S ilman et al (1984) demonstrated that an

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1 J Am Acd Audiol 6 : (1995) Long-Term Recovery nd No Recovery from the Auditory Deprivtion Effect with Binurl Amplifiction : Six Cses Stnley A. Gelfnd* Abstrct Six subjects who developed individully significnt uditory deprivtion effects ssocited with monurl mplifiction were trcked for 6.2 to 15.1 yers from the time of their initil hering id fitting. Ech subject received binurl hering ids fter the uditory deprivtion effect becme pprent nd used binurl mplifiction for t lest 4 yers. The findings corroborte nd expnd upon existing cse reports. Severl generl configurtions of recovery nd no recovery following the introduction of binurl mplifiction were identified : (1) cses in which uditory deprivtion effects developed within bout 2 yers nd recovered completely within bout 2 yers of binurl use ; (2) cses with significnt but incomplete recovery ; nd (3) cses in which the uditory deprivtion effect took severl yers to develop nd did not recover following severl yers of binurl mplifiction. Clinicl implictions of the results re proposed. Key Words: Auditory deprivtion, binurl mplifiction, monurl mplifiction, speech recognition, unided er effect S ilmn et l (1984) demonstrted tht n uditory deprivtion effect my occur in dults when one er regulrly receives uditory input but the other er is deprived of dequte uditory stimultion for period of time. It is observed s reduction in the speechrecognition bility of the understimulted er. The uditory deprivtion effect occurs in the unided er of ptients with bilterl sensorineurl hering loss (SNHL) who use monurl mplifiction. Their ided ers remin unchnged, s do both ers of similr ptients using binurl mplifiction. This unided er effect hs been repetedly corroborted (Gelfnd et l, 1987 ; Gtehouse, 1989, 1992 ; Stubblefield nd Nye, 1989 ; Emmer, 199 ; Silvermn, 1989 ; Silvermn nd Silmn 199 ; Silmn et l, 1992, 1993 ; Hurley, 1993 ; Poole nd Jerger, 1994). 'Deprtment of Communiction Arts nd Sciences, Queens College, City niversity of New York, Flushing, New York, nd Doctorl Progrm in Speech nd Hering Sciences, Grdute School, City niversity of New York, New York, New York Reprint requests : Stnley A. Gelfnd, Deprtment of Communiction Arts nd Sciences, Queens College of CNY, 65-3 Kissen Boulevrd, Flushing NY Auditory deprivtion effects lso occur for the poorer ers of ptients with symmetric SNHLs (Silvermn nd Emmer, 1993), nd n nlogous phenomenon effect hs been reported in ptients with Meniere's disese (Hood, 1984, 199). The uditory deprivtion effect is not limited to dults. Gelfnd nd Silmn (1993) recently demonstrted tht children with bilterl moderte SNHLs developed n uditory deprivtion effect when using monurl hering ids. Supportive findings were reported by Httori (1993) for children with severe bilterl losses. Studies tht follow individul cses longitudinlly provide insights bout uditory deprivtion effects tht my not lwys be redily pprent from group studies. For exmple, it hs been demonstrted tht individully significnt uditory deprivtion effects cn develop fter s little s 2 yers of monurl hering id use (Silmn, et l, 1992 ; Hurley, 1993) or my tke mny yers to develop (Silvermn, 1989 ; Silvermn nd Silmn, 199; Hurley, 1993). Cse studies hve lso reveled tht t lest some ptients with uditory deprivtion effects experience significnt though usully incomplete recovery following the use of binurl hering ids for some time (Silvermn nd Silmn, 199 ;

2 Journl of the Americn Acdemy of Audiology/Volume 6, Number 2, Mrch 1995 Hurley, 1993). Providing mplifiction to the previously unided ers of subjects with symmetric sensorineurl losses hs lso been found to reverse the uditory deprivtion effect in some cses (Silvermn nd Emmer, 1993). Supportive evidence lso comes from cse report by Boothroyd (1993) in which child with bilterl severe-to-profound loss ws followed through young dulthood. This child used monurl mplifiction nd hd very low speech-recognition score (SRS) in her unided er, which improved with the introduction of binurl mplifiction. This score worsened fter she refused to continue using the second id. Burkey nd Arkis (1993) compred the SRSs of ptients who purchsed binurl hering ids fter severl yers of monurl hering id use nd then fter bout 1 yer of binurl mplifiction. They concluded tht the prevention of uditory deprivtion is not reson to recommend binurl hering ids. This conclusion could only be supported if virtully ll uditory deprivtion effect cses would experience essentilly complete recovery within short time fter the introduction of binurl hering ids. Even though recovery from the uditory deprivtion effect due to the introduction of binurl mplifiction is n importnt issue with prcticl pplictions, it is still poorly understood. This report ttempts to increse our knowledge regrding this issue by describing six subjects who were provided with binurl hering ids fter developing significnt uditory deprivtion effects. Ech cse ws trcked for severl yers. These cses provide vluble informtion becuse detils bout the time course of uditory deprivtion development nd recovery re not ffected by verging cross subjects. The current findings identify severl brod ctegories of recovery/no recovery of the uditory deprivtion effect following the introduction of binurl hering ids. Clinicl suggestions re offered bsed on these findings. METHOD he pproch ws cse-by-cse longitudinl T time-series study of subjects with significnt uditory deprivtion effects who subsequently received nd used binurl mplifiction for resonbly long period of time. A significnt uditory deprivtion effect ws defined s n SRS tht fell below the initil score obtined prior to the introduction of mplifiction by n mount tht exceeded the 95 percent confidence limits (CLs) (Thornton nd Rffm, 1978). Specif- iclly, the time series for ech subject included the period beginning with premplifiction evlution, the initition of monurl mplifiction, the durtion over which significnt uditory deprivtion effect developed, the introduction of binurl mplifiction, nd 4 or more yers of binurl hering id use. In order to ccomplish this, it ws necessry for the dt to be collected in prt retrospectively nd in prt prospectively. The retrospective spect utilized the records of severl subjects who were involved in prior study (Gelfnd et l, 1987), s described below. The prospective spect involved trcking the progress of these subjects therefter. Subjects The subjects were six dult mles who rnged in ge from 31 to 64 yers t the time of their initil (premplifiction) evlutions nd who were trcked for time periods tht rnged from 6.2 to 15.1 yers from the time of their originl monurl fittings. They were the six individuls mong 48 monurlly fitted subjects used in n erlier study (Gelfnd et l, 1987) who met both of the following criteri : (1) n individully significnt uditory deprivtion effect nd (2) subsequent binurl mplifiction for t lest 4 yers. All subjects hd SNHLs of presumbly cochler origin bsed on the following criteri : (1) pure-tone verges (PTAs) for 5, 1, nd 2 Hz nd speech reception thresholds (SRTs) of >_ 35 db HL (ANSI 1969) for both ers ; (2) no significnt ir-bone gps (Studebker, 1962) for both ers ; (3) norml tympnogrms nd contrlterl coustic reflex thresholds within the 9th percentiles for cochler impirments (Silmn nd Gelfnd, 1981 ; Wiley et l, 1987 ; Gelfnd et l, 199) for both ers ; (4) negtive tone decy (Olsen nd Noffsinger, 1974) for both ers ; nd (5) no history of neurologic or er disese. Their SRSs were obtined with recorded, 5-word test lists (CID W-22 or N-6) t 4 (±5) db SL re : SRT t intervls over the period studied. The subjects reported using their hering ids 8 or more hours per dy over the course of the study. T RESLTS ble 1 shows the subjects' initil ir-conduction pure-tone thresholds, PTAs, SRTs, nd SRSs, which were obtined when they were first fit with monurl mplifiction. Figures 1 to 6 show the SRSs over time for ech subject. 142

3 Auditory Deprivtion Effect/Gelfnd Tble 1 Initil Pure-tone Air-conduction Thresholds*, PTAs,* SRTs,* nd SRSst for Ech Subject Subject nd Er Frequency (Hz) PTA SRT SRS Right Left t Right Left' Right Left t Right Left ' Right' Left Right Left $ *In db HL (ANSI,1969),'in percent. 'The er tht ws ided while using monurl mplifiction. Similr grphs re lso shown for the subjects' PTAs in order to summrize their pure-tone sensitivity over the time period studied. Cse 1 This ptient ws 5 yers old when he received his first hering id, which ws monurl fitting in the left er. At tht time, he hd bilterl SNHL for which the PTA ws 37 db HL nd the SRT ws 35 db HL in the right er, nd the PTA nd SRT were both 4 db HL in the left er. Figure 1 shows this ptient's SRSs over period of 8.6 yers beginning with the time when he first received the hering id for his left er. His SRSs were 96 percent in the right er nd 88 percent in the left er when he first received the hering id. Subsequent SRSs were considered significntly different from these initil scores if they fell below 86 percent for the right er nd 74 percent for the left, which re the lower cut-offs of the 95 percent confidence intervls (CIs) for these scores (Thorton nd Rffm, 1978). sing this criterion, there were no significnt chnges in the SRSs over the 8.6-yer period for the left er, which ws ided from the outset. After 6 months of monurl hering id use, the unided right er's SRS fell to 86 percent, which is just within the 95 percent CI. N t v v V 7l d Initil Time of Test (Yers) IX-M o- O -o Initil Time of Test (Yers) Figure 1 Findings over time for subject 1. pper pnel: SRSs in percent over time ; lower pnel : PTAs in db HL (ANSI, 1969). Circles denote right er dt nd crosses denote dt for the left er. The sterisk shows when binurl mplifiction ws introduced. (Note tht the time scle is not liner. Insted, the test dtes re eqully spced long the bsciss for ese of presenttion.)

4 Journl of the Americn Acdemy of Audiology/Volume 6, Number 2, Mrch 1995 The SRS of the unided er fell below the 95 percent CL to 66 percent by 1.9 yers fter monurl mplifiction ws initited. Binurl mplifiction ws introduced t this point. The SRS of the previously unided right er returned to 88 percent fter only 1 months of binurl mplifiction (2.7 yers on the grph) nd remined t this level for the reminder of the 8.6 yers trcked in this cse. There were no chnges in the ptient's sttus tht could ccount for ny of the chnges observed in his SRSs over time. This ws lso true for the other five subjects. Cse 2 Subject 2 ws 5-yer-old mle with moderte-to-severe bilterl SNHL when he received monurl hering id for his left er. His initil PTAs were 58 db HL for the right er nd 53 db HL for the left er, nd his SRTs were 6 db HL in both ers. He ws followed for 14.1 yers, beginning with the first fitting (Fig. 2). This ptient's initil SRSs were 8 percent nd 92 percent for the right nd left ers, respectively. The lower 95 percent CLs for these scores re 64 percent for the right er nd 78 percent for the left. No significnt SRS chnges occurred for the left er, which ws ided over the entire period. The SRS of the unided right er decresed significntly to 48 percent 7 months (.6 yers) fter monurl mplifiction ws initited nd ws 56 percent fter 2.7 yers. Binurl hering ids were introduced t tht time. The previously unided right er's SRS returned to 84 percent within 1.2 yers of binurl hering id use (3.9 yers) nd styed within the 95 percent Cl of the initil score therefter. Cse 3 Subject 3 hd moderte-to-severe bilterl SNHL t ge 64, when he begn using monurl mplifiction on his left er. At the time of the initil hering id fitting, his right nd left ers hd PTAs of 47 db HL nd 35 db HL nd SRTs of 5 db HL nd 35 db HL, respectively. Figure 3 demonstrtes tht the difference between the losses of the two ers nrrowed s the loss in the left (lwys ided) er progressed slightly over the 6.2 yer period, t the end of which the PTAs were 5 db HL for the right er nd 47 db HL for the left. This ptient hd initil SRSs of 86 percent for the right er nd 9 percent for the left er. 1 8 c V L d t c v N Initil Initil Time of Test (Yers) Time of Test (Yers) Initil Time of Test (Yers) Figure 2 Findings over time for subject 2. Dt nd symbols re the sme s in Figure 1. (The time scle is not liner.) 1 x 8 m r x-x--x~~x x Initil Figure 3 Findings over time for subject 3. Dt nd symbols re the sme s in Figure 1. (The time scle is not liner.) 144

5 Auditory Deprivtion Effect/Gelfnd The lower 95 percent CLs for these initil scores re 7 percent for the right er nd 76 percent for the left er. As shown in Figure 3, the SRSs of the lwys-ided left er did not chnge significntly over the next 6.2 yers. The unided right er's score decresed only slightly fter.9 yers. However, it decresed significntly to 68 percent t 2.3 yers nd fell to 4 percent fter 4 yers of monurl hering id use. Binurl hering ids were then introduced. The right er's SRS remined unchnged t 44 percent fter 4 months (4.3 yers). It rose to 66 percent fter 1.4 yers of binurl mplifiction (5.4 yers), which ws still significntly below the 95 percent CL of the initil score. The right er's SRS incresed to 7 percent fter 2.2 yers of binurl usge (6.2 yers), which is equl to the originl score's lower 95 percent CL. Cse 4 Subject 4 obtined monurl hering id for his left er t ge 54 yers. He hd bilterl moderte SNHL with PTAs of 43 db HL for the right er nd 5 db HL for the left, nd SRTs of 45 nd 5 db HL, respectively. His initil SRSs were 88 percent in the right er nd 9 percent in the left er. The lower 95 percent V N 1 8 X X-X-- X c 6 t V c ' V 4 c 2 CLs for these scores re 74 percent nd 76 percent, respectively. The SRSs nd PTAs obtined for this subject t vrious times re presented in Figure 4. This subject's PTAs remined essentilly unchnged for 11.7 yers fter the initil fitting. The SRSs of the lwys-ided left er did not chnge significntly during this period. The SRS of the unided right er ws unchnged 4.2 yers fter the initil fitting but fell significntly to 6 percent t 5.5 yers. The unided er's score ws 56 percent t 6.3 yers, when binurl mplifiction ws introduced. The SRS of the previously unided er incresed grdully over the next 5.4 yers nd eventully rose to 74 percent, which is just within the 95 percent CI of the initil score. Cse 5 Subject 5 ws 31-yer-old mle with moderte-to-severe bilterl SNHL who received monurl hering id for his right er. At tht time, he hd SRTs of 55 db HL in both ers, with PTAs of 55 db HL for the right er nd 58 db HL for the left. This individul's initil SRSs were 82 percent in the right er nd 8 percent in the left er, for which the lower 95 percent CLs re 66 percent nd 64 percent, respectively. His Initil Initil Time of Test (Yers) Time oftest (Yers) 1 1 m 8 6 Y m v v `v `v O- ~~ Q ---~r XCii v 4 c f- F u Initil Initil Time oftest (Yers) Time of Test (Yers) Figure 4 Findings over time for subject 4. Dt nd symbols re the sme s in Figure 1. (The time scle is not liner.) Figure 5 Findings over time for subject 5. Dt nd symbols re the sme s in Figure 1. (The time scle is not liner.)

6 Journl of the Americn Acdemy of Audiology/Volume 6, Number 2, Mrch 1995 performnce ws monitored for 12.3 yers fter the initil fitting (Fig. 5) This ptient's SRSs remined essentilly unchnged in both ers for 5.4 yers following the initil monurl fitting of the right er. The scores styed the sme for the reminder of the 12.3 yers for the right er, which lwys used hering id. However, the SRSs of the unided left er fell below the 95 percent CL fter 6.2 yers of monurl mplifiction, t which point the score ws 58 percent. Five months lter (6.6 yers), the left er's SRS ws 52 percent, nd binurl mplifiction ws begun t tht time. As shown in Figure 5, the SRSs of the previously unided left er did not improve over the next 6 yers even though the ptient reported tht binurl mplifiction ws used over tht period. Cse 6 Subject 6 hd moderte-to-severe bilterl SNHL when he begn using monurl hering id for his left er t ge 46 yers. At tht time, his right nd left ers hd PTAs of 57 db HL nd 58 db HL, SRTs of 55 nd 5 db HL, nd SRSs of 76 percent nd 72 percent, respectively. The lower 95 percent CLs re 58 percent for the right er nd 54 percent for the left er. Figure 6 displys his SRSs nd PTAs obtined during six subsequent evlutions tht took plce over period of 15.1 yers following the initil hering id fitting. The SRSs of the lwys-ided left er did not fll below the initil score. These scores ctully incresed to nd remined within the 8 to 88 percent rnge for ll subsequent tests, severl of which exceeded the upper 95 percent CL of 86 percent. The SRSs of the unided right er lso did not decrese during the first 7.7 yers of monurl hering id use but did drop significntly to 48 percent by 9.5 yers. Binurl mplifiction ws introduced t 1.2 yers nd ws reportedly used regulrly therefter. However, the SRSs of the previously unided er filed to improve during the succeeding 4.9 yers of binurl hering id use. COMMENTS T he dt from subjects 1 nd 2 corroborte the cse reported by Silmn et l (1992). Tken together, they demonstrte tht (1) significnt uditory deprivtion effect cn develop within bout 2 yers of monurl hering id use, nd (2) the SRS of the previously unided er cn return to its originl level within bout 1 8 c 6 C d y 4 1 x 8 m Y 4 S v 2 Initil Time of Test (Yers) 6 x x-x~x-x- Initil Figure 6 Findings over time for subject 6. Dt nd symbols re the sme s in Figure 1. (The time scle is not liner.) 2 yers fter binurl mplifiction is introduced. Additionlly, the cses described here revel tht n uditory deprivtion effect cn develop s quickly s 7 months fter use of monurl hering id (subject 2) nd tht essentilly complete resolution cn occur s quickly s 1 months fter introducing binurl mplifiction (subject 1). Binurl mplifiction provided subjects 3 nd 4 with significnt but incomplete resolution of their uditory deprivtion effects over period of severl yers. This course of improvement ws lso found in severl cses reported by Silvermn nd Silmn (199) nd Hurley (1993). Thus, significnt but incomplete improvement of the SRS in the previously unided er ppers to be somewht typicl pttern of resolution of the uditory deprivtion effect following the introduction of binurl hering ids. However, the subjects with this pttern of resolution vry considerbly in terms of (1) how long they used monurl id before significnt uditory deprivtion effect developed nd (2) the dely between introducing binurl mplifiction nd the improvement of the SRS to within the initil CLs for the ffected er. Subjects 5 nd 6 hd "delyed-onset" uditory deprivtion effects tking 6 or more yers x 146

7 Auditory Deprivtion Effect/Gelfnd to develop nd no resolution of the uditory deprivtion effect following the introduction of binurl mplifiction, even fter severl yers of use. These cses demonstrte tht t lest some uditory deprivtion effects re not reversible. Why did these two ptients continue using binurl hering ids for so mny yers in spite of unimproved SRSs in their ffected ers? Clerly, binurl hering ids must hve been providing enough of n dvntge in dily living compred to monurl mplifiction to justify their continued use. Even though binurl mplifiction filed to reverse the uditory deprivtion effect, it did not men tht these ptients were unble to derive ny benefit from binurl stimultion. This point is supported by the fct tht both of these ptients hd severe bilterl losses, with PTAs of bout 6 to 65 db HL. It is perhps noteworthy tht the monurl fittings were in the left er for five of the subjects (1-4, who experienced recovery, nd 6, who hd no recovery), nd in the right er for one of them (subject 5, who did not recover). However, there is no obvious reson why this brekdown of originlly fitted ers should hve ffected the outcome. Burkey nd Arkis (1993) contended tht the unided er effect cn lwys be reversed by introducing binurl mplifiction, thus negting the need for initilly fitting both ers to protect ginst the effect. However, the ccumulting informtion from this nd other crefully executed cse studies contrdicts this viewpoint. It is undenible tht recovery from the uditory deprivtion effect cn result from the subsequent introduction of binurl mplifiction. This is clerly shown here by Silvermn nd Silmn (199) nd by Hurley (1993). However, these studies lso show tht binurl mplifiction does not reverse the uditory deprivtion effect in every cse, nor does it necessrily result in the complete resolution of SRSs to their initil vlues. In fct, the dt reported by Burkey nd Arkis (1993, Tble 3) revel tht the SRS mens for their poorerhering (men PTA = 48.4 db HL) subjects' unided ers fell from 88.6 percent initilly to 73.8 percent fter monurl mplifiction nd then prtilly recovered to 81 percent fter bout 1 yer of binurl use. Further, their less-impired subjects (men PTA = 34.4 db HL) did not pper to experience ny recovery on group bsis, s reflected by their men SRSs of 96 percent initilly, 83.8 post-monurl use, nd 85.4 percent post-binurl use. Moreover, the very possibility of reversing the uditory deprivtion effect depends upon the cceptnce of binurl hering id by ptient who hs been using one instrument. Additionlly, severl of Hurley's (1993) subjects returned their second instruments even when binurl mplifiction resulted in significnt recovery from the uditory deprivtion effect. The cses reported here provide n existence proof of vrious ptterns in the development nd resolution of the uditory deprivtion effect. At lest one more ctegory is represented by those who reject binurl mplifiction even though their unided er effects re reversed by its use, s reported by Hurley (1993). Thus, the uditory deprivtion effect my not be unitry phenomenon but rther constelltion of either relted effects nd/or different underlying effects tht re provoked by similr conditions. For exmple, one possible set of explntions for the vrious findings would be to suggest tht subjects 1 nd 2 might reflect behviorl chnges, tht subjects 3 nd 4 might exemplify physiologic effects tht re reversible, nd tht subject 5 nd 6 my be cses of physiologic chnges tht re not reversible. In ny cse, uditory deprivtion development nd recovery ptterns pper to be disclosing tht there is probbly greter degree of plsticity in the uditory system thn previously supposed nd tht the potentil for plsticity seems to extend well into dulthood. The similr precipitting conditions for ech of the outcomes observed pper to involve symmetry t the two ers. This might be due to differences in the mount or qulity of the uditory input to the two ers (becuse of monurl mplifiction) nd/or to the effects of n symmetric hering loss. The concept tht there my be vriety of different effects of symmetry, which to dte hve been reveled s unilterlly reduced SRSs, suggests severl lines of reserch, which might ddress (1) behviorl versus physiologic explntions for the uditory deprivtion effect ; (2) the prmeters nd underlying resons for different ptterns of development nd recovery ; (3) the prmeters underlying the cceptnce or rejection of binurl mplifiction fter long-term monurl hering id use ; nd (4) the development of profiles chrcterizing ptients who most likely will or will not develop uditory deprivtion effects. Moreover, there ppers to be need to consider the use of uditory mesures other thn just the trditionl SRS to describe nd help explin the effects of uditory deprivtion.

8 Journl of the Americn Acdemy of Audiology/Volume 6, Number 2, Mrch 1995 The existence of individul differences tht re not yet fully known or understood highlights the importnce of using individul subject studies to supplement more forml group designs in this re. Cse mteril mkes it possible to identify effects tht re often obscured in group dt. The cses reported here revel tht this is problemtic issue when studying uditory deprivtion effects tht vry widely with respect to the time frmes over which they develop nd resolve. Thus, individul subject dt llow us to identify chrcteristics tht would be verged out in group dt nd tht could potentilly ffect the criteri used for ssigning subjects to groups. Although the resons for vribility in the development nd resolution of the uditory deprivtion effect re uncler, severl clinicl implictions of these nd relted findings re strightforwrd. The best tretment for n uditory deprivtion effect is to void it in the first plce. Thus, binurl mplifiction should be the first considertion in cses of bilterl hering loss. This does not imply tht binurl hering ids re best for every ptient. A binurl fitting might be rejected due to ny number of physicl, behviorl, uditory, cognitive, emotionl, or finncil considertions. Of prticulr interest in this context is study by Jerger et l (1993), who recently described binurl interference phenomenon in which binurl performnce is impired by the prticiption of the poorer er. Even though regulr udiologic follow-up is pproprite for ny hering-impired individul, monitoring is ll the more importnt for monurl hering id users so tht n uditory deprivtion effect cn be identified s erly s possible. This is essentil becuse the cse study dt presented here hve clerly demonstrted tht n uditory deprivtion effect cn develop in s short period s 7 months or fter s long period s yers. The pproprite strtegy to follow when n uditory deprivtion effect is observed is to introduce binurl mplifiction. In fct, unless there is reson to discontinue use of binurl mplifiction, it my be prudent to encourge ptients with uditory deprivtion effects to continue using binurl mplifiction even if improved SRSs re not observed for quite some time. However, binurl mplifiction my not necessrily be the only pproch. For exmple, the use of lternting monurl mplifiction (Httori, 1993) my lso be pproprite. There is cler need for further reserch deling with intervention pproches for uditory deprivtion effects. Acknowledgments. I would like to thnk the editorin-chief nd three nonymous reviewers for their vluble suggestions. Portions of this mteril were presented t the Convention of the Americn Acdemy of Audiology, Richmond, VA, April-My REFERENCES Americn Ntionl Stndrd Institute. (1969). Americn Ntionl Stndrd Specifiction for Audiometers. (ANSI S ). New York : ANSI. Boothroyd A. (1993). Recovery of speech perception performnce fter prolonged uditory deprivtion: cse study. J Am Acd Audiol 4: Burkey JM, Arkis MA. (1993). Word recognition chnges fter monurl, binurl mplifiction. Her Instr 44(1):8-9. Emmer MB. (199). The effect of lck of mplifiction on speech recognition in the unided er. Her Instr 41(9) :16. Gtehouse S. (1989). Apprent uditory deprivtion of lte-onset : the effects of presenttion levels. JAcoust Soc Am 86: Gtehouse S. (1992). The timecourse nd mgnitude of perceptul cclimtiztion to frequency responses : evidence from monurl fitting of hering ids. JAcoust Soc Am 92: Gelfnd SA, Schwnder TS, Silmn S. (199). Acoustic reflex thresholds in norml nd cochler-impired ers : effects of no-response rtes on 9th percentiles in lrge smple. J Speech Her Disord 55: Gelfnd SA, Silmn S. (1993). Apprent uditory deprivtion in children : implictions of monurl versus binurl hering. J Am Acd Audiol 4: Gelfnd SA, Silmn S, Ross L. (1987). Long-term effects of monurl, binurl nd no mplifiction in subjects with bilterl hering loss. Scnd Audiol 16: Jerger J, Silmn S, Lew HL, Chmiel R. (1993). Cse studies in binurl interference : converging evidence from behviorl nd electrophysiologic mesures. JAm Acd Audiol 4: Httori H. (1993). Er dominnce for nonsense-syllble recognition bility in sensorineurl hering-impired children : monurl versus binurl mplifiction. JAm Acd Audiol 4: Hood JJ. (1984). Speech discrimintion in bilterl nd unilterl hering loss due to Meniere's disese. Br J Audiol 18:

9 Auditory Deprivtion Effect/Gelfnd Hood JJ. (199). Problems in centrl binurl integrtion in hering loss cses. Her Instr 41(4):6, 8, 11, 56. Hurley RM. (1993). Monurl er effect : cse presenttions. J Am Acd Audiol 4: Olsen WO, Noffsinger C. (1974). Comprison of one new nd three old tests of uditory dpttion. Arch Otolryngol 99 : Poole C, Jerger J. (1994). Auditory Deprivtion in Monurl Hering Aid sers. Poster presented t the April Convention of Americn Acdemy of Audiology, Richmond, VA. Silmn S, Gelfnd SA. (1981). The reltionship between mgnitude of hering loss nd coustic reflex threshold levels. J Speech Her Disord 46 : Silmn S, Gelfnd SA, Silvermn CA. (1984). Lte-onset uditory deprivtion : effects of monurl versus binurl hering ids. JAcoust Soc Am 76: Silmn S, Silvermn CA, Emmer MB, Gelfnd SA. (1992). Adult-onset uditory deprivtion. J Am Acd Audiol 3: Silmn S, Silvermn CA, Emmer MB, Gelfnd SA. (1993). Effects of prolonged lck of mplifiction on speech- recognition performnce : preliminry findings. J Rehbil Res Dev 3: Silvermn CA. (1989). Auditory deprivtion. Her Instr 41(9):16, Silvermn CA, Emmer MB. (1993). Auditory deprivtion from nd recovery in dults with symmetric sensorineurl hering impirment. JAm Acd Audiol 4: Silvermn CA, Silmn S. (199). Apprent uditory deprivtion from monurl mplifiction nd recovery with binurl mplifiction : two cse studies. J Am Acd Audiol 1: Stubblefield J, Nye C. (1989). Aided nd unided timerelted differences in word discrimintion. Her Instr 4(9) :38-43, 78. Studebker GA. (1962). On msking in bone conduction testing. J Speech Her Res 5: Thornton AR, Rffin MJM. (1978). Speech discrimintion scores modeled s binomil vrible. J Speech Her Res 21: Wiley TL, Ovitt DL, Block MG. (1987). Acoustic-immittnce mesures in norml ers. J Speech Her Res 3: