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Background stimuli as a reminder after spontaneous forgetting potentiation by MRF stimulation
86 The DSP4 treatment described above resulted in a s i g n i f i c a n t (P < 0.001) depletion of noradrenaline from samples of the chicks' medial f o r e b r a i n . The reduction (58%) was s i m i l a r to that associated with the prevention of i m p r i n t i n g in a previous study (2). Thus although in the present experiment DSP4 treatment depleted l e v e l s of noradrenaline in the telencephalon, i t did not a f f e c t the chicks' a b i l i t y
to learn a s i n g l e t r i a l
passive avoidance task.
REFERENCES I . Cherkin, A. Kinetics of memory c o n s o l i d a t i o n : r o l e of amnesic treatment parameters. Proc. Nat. Acad. Sci. USA., 63 (1969) 1094-1101. 2. Davies, D.C., Horn, G. and McCabe, B.J. Noradrenaline and l e a r n i n g : the e f f e c t s of the noradrenergic neurotoxin DSP4 on i m p r i n t i n g in the domestic chick. Behav. Neurosci., (in press).
BACKGROUND STIMULI AS A REMINDER AFTER SPONTANEOUSFORGETTING POTENTIATION BY MRF STIMULATION DEKEYNE, A., DEWEER, B. AND SARA, S.J. Laboratoire de Physiologie Nerveuse, Departement de Psychophysiologie C.N.R.S., 91190, G i f - s u r Yvette, France Reliable f o r g e t t i n g of a r e l a t i v e l y complex maze is seen in rats when the t r a i n i n g - t o - t e s t
in-
t e r v a l is 25 days. Forgetting is measured by longer time to run the maze and by an increase in the number of errors from the l a s t t r a i n i n g t r i a l s
to the t e s t t r i a l .
A reminder - a 90-sec exposure
to background s t i m u l i in the experimental room - s i g n i f i c a n t l y a l l e v i a t e s f o r g e t t i n g when presented j u s t p r i o r to the t e s t t r i a l , (I).
but is only m a r g i n a l l y e f f e c t i v e when given I or 24 h before t e s t i n g
This f o r g e t t i n g can also be a l l e v i a t e d by pretest s t i m u l a t i o n of the mesencephalic r e t i c u l a r
formation (MRF) (2). The present experiments, using the same task and the same f o r g e t t i n g paradigm, test the hypothesis t h a t such marginal cuing e f f e c t s can be potentiated by t h i s MRF s t i m u l a t i o n . In the f i r s t
experiment, h a l f of the animals were exposed f o r 90 seconds to the experimental
room (reminder c o n d i t i o n ) , while the other h a l f were exposed to the colony room (pseudo-reminder c o n d i t i o n ) , I h before t e s t i n g . These two groups were divided i n t o 2 subgroups, stimulated and pseudo-stimulated. The plan of the second experiment was the same, but the c u i n g - t o - t e s t i n t e r v a l was 24 h. The r e s u l t s , in terms of e r r o r s , showed t h a t : a)
There was no s i g n i f i c a n t e f f e c t of reminder alone: animals reminded I h or 24 h before t e s t i n g performed at the same level as pseudo-reminded animals.
b)
MRF s t i m u l a t i o n given during reminder exposure I h before t e s t i n g a l l e v i a t e d f o r g e t t i n g . This
c)
MRF s t i m u l a t i o n had no e f f e c t when administered in the colony room ( i . e .
p o t e n t i a t i o n of a reminder e f f e c t was not seen with the 24 h c u i n g - t o - t e s t i n t e r v a l . in conjunction with an
i r r e l e v a n t cue). MRF s t i m u l a t i o n had absolutely no e f f e c t on run time. This is an argument against an i n t e r p r e t a t i o n in terms of performance f a c i l i t a t i o n as locomotion or m o t i v a t i o n .
due to treatment e f f e c t s on n o n - s p e c i f i c factors such
87 Experiments using an interference paradigm are presently in progress in order to determine to what extent the effects of MRF stimulation are a function of the relevance of the reminder cue to the target memory. REFERENCES I . Deweer, B. and Sara, S.J., Anim. Learning and Behavior, 12, no. 2 (1984) 238-247. 2. Sara, S.J., Deweer, B. and Hars, B., Neurosci. L e t t r . ,
18 (1980) 211-217.
INTERHEMISPHERIC INTERACTIONS AS INFERRED BY CHOICE RTs TO VISUAL DISCRIMINATIONS IN PIGEONS DI STEFANO, M., KUSMIC, C. AND MUSUMECI, D. I s t i t u t o di F i s i o l o g i a d e l l ' U n i v e r s i t a e I s t i t u t o di Neurofisiologia del C.N.R., Via S. Zeno 3~, 561000 Pisa, I t a l y In pigeons, l a t e r a l l y positioned eyes and anatomical organization of visual pathways g r e a t l y promote l a t e r a l i z a t i o n of the visual information monocularly learned. Although binocular interact i o n s , such as i n t e r o c u l a r equivalence, have been repeatedly demonstrated, there are controversial evidences about integrated hemispheric a c t i v i t y during visual learning, since some works report that monocular learning is preferred even when visual s t i m u l i are simultaneously presented to both eyes. Two p o s s i b i l i t i e s can be considered f o r attempting to explain such a monocular bias. F i r s t l y , as recently shown in chickens, asymmetrical functioning of the visual centers connected to each eye could provide the advantage of one eye over the other. The second p o s s i b i l i t y implies independent incoming of visual information in the two halves of the brain. As visual input is not simultaneously transmitted to both sides of the brain, other than when i t is displayed on the binocular visual f i e l d which has in pigeons a very narrow extent, monocular viewing would generally be prevalent. With the aim to v e r i f y these hypotheses we analyzed choice reaction times to grating,brightness and pattern visual discriminations in pigeons trained in one or two choice-keys skinner box. Monocular choice RTs were measured in six pigeons which had already achieved the learning c r i t e r i o n for each eye, according to a simultaneous choice (two-keys) paradigm. Our r e s u l t s did not e x h i b i t any s i g n i f i c a n t systemic difference between the two eyes, supporting the view that the underlying visual centers do not d i f f e r in visual encoding a b i l i t y .
The only s i g n i f i c a n t e f f e c t was found f o r the i n -
teraction stimulus position/exposed eye: in f a c t , when the visual stimulus is displayed i p s i l a t e r a l l y to the viewing eye, RTs are much f a s t e r than in opposite condition. The difference between i p s i l a t e r a l vs c o n t r a l a t e r a l position of the visual stimulus (respect to the exposed eye) can simply be due to the experimental set-up. Since the two visual keys are located 30 ° apart from each other, the animal is forced, during monocular viewing to t i l t
i t s head by several degrees in order to d i s c r i m i -
nate visual s t i m u l i when the p o s i t i v e one is displayed in the visual f i e l d c o n t r a l a t e r a l to the exposed eye. In the second experiment we measured choice-RTs during monocular and binocular discriminations when the visual f i e l d of animal was l i m i t e d by goggles to the r e s t r i c t e d area of binocular v i s i o n . The experimental procedure consisted of a go-no go paradigm in which the visual stimulus (30 ° wide)
to learn a s i n g l e t r i a l
passive avoidance task.
REFERENCES I . Cherkin, A. Kinetics of memory c o n s o l i d a t i o n : r o l e of amnesic treatment parameters. Proc. Nat. Acad. Sci. USA., 63 (1969) 1094-1101. 2. Davies, D.C., Horn, G. and McCabe, B.J. Noradrenaline and l e a r n i n g : the e f f e c t s of the noradrenergic neurotoxin DSP4 on i m p r i n t i n g in the domestic chick. Behav. Neurosci., (in press).
BACKGROUND STIMULI AS A REMINDER AFTER SPONTANEOUSFORGETTING POTENTIATION BY MRF STIMULATION DEKEYNE, A., DEWEER, B. AND SARA, S.J. Laboratoire de Physiologie Nerveuse, Departement de Psychophysiologie C.N.R.S., 91190, G i f - s u r Yvette, France Reliable f o r g e t t i n g of a r e l a t i v e l y complex maze is seen in rats when the t r a i n i n g - t o - t e s t
in-
t e r v a l is 25 days. Forgetting is measured by longer time to run the maze and by an increase in the number of errors from the l a s t t r a i n i n g t r i a l s
to the t e s t t r i a l .
A reminder - a 90-sec exposure
to background s t i m u l i in the experimental room - s i g n i f i c a n t l y a l l e v i a t e s f o r g e t t i n g when presented j u s t p r i o r to the t e s t t r i a l , (I).
but is only m a r g i n a l l y e f f e c t i v e when given I or 24 h before t e s t i n g
This f o r g e t t i n g can also be a l l e v i a t e d by pretest s t i m u l a t i o n of the mesencephalic r e t i c u l a r
formation (MRF) (2). The present experiments, using the same task and the same f o r g e t t i n g paradigm, test the hypothesis t h a t such marginal cuing e f f e c t s can be potentiated by t h i s MRF s t i m u l a t i o n . In the f i r s t
experiment, h a l f of the animals were exposed f o r 90 seconds to the experimental
room (reminder c o n d i t i o n ) , while the other h a l f were exposed to the colony room (pseudo-reminder c o n d i t i o n ) , I h before t e s t i n g . These two groups were divided i n t o 2 subgroups, stimulated and pseudo-stimulated. The plan of the second experiment was the same, but the c u i n g - t o - t e s t i n t e r v a l was 24 h. The r e s u l t s , in terms of e r r o r s , showed t h a t : a)
There was no s i g n i f i c a n t e f f e c t of reminder alone: animals reminded I h or 24 h before t e s t i n g performed at the same level as pseudo-reminded animals.
b)
MRF s t i m u l a t i o n given during reminder exposure I h before t e s t i n g a l l e v i a t e d f o r g e t t i n g . This
c)
MRF s t i m u l a t i o n had no e f f e c t when administered in the colony room ( i . e .
p o t e n t i a t i o n of a reminder e f f e c t was not seen with the 24 h c u i n g - t o - t e s t i n t e r v a l . in conjunction with an
i r r e l e v a n t cue). MRF s t i m u l a t i o n had absolutely no e f f e c t on run time. This is an argument against an i n t e r p r e t a t i o n in terms of performance f a c i l i t a t i o n as locomotion or m o t i v a t i o n .
due to treatment e f f e c t s on n o n - s p e c i f i c factors such
87 Experiments using an interference paradigm are presently in progress in order to determine to what extent the effects of MRF stimulation are a function of the relevance of the reminder cue to the target memory. REFERENCES I . Deweer, B. and Sara, S.J., Anim. Learning and Behavior, 12, no. 2 (1984) 238-247. 2. Sara, S.J., Deweer, B. and Hars, B., Neurosci. L e t t r . ,
18 (1980) 211-217.
INTERHEMISPHERIC INTERACTIONS AS INFERRED BY CHOICE RTs TO VISUAL DISCRIMINATIONS IN PIGEONS DI STEFANO, M., KUSMIC, C. AND MUSUMECI, D. I s t i t u t o di F i s i o l o g i a d e l l ' U n i v e r s i t a e I s t i t u t o di Neurofisiologia del C.N.R., Via S. Zeno 3~, 561000 Pisa, I t a l y In pigeons, l a t e r a l l y positioned eyes and anatomical organization of visual pathways g r e a t l y promote l a t e r a l i z a t i o n of the visual information monocularly learned. Although binocular interact i o n s , such as i n t e r o c u l a r equivalence, have been repeatedly demonstrated, there are controversial evidences about integrated hemispheric a c t i v i t y during visual learning, since some works report that monocular learning is preferred even when visual s t i m u l i are simultaneously presented to both eyes. Two p o s s i b i l i t i e s can be considered f o r attempting to explain such a monocular bias. F i r s t l y , as recently shown in chickens, asymmetrical functioning of the visual centers connected to each eye could provide the advantage of one eye over the other. The second p o s s i b i l i t y implies independent incoming of visual information in the two halves of the brain. As visual input is not simultaneously transmitted to both sides of the brain, other than when i t is displayed on the binocular visual f i e l d which has in pigeons a very narrow extent, monocular viewing would generally be prevalent. With the aim to v e r i f y these hypotheses we analyzed choice reaction times to grating,brightness and pattern visual discriminations in pigeons trained in one or two choice-keys skinner box. Monocular choice RTs were measured in six pigeons which had already achieved the learning c r i t e r i o n for each eye, according to a simultaneous choice (two-keys) paradigm. Our r e s u l t s did not e x h i b i t any s i g n i f i c a n t systemic difference between the two eyes, supporting the view that the underlying visual centers do not d i f f e r in visual encoding a b i l i t y .
The only s i g n i f i c a n t e f f e c t was found f o r the i n -
teraction stimulus position/exposed eye: in f a c t , when the visual stimulus is displayed i p s i l a t e r a l l y to the viewing eye, RTs are much f a s t e r than in opposite condition. The difference between i p s i l a t e r a l vs c o n t r a l a t e r a l position of the visual stimulus (respect to the exposed eye) can simply be due to the experimental set-up. Since the two visual keys are located 30 ° apart from each other, the animal is forced, during monocular viewing to t i l t
i t s head by several degrees in order to d i s c r i m i -
nate visual s t i m u l i when the p o s i t i v e one is displayed in the visual f i e l d c o n t r a l a t e r a l to the exposed eye. In the second experiment we measured choice-RTs during monocular and binocular discriminations when the visual f i e l d of animal was l i m i t e d by goggles to the r e s t r i c t e d area of binocular v i s i o n . The experimental procedure consisted of a go-no go paradigm in which the visual stimulus (30 ° wide)