Voluntary exercise ameliorates the good limb training effect in a mouse model of stroke.

Stroke is the leading cause of long-term disability in the United States, making research on rehabilitation imperative. Stroke rehabilitation typically focuses on recovery of the impaired limb, although this process is tedious. Compensatory use of the intact limb after stroke is more efficient, but it is known to negatively impact the impaired limb. Exercise may help with this problem; research has shown that exercise promotes neuronal growth and prevents cell death. This study used a mouse model to investigate if post-stroke exercise could prevent deterioration of the function of the impaired limb despite compensatory training of the intact limb. Results showed that mice that exercised, in combination with intact limb training, demonstrated improved functional outcome compared to mice that received no training or compensatory limb training only. These findings suggest that exercise can prevent the deterioration of impaired limb functional outcome that is typically seen with intact limb use.

Patterns of Arc mRNA expression in the rat brain following dual recall of fear- and reward-based socially acquired information.

Learning can occur via direct experience or through observation of another individual (i.e., social learning). While research focused on understanding the neural mechanisms of direct learning is prevalent, less work has examined the brain circuitry mediating the acquisition and recall of socially acquired information. Here, we aimed to further elucidate the mechanisms underlying recall of socially acquired information by having male and female rats sequentially recall a socially transmitted food preference (STFP) and a fear association via fear conditioning by-proxy (FCbP). Brain tissue was processed for mRNA expression of the immediate early gene (IEG) Arc, which expresses in the nucleus following transcription before migrating to the cytoplasm over the next 25 min. Given this timeframe, we could identify whether Arc transcription was triggered by STFP recall, FCbP recall, or both. Contrary to past research, we found no differences in any Arc expression measures across a number of prefrontal regions and the ventral CA3 of the hippocampus between controls, demonstrators, and observers. We theorize that these results may indicate that relatively little Arc-dependent neural restructuring is taking place in the prefrontal cortices and ventral CA3 following recall of recently socially acquired information or directly acquired fear associations in these areas.

Appetitive Behavior in the Social Transmission of Food Preference Paradigm Predicts Activation of Orexin-A producing Neurons in a Sex-Dependent Manner.

Orexin-producing cells in the lateral hypothalamic area have been shown to be involved in a wide variety of behavioral and cognitive functions, including the recall of appetitive associations and a variety of social behaviors. Here, we investigated the role of orexin in the acquisition and recall of socially transmitted food preferences in the rat. Rats were euthanized following either acquisition, short-term recall, or long-term recall of a socially transmitted food preference and their brains were processed for orexin-A and c-Fos expression. We found that while there were no significant differences in c-Fos expression between control and experimental subjects at any of the tested timepoints, females displayed significantly more activity in both orexinergic and non-orexinergic cells in the lateral hypothalamus. In the infralimbic cortex, we found that social behavior was significantly predictive of c-Fos expression, with social behaviors related to olfactory exploration appearing to be particularly influential. We additionally found that appetitive behavior was significantly predictive of orexin-A activity in a sex-dependent matter, with the total amount eaten correlating negatively with orexin-A/c-Fos colocalization in male rats but not female rats. These findings suggest a potential sex-specific role for the orexin system in balancing the stimulation of feeding behavior with the sleep/wake cycle.

Intermittent Skill Training Results in Moderate Improvement in Functional Outcome in a Mouse Model of Ischemic Stroke.

BACKGROUND: Stroke is a leading cause of disability worldwide. Focused training of the impaired limb has been shown to improve its functional outcome in animal models. However, most human stroke survivors exhibit persistent motor deficits, likely due to differences in rehabilitation intensity between experimental (animal) and clinical (human) settings. OBJECTIVE: The current study investigated the effect of training intensity on behavioral outcome in a mouse model of stroke. METHODS: Mice were trained preoperatively on a skilled reaching task. After training, mice received a unilateral photothrombotic stroke. Postoperatively, animals received either daily rehabilitative training (traditional intensity), intermittent rehabilitative training (every other day), or no rehabilitative training (control). Assessment of the impaired limb occurred after 14 training sessions (14 days for the Traditional group; 28 days for the Intermittent group). RESULTS: Assessment of the impaired limb illustrated that traditional, daily training resulted in significantly better performance than no training, while intermittent training offered moderate performance gains. Mice receiving intermittent training performed significantly better than control mice but did not exhibit reaching performance as strong as that of animals trained daily. CONCLUSIONS: The intensity of rehabilitation is important for optimal recovery. Although intermediate intensity offers some benefit, it is not intensive enough to mimic the performance gains traditionally observed in animal models. These results suggest that intensive training, which is often unavailable for human stroke survivors, is necessary to achieve an optimal functional outcome. The lower bounds of training intensity for functional benefit still need to be determined.

Altering Perceived Context: Transportation Cues Influence Novelty-Induced Context Exploration.

Context is the milieu in which everything occurs. Many research studies consider context, or even explicitly manipulate it; yet it remains challenging to characterize. We know that a context surrounds and influences tasks; however, the boundaries of its influence are difficult to define. In behavioral science, context is often operationalized by the physical environment in which the experiment takes place, and the boundaries of the context are assumed to begin at the entrance to that of the room or apparatus. Experiences during transportation to the testing space have been shown to impact rodent behavior and memory, but transportation's relationship with novelty and physical environment is not fully understood. The current study explored how familiar vs. novel cues, both within a physical environment and preceding it, impact the perception of a context. We manipulated context on three levels: physical testing environment, object cues within that environment, and transportation cues preceding entrance to the testing environment. We found that novel transportation cues can change rats' perception of both familiar and novel contexts. The effects of transportation on perceived context may be affected by the length of the retention interval, testing environment, and behavioral range. These data suggest that context is a broad concept that includes cues across time and is sensitive to small differences in experience.