Spatial learning in rats is impaired after degeneration of the nigrostriatal dopaminergic system

Abstract

We investigated spatial learning in rats with unilateral and bilateral lesions of the nigrostriatal dopaminergic system. We used the Morris water maze paradigm, which tests spatial forms of learning and memory and allows discrimination between sensory-motor and learning disabilities. Animals were trained preoperatively to learn the location of a spatially fixed hidden platform to escape from the swimming pool (acquisition training). A visual and a probe test were used before and after the acquisition training, respectively. Our results show that animals with unilateral lesions, although displaying longer escape latencies, have normal spatial memory abilities. Animals with bilateral lesions were able to swim as fast or even faster than animals with unilateral lesion. Despite the fact that these animals had learned the spatial navigation tasks preoperatively, bilateral dopaminergic lesions led to a profound deficit in ability to find a hidden platform during an acquisition task. In general, animals with bilateral lesions persisted in swimming along the pool walls and their spatial navigation performance during a probe test was very poor. These results suggest that deficit of the nigrostriatal dopaminergic system can affect the selection and maintenance of behavioral strategies in spatial navigation.

Restriction of dopamine signaling to the dorsolateral striatum is sufficient for many cognitive behaviors

“…Our conclusions are consistent with observations from rodent models of PD, where lesioning of DA neurons in the SNc results in deficits of visuospatial function (24)(25)(26). However, these models make no distinction between loss of DA signaling versus loss of DA neurons and do not separate performance from cognitive deficits.…”

“…In accordance with these observations, data from rodent models of PD indicate that the dorsal striatum contributes to various forms of learning and memory (22)(23)(24)(25)(26).…”

Animal Foraging and the Evolution of Goal‐Directed Cognition

“…Rats show similar defects in feeding and finding behaviors when suffering from dopaminergic insults. After learning the location of a platform target in the Morris water maze, rats are unable to find that target if their nigrostriatal dopaminergic neurons have been selectively killed (Mura & Feldon, 2003). Similarly, pharmacological agonists and antagonists of dopamine block performance in the water maze (Whishaw & Dunnett, 1985).…”

“…Benedix (1993) described a similar situation for rodents. For rats, this turning in response to resources is directly related to dopaminergic signaling, which apparently leads to preferential activation of specific neurons associated with the reward and subsequent behaviors associated with its acquisition (Mura & Feldon, 2003). In cognition, the analog of turning becomes a prolonged dopaminergic activation of local cell assemblies associated with the reward.…”

Dopaminergic deficiency syndrome in the picture of severe brain injury in the presence of protracted depression of consciousness

“…Данный синдром отмечается у обследованных нами пациен-тов в состояниях вегетативного статуса, акинетического му-тизма и мутизма с пониманием речи, а также, в одном слу-чае, -в коматозном состоянии. В литературе описана важная роль дофаминергиче-ской системы в процессах внимания, эмоционального контроля и психической активности [64][65][66][67][68][69][70][71][72][73][74][75][76]. В связи с этим ее критический дефицит у пациентов в вегетативном статусе может объяснять не только неврологические сим-птомы, но и стойкие перечисленные выше нарушения, включая внимание как базовый компонент сознания.…”