even uinder thcsc conditions eaLchpigeoll responded to the stinlulustrained as negaltive (S ) zis if it wer-cpositive dLurin2 tests of interocUlartransfer with thc untr-ained eve aloneopen.

ThuLs evidence froml anatomcicl.physiological, and ebhavioral sourcesargLies against C'umming- Siegel, andJohnson's proposal that inter-henli-

0D 0il -

spheric transfer of a 110monocullarlylearnedi pattern liscrimination is literal-ly 'inter-ocular.'

NANCY K. MELLoStanleY Cohl(h Lahoratorie.s,M.as'.vach(uIi.tt% CGeneLral H11p/)ital, and

Ha(lrv'ar(d Medic(aI(YlISIhool/ Bo,stoli

Referellces

1. N. K. Siello, sciiwe 148. >2 ( 196).2. N. K. M1ll.o F. R. Irvini S. Cobh. Bol. In.%t.

I- l,cstud RiBol. Mlcx. 21. 5l9 1963).

3 Aucust 1'965

2*V mL

20 m SEC.

0D

FLASH TO LEFT EYIf ROKTAL FIELD)

0.

FLASH TO RIGHT EYFRONTAL FIELD)

FLASH TO RIGHT E(LATERAL FIELD)

Fic 2 Evoked potentials to flfrom the right optic tectuLm cwith a chronic ablation of ttectuLm. Small, tuLngsten in gl(abouLt 10 ny tip) were uLsedwas anesthetized with nemg/ kg ). Flash stimulli wereI per second at maximtthrouLgh a black cone directecorbit. The terminal apertulr-ein diameter.

1'52(

Stone Migration bi! Freezing of Soil

I hase read ssith great interest D. RZ.Inglis's explanition of the Upliftilln of a

large object sLuch as a stone or tfcelccpost during freezing ot soil IS(-il(,c

trn,rd 148 1616 ( 1965)] As earls ats 19358.uIsing time-lapse color photography. I

nmade ohser\'.ations of this phenomienionat the U.S. Arniv Arctic C onstructionand Frost Elfccts Lahoratorv. Walthtiami.NI assachu-Isetts ( 1nOs 1m1erbed s ith U.S.Arnmy Cold Regions Research atInd Fn-g inccring _Iahoraltors. Hanovcr. NessHalaipshire). A 1 5-minilltitC sOuIlld aind

I color- filni entitlcd Frost actioil in soils* as,,'IS presenitecd at the International lerin3-

afrost C onferencc at PLurduLeC Univcrsityin Nosemier 1963. and has hecii in con-tinuLed circulation since. It has beenshown IAt s arious gather-inigs ot theAmericaln Society of Civil Engineer's.It has also lbeeni shown in Japan andSwede ii.

I This filml dcelmonstrates, amiong otherthings. the LIpW,sad nmovemcrent of aL stoIne

and sinulakted piles withinii a silt soilby frost action. when frezilng is tfromlthe top doown in an open-sN stenm test.The narration accom pansving the filmil isin vers close a(gYreemient (with soaime ex-ceptions) \sith the explaation setftorthbv Inglis. The filmil shosss that adhcsioinof ice to the top of the stone wsas not

the lifting torcc.ealthough it mnight pos-siblyv be lindei ccrtain conditions of oh-ject shape and relaltive position. WVhatactually, happenied in the frost-SuLscepti-ble niaterial stuidied- was that the soildirectly over a stone was lifted above

lash recorded the stone, leaving a void. A stone risesf the pigeon onilv when the adfreeze force arouind ithe left optici1ss electrodes is greater than the forces holdinog it in

l. The pigeon place. The total movement of the stonenibui_tal (30 from its initial position depends uponpiesented at the heaving rate of the soil and the.im intensity *i tiwa-ds the time required for freezing to penetratewas 1.6 cm down to a level below the cavity formed

tinder the stone. In satuirated non-frost-

Figs. 1-4 (top to bottom ). Movemilent ofa stone ( Ictuial size, aboUt 3 cm diam-eter) in freezing soil. ( -1he object part-IN, visible at the lower right is a wristwsatch. ) Fig. 1: frost line approachingthe top of the stone. Fig. 2 ( aboUt 30hours lateri): the soil above the stone

has heaved, leaving a void. Fig,. 3(abouLt 1 2 houLrs later) the stone isbeing lifted by the grip of the frozenisoil; there is now a void under the stone.Fig. 4 ( about 79 houLrs later) the stonehas moved up a considerable distance, andthe cavity below has become slightlynarrower and filled with water, whichhas frozen.

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susceptible soils in a closed system, up-lift by the expansion of water uponfreezing, as proposed by Inglis, is pos-sible. Figures 1-4 illustrate the se-quence of events.

The film is available on loan from theCommanding Officer, U.S. Army ColdRegions Research and Engineering Lab-oratory, Hanover, New Hampshire. Fur-ther study of the freezing of soils andrelated phenomena is being carried onin that laboratory.

CHESTER W. KAPLARU.S. Army Cold Regions Research andEngineering Laboratory,Hanover, New Hampshire 037556 July 1965

Retrograde Amnesia

Failure of persons to recall eventsthat occurred just prior to a severeconcussion or electroconvulsive shock(ECS) has been of considerable interestto neurologists, psychologists, and phys-iologists. Such failure, called retro-grade amnesia, seems to imply thatmemory traces are initially in a rela-tively vulnerable state, and that theyrequire a period to become "consoli-dated." In view of current efforts toidentify the physical or chemical natureof the trace mechanism, great impor-tance is attached to estimates of thelength of the period of retrograde am-nesia.

Currently it has become evident thatthe time course of consolidation, asinferred from experiments in whichelectroconvulsive shock is administeredto animals at various times after learn-ing, needs careful reconsideration.Shock, especially with repeated ad-ministration, has aversive effects whichin many of the classical studies haveled to a confounding of variables (1).In some cases amnestic effects havebeen erroneously inferred even in stud-ies in which a single shock treatmentwas used (2). In this respect Tenen'srecent report (3) has been of interest,for it seems to have overcome many ofthe objections to former studies. Wewould, however, like to express ourconcern regarding the conclusion Tenendraws. He suggests, on the basis of hisown study and -the studies of others,that electroconvulsive shock might ex-ert limited amnestic effects even 3 hoursafter reinforcement. This conclusionseems to be unwarranted on at leasttwo grounds:24 SEPTEMBER 1965

1) Tenen employed only two inter-vals between -learning and shock, 12seconds and 3 hours. In order to estab-lish the nature of the amnestic gradient,several other intervals should have beenused. Since the group subjected toshock after a 3-hour interval does notshow a significant amnestic effect, theonly thing Tenen can conclude is thatelectroconvulsive shock produces retro-grade amnesia when administered 12seconds after learning.

2) The effects described in the studyTenen cites in support of the 3-houreffect (4) are probably not due to retro-grade amnesia (2).We have been carrying out a series

of experiments in the psychology de-partment at M.I.T. on the time courseof retrograde amnesia. When confound-ing variables are eliminated, the am-nestic effects of electroconvulsive shockseem to be very short, perhaps nolonger than 10 seconds. This seems toapply to one-trial learning situationsinvolving both positive and negativereinforcement (5).

STEPHAN L. CHOROVERPETER H. SCHILLER

Massachusetts Institute of Technology,Cambridge 02139

References

1. E. E. Coons and N. E. Miller, J. Comp.Physiol. Psychol. 53, 524 (1960); W. J. Hud-speth, J L. McGaugh, C. W. Thompson, ibid.57, 61 (1964).

2. S. L. Chorover and P. H. Schiller, ibid., inpress.

3. S. S. Tenen, Science 148, 1248 (1965).4. J. Buret and 0. BuretovE, J. Comp. Physiol.

Psychol. 56, 268 (1963).5. S. L. Chorover, in Learning, Remembering and

Forgetting (American Institute of BiologicalSciences, Washington, D.C., 1965), vol. 1;

and P. H. Schiller, J. Comp. Physiol.Psychol. 59, 73 (1965).

5 August 1965

Chorover and Schiller object to asentence in the last paragraph of mypaper. The sentence is here italicized:

However, the greater number of holeexplorations of the delayed-ECS groupover the immediate-ECS group did notreach significance (p = .10). Thus it seemspossible that ECS might exert somelimited retrograde amnestic effects even3 hours after reinforcement. A longer re-inforcement-ECS interval might have pro-duced a significant difference making thefindings more conclusive.

I think Chorover and Schiller havemistaken a control group for an experi-mental one and have elevated a posthoc speculation to a conclusion. Therats given shock after a 3-hour delayprovided a control to assess the pro-active effects on the test performance

of the one-trial learning task. I origi-nally thought that a 3-hour intervalwould be clearly long enough to pre-vent any interference with a possibleconsolidation process. In order to dem-onstrate that the delayed ECS had noproactive effects, three criteria, involv-ing statistical comparison of groups,had to be met. Two of these were met,whereas the statistical test of the third(the one stated above) only approachedsignificance. Although it was possiblethat a larger N might have resulted inthe expected significant difference, sev-eral other considerations led me tospeculate that a longer interval betweenreinforcement and ECS might be themore crucial variable. However, Chor-over and Schiller are completely correctin pointing out that this study was not(nor was it intended to be) designedto explore reinforcement-ECS intervalsand that one cannot conclude from thedata presented that the delayed ECSproduced any retrograde amnestic ef-fects.

I have since conducted an experi-ment in which the reinforcement-ECSintervals were: immediate (about 15seconds), 5 minutes, 10 minutes, 15minutes, 30 minutes, 60 minutes, and5 hours. All intervals up to the 5-hourone resulted in scores significantlylower (p < .05) than that of the rein-forced pseudo-ECS group. The scoreof the 5-hour group was also lowerbut not significantly so. This suggeststhat shock delayed as much as 1 hourproduces retrograde amnesia and justi-fies, in part, the post hoc speculationin the report. This interval is consider-ably longer than the 10-second limitsuggested by Chorover and Schiller.These authors' analysis of the effectsof a long interval between reinforce-ment and ECS found with negative-re-inforcement techniques does not applyto an appetitive reinforcement. It ispossible that the retrograde amnesiaproduced by ECS is a result of morethan one mechanism and hence thatthe hypothesis of a consolidation proc-ess (or processes) need not always beinvoked. Even if one adheres to thishypothesis, the time course of consoli-dation and its stability might vary withdifferent tasks or reinforcement systems.All that is clear at this point is thatadditional investigation is necessary.

S. S. TENENMedical Research Laboratories,Chas. Pfizer & Co., Inc.,Groton, Connecticut20 August 1965

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Stone Migration by Freezing of SoilChester W. Kaplar

DOI: 10.1126/science.149.3691.1520 (3691), 1520-1521.149Science 

ARTICLE TOOLS http://science.sciencemag.org/content/149/3691/1520

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1965 by the American Association for the Advancement of Science

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