Brief Communications

Consolidated long-term fear memories become labile and can be disrupted after being reactivated by the presentation of the unconditioned stimulus (US). Whether this is due to an alteration of the conditioned stimulus (CS) representation in the lateral amygdala (LA) is not known. Here, we show in rats that fear memory reactivation through presentation of the aversive US, like CS presentation, triggers a process which,when disrupted, results in a selective depotentiation of CS-evoked neural responses in the LA in correlation with a selective suppression of CS-elicited fear memory. Thus, an aversive US triggers the reconsolidation of its associated predictor representation in LA. This new finding suggests that sensory-specific associations are stored in the lateral amygdala, allowing for their selective alteration by either element of the association.

Learning & Memory, 2011

Modern views on learning and memory accept the notion of biological constraints—that the formation of association is not uniform across all stimuli. Yet cellular evidence of the encoding of selective associations is lacking. Here, conditioned stimuli (CSs) and unconditioned stimuli (USs) commonly employed in two basic associative learning paradigms, fear conditioning and taste aversion conditioning, were delivered in a manner compatible with a functional cellular imaging technique (Arc cellular compartmental analysis of temporal gene transcription by fluorescence in situ hybridization [catFISH]) to identify biological constraints on CS–US convergence at the level of neurons in basolateral amygdala (BLA). Results indicate coincident Arc mRNA activation within BLA neurons after CS–US combinations that yield rapid, efficient learning, but not after CS–US combinations that do not.

Recognizing predictive relationships is critical for survival, but an understanding of the underlying neural mechanisms remains elusive. In particular, it is unclear how the brain distinguishes predictive relationships from spurious ones when evidence about a relationship is ambiguous, or how it computes predictions given such uncertainty. To better understand this process, we introduced ambiguity into an associative learning task by presenting aversive outcomes both in the presence and in the absence of a predictive cue. Electrophysiological and optogenetic approaches revealed that amygdala neurons directly regulated and tracked the effects of ambiguity on learning. Contrary to established accounts of associative learning, however, interference from competing associations was not required to assess an ambiguous cue-outcome contingency. Instead, animals' behavior was explained by a normative account that evaluates different models of the environment's statistical structure. These findings suggest an alternative view of amygdala circuits in resolving ambiguity during aversive learning. advance online publication nature neurOSCIenCe

Neuroscience, 1993

NeuroReport, 2006

Whether the amygdala responds in a stimulus-or a task-speci¢c way, and how it corresponds to such e¡ects in sensory cortices is dubious. Eighteen volunteers participated in a functional magnetic resonance imaging study in which they were asked to identify either emotion or gender in visually presented scenes, faces, and sentences. Amygdala and the lateral occipital complex showed similar stimulus e¡ect with greater activation to scenes than to faces and sentences, whereas the superior temporal complex responded preferentially to sentences. No task e¡ect was observed in the amygdala, whereas lateral occipital complex and superior temporal complex showed left lateralized selectivity to the emotional task. These results suggest that the amygdala is more sensitive to stimulus than explicit task parameters when processing emotion.

Journal of Neuroscience, 2012

Behavioural Brain Research, 1991

Rats with amygdaloid lesions were trained on learning set tasks designed to tax stimulus-reward associations. Lesions centred in the medial and ventral halfofthe amygdala had no effect on the acquisition of two object discriminations but did impair successive reversals of the second discrimination. The same lesions had no effect, however, on the acquisition of a spatial win-stay lose-shift task which taxed one-trial place-reward associations. In a second experiment it was found that lesions in the central and basolateral regions of the amygdala disrupted performance of the same spatial win-stay lose-shift task although, as before, acquisition was unaffected. Taken together these findings support a role for the amygdala in stimulus-reward associations and indicate that it may be particularly important when differing values of reward must be distinguished.

2016

The amygdala, a structure deep in the temporal lobe of the brain, is an essential region for emotional and fearful processing. Neuronal coding in the lateral nucleus of the amygdala (LA) endows the brain with the ability to acquire enduring aversive associations, physically represented by experience-dependent synaptic modifications within a small population of neurons selectively recruited during learning. Understanding the precise mechanisms underlying neuronal selection and plasticity during memory formation has been among the most fundamental questions in neuroscience for the past century. Defining the distribution of neuronal activity would further elucidate the conditions by which memories are expressed and how neurons are differentially recruited into distinct memory engrams. The aim of this thesis was to utilize reliable methods to capture, visualize, monitor and modulate defined neuronal populations to expand our knowledge regarding the above questions. Chapter 1 of this the...

2000

In this chapter, we review data from appetitive conditioning studies using measures of pavlovian approach behaviour and of the effects of pavlovian conditioned stimuli on instrumental behaviour, including the pavlovian-to-instrumental transfer effect and conditioned reinforcement. These studies consistently demonstrate double dissociations of function between the basolateral area and the central nucleus of the amygdala. Moreover, these data show marked parallels with data derived from studies of aversive (fear) conditioning, and are consistent with the idea that these subsystems of the amygdala use different associative representations formed during conditioning, as part of a larger limbic cortico-striatal circuit. We suggest that the basolateral amygdala is required for a conditioned stimulus to gain access to the current value of its specific unconditioned stimulus, while the central nucleus is responsible for conditioned motivational responses using a simpler stimulus-response representation. Though these systems normally operate together, they modulate ongoing behaviour in distinct ways. We illustrate this by considering the contributions of both systems to the process of drug addiction, using second-order schedules of intravenous drug self-administration. Neural network underlying conditioned reinforcement and its potentiation by psychomotor stimulants CeN Appetitive CS VTA