Complementary effects of unilateral striatal dopamine depletion and amphetamine infusions on a lateralized visual reaction time task in rats

78 COMPLEMENTARYEFFECTS OF UNILATERAL STRIATAL DOPAMINE DEPLETION AND AMPHETAMINE INFUSIONS ON A LATERALIZED VISUAL REACTION TIME TASK IN RATS CARLI, M.**, JONES, G.H.* AND ROBBINS, T.W.* * Department of Experimental Psychology, U n i v e r s i t y of Cambridge, Cambridge, United Kingdom ** Mario Negri I n s t i t u t e , Milan, I t a l y A p r e v i o u s l y described paradigm ( I ) f o r d i s t i n g u i s h i n g between visual sensory neglect (or " i n a t t e n t i o n " ) and response bias was used to compare the e f f e c t of u n i l a t e r a l dopamine (DA) deplet i o n from the caudate nucleus or nucleus accumbens or both regions. The neurotoxin 6-hydroxydopamine (8 ~g/2 ~ I ) was infused u n i l a t e r a l l y

i n t o e i t h e r the nucleus accumbens (N.AC) or the caudate nucleus

(CAUD) to produce s e l e c t i v e DA depletion to about 20% of the i n t a c t side. Four groups of rats received i n f u s i o n s i n t o e i t h e r CAUD or N.AC alone, or infusions i n t o both regions on e i t h e r the same side (SAME) or on opposite sides (OPP). The CAUD alone and SAME groups e x h i b i t e d s i g n i f i c a n t l y enhanced i p s i l a t e r a l

response bias and r e t a r d a t i o n of i n i t i a t i o n ,

wards c o n t r a l a t e r a l space. There was no e f f e c t

but not execution, of responses to-

on d i s c r i m i n a t i v e s e n s i t i v i t y .

groups showed no s i g n i f i c a n t e f f e c t s on any measure. The degree of i p s i l a t e r a l

The N.AC and OPP bias was s i g n i f i c a n t -

l y correlated with DA depletion from the caudate nucleus, but not the nucleus accumbens. In a second series of experiments, the i n d i r e c t DA agonist d-amphetamine was infused u n i l a t e r a l l y i n t o e i t h e r the CAUD or N.AC (10-30 ~g). The pattern of r e s u l t s complemented those f o l l o w i n g u n i lateral striatal

DA d e p l e t i o n . Thus, CAUD i n j e c t i o n s s i g n i f i c a n t l y enhanced responding to contra-

l a t e r a l space. These i n f u s i o n s also increased the incidence of premature responses though only towards the c o n t r a l a t e r a l

side. By c o n t r a s t , u n i l a t e r a l N.AC i n f u s i o n s increased premature responses

on both sides, w i t h o u t a f f e c t i n g other aspects of performance. These r e s u l t s support the hypothesis that the mesencephalic DA p r o j e c t i o n to the caudate nucleus is involved in l a t e r a l i z e d response i n i t i a t i o n

rather than sensory a t t e n t i o n whereas the p r o j e c t i o n

to the nucleus accumbens has u n i l a t e r a l i z e d f u n c t i o n s . REFERENCES I.

C a r l i , M. et a l . ,

Nature, 313 (1985) 679-682.

EARLY BINOCULAR VISUAL DEPRIVATION AND THE FUNCTION OF AREA 19 OF MONKEYS (MACACA SPECIOSA) CARLSON, S. AND TANILA, H. Department of Physiology, U n i v e r s i t y of H e l s i n k i , Finland Early binocular visual d e p r i v a t i o n a l t e r s the processing of visual information profoundly in the central nervous system. As a r e s u l t of e a r l y binocular d e p r i v a t i o n the f u n c t i o n of the primary v i sual cortex is altered and i t has also been shown that the representation of v i s i o n is profoundly reduced in Brodmann's area 7 of monkeys. In one study binocular visual d e p r i v a t i o n has been reported to a l t e r the modality of neuronal