efecto olor en abejas

7/27/2019 Efecto Olor en Abejas

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Training concentrationl-Hexanol - - - LOW- - - INT- - HIGH

I I I I I ! I I1 2 3 4 5 6 Condit ioned Novel

Geraniol

I I I I I I1 2 3 4 5 6

Training trialI |Conditioned Novel

Test stimulusFIG. 1 . St imulus acquis i t ion and genera l iza t ion across odorants as a func-tion of concentration. Ac quisit io n responses (left set of graph s) to dif-feren t training concentrations of an odoran t during excita tory condition-ing in 6 independent t rea tment groups. Ext inct ion responses (r igh t se t o fgraph s) to alternate presentations of conditione d and novel odorants atthe training co ncentra tion were tested 1 h after conditioning. Ger aniolserved as the novel odoran t when subjec ts were t ra ined to 1-hexanol(top) and v ice versa (bo t tom). T ra in ing concent rat ions are 0 .0002 M(LO W ), 0 .0 2 M ( IN T) , a n d p u re o d o ran t (HIGH ) c o nc e nt ra ti on s . Sa m-ple sizes for each graph at 0.0002, 0.02, and pure odo rant concentrationsare 40, 40, and 48 subjects, respectively.

a i i z at i o n g r a d i e nt s f o l l o w i n g e x c i t a t o r y c o n d i t i o n i n g m i g h t r e -s u l t , a t l e a s t i n p a r t , f r o m a d a p t a t i o n i n t h e p e r i p h e r a l s e n s o r ys y s t e m .

METHODSG e n e r a l M e t h o d s

Subje c t s . W o r k e r h o n e y b e e s w e r e c o l l e c te d f r o m a n o u t d o o rc o l o n y d u r i n g t h e s u m m e r a n d f r o m a c o l o n y m a i n t a i n e d i n a ni n d o o r f l i g h t - r o o m d u r i n g t h e w i n t er , T h e s e c o l o n i e s w e r e e s t a b -l i s h e d w i t h a s i n g l e o p e n - m a t e d q u e e n . F o r e x p e r i m e n t s c o n -d u c t e d i n s u m m e r , p o l l e n f o r a g e r s i d e n t i f i e d b y t h e p o l l e n o nt h e i r h i n d l e g s w e r e c o l l e c t e d a s t h e y r e t u r n e d t o t h e c o l o n y . I ne x p e r i m e n t s p e r f o r m e d i n w i n t e r , b e e s w e r e c o l l e c t e d as t h e yf l e w t o w a r d a l ig h t s o u r c e a b o v e t h e f l i g h t c a g e a n d l a n d e d o nt h e c e i l in g o f t h e c a g e . W o r k e r s w e r e c o l l e c t e d i n d iv i d u a l l y i ng l a s s v i a l s d u r i n g e a r l y a f t e r n o o n o n t h e d a y p r i o r t o t h e e x p e r -i m e n t , a n d t h e v i a l s w e r e p l a c e d s h o r t l y t h e r e a f t e r i n a n i c e - w a t e rb a t h . A s s o o n a s a b e e s t o p p e d m o v i n g i t w a s r e s t r a i n e d i n as m a l l m e t a l h a r n e s s b y p l a c i n g a s t r i p o f d u c t t a p e b e t w e e n t h eh e a d a n d t h o r a x . B e e s w e r e f e d 3 0 m i n l a t er w i t h a 2 . 0 - M s u c r o s es o l u t i o n u n t i l s a ti a t i o n a n d l e f t o v e r n i g h t . O n l y b e e s t h a t v i g o r -o u s l y e x t e n d e d t h e i r p ro b o s c i d e s w h e n t e s t e d f o r m o t i v a t i o n ( b yp r e s e n t i n g s u c r o s e o n l y t o t h e i r a n t e n n a a n d n o t f o l l o w e d b y

Excitatory Conditionj~ag Ge n e ra l i z a t i o n Te s t10080

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l -Hexanol Trainingconcentration- - - LOW- - - INT-- HIGH

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Geraniol

I I I l | I

l 2 3 4 5 6Training trial

I i I0 . 0 00 2 0 . 0 2 0 0 2 . 0 00 0

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I I I0 . 0 00 2 0 . 0 2 0 0 2 . 0 00 0Test concentration (M)FIG. 2. CS intensity effects on acquisit ion and generalization gradientsacross concentrations of the cond itioned odorant. Sam e as in Fig. 1,except HIG H was 2 .0 M concent ra t ion and , during ex t inc t ion t r ia l s, sub-jec ts from each t rea tmen t group were tes ted wi th 0 .0002 , 0 .02 , and 2 .0M concentrations of the conditione d odorant. Test concentration pres-en ta t ions were pseudo randomized during the genera l iza t ion tes t. S amplesizes at 0.0002, 0 .02, and 2.0 M training conce ntrations are 30, 29, and30 subjects, r espec tively, for the top set of graphs an d 28, 29 and 30subjects, respectively, for the bottom set of graphs.

f e e d i n g ) o n t h e f o l l o w i n g m o r n i n g w e r e u s e d f o r th e e x p e r i m e n to n t h a t s a m e d a y .Probosc is ex tension condit ioning. S u b j e c t s t h at w e r e m o t i v a t e do n t h e m o r n i n g o f t h e e x p e r i m e n t w e r e a s s a y e d f o r r e s p o n s e s t oo d o r s u s i n g t h e p r o b o s c i s e x t e n s i o n c o n d i t i o n in g p a r a d i g m ( 4 , 1 2 ) .T w o h o u r s b e f o r e a n e x p e r i m e n t , o d o r c a r t ri d g e s w e r e p r e p a r e d b yp l a c i n g e i t h e r 3 # 1 o f a p u re o d o ra n t o r 5 # 1 o f a n o d o ra n t d i l u t e di n h e x a n e o n t o a s t r i p o f f i l t e r p a p e r . Th i s o d o r - l a d e n f i l te r p a p e rwa s t h e n i n se r t e d i n t o a 1 -ml t u b e rc u l i n g l a s s sy r i n g e .

A l l t r ia l s w e r e b e g u n b y p l a c i n g a s u b j e c t i n t o t h e tr a i n i n ga r e n a, t h r o u g h w h i c h a s l o w l y m o v i n g a i r s t re a m w a s v e n t e d i n t oa n e x h a u s t h o o d . O d o r ( c o n d i t i o n e d s t i m u l u s , C S ) w a s d e l i v e r e d3 0 s l a t e r b y s h u n t i n g a i r t h r o u g h t h e o d o r c a r t r i d g e f o r 3 s b yo p e n i n g f l o w - v a l v e s v i a a c o m p u t e r - c o n t r o l l e d r e l a y. U s i n g aG i l m o n t m i c r o m e t e r g la s s s y r i n g e ( G i l m o n t I n s t r u m e n t s , B a r -r i n g t o n , I L ) , 2 #1 o f 2 M s u c r o s e s o l u t i o n ( u n c o n d i t i o n e d s t i m -u l u s , U S ) w a s p r e s e n t e d f i rs t t o t h e a n t e n n a e a n d , f o l l o w i n g s u b -s e q u e n t p r o b o s c i s e x t e n s io n , t o t h e p r o b o s c is . A n i m a l s w e r e f e df o r 2 s . I n d i s c r i m i n a t i o n e x p e r i m e n t s , t h e a p p e t i t i v e U S w a s 2M s u c r o s e s o l u t i o n , a n d 3 . 0 M s a l t s o l u t i o n d r a w n i n t o a 1 - m lg l a s s t u b e r c u l i n s y r i n g e s e r v e d a s th e a v e r s i v e U S . T h e a v e r s i v eU S w a s p r e s e n t e d t o t h e a n t e n n a , b u t t h e s u b j e c t s w e r e n e v e r f e dw i t h t h e s a l t s o l u t io n .M o s t e x p e r i m e n t s u t i l i z e d f o r w a r d - p a i r i n g c o n d i t i o n in gt r ia l s , a s j u s t d e s c r i b e d , d u r i n g w h i c h t h e o n s e t o f t h e C Sp r e c e d e d t h e p r e s e n t a t i o n o f U S b y 2 s . I n a d d i t i o n t of o r w a r d - p a i r i n g t r ia l s , s e v e r a l o t h e r t y p e s o f tr i a l s w e r e u s e di n d i f f e r e n t s u b j e c t g r o u p s f o r E A G 2 e x p e r i m e n t s . I n b a c k -

2 Abb reviation s: PEC, probos cis extension conditioning; EA G, electroantennogram.


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ODOR INTENSITY EFFECTS ON OLFACTORY CONDITIONING 109

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1 -HexanolO No odor exposureQ Forward-pairing

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0.001 0.01 0.1 1 0.001 0.01 0.1 1Concentrat ion (M) C o n c e n t r a t i o n ( M )

FIG. 3. Electroantennogram responses to different concentrations of an odorant (listed top left in each graph) in 2 independent treatment groups. Onegroup of 20 subjects received no prior conditioning experience and the second group of 20 subjects were conditioned to 2.0 M concentration of theodorant over 6 forward-pairing trials.

ward-pairing groups, the US preceded the CS by 1 s. In theunpaired group, subjects received expli citly unpaired presen-tations of CS and US in 2 successive repeats of the followingsequence: US, CS, CS, US, CS, US, US, CS. In this group,trials consisted of presentation of the CS or the US on eachtrial, but never both together. In CS-only groups, subjects re-ceived only 3 s odor stimulation. Subjects in the US-onlygroups received only 2 s sucrose presentations, first to antennaand, finally, followed by feeding. To maintain the same num-ber of total trials in all groups (i.e., placements into the train-ing arena), subjects in forward-pairi ng, backward pairing , C S-only and US-only groups received placement (P) trials.During the placement trials, subjects were placed in the train-ing station, but received no stimulation with odorants or theUS. These trials were interspersed with stimulation (S) trialsin 2 successive repeats of the following sequence: S, P, P, S,P, S, S, P.

After conditioning was complete, a series of extinction trials,during which subjects received only odor presentations, was usedto test responses to odorants. The sequence of presentation of testodorants across subjects was alternated over 2 test trials or pseu-dorandomized over 3 test trials. The intertrial interval (ITI) forany given experiment was the same for the acquisition and ex-tinction phases using the PEC paradigm. Subjects were always

tested 1 h after they were trained, to minimize nonassociativeeffects such as sensitization.EAG recordings. Electroantennograms were obtained fromantennae of isolated heads using the protocol described in de-tail elsewhere (3). Briefly, the cut tip of one antenna wasinserted into a glass pipette that was filled with saline and wasin contact with the recording electrode. The other antenna wasremoved to prevent disturbance due to movement. A groundelectrode was inserted into the saline-filled petri dish. Elec-trodes were connected to a DC amplifier and the unfilteredoutput was amplified ( 10 ) and fed into an oscilloscope forviewing responses. Odor cartridges were prepared by placing5 #1 of an odorant diluted in hexane to obtain a given concen-tration on a strip of filter paper. The latter was then insertedinto a 2 inch Teflon tube (5/32" - i.d.) that was capped witha barbed polypropylene fitting. These cartridges were replacedwith new ones after 5 stimulations with each cartridge to con-trol for stimulus depletion over time.

For EAG recordings, the antenna was continuously subjected toair at a rate of 97 ml/min to adapt out the mechanosensory receptors.During stimulation, the rate of air flow through a cartridge was 129ml/min. Background recordings to air and solvent were obtained byshunting air through a cartridge that was either empty or carried astrip of filter paper wi th so lvent on it, respectively.


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110 BHAGAVA N AND SMITH

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C o n c e n t r a t i o n ( M ) C o n c e n t r a t i o n ( M )FIG. 4. EAG responses to different concentrations of an odorant in 12 independent treatment groups. For each odorant (listed top left in eachgraph), 5 treatment groups of 12 subjects each were conditioned to 2 M concentration of odorant using either forward-pairing trials, backward-pairing trials, CS only, US only, or explicitly unpaired presentations of CS and US. One treatment group of 12 subjects that received no conditioningprior to testing served as control.

Each an tenn a received 6 recorded stimulations, each lastingfor 1 s. The initial 2 stimulations with air and solvent were fordetermination of background EA G responses. Test odorants werepresented in a pseudorandomized sequence. The last stimulationwith solvent was to determine any change in background re-sponse from that recorded earlier in the test sequence. A 2-mininterval separated each of these 6 stimulations.O d o r a n t s . Odorants used in this study were geraniol and 1-hexanol (99% purity; Sigma, St. Louis, MO). Geraniol is amonoterpenoid component of the honey bee Nasonov pheromone(17), as well as a common component of floral odors (11).These odorants were serially diluted in hexane from 2.0 M stocksolutions to obtain low, intermediate, and high (0.0002, 0.02, and2.0 M, respectively) concentrations for this study. The highestconcentration of each odor reaches saturation in EAG analyses,whereas the lower concentrations yield EAG responses that areabove background, but below saturation (3). In one set of ex-periments, the pure odorant was used.Sta t i s t i c a l analy se s . Acquisition and EAG data were analyzedusing nonparametric statistical tests ( 22). Comparisons betweensummed numbers of conditioned responses (proboscis extensionto CS prior to US onset) for each subject across 6 acquisitiontrials were made between different treatment groups. For exam-

pie, each subject could have 0 to 6 responses, depending on thenumber of trials during which it responded. For E AG data, re-sponse to an odor stimula tion was subtracted from the responseto the solvent for each subject within a group, and these differ-ences were averaged for each treatment group. The response toan odor stimulation was recorded as zero when the response tothe solvent slightly exceeded the respon se to odorant stimulation.All analyses of EAG data compared these adjusted responses ineach treatment group. Mann -Whi tne y (U) or Kruskal-Wallis(H) test analyses were used for comparing differences in re-sponses between 2 or 3 groups, respectively.For data obtained from extinction trials, we analyzed the per-cent proboscis extension responses. Subjects within each groupfor an experiment were classified according to whether or notthey responded to the test stimulation. To test if the degree ofassociation between the response (C) to a test odorant (B) dif-fered for different training conditions (A), a log-linear model(AB . AC- BC; three-factor effects) ( 22) was fitted. According tothis model, a significant test statistic (Pear son' s chi-squa re),which denotes the 3-factor interaction term, denotes that the de-gree of association (interaction) between any pair of factorswould depend up on the different levels of a third factor. In ad-dition, for data in Fig. 2 (top pa nel), Pearson's chi-square anal-


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O D O R I N T E N S IT Y E F F E C TS O N O L F A C T O R Y C O N D I T I O N I N G 111

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a i i I I i i i i | I1 2 3 4 5 6 7 8 9 10

T r i a lFIG. 5 . Acquisi t ion curves for d iscriminat ion condi t ion ing to a low con-cent ra t ion of an odoran t associa ted wi th an appet i t ive re inforcer (s t ra igh tl ines) and a h igh concent ra t ion of the same odorant associa ted wi th anaversive re inforcer (broken l ines) . Di fferen t ia l ly re inforced concent ra-t ions are ind ica ted in each graph . Top , geran io l (n = 23); bo t tom, 1-hexanol (n = 25).

y s e s ( 2 2 ) w e r e p e r f o r m e d t o te s t t he a s s o c i a ti o n b e t w e e n e x t i nc -t i o n r e s p o n s e s u n d e r d i f f e r e n t t r a i n i n g c o n d i t i o n t o t h ei n t e r m e d i a t e t e s t c o n c e n t r a ti o n . A l l a n a l y se s w e r e p e r f o r m e dw i t h S Y S T A T ( v e r s io n 5 . 0 ) f o r th e M a c in t os h .

E x p e r i m e n t a l D e s i g n sG e n e r a l i z a t i o n e x p e r i m e n t s . T h e f i r st s e t o f e x p e r i m e n t s

t e s t e d t h e e f f e c t o f t r a i n i n g c o n c e n t r a t i o n o n g e n e r a l i z a t i o n t o ad i f f e r e n t o d o r a n t. S u b j e c t s c o l l e c t e d i n s u m m e r w e r e t r a i n ed i n6 f o r w a r d - p a i r i n g ( I T I = 3 0 s ) t r i a l s . P u r e o d o r a n t , 0 . 0 2 , a n d0 . 0 0 0 2 M c o n c e n t r a ti o n s o f 1 - h e x a n o l o r g e r a n i o l w e r e u s e d a st h e C S i n d i f f e r e n t g r o u p s o f s u b j e c t s . D u r i n g e x t i n c t i o n t r i a l s ,s u b j e c t s w i t h i n e a c h o f th e 6 g r o u p s w e r e t e s t e d t w i c e , o n c e e a c hw i t h 1 - h e x a n o l a n d g e r a n i o l a t t h e C S c o n c e n t r a t i o n .

T h e s e c o n d s e t o f e x p e r i m e n t s t e s t e d g e n e r a l i z a ti o n a c r o s s ar a n g e o f c o n c e n t r a t i o n s o f t h e c o n d i t i o n e d o d o r a n t . S u b j e c t s f r o md i f f e r e n t g r o u p s w e r e t r a i n e d i n 6 f o r w a r d - p a i r i n g t r i a l s to g e -r a n i o l o r 1 - h e x a n o l . I n t h i s e x p e r i m e n t , w e u s e d a 6 - m i n I T I t om a t c h t h e I T I u s e d i n E A G a n a ly s e s . T h e C S w a s a 0 . 0 0 0 2 , 0 . 02 ,o r 2 . 0 M c o n c e n t r a t i o n o f o d o r a n t. O n e h o u r a f t e r c o n d i t i o n i n g ,s u b j e c t s f r o m e a c h g r o u p w e r e t e s t e d w i t h 0 . 0 0 0 2 , 0 . 0 2 , a n d 2 . 0M c o n c e n t r a t i o n s o f t h e s a m e o d o r a n t t h a t w a s u s e d d u r i n g t h et r a i n i n g p h a s e .

D i s c r i m i n a t i o n e x p e r i m e n t s . I n t h e f o l l o w i n g s e t o f e x p e r i -m e n t s , s u b j e c t s r e c e i v e d 2 0 f o r w a r d - p a i r i n g t r i a l s ( I T I = 3 m i n ) .F o r 1 0 o f t h o s e c o n d i t i o n i n g t r i a l s , a g i v e n c o n c e n t r a t i o n o f a no d o r a n t w a s f o l l o w e d b y s u c ro s e f e e d i n g ( C S + ) . I n th e r e m a i n -i n g 1 0 t r ia l s , a d i f f e r e n t c o n c e n t r a t i o n o f th e s a m e o d o r a n t w a sf o l l o w e d b y p r e s e n t a t io n o f s a l t s o l u ti o n t o t h e a n te n n a ( C S - ) .T h e s e q u e n c e o f p r e s e n ta t i o n o f C S + a n d C S - w a s i d e n t ic a l f o re a c h s u b j ec t : 2 a n d 1 h a l f s u c c e s si v e s e q u e n c e s o f C S + , C S - ,C S - , C S + . C S - , C S + , C S + , C S - . N i n e s ub je ct s w e r e t es te dd a i l y a n d o d o r s w e r e c o u n t e r - b a l a n c e d o v e r a 2 - d a y p e r i o d . T op r e v e n t d e c r e a s e i n s t i m u l u s c o n c e n t r a t i o n d u e t o u s e o f t h e s a m eo d o r c a r t r i d g e o v e r 2 0 t r i a ls , e a c h o d o r c a r t r i d g e w a s r e p l a c e da f t e r u se fo r 1 0 t r i a l s .

I n a l l b u t t h e i n i ti a l s e t o f d i s c r i m i n a t i o n e x p e r i m e n t s , s u b j e c t sw e r e t e s t e d w i t h s o l v e n t a n d 2 n o v e l c o n c e n t r a t i o n s ( 0 . 0 0 2 a n d0 . 0 0 0 0 2 M ) o f t he s a m e o d o r a n t b e g i n n i n g 1 h a f t e r c o m p l e t i o no f c o n d i t i o n i n g .P E C - E A G e x p e ri m e n t s. A n e x p e r i m e n t w a s p e r f o r m e d t ot e s t w h e t h e r o r n o t b e h a v i o r a l e f f e c t s o n g e n e r a l i z a t i o n g r a d i e n t sm i g h t b e d u e t o m o d u l a t i o n o f s e n s o r y r e c e p t o r s . F o u r i n d e p e n -d e n t g r o u p s o f s u b j e c t s w e r e t e s t e d w i t h g e r a n i o l o r 1 - h e x a n o l ,u s i n g t h e E A G p r o t o c o l . T w o g r o u p s o f s u b j ec t s w e r e c o n d i -t i o n e d t o 2 .0 M c o n c e n t r a t i o n o f g e r a n i o l o r 1 - h e x a n o l o v e r 6f o r w a r d - p a i r i n g t r i al s p r i o r to b e i n g t e s t e d . T h e I T I w a s 6 r a i n ,a s in t h e s e c o n d s e t o f g e n e r a l i z a t i o n e x p e r i m e n t s . T h e s e c o n dg r o u p o f s u b j e c ts w a s t e s te d f o r E A G r e s p o n s e s w i t h o u t p r i o rc o n d i t i o n i n g t o 1 - h e x a n o l o r g e r a n i o l . T e n s u b j e c t s ( 5 p e r g r o u p )w e r e u s e d d a i l y . G e r a n i o l a n d 1 - h e x a n o l w e r e t e s t e d o n a l t e r n a t ed a y s .

T h e e x p e r i m e n t w a s r e p e a t e d i n s u m m e r w i t h 4 a d d i t i o n a lc o n d i t i o n i n g g r o u p s ( b a c k w a r d - p a i r i n g , C S o n l y , U S o n l y , a n da n u n p a i r e d g r o u p ) f o r e a c h o d o r a n t . T h e C S , e i t h e r g e r a n i o l o r1 - h e x a n o l a t 2 M c o n c e n t r a t i o n , w a s p r e s e n t e d a t 6 r a i n I T I s a si n t h e s e c o n d g e n e r a l i z at i o n e x p e r i m e n t d e s c r i b e d a b o v e . T w e l v es u b j e c t s ( 2 p e r g r o u p ) w e r e t e s t e d d a i l y . A s i n t h e p r e v i o u s e x -p e r i m e n t , 1 - h e x a n o l a n d g e r a n i o l w e r e t e s t e d o n a l t e r n a t e d a y s .S u b j e c t s t h a t r e c e i v e d a n y t y p e o f t r a i n i n g w e r e t e s t e d f o r E A Gre sp o n se s 1 h l a te r .

RESULTSA c q u i s i t i o n a n d G e n e r a l i z a t i o n A c r o s s C o n c e n t r a t i o n s

T h e f i r s t s e t o f g e n e r a l i z a t i o n e x p e r i m e n t s m e a s u r e d t h e e f f e c to f t r a in i n g o d o r a n t c o n c e n t r a t i o n o n g e n e r a l i z a t i o n f r o m t h e C St o a d i f f e r e n t o d o r a n t ( F i g . 1 ) . S u b j e c t s i n 6 i n d e p e n d e n t t r e a t-m e n t g r o u p s a c q u i r e d t h e c o n d i t i o n e d r e s p o n s e t o a l l c o n c e n t r a -t i o n s o f 1 - h e x a n o l a n d g e r a n i o l w i t h i n a f e w t r i a l s ( l e f t s e t o fg r a p h s ) . L e v e l s o f c o n d i t i o n e d r e s p o n d in g w e r e n o t d i f f e r e n t b e -t w e e n s u b j e c t s t r a i n e d to p u r e o d o r a n t , i n t e r m e d i a t e , a n d l o wc o n c e n t r a t i o n s o f 1 - h e x a n o l ( t o p p a n e l ; H = 0 . 9 0 7 , N S ) o r g e -r a n i o l ( b o t t o m p a n e l ; H = 1 . 0 42 , N S ) . T h a t i s , a l l l i n e s r e a c ht h e s a m e a p p r o x i m a t e a s y m p t o t i c l e v e l o f r e s p o n d i n g b y a b o u tt h e s e c o n d o r t h i r d t r i a l.

E x t i n c t i o n r e s p o n s e s ( F i g . 1 , r i g h t s e t o f g r a p h s ) a c r o s s t r e a t-m e n t g r o u p s m e a s u r e d 1 h a f t e r a c q u i s i t i o n p r e s e n t a s o m e w h a td i f f e r e n t p ic t u r e . W h e n 1 - h e x a n o l w a s t h e c o n d i t i o n i n g o d o r a n t ,t h e r e w a s n o s i g n i f i c a n t i n t e r a c t i o n b e t w e e n d i f f e r e n t t r a i n in gc o n c e n t r a t i o n s a n d t h e r e s p o n s e s t o c o n d i t i o n e d a n d n o v e l ( g e -r a n i o l ) o d o r a n t s ( t o p p a n e l , ( X 2 = 8 . 0 8 , N S ) . T h a t i s , t h e 3 li n e sa r e s t a t i s t i c a l l y p a r a l l e l e v e n t h o u g h t h e r e i s a t r e n d t o w a r d ah i g h e r r e s p o n s e t o 1 - h e x a n o l w h e n t h e h i g h t r a i n i n g c o n c e n t r a -t i o n w a s u s e d .

W h e n g e r a n i o l w a s u s e d f o r c o n d i t io n i n g ( b o t t o m p a n e l ) ,t h e r e w a s s i g n i f i c a n t i n t e r a c t i o n b e t w e e n t h e d i f f e r e n t t r a i n i n gc o n d i t i o n s a n d t h e r e s p o n s e s t o c o n d i t i o n e d a n d n o v e l ( l - h e x -


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112 BHAGAVAN AND SMITH

Geraniol L+/H- Discrimination- 8. 90&M_-- .8

100 B - solvent80 ___ 0.0002 M

solvent___ 0.02 M

100908070605040302010

0IGeneralization testTraining experience:;l Csolvent o.obOO2 0.002

Test concentration (M)

1 2 3 4 5 6 7 8 9Trial

FIG. 6. Acquisition curves for discrimination conditioning to geraniol at appetitively reinforced LOW concentrations (straight lines) and aversivelyreinforced HIGH stimulus concentrations (broken lines). (A) n = 15; (B) n = 15; (C) n = 30. Extinction responses (graph on right) to pseudor-andomized presentations of solvent and 2 novel concentrations (0.00002 and 0.002M) were recorded from each treatment group 1 h after discrim-ination conditioning.

anol) odorauts (x2 = 11.06, p < 0.05). In this case, the linesare not parallel. After training to an intermediate or high concen-tration of geraniol, the response to geraniol is higher than theresponse to the novel (1-hexanol) odorant. However, when thelow training concentration was used, the gradient is flat.

The second set of generalization experiments measured gen-eralization across concentrations of the conditioned odorant (Fig.2). Summed conditioned responses in the acquisition phase didnot differ between 2 different groups of subjects trained to lowand intermediate concentrations of 1-hexanol (top left set ofgraphs; LOW vs. INT: U = 439.5, NS). However, conditionedresponding at either of those concentrations was significantlylower than the acquisition responses to high concentration of l-hexanol (LOW vs. HIGH: U = 434.5, p < 0.05; INT vs. HIGH:U = 415.0, p < 0.05). Responses to geraniol (bottom left set ofgraphs) at the low concentration were significantly lower thanresponses to intermediate (LOW vs. INT: U = 244.5, p < 0.05)and to high concentrations (LOW vs. HIGH: U = 183.0, p

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