Some evidence in favor of this idea comes from the observations that the effects of GnRH and FMRFamide on retinal activity vary depending on the season; their effects are weaker during periods of sexual inactivity (Stell et al., 1987). “
“Recognizing when the world has changed—and when it has not—is a fundamental yet much ignored component of associative

learning. Imagine relocating to Sydney, Australia. While much there might be familiar, one prominent difference is of life-or-death import: the cars come from the right. If you don’t learn to look right-left-right before crossing, your visit might be quite short. Transferase inhibitor On the other hand, since you plan to venture to proper-side-of-the-road-driving countries periodically, it would behoove you to also maintain your previous left-right-left behavior, applying that when appropriate.

Optimally, rather than overwriting your original strategy for crossing Palbociclib molecular weight the street, upon experiencing the strange driving habits in your new hometown, you would form a new “state” of “I am in Sydney” and learn new mappings from actions to goals (“policies” in the jargon of reinforcement learning, “action-outcome associations” in terms of learning theory) relevant to that state. Linking these learned policies to the new state would, conveniently, protect the old policies linked to the

old state from being secondly overwritten, so that behavior could be modified quickly if the old state were to reappear. As this example illustrates, appropriate recognition of when to form new states to which to attach information is vital to adaptive behavior. In this issue of Neuron, Bradfield and colleagues ( Bradfield et al., 2013) use a series of complex yet highly controlled behavioral manipulations to show that input from a part of the thalamus, the parafascicular nucleus, onto cholinergic interneurons in the posterior compartment of the dorsomedial striatum (pDMS), is critical to the appropriate creation of new states during learning. Note that we use “state” here to refer to a high-order representation of the environment in which actions are being chosen—a notion that encompasses the animal learning theory terms of “context,” “discriminative stimulus,” and “occasion setter” as well as the statistical learning theory term “latent cause” ( Gershman and Niv, 2010), but is different from common usage of the term in reinforcement learning. In the first phase of training, Bradfield et al. (2013) taught rats to associate two levers with two different, but equally valued, rewards (pellets or sucrose).