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Traits of pattern discrimination learning in monkeys
S30 TRAITS
OF P A T T E R N
DISCRIMINATION
LEARNING
IN M O N K E Y S
SHIGEYA YAGINUMA, YASUTAKA OSAWA*, KIYOKO YAMAGUCHI*, KENJI OMATA*, HIROKI and E I I C H I IWAI. Dept. B e h a v i o r a l Physiol., T o k y o M e t r o p o l i t a n Inst. for Neurosci., 2-6 M u s a s h i d a i , F u c h u - C i t y , T o k y o 183
OKUDA*,
In m o n k e y s , s m a l l d e g r e e s of c u e - r e s p o n s e s e p a r a t i o n a f f e c t the rate of a c q u i s i t i o n of p a t t e r n d i s c r i m i n a t i o n by p r o l o n g i n g the p e r i o d of p e r f o r m a n c e at the c h a n c e level (Iwai, Y a g i n u m a , and M i s h k i n , J. Comp. Psychol., 100: I, 30-36, 1986). To e l u c i d a t e the n a t u r e of p a t t e r n d i s c r i m i n a t i o n l e a r n i n g at s m a l l c u e - r e s p o n s e s e p a r a t i o n s in m o n k e y s further, we p e r f o r m e d t h r e e e x p e r i m e n t s . In one e x p e r i m e n t , t r a i n i n g on a p a t t e r n d i s c r i m i n a t i o n w i t h a s m a l l s e p a r a t i o n b e t w e e n the cue and the r e s p o n s e site w a s d i s c o n t i n u e d d u r i n g p e r f o r m a n c e at the c h a n c e level. In this case, the d i s c o n t i n u e d t r a i n i n g s h o w e d no s a v i n g e f f e c t on t h e r a t e of l e a r n i n g a s e c o n d t a s k w i t h c u e s i d e n t i c a l to t h o s e of t h e f i r s t t a s k but w i t h a d i f f e r e n t c u e - r e s p o n s e s e p a r a t i o n . In a s e c o n d e x p e r i m e n t , t r a i n i n g w a s d i s c o n t i n u e d at a p e r f o r m a n c e level a l i t t l e b e t t e r than chance. In this case, t h e r e w a s s i g n i f i c a n t s a v i n g on l e a r n i n g a s e c o n d task. A f t e r l e a r n i n g the s e c o n d t a s k , a t h i r d t a s k w i t h n e w p a t t e r n c u e s w a s l e a r n e d in the l a s t experiment. The t h i r d task w a s l e a r n e d w i t h m a r k e d s a v i n g on the d u r a t i o n of p e r f o r m a n c e at the c h a n c e level. The r e s u l t s s u p p o r t the v i e w that (I) d u r i n g the i n i t i a l s t a g e of p e r f o r m a n c e at t h e c h a n c e l e v e l , m o n k e y s do n o t a t t e n d to c u e s if t h e r e is even a s m a l l s e p a r a t i o n b e t w e e n the cue and the r e s p o n s e site and (2) m o n k e y s learn to d i s c r i m i n a t e p a t t e r n c u e s w i t h i n a s m a l l n u m b e r of t r i a l s o n l y late d u r i n g the t r a i n i n g period.
CHARACTERISTICS OF C O P U L A T O R Y BEHAVIOR INDUCED L A T E R A L M E S E N C E P H A L I C T E G M E N T U M IN M A L E RATS.
BY E L E C T R I C A L
TSUYOSHI SHIMURA* and MINORU SHIMOKOCHI, Sciences, O s a k a U n i v e r s i t y , S u i t a 565
Behav.
Dept.
STIMULATION
Physiol.,
Faculty
OF T H E
of H u m a n
Lesion studies have suggested that neural connections between the medial p r e o p t i c a r e a (MPO) a n d the l a t e r a l m e s e n c e p h a l i c t e g m e n t u m (LMT) are e s s e n t i a l for male sexual behavior. We have already reported several act-specific p a t t e r n s of neuronal activities in t h e LMT around pursuit-mounting behavior. In t h i s experiment, we investigated the effects of e l e c t r i c a l stimulation upon free c o p u l a t o r y b e h a v i o r of m a l e rats. S u b j e c t s w e r e s e x u a l l y a c t i v e m a l e W i s t a r rats. The bipolar electrodes were made of s t a i n l e s s steel wire, 0.08 m m in dia., i n s u l a t e d e x c e p t at the l o w e r surface. T h e y w e r e i m p l a n t e d s t e r e o t a x i c a l l y in e a c h animal under sodium pentobarbital anesthesia aimed for the LMT (just above the l a t e r a l half of the s u b s t a n t i a nigra). A f t e r s u r g i a l r e c o v e r y , L M T u n i t a c t i v i t i e s w e r e r e c o r d e d d u r i n g free c o p u l a t o r y behavior. T e s t s of c o p u l a t o r y a c t i v i t y w e r e then conducted every third to f o u r t h day for each animal under electrical stimulation or n o n s t i m u l a t i o n control. The e l e c t r i c a l s t i m u l u s w a s a 30 sec t r a i n of m o n o p h a s i c s q u a r e w a v e s (0.1 msec) at 60 Hz. It w a s d e l i v e r e d r e p e t i t i v e l y in a 30 s e c - o n , 3 0 - s e c o f f p a t t e r n b e g i n n i n g from the introduction of a f e m a l e . T w o m a j o r e f f e c t s of L M T s t i m u l a t i o n u p o n m a l e c o p u l a t o r y a c t i v i t y w e r e o b s e r v e d : I) the o c c u r r e n c e of i n t r o m i s s i o n s w e r e s u p p r e s s e d d u r i n g 30 sec s t i m u l u s - o n p e r i o d s (87.5%: 14/16), 2) t h e n u m b e r of i n t r o m i s s i o n s preceding ejaculation and the latency of e j a c u l a t i o n were reduced (62.5%: 10/16), but the postejaculatory refractory period was unchanged. B o t h e f f e c t s w e r e o b s e r v e d in 9 out of 16 a n i m a l s (56.3%). The n e u r o n a l a c t i v i t i e s r e c o r d e d p r e c e d i n g the s t i m u l a t i o n s e s s i o n s t e n d e d to i n c r e a s e immediately after intromissions in s u b j e c t s showing both effects. F u r t h e r m o r e , m o r e t h a n h a l f of the r a t s l e a r n e d to s e l f - s t i m u l a t e u s i n g the s i m i l a r i n t e n s i t y as u s e d in e a r l i e r t e s t s of c o p u l a t o r y activity. Comparing these data w i t h t h o s e of t h e M P O , w e m a y c o n c l u d e t h a t t h e L M T is i n v o l v e d in t h e m o t o r c o n t r o l n e c e s s a r y to the n o r m a l e x e c u t i o n of the m a l e c o p u l a t o r y b e h a v i o r .
OF P A T T E R N
DISCRIMINATION
LEARNING
IN M O N K E Y S
SHIGEYA YAGINUMA, YASUTAKA OSAWA*, KIYOKO YAMAGUCHI*, KENJI OMATA*, HIROKI and E I I C H I IWAI. Dept. B e h a v i o r a l Physiol., T o k y o M e t r o p o l i t a n Inst. for Neurosci., 2-6 M u s a s h i d a i , F u c h u - C i t y , T o k y o 183
OKUDA*,
In m o n k e y s , s m a l l d e g r e e s of c u e - r e s p o n s e s e p a r a t i o n a f f e c t the rate of a c q u i s i t i o n of p a t t e r n d i s c r i m i n a t i o n by p r o l o n g i n g the p e r i o d of p e r f o r m a n c e at the c h a n c e level (Iwai, Y a g i n u m a , and M i s h k i n , J. Comp. Psychol., 100: I, 30-36, 1986). To e l u c i d a t e the n a t u r e of p a t t e r n d i s c r i m i n a t i o n l e a r n i n g at s m a l l c u e - r e s p o n s e s e p a r a t i o n s in m o n k e y s further, we p e r f o r m e d t h r e e e x p e r i m e n t s . In one e x p e r i m e n t , t r a i n i n g on a p a t t e r n d i s c r i m i n a t i o n w i t h a s m a l l s e p a r a t i o n b e t w e e n the cue and the r e s p o n s e site w a s d i s c o n t i n u e d d u r i n g p e r f o r m a n c e at the c h a n c e level. In this case, the d i s c o n t i n u e d t r a i n i n g s h o w e d no s a v i n g e f f e c t on t h e r a t e of l e a r n i n g a s e c o n d t a s k w i t h c u e s i d e n t i c a l to t h o s e of t h e f i r s t t a s k but w i t h a d i f f e r e n t c u e - r e s p o n s e s e p a r a t i o n . In a s e c o n d e x p e r i m e n t , t r a i n i n g w a s d i s c o n t i n u e d at a p e r f o r m a n c e level a l i t t l e b e t t e r than chance. In this case, t h e r e w a s s i g n i f i c a n t s a v i n g on l e a r n i n g a s e c o n d task. A f t e r l e a r n i n g the s e c o n d t a s k , a t h i r d t a s k w i t h n e w p a t t e r n c u e s w a s l e a r n e d in the l a s t experiment. The t h i r d task w a s l e a r n e d w i t h m a r k e d s a v i n g on the d u r a t i o n of p e r f o r m a n c e at the c h a n c e level. The r e s u l t s s u p p o r t the v i e w that (I) d u r i n g the i n i t i a l s t a g e of p e r f o r m a n c e at t h e c h a n c e l e v e l , m o n k e y s do n o t a t t e n d to c u e s if t h e r e is even a s m a l l s e p a r a t i o n b e t w e e n the cue and the r e s p o n s e site and (2) m o n k e y s learn to d i s c r i m i n a t e p a t t e r n c u e s w i t h i n a s m a l l n u m b e r of t r i a l s o n l y late d u r i n g the t r a i n i n g period.
CHARACTERISTICS OF C O P U L A T O R Y BEHAVIOR INDUCED L A T E R A L M E S E N C E P H A L I C T E G M E N T U M IN M A L E RATS.
BY E L E C T R I C A L
TSUYOSHI SHIMURA* and MINORU SHIMOKOCHI, Sciences, O s a k a U n i v e r s i t y , S u i t a 565
Behav.
Dept.
STIMULATION
Physiol.,
Faculty
OF T H E
of H u m a n
Lesion studies have suggested that neural connections between the medial p r e o p t i c a r e a (MPO) a n d the l a t e r a l m e s e n c e p h a l i c t e g m e n t u m (LMT) are e s s e n t i a l for male sexual behavior. We have already reported several act-specific p a t t e r n s of neuronal activities in t h e LMT around pursuit-mounting behavior. In t h i s experiment, we investigated the effects of e l e c t r i c a l stimulation upon free c o p u l a t o r y b e h a v i o r of m a l e rats. S u b j e c t s w e r e s e x u a l l y a c t i v e m a l e W i s t a r rats. The bipolar electrodes were made of s t a i n l e s s steel wire, 0.08 m m in dia., i n s u l a t e d e x c e p t at the l o w e r surface. T h e y w e r e i m p l a n t e d s t e r e o t a x i c a l l y in e a c h animal under sodium pentobarbital anesthesia aimed for the LMT (just above the l a t e r a l half of the s u b s t a n t i a nigra). A f t e r s u r g i a l r e c o v e r y , L M T u n i t a c t i v i t i e s w e r e r e c o r d e d d u r i n g free c o p u l a t o r y behavior. T e s t s of c o p u l a t o r y a c t i v i t y w e r e then conducted every third to f o u r t h day for each animal under electrical stimulation or n o n s t i m u l a t i o n control. The e l e c t r i c a l s t i m u l u s w a s a 30 sec t r a i n of m o n o p h a s i c s q u a r e w a v e s (0.1 msec) at 60 Hz. It w a s d e l i v e r e d r e p e t i t i v e l y in a 30 s e c - o n , 3 0 - s e c o f f p a t t e r n b e g i n n i n g from the introduction of a f e m a l e . T w o m a j o r e f f e c t s of L M T s t i m u l a t i o n u p o n m a l e c o p u l a t o r y a c t i v i t y w e r e o b s e r v e d : I) the o c c u r r e n c e of i n t r o m i s s i o n s w e r e s u p p r e s s e d d u r i n g 30 sec s t i m u l u s - o n p e r i o d s (87.5%: 14/16), 2) t h e n u m b e r of i n t r o m i s s i o n s preceding ejaculation and the latency of e j a c u l a t i o n were reduced (62.5%: 10/16), but the postejaculatory refractory period was unchanged. B o t h e f f e c t s w e r e o b s e r v e d in 9 out of 16 a n i m a l s (56.3%). The n e u r o n a l a c t i v i t i e s r e c o r d e d p r e c e d i n g the s t i m u l a t i o n s e s s i o n s t e n d e d to i n c r e a s e immediately after intromissions in s u b j e c t s showing both effects. F u r t h e r m o r e , m o r e t h a n h a l f of the r a t s l e a r n e d to s e l f - s t i m u l a t e u s i n g the s i m i l a r i n t e n s i t y as u s e d in e a r l i e r t e s t s of c o p u l a t o r y activity. Comparing these data w i t h t h o s e of t h e M P O , w e m a y c o n c l u d e t h a t t h e L M T is i n v o l v e d in t h e m o t o r c o n t r o l n e c e s s a r y to the n o r m a l e x e c u t i o n of the m a l e c o p u l a t o r y b e h a v i o r .