Role of dopaminergic system Flashcards
Classic study of the effects of DA depletion from the frontal cortex in delayed attention performance Prefrontal DA depletion impairs spatial working memory. DA agonists (L-DOPA) remediate working memory deficits
Brozoski et al 1979
Local injections of selective D1 antagonists into the PFC of rhesus monkeys. Induced errors and increased latency in an oculomotor task that required memory guided saccades. The deficit was dose-dependent and sensative to the duration of the delay period. D1 antagonists had no effect on performance of a control task requiring visually guided saccades, indicating that sensory and motor functions were unaltered.
Goldman-Rakik and Sawaguchi 1991 Science
L-DOPA withdrawal in PD leads to impairments in working memory and planning. L-DOPA speeds thinking time in PD.
Lange et al 1992
Single unit studies seem to indicate that DA has a role in reinforcement learning. Single nerve units found to encode predictions of reward
Schulz
Selective activation of PFC DA system by mild stress can be nmimicked by anxiogenic beta-carbolines. Study investigated the effects of FG7142 on the performance of spatial working memory tasks in the rat and monkey.
- FG7142 selectively increased prefrontal dopamine turnover, and significantly impaired performance on spatal working memory.
- Spatial discrimination (a task with similar motor and motivational demands- rats) or delayed response performance following zero second delaye (monkeys) was unaffected.
- Cognitive deficits in both rats and monkeys were prevented by pretreatment with the Bz receptor antagonist, which blocked increased in DA turnover, and the DA receptor antagonists,.
Murphy, Arnsten, Goldman-Rakic and Roth 1996
D-amphetamine enhancement of LTM post-trial is possible with intra-cadate (but not intra-accumbens) administration, and these effects are due to actions at DA receptors.
White & Viaud 1991
Similar findings to White and Viaud for appetitive win-stay memory performance in the radial 8 armed maze
Post-trial, intra-caudate facilitation of appetitive memory by d-amphetamine and DA receptor agonists.
Packard & White 1991
Acquisition and performance of instrumental actions are assumed to require both action-outcome and stimulus-response habit processes. Over the course of extended training, control over instrumental performance shifts from goal directed action-outcome associations to S-R associations that progressively gain dominance over behavior.
Study examined ability of rats subject to bilateral 6-hydroxydopamine lesions of the nigriostriatal dopaminergic pathway to develop behavioral autonomy with overtraining.
- Given extended training on 2 cued instrumental tasks associating a stimulus with an instrumental action, and a food reward.
- Overtaining was followed by a test of goal sensitivity by satiety specific devaluation of reward.
Results demonstrated that striatal DA loss prevents the formation of S-R habits in rats (in line with White’s speculation that DA strengthenes S-R learning in the striatum)
- In control animals, one action (lever press) was insensitive to reward devaluation- i.e. had become a habit, whereas the second action (chain pull) was still sensitive to goal devaluation
- Indicated that the development of habit learning may depend on the characteristics of the response.
- In dopamine-depleted rats, lever press and chain pull remained sensitive to reward devaluation. evidencing a role of striatal DA transmission in habit formation.
Faure et al 2005
Habits are controlled by antecedent stimuli rather than by goal expectancy. Interval schedules of feedback have been shown to generate habits, as revealed by the insensitivity of behavior acquired under this schedule to outcome devaluation treatments.
Study assessed role of dorsolateral striatum in habit learning.
- Sham operated controls and rates with dorsolateral striatum lesions were trained to press a lever for sucrose under interval schedules.
- After training, sucrose was devalued by inducing taste aversion with lithium chloride. Saline injections were given to controls. Only rats given the devaluation treatment reduced their consumption of sucrose, and this reduction was similar in both sham and lesion groups.
- All rats were then returned to the instrumental chamber for an extinction test: lever was extended but no sucrose delivered
- Second experiment conducted in which a group of lesions of dorsomedial striatum was added
Results: direct evidence that dorsolateral (but not dorsomedial) striatum is necessary for habit formation.
- In contrast to sham-operated controls, and dorsomedial lesioned rats, rats with dorsolateral striatum lesions refrained from pressing the lever if the outcome was devalued.
Yin et al 2004
