The effects of hippocampal lesions upon spatial and nonspatial tests of working memory

Behavioural Brain Research, 20 (1986) 65-159 Elsevier

65

SOCIAL CONTRACEPTION IN SUBORDINATE MARMOSETMONKEYS ( C a l l i t h r i x

jacchus jacchus)

ABBOTT, D.H., GEORGE, L.M. AND MOORE, G.F. MRC/AFRC Comparative

Physiology Group, I n s t i t u t e of Zoology, Regent's Park, London NWI 4RY,

England The marmoset monkey employs social contraception to l i m i t reproduction to only the dominantanimals in each social group. In both f r e e - l i v i n g and captive groups of marmosets, only the dominant (Rank I ) female reproduces, but i t

is not yet c l e a r whether the dominant (Rank I) male enjoys a s i -

m i l a r reproductive monopoly. To i n v e s t i g a t e the behavioural and endocrinological mechanisms operat i n g to suppress reproduction

in subordinate marmosets, seven captive groups of marmosets were es-

t a b l i s h e d , mostly comprising three unrelated adult males and three unrelated a d u l t females. Each group was observed over two six-week periods f o r a t o t a l of 40 h per group (100 min/day; I-2 times per week), a l l animals were blood sampled twice a week f o r 8-12 months and t h e i r l u t e i n i s i n g hormone (LH) responses t o a s i n g l e b o l u s i n j e c t i o n

of LHRH (50 ng i . m . : the previously determined mini-

mum e f f e c t i v e dose) were tested. Only the dominant (Rank I) females received e j a c u l a t o r y mounts. In any group, subordinate females received less than 10% of male mounts and none were i n t r o m i t t e d .

In

four groups, the e j a c u l a t o r y mounts received by the dominant female o r i g i n a t e d from the dominant male, whereas in the remaining three groups, both the dominant and one subordinate male were equally involved. However, copulating subordinates were subsequently harassed by the dominant animal of t h e i r own sex. Nine of the t h i r t e e n subordinate females had no ovarian cycles during the 8-12 months of blood sampling (plasma progesterone

<10 ng/ml), w h i l s t the remaining four ovulated once, but an

inadequate l u t e a l phase followed on a l l occasions. Plasma testosterone l e v e l s were only estimated in males from f i v e of the seven groups: seven of the e i g h t subordinate males had s i g n i f i c a n t l y

lower

testosterone concentrations than the dominant (Rank I) male in t h e i r group. In comparison to dominant animals (males: 133.6 ± 21.9 mlU/ml; females: 81.2 ± 11.0 mlU/ml), mean (± s.e.m.) peak plasma LH responses to LHRH in subordinates were g r e a t l y reduced (males: 4.8 ± 1.6 mlU/ml; females: 3.7 ± 1.2 mlU/ml). Social contraception in marmoset monkeys apparently leads to complete reproductive failure

in a l l

subordinate females but only in some subordinate males.

THE EFFECTS OF HIPPOCAMPAL LESIONS UPON SPATIAL AND NONSPATIAL TESTS OF WORKING MEMORY AGGLETON, J.P.

AND RA$&INS, J.N.P.

*Department of Psychology, U n i v e r s i t y of Durham, DHI 3LE, England **Department of Experimental Psychology, U n i v e r s i t y of Oxford, OXI 3UD, England Considerable i n t e r e s t has been aroused by the proposal t h a t hippocampal damage in rats s e l e c t i vely d i s r u p t s the a b i l i t y

to learn information which is useful f o r one t r i a l

is i r r e l e v a n t on subsequent t r i a l s

of an experiment but

(working memory). In contrast the learning of constant response

associations (reference memory) does not require the hippocampus ( I ) .

One p e r s i s t e n t c r i t i c i s m of

t h i s proposal has been the r e l i a n c e on spatial tasks in order to demonstrate the s e n s i t i v i t y of working memory to hippocampal damage.

66 The present study compared the performance of rats with hippocampal lesions on a spatial and nonspatial test of working memory. I t was found that while extensive hippocampal damage produced a severe impairment in forced-choice a l t e r n a t i o n (spatial working memory) the same lesions did not a f f e c t the a c q u i s i t i o n of a nonspatial test of working memory, delayed nonmatching-to-sample. This t e s t of object recognition required the rats to select that arm in a Y-maze which contained an unf a m i l i a r stimulus. As the s t i m u l i were changed a f t e r every t r i a l Furthermore, those rats with hippocampal lesions could s t i l l t e r r e t e n t i o n delays as long as 60 sec.

t h i s task required working memory.

perform the task at normal levels a f -

Subsequent control experiments helped confirm that the

rats had indeed l e a r n t a nonspatial t e s t of working memory. This pattern of r e s u l t s is incompatible with the working memory hypothesis. The f i n a l experiment showed that r e p e t i t i o n of t e s t s t i m u l i w i t h i n a session, which increased proactive i n t e r f e r e n c e , did not d i f f e r e n t i a l l y

impair the animals

with hippocampal lesions. REFERENCES I.

Olton, Becker and Handel man, Behav. Brain S c i . , 2 (1979) 315-365.

INFLUENCE OF ARGININE-VASOPRESSIN AND/OR HIPPOCAMPALLESIONS ON RETRIEVAL PROCESSES IN BALB/C MICE ALESClO-LAUTIER, B. AND SOUMIREU-MOURAT,B. Laboratoire de Neurobiologie des Comportements (U.A. 372), Universit~ de Provence, 13397 Marseille Cedex 13, France In the recent years, a l o t of experiments have studied the e f f e c t s of arginine-vasopressin (AVP) on learning and memory. On another hand, i t

is commonly accepted that hippocampus is involved in

memory processes. On the c o n t r a r y , r e t r i e v a l processes have not been so much i n v e s t i g a t e d . Conseq u e n t l y , we f i r s t l y retrieval.

studied the e f f e c t s of i n t r a c e r e b r o - v e n t r i c u l a r (ICV) a d m i n i s t r a t i o n of AVP on

In a second experiment, we studied the e f f e c t s of p o s t - l e a r n i n g hippocampal lesions on

long-term r e t e n t i o n .

In a l a s t experiment, the e f f e c t s of both AVP and lesions were analyzed using

the same paradigms. Behavioral t e s t i n g consisted of a Go-NoGo a p p e t i t i v e d i s c r i m i n a t i o n task. BALB/c male mice underwent during 3 days a d a i l y session of l e a r n i n g , in order to d i s c r i m i n a t e between two p a r a l l e l runways (one w h i t e , one b l a c k ) ; h a l f of the animals were reinforced on the white side, the other h a l f on the black side. Every day, 12 randomized t r i a l s

were run (6 S+, 6 S-). The t e s t session was

run 24 days l a t e r in the same c o n d i t i o n s . A f t e r t h i s time i n t e r v a l , performance was c l e a r l y reduced in i n t a c t control mice. Surgery e v e n t u a l l y took place two days a f t e r the end of i n i t i a l chronic implantation of cannulae in the l a t e r a l

t r a i n i n g and consisted of e i t h e r

v e n t r i c l e s , or high frequency b i l a t e r a l

lesions of

the dorsal hippocampus, or b o t h . l n most of the cases, the lesion extended to about t w o - t h i r d s of the dorsal hippocampus. Controls were r e s p e c t i v e l y s a l i n e - i n j e c t e d or sham-lesioned mice or s a l i n e injected lesioned mice. In the f i r s t

and the t h i r d experiments, AVP (40 ng/kg; i . e .

I ng per animal) was injected 15