation water temperature and discharge rate. Open bet~een circles, increasing temperatures; closed circles, decreasing temperatures; broken lines, Qlo- values for comparison. (After Enger and Szabo. 1968.) Attem?ts have also been made to condition the discharge rate of • with both classical and operant methods. Mandriota et al. (1965) morn~rids report that three species of would briefly increase their ~ormvridae dis~ charge frequency (conditioned response) in response to light (conditioned stimulus) following training trials in which light was paired with shock (unconditioned stimulus). Mandriota et al. (1965) later discovered that operant (avoidanc.e) conditioning was also effective in these fish and, in fact, was ucre efficient than classical conditioning in that fewer shocks were requi.red to establish the response. III. CURRENT STUDY: THE SENSITIVU'Y AND RESPONSE OF STEIU\ARCHUS ALBIFRONS TO STATIC AND PULSED MAGNETIC FIELDS. A. Problems and hypotheses. The hypotheses of this study were concerned with the problem p~iroary of determining whether weakly electric fish are sensitive to magnetic fields and, if so, how this sensitivity might vary as the field i.s changed from a static to an alter·nating and to a pulsed one, as the frequency of the field is increased or decreased in relation to the normal discharge frequency of the subject, and as the strength of the field is The image contains a single page of a declassified document with printed text. The text is organized into paragraphs and sections, with a heading "B. Electrosensitivity" at the top. There are no photographs, handwritten annotations, signatures, stamps, forms, diagrams, schematics, or structured data visible on the page. There are no redactions or obscured content. The content of the page appears to be scientific or academic in nature, discussing research on fish electro-sensitivity. so, how this sensitivity might vary as the field i.s changed from a static to an alter·nating and to a pulsed one, as the frequency of the field is increased or decreased in relation to the normal discharge frequency of the subject, and as the strength of the field is varied. A secondary problem concerned with effects of various dt'ugs on the electrical activity of the fi.sh was also investigated. H0t-1ever, before the data could be collected, it was necessary to find a source from which weakly electric fish could be obtained, develop life-support systems for the subjects, and design and construct the required equipment and apparatus. 1. Subjects. A total of 18 fish were purchased, consisting of 9 Sternarchus albifrons, 6 !· leptot~~. and 3 weakly electric fish of an un known species. Most of the specimens were bought from the Cappet Corporation in Alexandria, Virginia, and a fev from local pet shops. Four of the fish, all!· albifrons, remained hea~thy during the peri od of the study, and ~Jere the only ones used in the final experiments. nteir size is shown in Table 2. With few exceptions,. the others died within one week of purchase, Table 2. Size of the four experimental~· albifrons. Length Eish Dl 18 em· Fish 112 21 em Fish 13 14 em Fish 114 11 .em 7 The subjects were in individual tanks of either 14 or 20 kep~ liter capacity. The water was aerated with conventional air pumps working through charcoal and gl<lss wool filters. 11le temperature was maintained at about 26.8°C and the pH at 6.7 to 6.9. Food con• sisted of either live or dehydrated brine shrimp. The fish were fed 2 - 3 tirr~s a day, and once a week an antibacterial agent was added to the wAter to suppress the growth of bacteria. 2. Equipment and apparatus. A plastic Y maze (Figure 4) was constructed for tests with the the or steady magnetic field. Its three arms were joined at_ ~tatic angles of· 120°, and the maze itself made of 0.040" sheet styrene fastened with styrene solvent. The water in the maze was drawn from a continuously aerated and filtered source with a pH of 6.8 and a temperature of 26.8°C. It was exchanged every %hour, within which tiue the temperature drop was 0.2oc. However, because approxi~~tely of its inadequate size, this maze proved unsatisfactory, i.e., the larger subjects The document contains two scientific figures. Figure 2 presents three line graphs with data points illustrating discharge rate as a function of temperature for different groups (G1, G2, G3). Figure 3 is a scatter plot depicting the relation between water temperature and discharge rate, with different symbols and lines representing various species and measurements. Both figures are accompanied by detailed captions that explain the plotted data and their origins. There are no photographs, handwritten annotations, official stamps, forms, or redactions visible on this page. The page is from a declassified CIA document and contains an excerpt of text along with a table. The text discusses experiments on electric fish and their sensitivity to magnetic fields. The table, labeled "Table 2. Size of the four experimental S. albifrons," presents structured data with two columns: "Subject" and "Length," listing four fish specimens with corresponding measurements. There are no photographs, handwritten annotations, signatures, official stamps, diagrams, schematics, forms, or visual evidence of experimental procedures. The page also includes a circled black dot near the top, which appears to be a typographical artifact. in the maze was drawn from a continuously aerated and filtered source with a pH of 6.8 and a temperature of 26.8°C. It was exchanged every %hour, within which tiue the temperature drop was 0.2oc. However, because approxi~~tely of its inadequate size, this maze proved unsatisfactory, i.e., the larger subjects could not be used in it. In addition, with a magnet• ic field of 8·10 gauss and the magnet centers at the distal end of one test arm, a field of 2 gauss was present at the farthest minimu~ point in the starting chamber~ The field was 4 gauss in the area of the fish's head when the subject was released from the starting cham ber. These problems with the Y maze may have contributed to the failure to find any response by the fish to the magnetic field in the initial experiments. A larger T maze (Figure 5) was then designed and constructed in an attempt to demonstrate a more positive response to one arm at the choice P"·int with the magnetic field as a cue. In the Y maze, the subject appeared to swim into the arm on the side of the starting chamber that the fish was closest to when the door to the starting area was opened. The length and depth of the T-maze arms were mueh greater than those of the Y maze, permitting the use of the largest specimens. This maze was also provided with continuous filtration and heating, It had a 10-liter capacity,·with an auxiliary 16-liter and 50-watt heater. An air lift and siphon were arranged so that heated, filtered water 'Jas slowly and continuously fed into the leg of the T from the tank. A return siphon ran from the distal end of each arm to the auxiliat7 tank. Temperature in the maze was held at 26.8°C by maintaining the temperature in the external tank at 32.5°C. The tank and siphons were wrapped with paper lagging and jacketed with aluminum foil to achieve and hold the desired temperature. The maze itself was made of sheet clear acrylic plastic, joined with ~" an appropriate solvent. The material proved to be light and strong, and permitted good observation of the fish. The cagnets were made by winding 5 pounds of Hl2 copper magnet wire on each of 2 aluminum tins of 23 em diameter. When in use, the 8 POWER SUPPLY 6-12 volt e appropriate solvent. The material proved to be light and strong, and permitted good observation of the fish. The cagnets were made by winding 5 pounds of Hl2 copper magnet wire on each of 2 aluminum tins of 23 em diameter. When in use, the 8 POWER SUPPLY 6-12 volt e 20-10 .Amp. battery eliminator Y-MAZE Constructed o£.04011 sheet styreoo Water ln'thc maze drawn and replenished hcJ!-hourly {rom 80-degree F, 1. 9 pH sour<:e. Temperature loss lo. the Interval - negligible. e ~ STlMULATOR 9 volt 22 mAmp thru stalnlcu steel electrodes . Figure 4. The plastic Y maze shown with the equipment (tuagnets. power supply and stimulator) used in teats of the static magnetic field. e --------------t inversion of 18 ..... .----...;;..... 7 . . • 5 cm .... 1 · 5 -- c = m - 1 --J cm:iru!.ll£ed! 'Wave ' 130cm '45cm . 8 II>. C.L """ ...._- """' -....... " ........ ' ' 11.\- ~':!:~======'~~=======~======== magnet -..:.. - ....._ ............. ............. ..._._ ............_. 1 .... ..... , \ ~-FI~J!'m -·- - > ---_ ' _ ' ' ...... ................ ' ' \ ...... '~ \ I ' . J ......... i. .... f .. ... l . _~ ..J..... L J'L '. ~l~m' l ( ', ' ' ' 0.24V 0.2V BOmV ·12mV -'JmV ' ., ' '- 24G 20G 8G -1.2G -5G ' Distribution of Magnetic Field' 41 ' Voltages shown are those i;,:luced and form of induced puise in em ' ' in a 300 turn test coil of 3cm di< the Electric Fish Tee Maze.· '· ' ' ' ' ' '·. ' ' ' .u;m ' ' ' ' ...... ...... ., ~5mV,2.5G ........ ',, e I', ' ....... . ........ -~ ...... ........ ~mV, ........ 1.6G ' ...... ' ...... '· .!J..::.v.o.sc cm.(l"O 10 em) -~1"\:is ~j_Jl depth em J?ig!Jilt'" :;. Th~ ':' 'l.Wll~l'll '-'lll<l the ~il!l:r.::l>\,~:1'-'":". of t;..~ ~:;~IS!':::~ ~:te:\t~ :'i.!':'l ~~t. 2 coils were wired in series and placed on either side of the maze arm, 13 em apart. The discharge patterns of the fish were recorded by means of probes of pure carbon rod. Above the water level, these probes were shielded in thick,•all aluminum tubing. Shielded cable was used to connect the probes with the oscilloscope input. The oscilloscope was a TEKTRONIX 502 A, and the built-in preamp was found to be suf ficient to record these fish This page contains a black and white photograph at the top, depicting a circular ink blot, which is likely an artifact from the scanning or printing process, rather than intentional content. The majority of the page is filled with densely packed text, describing experimental apparatus used in studies with fish, specifically mentioning "plastic Y maze" and "T maze" designs. There are no handwritten annotations, official stamps, filled-in forms, diagrams, or tables visible on this page. The text does not appear to have any redactions. The image is a technical drawing of experimental equipment for a "Y-MAZE" study. It depicts a Y-shaped maze made of styrene, with measurements indicating its dimensions. The drawing also shows a power supply, a stimulator with electrodes, and coils that likely generate a static magnetic field. Text accompanying the drawing provides details about the maze's construction, water conditions, and the specifications of the power supply and stimulator. There are no photographs of people, handwritten annotations, official stamps, forms, tables, or redacted content visible on this page. probes of pure carbon rod. Above the water level, these probes were shielded in thick,•all aluminum tubing. Shielded cable was used to connect the probes with the oscilloscope input. The oscilloscope was a TEKTRONIX 502 A, and the built-in preamp was found to be suf ficient to record these fish at distances over 50 em, which exceeded our needs for these experiments. In recording, the probe shields, the cable shields, and the scope ground were all connected to ~ doub• le wrap of heavy aluminum foil around the chamber conta