Neurobiology of learning and memory
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Neurobiol Learn Mem · Jan 2012
Loss of activity-dependent Arc gene expression in the retrosplenial cortex after hippocampal inactivation: interaction in a higher-order memory circuit.
The rodent hippocampus is well known for its role in spatial navigation and memory, and recent evidence points to the retrosplenial cortex (RSC) as another element of a higher order spatial and mnemonic circuit. However, the functional interplay between hippocampus and RSC during spatial navigation remains poorly understood. To investigate this interaction, we examined cell activity in the RSC during spatial navigation in the water maze before and after acute hippocampal inactivation using expression of two immediate-early genes (IEGs), Arc and Homer 1a (H1a). ⋯ Importantly, bilateral inactivation of hippocampus resulted in loss of behavior-induced Arc expression in RSC. Despite a lateralized effect in CA1, Arc expression was equivalently and bilaterally decreased in RSC of uni-TTX rats, consistent with a network level interaction between hippocampus and RSC. We conclude that the loss of hippocampal input alters activity of RSC neurons and compromises their ability to engage plastic processes dependent on IEG expression.
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Neurobiol Learn Mem · Jan 2012
Different types of exercise induce differential effects on neuronal adaptations and memory performance.
Different exercise paradigms show differential effects on various forms of memory. We hypothesize that the differential effects of exercises on memory performance are caused by different neuroplasticity changes in relevant brain regions in response to different exercise trainings. We examined the effects of treadmill running (TR) and wheel running (WR) on the Pavlovian fear conditioning task that assesses learning and memory performance associated with the amygdala (cued conditioning) and both the amygdala and hippocampus (contextual conditioning). ⋯ Injection of K252a, a TrkB kinase inhibitor, in the dorsal hippocampus or basolateral amygdala abolished the exercise-facilitated contextual or cued fear learning and memory performance, respectively, regardless of the types of exercise. In summary, our results supported that different types of exercise affect the performance of learning and memory via BDNF-TrkB signaling and neuroplasticity in specific brain regions. The brain region-specific neuronal adaptations are possibly induced by various levels of intensity/stress elicited by different types of exercise.
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Neurobiol Learn Mem · Jan 2012
Activation and role of the medial prefrontal cortex (mPFC) in extinction of ethanol-induced associative learning in mice.
Although the medial prefrontal cortex (mPFC) has been shown to be integrally involved in extinction of a number of associative behaviors, its role in extinction of alcohol (ethanol)-induced associative learning has received little attention. Previous reports have provided evidence supporting a role for the mPFC in acquisition and extinction of amphetamine-induced conditioned place preference (CPP) in rats, however, it remains unknown if this region is necessary for extinction of ethanol (EtOH)-induced associative learning in mice. ⋯ In order to confirm a functional role of the mPFC in regulating the extinction process, we then showed that electrolytic lesions of the mPFC following acquisition blocked subsequent extinction of EtOH-CPP. Together, these experiments indicate a role for the PL and IL subregions of the mPFC in processing changes of the EtOH-cue contingency, as well as in regulating extinction of EtOH-induced associative learning in mice.