Journal of Neuroscience, Vol 9, 983-989, Copyright © 1989 by Society for Neuroscience
Deficits in response space following unilateral striatal dopamine depletion in the rat
VJ Brown and TW Robbins
Department of Experimental Psychology, University of Cambridge, United Kingdom.
Hungry rats were trained to report the occurrence and location of brief,
unpredictable visual stimuli presented to the left of their heads in 1 of 2
response locations. After training, they received unilateral infusions of
6-hydroxydopamine, depleting dopamine throughout the head of the caudate
putamen, either on the left or the right side, that is, either ipsilateral
or contralateral to the side on which they were required to respond.
Following an ipsilateral lesion there were no impairments in localization
of the visual discriminanda and there was no lengthening of reaction time.
The contralaterally lesioned rats, however, showed considerably lengthened
reaction times to both stimuli and a profound bias to the nearer of the 2
response locations. Evidence from probe trials in which the visual stimuli
were presented separately or simultaneously showed that the impairment was
not due to a failure to localize the stimuli in contralateral space but,
rather, resulted from a deficit in directing responses in contralateral
space. It is suggested that this may be due to a distortion in the
representation of response space.