Acquisition and extinction of the conditioned emotional response (CER) was studied in 24 male hooded rats which, prior to training, received small electrolytical lesions in the dorsal hippocampus, the ventral hippocampus, the entorhinal cortex, or were given sham operations. The rate of the on-going bar-pressing behavior for food pellets was highest in rats with lesions in the ventral hippocamp...

The dorsal hippocampus is crucial for learning the hidden-platform location in the hippocampus-dependent, spatial watermaze task. We have previously demonstrated that the postburst afterhyperpolarization (AHP) of hippocampal pyramidal neurons is reduced after acquisition of the hippocampus-dependent, temporal trace eyeblink conditioning task. We report here that the AHP and one or more of its a...

Decision-making studies across different domains suggest that decisions can arise from multiple, parallel systems in the brain: a flexible system utilizing action-outcome expectancies and a more rigid system based on situation-action associations. The hippocampus, ventral striatum, and dorsal striatum make unique contributions to each system, but how information processing in each of these stru...

A topographical relationship exists between the hippocampus-entorhinal cortex and the neocortex. However, it is not known how these anatomical connections are utilized during information exchange and behavior. We recorded theta oscillations along the entire extent of the septotemporal axis of the hippocampal CA1 pyramidal layer. While the frequency of theta oscillation remained same along the e...

Male Long-Evans rats were injected with 32 ng/mul of the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) or vehicle and trained to locate a hidden platform in a different location (reversal training) than used on the initial 4 days of training. Rats treated with vehicle or CPP into the dorsal hippocampus, basolateral amygdala, or mediod...

Despite decades of research being conducted to understand what physiological deficits in the brain are an underlying basis psychiatric diseases like schizophrenia, it has remained difficult establish a direct causal relationship between neuronal dysfunction and specific behavioral phenotypes. Moreover, remains unclear how metabolic processes, including amino acid metabolism, affect function con...

Previous reports on dorsal and ventral hippocampal regulation of context learning versus anxiety have been mixed. In this issue of Neuron, a new study by Kheirbek et al. (2013) using optogenetics demonstrates that dentate gyrus granule cell activity in dorsal hippocampus encodes contextual fear learning while ventral granule cell activity regulates anxiety behavior.

INTRODUCTION The selective breeding of Roman High- (RHA) and Low-Avoidance (RLA) rats for, respectively, rapid versus poor acquisition of the active avoidance response has generated two distinct phenotypes differing in many behavioral traits, including coping strategies to aversive conditions. Thus, RLA rats are considered as a genetic model of vulnerability to stress-induced depression whereas...

The modulation of memory processes is one of the several functions of the endocannabinoid system (ECS) in the brain, with CB1 receptors highly expressed in areas such as the dorsal hippocampus. Experimental evidence suggested an important role of the ECS in aversively motivated memories. Similarly, glucocorticoids released in response to stress exposure also modulates memory formation, and both...

Stress induces a shift from hippocampus-dependent "cognitive" toward dorsal striatum-dependent "habit" memory. However, not all individuals are susceptible to this shift under stress. Based on pharmacological studies indicating a critical role of the mineralocorticoid receptor (MR) in the stress-induced bias toward dorsal striatal learning, we hypothesized that MR gene variants contribute to th...