The neuronal systems that promote protective defensive behaviours have been studied extensively using Pavlovian conditioning. In this paradigm, an initially neutral-conditioned stimulus is paired with an aversive unconditioned stimulus leading the subjects to display behavioural signs of fear. Decades of research into the neural bases of this…

We tested the hypothesis that conceptual similarity promotes generalization of conditioned fear. Using a sensory preconditioning procedure, three groups of subjects learned an association between two cues that were conceptually similar, unrelated, or mismatched. Next, one of the cues was paired with a shock. The other cue was then reintroduced to…

Adults can rapidly learn artificial phonotactic constraints such as /"f"/ "occurs only at the beginning of syllables" by producing syllables that contain those constraints. This implicit learning is then reflected in their speech errors. However, second-order constraints in which the placement of a phoneme depends on another…

Truly flower-naive bumblebees, with no prior rewarded experience for visits on any visual patterns outside the colony, were tested for their choice of bilaterally symmetric over asymmetric patterns in a radial-arm maze. No preference for symmetry was found. Prior training with rewarded black and white disks did, however, lead to a significant…

We examined the roles of the amygdala and hippocampus in the formation of emotionally relevant memories using an ethological model of conditioned fear termed conditioned defeat (CD). Temporary inactivation of the ventral, but not dorsal hippocampus (VH, DH, respectively) using muscimol disrupted the acquisition of CD, whereas pretraining VH…

The terrestrial slug "Limax" exhibits a highly developed ability to learn odors with a small nervous system. When a fluorescent dye, Lucifer Yellow (LY), is injected into the slug's body cavity after odor-taste associative conditioning, a group of neurons in the procerebral (PC) lobe, an olfactory center of the slug, is labeled by LY. We examined…

It is well known that emotions participate in the regulation of social behaviors and that the emotion displayed by a conspecific influences the behavior of other animals. In its simplest form, empathy can be characterized as the capacity to be affected by and/or share the emotional state of another. However, to date, relatively little is known…

The Src protein tyrosine kinase plays a central role in the regulation of N-methyl-d-aspartate receptor (NMDAR) activity by regulating NMDAR subunit 2B (NR2B) surface expression. In the amygdala, NMDA-dependent synaptic plasticity resulting from convergent somatosensory and auditory inputs contributes to emotional memory; however, the role of Src…

Norepinephrine receptors have been studied in emotion, memory, and attention. However, the role of alpha1-adrenergic receptors in fear conditioning, a major model of emotional learning, is poorly understood. We examined the effect of terazosin, an alpha1-adrenergic receptor antagonist, on cued fear conditioning. Systemic or intra-lateral amygdala…

Within the amygdala, most N-methyl-D-aspartic acid (NMDA) receptors consist of NR1 subunits in combination with either NR2A or NR2B subunits. Because the particular subunit composition greatly influences the receptors' properties, we investigated the contribution of both subtypes to fear conditioning and expression. To do so, we infused the…

A. Redish et al. (2007) proposed a reinforcement learning model of context-dependent learning and extinction in conditioning experiments, using the idea of "state classification" to categorize new observations into states. In the current article, the authors propose an interpretation of this idea in terms of normative statistical inference. They…

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…

A simple extension of a network model of conditioning developed by N. Schmajuk and J. Di Carlo (1992) is applied to descriptions of two different conditioned stimulus (CS) functions: (1) a simple CS eliciting conditioned responses by signaling the occurrence of an unconditioned stimulus; and (2) an occasion setter controlling the responses…

Brain-derived neurotrophic factor (BDNF) has been implicated as a molecular mediator of learning and memory. The BDNF gene contains four differentially regulated promoters that generate four distinct mRNA transcripts, each containing a unique noncoding 5[prime]-exon and a common 3[prime]-coding exon. This study describes novel evidence for the…

This essay introduces a series of studies developing a statistical theory of elementary learning processes. An attempt is made to derive relations among commonly used measures of behavior and quantitative expressions describing simple learning phenomena. Laws of the theory state probability relations between momentary changes in behavioral and…