Behavioural brain research
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In humans and other mammals, the unexpected loss of a resource can lead to emotional conflict. Consummatory successive negative contrast (cSNC) is a laboratory model of reward devaluation meant to capture that conflict. In this paradigm, animals are exposed to a sharp reduction in the sucrose concentration of a solution after several days of access. ⋯ The current analysis applied latent growth mixture modeling to test for and characterize heterogeneity in recovery from cSNC among rats (N=262). Although most animals exhibited recovery of consummatory behavior after a sharp drop in consumption in the first postshift trial (Recovery class; 83%), two additional classes were identified including animals that did not change their consumption levels after downshift (No Contrast class; 6%), and animals that exhibited an initial response similar to that of the Recovery class but did not recover to preshift consumption levels (No Recovery class; 11%). These results indicate heterogeneity in recovery from reward loss among rats, which may increase the translatability of this animal model to understand diverse responses to loss among humans.
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The rodent has been the preferred research model for evaluating the mechanisms related to, and potential treatments for, traumatic brain injury (TBI). Many therapies previously determined to be effective in pre-clinical investigations have failed to show the same effectiveness in clinical trials. The environment a rodent is housed in plays an important role in brain and behavioral development. ⋯ The TBI and sham groups that were raised, and remained, in the SE performed worse than any of the EE groups on the RR. TBI rats that were placed in the EE had larger cortices and more cells in the hippocampus than the TBI rats housed in the SE. These data strongly suggest that the pre-injury housing environment should be considered as investigators refine pre-clinical models of TBI.