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The role of the GABA"A agonist muscimol on memory performance: Reward contingencies determine the nature of the deficit [An article from: Neurobiology of Learning and Memory]
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This digital document is a journal article from Neurobiology of Learning and Memory, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.
Description:
A matching-to-position (MTP) paradigm was altered to influence the type of associations a rat would use to solve the task. Our main behavioral manipulation was the application of the differential outcomes procedure (DOP). The DOP involves correlating each to-be-remembered event with a distinct reward condition. This procedure results in the development of unique reward expectancies that enhance and guide choice behavior. Such distinct reward expectancies are not formed when either a common or random assignment of reward is used (a non-differential outcomes procedure [NOP]). Intracerebroventricular infusions of the amnestic agent muscimol (GABA"A agonist) or aCSF were delivered to male rats trained on a delayed MTP task that implemented either the DOP or the NOP. Muscimol impaired performance in a dose dependent fashion in both groups-but the nature of the deficit differed as a function of reinforcement cotingencies. Rats trained with the DOP displayed a non-mnemonic delay-independent impairment: performance at all delay intervals was disrupted. In contrast, NOP-trained rats displayed a delay-dependent impairment demonstrating that muscimol can also have memory-disrupting effects. The difference in pattern of impairment appears to be a function of the associations formed during training and the type of cognitive strategies involved in maintaining behavior on a conditional delayed discrimination task when reinforcement contingencies are varied. Thus, these results demonstrate that increasing GABA"A receptor activation impairs a range of associative and memory functions.
Description:
A matching-to-position (MTP) paradigm was altered to influence the type of associations a rat would use to solve the task. Our main behavioral manipulation was the application of the differential outcomes procedure (DOP). The DOP involves correlating each to-be-remembered event with a distinct reward condition. This procedure results in the development of unique reward expectancies that enhance and guide choice behavior. Such distinct reward expectancies are not formed when either a common or random assignment of reward is used (a non-differential outcomes procedure [NOP]). Intracerebroventricular infusions of the amnestic agent muscimol (GABA"A agonist) or aCSF were delivered to male rats trained on a delayed MTP task that implemented either the DOP or the NOP. Muscimol impaired performance in a dose dependent fashion in both groups-but the nature of the deficit differed as a function of reinforcement cotingencies. Rats trained with the DOP displayed a non-mnemonic delay-independent impairment: performance at all delay intervals was disrupted. In contrast, NOP-trained rats displayed a delay-dependent impairment demonstrating that muscimol can also have memory-disrupting effects. The difference in pattern of impairment appears to be a function of the associations formed during training and the type of cognitive strategies involved in maintaining behavior on a conditional delayed discrimination task when reinforcement contingencies are varied. Thus, these results demonstrate that increasing GABA"A receptor activation impairs a range of associative and memory functions.
