Eyeblink conditioning given in the explicit presence of hippocampal ? results in accelerated learning and enhanced multiple-unit responses, with slower learning and suppression of unit activity under non-? conditions. Recordings from putative pyramidal cells during ?-contingent training show that pretrial ?-state is linked to the probability of…

Single prolonged stress (SPS) has been used to examine mechanisms via which stress exposure leads to post-traumatic stress disorder symptoms. SPS induces fear extinction retention deficits, but neural circuits critical for mediating these deficits are unknown. To address this gap, we examined the effect of SPS on neural activity in brain regions…

The present experiment tested whether or not the time course of a conditioned eyeblink response, particularly its duration, would expand and contract, as the magnitude of the conditioned response (CR) changed massively during acquisition, extinction, and reacquisition. The CR duration remained largely constant throughout the experiment, while CR…

Learning-induced modulation of neuronal intrinsic excitability is a metaplasticity mechanism that can impact the acquisition of new memories. Although the amygdala is important for emotional learning and other behaviors, including fear and anxiety, whether learning alters intrinsic excitability within the amygdala has received very little…

Narp knockout (KO) mice demonstrate an impaired extinction of morphine conditioned place preference (CPP). Because the medial prefrontal cortex (mPFC) has been implicated in extinction learning, we tested whether Narp cells in this region play a role in the extinction of morphine CPP. We found that intracranial injections of adenoassociated virus…

Activation of the infralimbic region (IL) of the medial prefrontal cortex (mPFC) reduces conditioned fear in a variety of situations, and the IL is thought to play an important role in the extinction of conditioned fear. Here we report a series of experiments using contextual fear conditioning in which the IL is activated with the GABAa antagonist…

After extinction of conditioned fear, memory for the conditioning and extinction experiences becomes context dependent. Fear is suppressed in the extinction context, but renews in other contexts. This study characterizes the neural circuitry underlying the context-dependent retrieval of extinguished fear memories using c-Fos immunohistochemistry.…

Rats were subjected to one or two cycles of context fear conditioning and extinction to study the roles of the prelimbic cortex (PL) and infralimbic cortex (IL) in learning and relearning to inhibit fear responses. Inactivation of the PL depressed fear responses across the first or second extinction but did not impair learning or relearning fear…

The role of adult brain neurogenesis (generating new neurons) in learning and memory appears to be quite firmly established in spite of some criticism and lack of understanding of what the new neurons serve the brain for. Also, the few experiments showing that blocking adult neurogenesis causes learning deficits used irradiation and various drugs…

The fear conditioning paradigm is used to investigate the roles of various genes, neurotransmitters, and substrates in the formation of fear learning related to contextual and auditory cues. In the brain, nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) functions as a retrograde neuronal messenger that facilitates synaptic…

Fear conditioning is a popular model for investigating physiological and cellular mechanisms of memory formation. In this paradigm, a footshock is either systematically associated to a tone (paired conditioning) or is pseudorandomly distributed (unpaired conditioning). In the former procedure, the tone/shock association is acquired, whereas in the…

A computational model of the neural substrates of elementary associate learning is developed. It is used to demonstrate that several higher order features of classical conditioning could be elaborations of the known cellular mechanisms for simple associative learning. (Author/LMO)

There is considerable evidence that in rats, the insular cortex (IC) and amygdala are involved in the learning and memory of aversively motivated tasks. The present experiments examined the effects of 8-Br-cAMP, an analog of cAMP, and oxotremorine, a muscarinic agonist, infused into the IC after inhibitory avoidance (IA) training and during the…

The basis of modern learning theory is questioned in view of Popper's philosophy and the anatomy and physiology of the nervous system. (Editor)

The [delta] subunit of the GABA[subscript [Alpha]] receptor (GABA[subscript [Alpha]]R) is highly expressed in the dentate gyrus of the hippocampus. Genetic deletion of this subunit reduces synaptic and extrasynaptic inhibition and decreases sensitivity to neurosteroids. This paper examines the effect of these changes on hippocampus-dependent trace…