Many psychological learning theories have noted commonalities between aversive states produced by presentation of negative reinforcers, such as electric shock, and the omission of expected positive reinforcers, such as food. Here, three groups of rats received training with one auditory cue paired with shock and another with the omission of expected food, a shock-paired cue and a food-omission control cue, or a food-omission cue and a shock control cue. Food-omission cues were established by contrast with food delivery; after extensive light-food pairings, the light was followed by the food-omission cue instead of food. Aversiveness of the food-omission cue was assessed with a conditioned punishment procedure, in which presentation of that cue was made contingent on performance of one previously trained instrumental response, whereas a second response had no consequences. We found that rats with lesions of amygdala central nucleus (CeA) showed impaired acquisition of freezing to the cue paired with shock and no evidence for acquisition of aversive properties by the cue that accompanied the omission of expected food. Furthermore, analyses of Arc and Homer1a mRNAs after rats were exposed to a two-epoch test procedure that allowed assessment of gene expression produced by two different test stimuli showed that both food-omission and shock-paired cues generated more neuronal activity in CeA than appropriate control cues. However, the number of neurons that were activated by both shock and food-omission cues was not significantly greater than expected by chance. Thus, under these test conditions, different subsets of CeA neurons represented these two aversive states.
"The aversive conditioned reinforcing properties of CSs can be assessed using procedures such as “conditioned punishment” (Killcross et al., 1997a,b), in which an instrumental response is associated with the probabilistic presentation of an aversive event such as an electric footshock paired with a CS. As for appetitive conditioned reinforcement, animals with BLA lesions are also impaired on aversive conditioned reinforcement (Killcross et al., 1997b); BLA-lesioned animals do not bias responding away from a lever associated with electric footshock and an aversive CS, though they still show reduced overall responding on the lever and on a control lever not paired with shock, i.e. intact conditioned suppression (Killcross et al., 1997b; Purgert et al., 2012). "
[Show abstract][Hide abstract] ABSTRACT: The amygdala has traditionally been associated with fear, mediating the impact of negative emotions on memory. However, this view does not fully encapsulate the function of the amygdala, nor the impact that processing in this structure has on the motivational limbic corticostriatal circuitry of which it is an important structure. Here we discuss the interactions between different amygdala nuclei with cortical and striatal regions involved in motivation; interconnections and parallel circuitries that have become increasingly understood in recent years. We review the evidence that the amygdala stores memories that allow initially motivationally neutral stimuli to become associated through pavlovian conditioning with motivationally relevant outcomes which, importantly, can be either appetitive (e.g. food) or aversive (e.g. electric shock). We also consider how different psychological processes supported by the amygdala such as conditioned reinforcement and punishment, conditioned motivation and suppression, and conditioned approach and avoidance behavior, are not only psychologically but also neurobiologically dissociable, being mediated by distinct yet overlapping neural circuits within the limbic corticostriatal circuitry. Clearly the role of the amygdala goes beyond encoding aversive stimuli to also encode the appetitive, requiring an appreciation of the amygdala's mediation of both appetitive and fearful behavior through diverse psychological processes.
"Salient information about the cues is relayed to the CeA via afferents from the basolateral amygdala. Cues paired with different forms of aversive stimuli, such as shock (orange) or omission of expected reward (blue), recruit nonoverlapping populations of neurons in both the lateral (CeL) and medial (CeM) subdivisions of the CeA (Purgert et al., 2012). We hypothesize that these networks of coactive neurons not only represent distinct aversive cues, but also target different downstream structures in order to select appropriate behavioral responses. "
[Show abstract][Hide abstract] ABSTRACT: Rodent behavioural tasks are indispensable to advance the understanding of gene×environment interactions in neuropsychiatric disorders and the discovery of new therapeutic strategies. Yet, the actual translation of rodent data to humans, and thereby the understanding of the pathophysiology of neuropsychiatric disorders is limited. The main reason for the translational flaw is that many behavioural tasks for rodents are based on face or predictive validity, whereas these types of validity often lack a pathophysiological basis. Furthermore, many behavioural tasks for rodents do not implement human task parameters or use task parameters in a controlled manner, whereas they are parameters that provide the environmental challenges to test gene function. The aim of this perspective is to address the status quo of behavioural tasks for rodents, their limitations and their strengths, and the reasons why they could lead to suboptimal translational research. I also suggest an approach to come closer to neuropsychiatric behavioural tasks for rodents, namely a more careful implementation of human task parameters and subdivision of behaviour into perceptional, motivational, activational and switching domains. Finally, I will touch upon behavioural tasks for rodents that are currently lacking and needed to catch up neuropsychiatric research.
Behavioural brain research 09/2012; 236(1):295-306. DOI:10.1016/j.bbr.2012.09.005 · 3.03 Impact Factor
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