【高二英语】阅读理解Exercisemayhelptosafeguardthemindagainstdepression(沮丧)throughpreviouslyunknowneffectsonworkingmuscles,accordingtoanewstudyinvolvingmice.Mentalhealthexpertshavelongbeenawarethatevenmild,

　　【高二英语】阅读理解Exercisemayhelptosafeguardthemindagainstdepression(沮丧)throughpreviouslyunknowneffectsonworkingmuscles,accordingtoanewstudyinvolvingmice.Mentalhealthexpertshavelongbeenawarethatevenmild,repeatedstresscancontributetothedevelopmentofdepressionandothermooddisordersinanimalsandpeople.Scientistshavealsoknownthatexerciseseemstocushionagainstdepression.Butpreciselyhowexercise,aphysicalactivitycanreducesomeone’sriskfordepression,amoodstate,hasbeenmysterious.Soforthenewstudy,researchersattheKarolinskaInstituteinStockholmstudiedthebrainsandbehaviorofmiceinacomplicatedandnovelfashion.Wecan’taskmiceiftheyarefeelingcheerfulorinlowspirits.Instead,researchershavepicturedcertainbehaviorsthatindicatedepressioninmice.Ifanimalsloseweight,stopseekingoutasugarsolutionwhenit’savailable—because,probably,theynolongerexperiencenormalpleasures—orgiveuptryingtoescapefromthecold-waterzonejustfreezeinplace,theyarecategorizedasdepressed.Andinthenewexperiment,afterfiveweeksoffrequentbutlow-levelstress,suchasbeinglightlyshocked,micedisplayedexactlythosebehaviors.Theybecamedepressed.Thescientistscouldthenhavetestedwhetherexerciseblunts(延缓)theriskofdevelopingdepressionafterstressbyhavingmicerunfirst.But,frankly,fromearlierresearch,theywantedtoknowhow,sotheybredpre-exercisedmice.Awealthofearlierresearchbythesescientistsandothershadshownthataerobicexercise,inbothmiceandpeople,increasestheproductionwithinmusclesofanenzyme(酶)calledPGC-1alpha.TheKarolinskascientistssuspected(怀疑)thatthisenzymesomehowcreatesconditionswithinthebodythatprotectthebrainagainstdepression.Then,thescientistsexposedtheanimals,whichwithoutexercising,wereinhighlevelsofPGC-1alphatofiveweeksofmildstress.Themicerespondedwithslightsymptomsofworry.Buttheydidnotdevelopdepression.Theycontinuedtoseekoutsugarandfoughttogetoutofthecold-waterzone.TheirhighlevelsofPGC-1alphaappearedtomakethemdepression-resistant(抵抗的).Finally,toensurethatthesefindingsarerelevanttopeople,theresearchershadagroupofadultvolunteerscompletethreeweeksoffr