Richard E. Frye,1,2 Richard L. Doty,1,2 and Paul Shaman,1,3

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1 BILATERAL AND UNILATERAL LFACTRY SENSITIVITY' RELATINSHIP T HANDEDNESS AND GENDER Richr E. Frye,1,2 Richr L. Doty,1,2 n Pul Shmn,1,3 INTRDUCTIN ISmell n Tste Center, 2Deprtment of torhinolryngology -- He n Neck Surgery, School of Meicine, n 3Deprtment of Sttistics, The Whrton School, University of Pennsylvni, Philelphi, Pennsylvni Unlike most mjor sensory systems, the mjority of olfctory projections re ipsilterl. Both hemispheres cn process olfctory informtion in mnner nlogous to wht is seen in other sensory systems, lthough, s note below, they my o so ifferently. Goron n Sperry (1969) foun tht ptients whose corpus cllosum n other forebrin commissures were surgiclly sectione coul only nmes oors presente to the left nostril; oors presente to the right nostril coul be ientifie by pointing to n object ssocite with the smell. A number of recent stuies hve suggeste tht suprthreshol olfctory tsks such s oor mtching n memory re processe by the right hemisphere (Eskenzi et l., 1988; Ztorre & Jones-Gotmn, 1990). Evience for lterliztion of olfctory sensitivity is less cler. Two stuies hve foun left-right threshol ifferences relte to hneness, lthough these stuies o not gree on the irection of the ifference (Toulouse n Vschie, 1900; Youngentub et l., 1982). ther stuies hve been unble to fin ny left:right ifferences in olfctory sensitivity (Koeleg, 1979; Ztorre & Jones-Gotmn, 1990). The present pper summrizes the slient finings of recent stuy in which we sought to etermine if one sie of the nose is better thn the other in etecting the oor of 2-butnone. A etermintion ws me s to the influence of hneness, gener, n blocking of the contrlterl nostril on unilterl olfctory sensitivity. METHDS Subjects Sixteen right hne men, 21 right hne women, 17 left hne men, n 211eft hne women serve s subjects (men ge , SD = 5.99). Hneness ws etermine using the revision by Briggs n Nebes (1975) of Annett's (1967) hneness inventory. None reporte hving ny problems smelling oornts n ll were in goo helth. Thirty six of the subjects performe the olfctor~ tests with their contrlterl nostril blocke by piece of 3M MicrofomT tpe, n 39 performe the test with it open. Chemicl Signls in Verlebrles VI. Eite by R.L. Doty n D. Mlil1er-Schwrze. Plenum Press, New York,

2 Generl Experimentl Design The esign of this stuy ws stright forwr. A subject first complete permission form n the Hneness Inventory. Nsl resistnce ws then etermine in ech nostril, followe by the etection threshol tests of the right n left sies of the nose. Nsl resistnce ws gin etermine, followe by suprthreshol olfctory function test (not escribe in this pper). Subsequently, the subject left the lbortory for brek of severl hours. Upon return, if the reltive nsl resistnce h not shifte to the opposite nostril, we ttempte to inuce shift by pplying pressure uner the rmpit, in the plm of the hn, or by uitory stimultion on the more ptent sie of the nose (Ro & Potr, 1970) n the subject ws reteste for smell function. lfctory!h!;:!!shol Mesur~ The concentrtion series of 2-butnone ws prouce by 10-stge ir-ilution ynmic olfctometer (Doty et l., 1988). The following hllog step oornt concentrtions were use (in ppm): 0.6, 1.0, 1.8, 3.2, 5.6, 10.0, 17.8, 31.6, 56.2, n loo. lfctory threshols were etermine using single stircse force-choice proceure escribe in etil elsewhere (Doty et l., 1984). Within the threshol test sessions the orer in which ech sie of the nose receive the stimulus ws rnom ize (with the exception tht given sie receive no more thn three consecutive trils). ~ Anlysis We sought to etermine whether gener, hneness, or blockge of the contrlterl nostril uring testing influence the mgnitue of either threshol mesure or the ifference between the right n left threshols. We subjecte the t to multivrite (left nostril, right nostril) repete mesures (session I, session 2) weighte nlysis of covrince. The threshol mesures n the nsl resistnce covrites (for ech nostril n ech session) were logrithmiclly trnsforme. Since the threshol mesurement ws clculte from trils occurring in pproximtely the lst thir of the test session, the post-test mximum rius irflow mesurement ws use in this nlysis. RESULTS Tble 1 lists the F-vlues n their respective E vlues for ech fctor in our nlysis. The column for combine threshols inictes if the fctor influence both the right n left sie of the nose. The threshol ifference column shows if ny fctor influence the ifference between the left n right threshol mesures. Essentilly, this ifference vlue represents the egree n irection of left:right superiority in olfctory sensitivity. Although both left n right threshols were lower for the secon test session thn the first, the ifference between the left n right threshols were the sme in both sessions; therefore, the effects of the first n secon sessions were combine in the nlysis. A significnt ifference between the left n right threshol vlues ws foun, with the left sie exhibiting slightly lower verge threshol 560

3 Tble 1. Sttisticl tests for the influence of gener, hneness, blockge of the contrlterl nostril uring testing, session, n irflow for the combine left n right olfctory threshol vlues n the ifference between the left n right threshol vlues. Fctors Combine Threshols f F Rtio P. Vlue Threshol Difference f F Rtio P. Vlue All Fctors Gener Hneness Blockge Gener x Hn Gener x Block Hn x Block Gener x Hn x Block Session 8/278 8/278 8/ /278 1/278 1/ ! thn the right [Men in log ppm (SE), Combine Left = (0.090), Right = (0.081)]. This is illustrte in Figure l, which is sctterplot of the left vs the right threshol vlue for ech subject. The igonl line seprtes those cses with higher threshol vlue for the right sie of the nose (those below the line) from those cses with higher vlue for the left sie of the nose (thqse bove the line). The mjority of these cses re below this line inicting tht, in generl, the left sie of the nose ws more sensitive. In generl, femles evience lower olfctory threshols thn mles (Figure lb). n verge, femles were slightly more sensitive on the right thn the left sie of the nose, wheres the opposite ws true for mles (Figure lb). Both mle n femle subjects who h their contrlterl nris blocke uring testing typiclly showe higher threshols thn those who i not hve their contrlterl nris blocke; this ifference ws greter for femles thn for mles (Figures lc & ). Contrlterl nris blockge lso influence which sie of the nose ws more sensitive. Greter sensitivity on the left thn the right sie of the nose ws observe when the contrlterl nostril ws open uring testing, wheres the opposite ws true when the contrlterl nris ws close (Figures lc & ). In generl, right hners were more sensitive to the test oor thn were left hners. However, hneness influence left n right threshol vlues for mles n femles ifferently. As cn be seen in Figure 2, left n right threshol vlues were higher for mle right hners thn mle left hners n lower for femle right hners thn femle left hners. However, the reltionship between hneness n threshol ws more pronounce in the left thn the right nostril, especilly for femles. Thus, left hne femles were more sensitive in the right thn the left nostril n right hne femles were more sensitive in the left thn the right nostril. The opposite reltionship occurre for the mle subjects. This effect ws increse by blockge of the contrlterl nris uring testing, with lrger increse occurring for femles thn for mles. 561

4 25 24 ~ Q 01.c (I) 0).E - : 1 0-0) 0!: CI) Q) :c: \-e\\?-\9"\ Nostril ~, b., 0) 0,,.c, 00 0).E 1 0- C!J "0.c w ~.c \.-6\\ ~9~\ Nostril Nostril Figure 1 () Averge left n right threshol vlues for ech subject. Men (~ SEM) threshols for (b) mles (tringles) n femles (circles), n subjects teste with thier contrlterl nostril (c) opene (empty symbols) n () blocke (fille symbols). 562

5 DISCUSSIN The literture concerning unilterl olfctory sensitivity n oor ientifiction is uncler. In the present stuy, we foun the verge ifference between the right n left threshols to be very smll (when untrnsforme this ifference is less thn 1 ppm). We hve shown tht the ifference between the right n left threshols is complex function of hneness n gener. verll, our finings suggest tht right hne subjects re more sensitive on the left sie of the nose n left hne subjects re more sensitive on right sie of the nose. These results re in ccor with Toulouse n Vschie (1900), but contrict those of Youngentub et l. (1982) who reporte tht left hne subject were more sensitive on the left sie of the nose n right hne subjects were more sensitive on the right sie of the nose. 4 ~ 3 Q J 2.c UJ ~.c Hneness 563

6 ACKNWLEDGEMENTS Supporte, in prt, by Grnt DC from the Ntionl Institute on Defness n ther Communiction Disorers n Grnt HL from the Ntionl Hert, Lung, n Bloo Institute. We thnk Ronl Hrtik, Bruce Lon, Dvi Mrshll, n Richr Meinel for technicl ssistnce uring the stuy. REFERENCES Annett, M., 1967, The binomil istribution of right, mixe n left hneness, Qurt. ~ ~ Psych., 19:327. Briggs, G.G. n Nebes, R.D., 1975, Ptterns of hn preference in stuent popultion, Cortex, 11:230. Doty, R.L., Deems, D.A., Frye, R.E., Pelberg, R. n Shpiro, A., 1988, lfctory sensitivity, nsl resistnce n utonomic function in ptients with multiple chemicl sensitiyities. ~ tolryngol. ~~~,114:1422. Doty, R.L., Shmn, P., Applebum, S.L., Giberson, R. n Sikorsky, L., Rosenberg, L., 1984, Smell ientifiction bility: Chnges with ge, Science, 226:1441. Eskenzi, B., Cin, W.S., Lipsitt, E.D. n Novelly, R.A., 1988, lfctory function n cllosomy: A report of two cses, Yle J. Bio. Me., Goron, 61:447. H.W. n Sperry, R.W., 1969, Lterliztion of olfctory perception in the surgiclly seprte hemispheres of mn, Neuropsychol., 7:111. Koeleg, H.S., 1979, lfction n sensory symmetry, Chem. Senses. Flv., 4: Ro, S. n Potr, A., 1970, Nsl irflow with boy in vrious positions, ~ ~ Physiol., 28:162. Toulouse, E. n Vschie, N., 1900, L'symetrie sensorielle olfctive, ~ Philosophique, 49:176. Youngentob, S.L., Kurtz, D.B., Leopol, D.A., Mozell, M.M. n Hornung, D.E., 1982, lfctory sensitivity: Is there lterlity?, ~ Senses, 7:11. Ztorre, R.J. n Jones-Gotmn, M., 1990, Right-Nostril vntge for iscrimintion of oors, Percept. Psychophys., 47: