RESEARCH ARTICLE◥

NEURODEVELOPMENT

Restoring auditory cortex plasticity inadult mice by restricting thalamicadenosine signalingJay A. Blundon,1* Noah C. Roy,1* Brett J. W. Teubner,1 Jing Yu,1 Tae-Yeon Eom,1

K. Jake Sample,1 Amar Pani,1† Richard J. Smeyne,1‡ Seung Baek Han,1

Ryan A. Kerekes,2 Derek C. Rose,2 Troy A. Hackett,3 Pradeep K. Vuppala,4§Burgess B. Freeman III,4 Stanislav S. Zakharenko1||

Circuits in the auditory cortex are highly susceptible to acoustic influences during an earlypostnatal critical period. The auditory cortex selectively expands neural representations ofenriched acoustic stimuli, a process important for human language acquisition. Adults lackthis plasticity. Here we show in the murine auditory cortex that juvenile plasticity can bereestablished in adulthood if acoustic stimuli arepairedwithdisruptionof ecto-5′-nucleotidase–dependent adenosine production or A1–adenosine receptor signaling in the auditory thalamus.This plasticity occurs at the level of cortical maps and individual neurons in the auditory cortexof awake adult mice and is associated with long-term improvement of tone-discriminationabilities.We conclude that, in adult mice, disrupting adenosine signaling in the thalamusrejuvenates plasticity in the auditory cortex and improves auditory perception.

Acoustic experiences change cortical repre-sentations in the auditory cortex. Thesechanges are a substrate for auditory cog-nition (1, 2). During a postnatal criticalperiod in rodents [postnatal day 11 (P11)

to P15], passive exposure to an acoustic toneexpands the cortical representation of that fre-quency in the primary auditory cortex (3–7). Inadulthood, passive exposure is insufficient toinduce plasticity. Cortical map plasticity duringthe critical period helps construct a stable, adaptedrepresentation of the auditory world. Similarphenomena in humans are likely necessary forlanguage acquisition (8, 9). The mechanism bywhich cortical plasticity becomes restricted inadults has been extensively debated (2, 3, 10–17).Long-term synaptic plasticity (e.g., long-term poten-tiation and long-term depression) at excitatorythalamocortical projections is restricted to thesame critical period as cortical map plasticity inauditory cortex (18–20). In adults, both auditorycortex map plasticity (11, 12, 21) and thalamo-

cortical long-term potentiation and long-termdepression are restored when thalamocortical ac-tivation is paired with activation of cholinergicinput from the nucleus basalis (18, 19). Thischolinergic modulation of thalamocortical syn-aptic plasticity is mediated by adenosine, whichinhibits neurotransmitter release via presynapticA1 adenosine receptors (A1Rs) (22, 23). Blocking ordeleting A1Rs removes this inhibition of neuro-transmitter release and thus enables the expressionof thalamocortical long-term potentiation and long-term depression in the auditory cortex of mice ma-tured beyond the early critical period in vitro (18, 19).

Thalamic adenosine signaling restrictsauditory cortex map plasticity

We tested whether auditory cortex map plasticitycan be reestablished after the early postnatal criticalperiodby restrictingA1R-adenosine signaling invivo.We compared auditory cortex map plasticity inmature (P45 to P56)wild-type (WT)mice andmicelackingA1Rs (A1R

–/–) exposed to pure tones for 5 to14 days (fig. S1). We mapped auditory cortex byrecording sound-evoked responses of neuronssituated 300 to 400 mm from the pial surface[corresponding to layer (L) 3/4 thalamorecipientneurons] in anesthetized mice. The characteristicfrequency (the frequency that evokes themaximalresponse at the lowest intensity) of each recordingsite was determined from responses to a range oftone frequencies and intensities. Auditory cortexmaps inmatureWTmicewere unaffected by toneexposure; however, the percentage of sites with acharacteristic frequency equal to the exposurefrequency increased in sound-exposedA1R

–/–mice(Fig. 1, A and B). This increase was specific to the

exposure tone frequency: A1R–/– mice exposed to

7.9 or 16.4 kHz showed a 2.6- or 2.9-fold increasein the percentage of recording sites with char-acteristic frequencies of 7.9 or 16.4 kHz, respec-tively, compared to naïve (not exposed to tone)A1R

–/–mice (Fig. 1B). We found no effect of toneexposure on tonotopic maps in the auditorythalamus [i.e., the ventral division of the medialgeniculate body of the thalamus (MGv)] ofmatureA1R

–/– mice (fig. S2).We tested multiple methods of reducing A1R

signaling and found that each enabled corticalmap plasticity in adult mice when paired withtone exposure. First, we injected lentiviruses con-taining small interfering RNAs (siRNAs) againstthe Adora1 gene, which encodes A1Rs, into MGvor auditory cortex of P45 to P56 mice. Knockingdown A1Rs in MGv only (figs. S3 and S4) wassufficient to induce auditory cortex map plas-ticity in mice exposed to a 9.8-kHz tone (Fig. 1,C to E). Neither naïve mice injected with thesesiRNAs in MGv nor tone-exposed mice injectedwith control (scrambled) siRNA showed corticalmap plasticity (Fig. 1, C to E). By contrast, toneexposure produced no cortical map plasticityin mice injected with the same Adora1 siRNAsinto auditory cortex (fig. S5), suggesting thatplasticity at thalamocortical synapses, but notcorticocortical synapses, is essential for the au-ditory cortex map plasticity that we observed.Auditory cortex map plasticity could also beinduced in aged (7- to 8-month-old) mice afterknocking down A1Rs in MGv (fig. S6).Second, we conditionally deleted Adora1 in

thalamic excitatory neurons of mature (10- to13-week-old) mice by injecting an adeno-associatedvirus (AAV) encoding Cre-GFP (AAV-CamKIIa-Cre-GFP) into MGv of newly generated Adora1 fl/f l

mice (GFP, green fluorescent protein) (fig. S7).After exposure to 9.8 kHz, the number of siteswith a 9.8-kHz characteristic frequency increasedin auditory cortex of Adora1 f l/f l mice injectedwith Cre-GFP (Adora1 f l/f l;Cre mice), comparedto Adora1 f l/f l mice injected with GFP alone(Adora1 f l/f l;GFP mice) (Fig. 1F). Adora1 f l/f l;Cremice exposed to the 9.8-kHz tone were betterat distinguishing changes in sound frequenciesaround 9.8 kHz than were Adora1 f l/f l;GFP mice(Fig. 1G). This improvement in auditory perceptionwas tone specific, as Adora1fl/f l;Cremice exposed toanother tone did not show improved performancearound 9.8 kHz (fig. S8). Exposure to 9.8 kHz didnot affect frequency-discrimination performancein WT mice (fig. S9). Neither exposure to 9.8 kHznor in vivo injection of Cre-GFP into MGv affectedhearing, as measured by auditory brain stemresponses or startle response (fig. S10).Third, we crossed Adora1 fl/f l andGbx2creERmice

to produce a line of mice with an inducibleAdora1 deletion in thalamocortical neurons.Tamoxifen injection reduced Adora1 mRNAin Gbx2creER;Adora1 f l/f l mice (fig. S11). In situhybridization in WT mice showed that Adora1is enriched in MGv (fig. S11), suggesting thatthalamocortical neurons are especially sensitiveto adenosine. Tone exposure produced corticalmap plasticity in Gbx2creER;Adora1 fl/fl mice. The

RESEARCH

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1Department of Developmental Neurobiology, St. JudeChildren’s Research Hospital, Memphis, TN 38105, USA.2Electrical and Electronics Systems Research Division, OakRidge National Laboratory, Oak Ridge, TN 37831, USA.3Department of Hearing and Speech Sciences, VanderbiltUniversity School of Medicine, Nashville, TN 37232, USA.4Preclinical Pharmacokinetics Shared Resource, St. JudeChildren’s Research Hospital, Memphis, TN 38105, USA.*These authors contributed equally to this work. †Present address:University of Tennessee Health Science Center, 855 MonroeAvenue, Memphis, TN 38163, USA. ‡Present address: ThomasJefferson University, 233 South 10th Street, Bluemle Hall, Room208, Philadelphia, PA 19107, USA. §Present address: KinderPharm,100 Arrandale Boulevard, Suite 101, Exton, PA 19341, USA.||Corresponding author. Email: stanislav.zakharenko@stjude.org

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number of sites with a 9.8-kHz characteristicfrequencywas increased in thesemice, but not incontrol mice (fig. S12).Fourth, pharmacologic inhibition of A1R signaling

enabled long-lasting auditory cortex map plasticity.We paired tone exposure with a selective, blood-brain barrier–permeable A1R antagonist FR194921{2-(1-methyl-4-piperidinyl)-6-[2-phenylpyrazolo(1,5-a)pyridin-3-yl]-3(2H)-pyridazinone}, which,after intraperitoneal injection, persists in the brainfor several hours (fig. S13). Pairing tone exposurewith FR194921 for 5 to 9 days induced auditorycortex map plasticity when measured the followingday (fig. S14A). Replacing FR194921 with vehicleor injecting naïve mice with the drug did not induceauditory cortex map plasticity (fig. S14A). Auditorycortex map plasticity induced by pairing tone ex-posure with FR194921 persisted for weeks afterpairing (fig. S14, B and C), as did improved auditoryperception (fig. S14, D to F). Cortical map plasticitywas malleable. Mice exposed to a second week ofFR194921 treatment, paired with a different fre-quency, exhibited an increased number of auditorycortex sites responding to the second frequencyand showed no residual increase in cortical sitesresponding to the first frequency (fig. S14G).

NT5E and adenosine are increased inadult mice

We then tested auditory cortex map plasticityafter reducing thalamic adenosine production.Of the ectonucleotidases that produce adenosinein the brain (24), only ecto-5′-nucleotidase (Nt5e)mRNA was increased in mature versus neonatalthalamus (Fig. 2A). NT5E protein expression washigher in the thalamus and, to a lesser degree, inauditory cortex of adults versus neonates (Fig. 2B).Consistent with this developmental NT5E increase,total (intracellular and extracellular) adenosine washigher in the thalamus and auditory cortex ofadults than of neonates (Fig. 2C). In Nt5e–/– mice,this age-dependent increase of adenosine was ab-sent in the thalamus but evident in auditory cortex(Fig. 2C). Auditory cortex map plasticity wasinduced in mature Nt5e–/– mice, but not in WTlittermates exposed to a pure tone (Fig. 2, D andE). Mature tone-exposedNt5e–/–mice distinguishedfrequencies better than naïveNt5e–/–mice (Fig. 2F),without any effect on the auditory brain stemresponse or startle response (fig. S15). We alsoknocked down Nt5e in the MGv by injectingtwo different Nt5e siRNAs that reduced thalamicNt5e (fig. S16) and produced auditory cortex mapplasticity after tone exposure (Fig. 2, G and H).Metabotropic glutamate receptor (mGluR) antag-onists inhibit synaptic plasticity at mature thal-amocortical synapses (18, 19). CTEP, an mGluR5inhibitor that crosses the blood-brain barrier (25),blocked auditory cortex map plasticity in tone-exposed Nt5e–/– mice (fig. S17).

A1R agonist inhibits cortical mapplasticity in juvenile mice

In a reverse experiment, we exposed pups to9.8 kHzduring the critical period (P11 to P15),whiletreating themwith theblood-brainbarrier–permeableA1R agonist 2-chloro-N 6-cyclopentyladenosine

(CCPA) or vehicle. We mapped auditory cortex 6 to10 weeks later (fig. S18A). Tone exposure in thesepups produced auditory cortex map plasticity whenpaired with vehicle, but not when paired withCCPA (fig. S18B).

Auditory plasticity can be reestablishedin individual neuronsTo test for auditory cortex map plasticity inindividual neurons, we used two-photon im-aging of sound-evoked calcium transients in

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Fig. 1. Deletion of A1Rs in auditory thalamus is sufficient for passive tone exposure to induceauditory cortex map plasticity. (A) Representative auditory cortex maps from WT or A1R

–/– miceexposed or unexposed (naïve) to a 16.4-kHz tone. Black and gray depict blood vessels. D, dorsal;V, ventral; R, rostral; and C, caudal. 0, unresponsive sites; X, sites that do not match the tonotopiccriteria of primary auditory cortex. (B) Percentage of recording sites versus characteristic frequenciesfor naïve (black circles, five mice per genotype) or tone-exposed (7.9 kHz: red open circles, five miceper genotype; 16.4 kHz: red filled circles, five mice per genotype) WT (top) and A1R

–/– (bottom) mice[two-way repeated measures analysis of variance (ANOVA): genotype WT, F1,5 = 0.644, P = 0.446;two-tailed Student’s t test: genotype A1R

–/– (7.9 kHz), t8 =10.516, *P < 0.001; A1R–/– (16.4 kHz), t8 =

5.452, *P < 0.001]. (C to E) Auditory thalamus (MGv) injections of siRNAs and recordings in auditorycortex: percentage of recording sites versus characteristic frequencies in auditory cortex of WTmiceexposed to 9.8 kHz (red circles) or naïve mice (black circles) after injections of Adora1 siRNA1 (123)(naïve, four mice; exposed, six mice; t8 = 4.839, *P = 0.001) (C); Adora1 siRNA2 (789) (naïve,four mice; exposed, four mice; t6 = 3.498, *P = 0.01) (D); or control siRNA (naïve, six mice; exposed,four mice; t8 = 0.802, P = 0.4) (E). (F) Percentage of recording sites versus characteristicfrequencies in Adora1fl/fl mice exposed to 9.8 kHz and injected with AAV-CamKIIa-GFP (black squares,eight mice) or AAV-CamKIIa-Cre-GFP (red squares, nine mice) into MGv (t15 = 4.612, *P = 0.0003).(G) (Top) Schematic of the prepulse-inhibition acoustic-startle experiment. Prepulse frequencies are9.800, 9.604, 9.408, 9.016, 8.232, or 6.664 kHz, which are, respectively, 0, 2, 4, 8, 16, or 32%different from the frequency of the background tone. (Bottom) Mean inhibition of the acoustic startleresponse in Adora1fl/fl mice exposed to 9.8 kHz after injection of AAV-CamKIIa-GFP (black squares,10 mice) or AAV-CamKIIa-Cre-GFP (red squares, nine mice) into MGv (F1,5 = 42.382, *P < 0.001).CF, characteristic frequency; WN, white noise; PPI, prepulse inhibition.

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thalamorecipient neurons of auditory cortexin mature awake mice before and after tone ex-posure. We infected L3/4 excitatory neurons inauditory cortex (fig. S19) with a recombinant AAVexpressing genetically encoded calcium indicatorGCaMP6f (26) under control of the excitatoryneuron–specific promoter CamKIIa (AAV-CamKIIa-GCaMP6f) (Fig. 3A). We determined each neuron’sbest frequency (i.e., the frequency that evokesthe greatest response across all intensities) fromcalcium transients (fig. S20) evoked by a rangeof tone frequencies and intensities (Fig. 3, B andC). We measured tuning changes by repeatedly

imaging the same auditory cortex neurons be-fore and after as many as 5 days of exposure to9.8 kHz (Fig. 3D and figs. S21 to S23).All tested approaches that reduced adenosine

signaling or production in MGv enabled plastic-ity in individual neurons when paired with toneexposure. A1R knockdown in MGv with Adora1siRNA paired with 9.8-kHz exposure shifted bestfrequencies of individual L3/4 neurons toward9.8 kHz but not in naïve mice with A1R knockdownor when control siRNA was paired with 9.8-kHzexposure (Fig. 3, D to J). Nt5e siRNA injectedinto MGv also shifted best frequencies of indi-

vidual neurons toward 9.8 kHz in mice exposedto this frequency but not in naïve mice (Fig. 3, Kto N). Pairing tone exposure with pharmacologicblockade of A1Rs also caused L3/4 neurons toshift best frequencies toward the exposure fre-quency. We measured receptive fields in the samepopulation of neurons at days 0, 1, 3, and 5 duringthe 9.8-kHz tone exposure combined with FR194921administration. L3/4 neurons in auditory cortexshifted their best frequencies toward 9.8 kHzstarting at day 1 and maintained this shift dur-ing all the days of tone exposure (fig. S24, A toF). By contrast, pairing 9.8-kHz exposure withvehicle did not shift best frequencies of L3/4neurons toward 9.8 kHz on any tested day (fig.S24, G to L).Similar experiments in Adora1 f l/f l;Cre mice

(lacking A1Rs in MGv neurons) showed thatL3/4 neurons in auditory cortex also shifted bestfrequencies toward the exposure frequency. Cor-tical neurons of Adora1 f l/f l mice, which receivedMGv injections of Cre-tdTomato (AAV-CamKIIa-Cre-tdTomato) (fig. S25) and were exposed to9.8 kHz, shifted best frequencies toward 9.8 kHzat day 1 and maintained this shift at days 3 and 5of tone exposure (fig. S24, M to R). By contrast,this best frequency shift was not seen in L3/4neurons of WT littermates injected with Cre-tdTomato into MGv and exposed to 9.8 kHz forthe same periods of time (fig. S24, S to X). Aswitch in best frequency after tone exposure didnot depend on a neuron’s receptive field proper-ties or GCaMP6f-response amplitudes (fig. S26).These findings suggest that an NT5E-mediated,

age-dependent increase in adenosine productionin the auditory thalamus terminates the juvenilecritical period of auditory cortex map plasticityvia A1R activation. A1R activation inhibits virtuallyevery neurotransmitter in the brain, and its strongestinhibitory action is on excitatory glutamatergicsynapses (22). A1R activation reduces presynapticCa2+ influx and hyperpolarizes presynaptic mem-brane potential by activating inwardly rectify-ing K+ channels (22). During the critical period,when adenosine levels are low, sustained activityin auditory thalamocortical synapses triggersenough glutamate release to activate mGluRs andproduce long-term potentiation or long-term de-pression. In adults, higher NT5E expression leadsto increased production of adenosine, which limitssustained glutamate release via A1R activation,blocking thalamocortical synaptic plasticity andthereby preventing cortical map plasticity. Re-stricting thalamic adenosine signaling is suffi-cient to restore higher levels of glutamate releaseand synaptic plasticity at thalamocortical synap-ses in brain slices from adult mice (18, 19, 27)and reestablish cortical map plasticity in adultmice in vivo.Experimental manipulations in adult mice

that were expected to enable thalamocorticalsynaptic plasticity (i.e., knockdown or deletionof A1Rs or knockdown of NT5E in thalamicneurons) also facilitated auditory cortex mapplasticity. Manipulations expected to inhibitthalamocortical synaptic plasticity (i.e., mGluR5antagonist treatment in Nt5e–/– adult mice and

Blundon et al., Science 356, 1352–1356 (2017) 30 June 2017 3 of 5

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Fig. 2. Age-dependent increase of adenosine production underlies cortical map plasticityrestrictions in adult mice. (A) Mean Nt5e, Acpp (prostatic acid phosphatase), and Tnap (liver-bone-kidney alkaline phosphatase) mRNA levels [normalized to Gapdh (glyceraldehyde-3-phosphatedehydrogenase)] in the auditory thalamus of neonatal (P5 to P12, gray bars, seven mice) ormature (P45 to P56, black bars, six mice) WTmice (Nt5e: t11 = 2.325, *P = 0.038; Acpp: t11 = 1.145,P = 0.276; Tnap: t11 = 0.101, P = 0.921). (B) Representative Western blots of MGv extracts (top)and mean NT5E protein levels in the auditory thalamus (t15 = 7.857, *P < 0.001) and auditory cortex(t15 = 3.342, *P = 0.005) (bottom) of neonatal (gray bars, eight mice) or mature (black bars,eight mice) WTmice. (C) Total adenosine concentrations in the auditory thalamus and auditory cortexof neonatal (gray bars, 10 mice) or mature (black bars, 10 mice) WTmice (thalamus: t18 = 11.257,*P< 0.001; auditory cortex: t18 = 10.036, *P < 0.001) and neonatal (pink bars, 9mice) ormature (red bars,10 mice) Nt5e–/– mice (thalamus: t17 = 0.961, P = 0.35; auditory cortex: t17 = 3.218, *P = 0.005). (D andE) Percentage of recording sites versus characteristic frequencies in auditory cortex of naïve (blackcircles) or 11.4-kHz tone–exposed (red circles) WTmice (naïve, four mice; exposed, five mice; t7 = 0.283,P = 0.785) (D) andNt5e–/–mice (naïve, five mice; exposed, six mice; t9 = 2.148, *P = 0.03) (E). (F) Meanprepulse inhibition as a function of prepulse frequency in Nt5e–/– mice exposed to 9.8 kHz (red circles,17mice) or naïve (black circles, 20mice) (F1,6 = 13.643, *P < 0.001). (G andH) Percentage of recordingsites versus characteristic frequencies in auditory cortex of naïve (black circles) or 9.8-kHz tone–exposed (red circles) WTmice after injection of Nt5e siRNA1 (1264) (naïve, three mice; exposed, fourmice; t5 = 3.33, *P = 0.02) (G) orNt5e siRNA2 (1366) (naïve, five mice; exposed, sevenmice; t10 = 4.79,*P = 0.0007) (H) into MGv. ACx, auditory cortex; CF, characteristic frequency; PPI, prepulse inhibition.

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A1R agonist treatment during the postnatal criticalperiod) blocked cortical map plasticity. Knockdownof A1Rs in cortical neurons failed to potentiatecortical map plasticity in adult mice. These re-sults point to thalamocortical long-term plas-ticity as the necessary step that leads to corticalmap plasticity and enhanced auditory percep-tion. However, our results do not exclude thepossibility that the improvement in auditoryperception may result from additional changes

at other synapses in the auditory cortex as adownstream consequence triggered by thalamo-cortical synaptic plasticity.

Implications for the human context

Pairing tone exposure with administration of thespecific A1R antagonist FR194921 resulted incortical map plasticity and improved auditoryperception in adult mice. These results implythat other A1R inhibitors, such as caffeine, could

be used to improve auditory perception in adulthumans. However, because caffeine, especiallyat high concentrations, inhibits other adenosinereceptors and affects intracellular cyclic adeno-sine 3′,5′-monophosphate (cAMP) and calciumlevels (28), its effectiveness at improving auditoryperception could be limited, compared to that ofFR194921 or other specific A1R inhibitors.Cortical plasticity in adults holds potential

as a strategy to restore normal neural activity

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Fig. 3. Restricting thalamic adenosinesignaling or production is sufficient for pas-sive tone exposure to cause a tuning shiftin individual neurons in auditory cortex ofawake mice. (A) Representative image ofGCaMP6f-expressing L3/4 excitatory neurons inauditory cortex. (B and C) Sound-evokedGCaMP6f fluorescence transients (B) andrespective receptive field map (C) of an L3/4neuron. Gray vertical bars in (B) representsound stimuli. (D) Examples of receptive fieldheat maps (normalized to maximum intensity)in the same neurons before (day 0) and after(day 5) three experimental conditions: Adora1siRNA1 (123) in MGv with no tone exposure(two left panels), Adora1 siRNA1 (123) in MGvwith 9.8-kHz exposure (four middle panels), andcontrol siRNA in MGv with 9.8-kHz exposure(two right panels). Vertical dotted lines indicate9.8 kHz. (E to G) Cumulative histograms ofbest frequencies of recorded neurons inauditory cortex before (black solid lines) andafter 9.8-kHz exposure (green lines) underthe same three experimental conditions as in(D) (three mice per condition) [(E): 19 neurons,P > 0.05; (F): 34 neurons, *P < 0.05; (G):25 neurons, P > 0.05]. (H to J) Heat maps (DBFmaps) depicting shifts in neuron numbers(normalized to percent sampled) as a functionof best frequencies between days 0 and5, under three experimental conditions as in(D), from data in (E) to (G) [(H): P > 0.05;(I): *P < 0.001; (J): P > 0.05). Diagonal linesrepresent no change in best frequencies.Vertical lines represent 9.8 kHz. (K to N) Asdescribed above for (E) to (J), under twoexperimental conditions (three mice percondition): Nt5e siRNA1 (1264) in MGv withno tone exposure [(K) and (M): 24 neurons,P > 0.05] or Nt5e siRNA1 (1264) in MGvwith 9.8-kHz exposure [(L) and (N):23 neurons; (L): *P < 0.05; (N): *P < 0.001].BF, best frequency. 4.8

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in patients with neurological diseases, such astinnitus and stroke (29–32). One current methodfor inducing therapeutic targeted cortical mapplasticity in patients is the pairing of sensorystimulation (i.e., a sound) or motor training withrepeated electrical stimulation of the vagus nerveby using surgically implanted electrodes. Our workoffers an alternative, noninvasive method forinducing lasting cortical map plasticity, namely,by pairing a sound with administration of a spe-cific A1R inhibitor that has a short half-life.Adult cortical plasticity is associated with im-

provedtone-frequency discrimination. In humans,tone discrimination is required for acquiring lan-guage andmusical skills. Tonal representation inauditory cortex is larger in musicians than innonmusicians (33). This difference is observed pri-marily in musicians who began practicing theirinstruments before 9 years of age (34); it is alsoassociated with improved linguistic skills (35, 36).Here we show that disruption of thalamic ade-nosine signaling in the adult mouse that restoresauditory cortex map plasticity also improves au-ditory perception. A similar mechanism mayimprove the ability of adult humans to learnlinguistic, musical, and other auditory skills.

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ACKNOWLEDGMENTS

This work was supported by NIH grants DC012833, MH097742(S.S.Z.), and DC015388 (T.A.H.), and by American LebaneseSyrian Associated Charities (ALSAC) (S.S.Z.). The funding sourceshad no role in the study design, data collection, data analysis,decision to publish, or preparation of the manuscript. We thankthe Vector Core Laboratories (St. Jude Children’s ResearchHospital and University of Tennessee Health Science Center) andJ. Westmoreland for assistance in producing AAVs and lentiviruses;F. Du for assistance in generating Adora1fl/fl mice and pharmacokineticstudies; J. Min and A. Mayasundari for help with FR194921;A. Onar-Thomas for statistical assistance; A. Uptain and K. Andersonfor assistance with imaging experiments and viral injections in vivo;and V. Shanker and A. McArthur for editing the manuscript. Thesupplementary materials contain additional data. S.S.Z. and J.A.B.are inventors on patent application PCT/US2016/018377 submittedby St. Jude Children’s Research Hospital, which covers the subjectof improved learning through inhibition of adenosine signaling inthe thalamus.

SUPPLEMENTARY MATERIALS

www.sciencemag.org/content/356/6345/1352/suppl/DC1Materials and MethodsFigs. S1 to S26References (37–61)

24 February 2016; resubmitted 9 February 2017Accepted 15 May 201710.1126/science.aaf4612

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Restoring auditory cortex plasticity in adult mice by restricting thalamic adenosine signaling

Stanislav S. ZakharenkoSeung Baek Han, Ryan A. Kerekes, Derek C. Rose, Troy A. Hackett, Pradeep K. Vuppala, Burgess B. Freeman III and Jay A. Blundon, Noah C. Roy, Brett J. W. Teubner, Jing Yu, Tae-Yeon Eom, K. Jake Sample, Amar Pani, Richard J. Smeyne,

DOI: 10.1126/science.aaf4612 (6345), 1352-1356.356Science 

, this issue p. 1352; see also p. 1335Scienceimproved tone discrimination abilities.Kehayas and Holmaat). Disruption of adenosine production or adenosine receptor signaling in adult mice leads toadenosine signaling in mice, some plasticity of the adult auditory cortex can be regained (see the Perspective by

show that by manipulatinget al.facility may form the basis for childhood language acquisition in humans. Blundon postnatal days. The youthful brain tunes circuits to sounds in its environment in a way that the adult brain does not. Thisperiods, during which acquisition of certain skills is optimal. In mice, an auditory critical period is only open in early

Young brains, compared with adult brains, are plastic. This phenomenon has given rise to the concept of criticalReopening a critical period

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