Researchers have wondered how the brain creates emotions since the early days of psychological science. With a surge of studies in affective neuroscience in recent decades, scientists are poised to answer this question. In this target article, we present a meta-analytic summary of the neuroimaging literature on human emotion. We compare the locationist approach (i.e., the hypothesis that discrete emotion categories consistently and specifically correspond to distinct brain regions) with the psychological constructionist approach (i.e., the hypothesis that discrete emotion categories are constructed of more general brain networks not specific to those categories) to better understand the brain basis of emotion. We review both locationist and psychological constructionist hypotheses of brain-emotion correspondence and report meta-analytic findings bearing on these hypotheses. Overall, we found little evidence that discrete emotion categories can be consistently and specifically localized to distinct brain regions. Instead, we found evidence that is consistent with a psychological constructionist approach to the mind: A set of interacting brain regions commonly involved in basic psychological operations of both an emotional and non-emotional nature are active during emotion experience and perception across a range of discrete emotion categories.

/pdf/the-brain-basis-of-emotion-a-meta-analytic-review-32zzrbb78z.pdf

The brain basis of emotion: A meta-analytic review

▪ Abstract Learning the relationships between aversive events and the environmental stimuli that predict such events is essential to the survival of organisms throughout the animal kingdom. Pavlovian fear conditioning is an exemplar of this form of learning that is exhibited by both rats and humans. Recent years have seen an incredible surge in interest in the neurobiology of fear conditioning. Neural circuits underlying fear conditioning have been mapped, synaptic plasticity in these circuits has been identified, and biochemical and genetic manipulations are beginning to unravel the molecular machinery responsible for the storage of fear memories. These advances represent an important step in understanding the neural substrates of a rapidly acquired and adaptive form of associative learning and memory in mammals.

/pdf/neurobiology-of-pavlovian-fear-conditioning-3beoazhpf8.pdf

Neurobiology of Pavlovian fear conditioning.

Conditioned place preference (CPP) continues to be one of the most popular models to study the motivational effects of drugs and non-drug treatments in experimental animals. This is obvious from a steady year-to-year increase in the number of publications reporting the use this model. Since the compilation of the preceding review in 1998, more than 1000 new studies using place conditioning have been published, and the aim of the present review is to provide an overview of these recent publications. There are a number of trends and developments that are obvious in the literature of the last decade. First, as more and more knockout and transgenic animals become available, place conditioning is increasingly used to assess the motivational effects of drugs or non-drug rewards in genetically modified animals. Second, there is a still small but growing literature on the use of place conditioning to study the motivational aspects of pain, a field of pre-clinical research that has so far received little attention, because of the lack of appropriate animal models. Third, place conditioning continues to be widely used to study tolerance and sensitization to the rewarding effects of drugs induced by pre-treatment regimens. Fourth, extinction/reinstatement procedures in place conditioning are becoming increasingly popular. This interesting approach is thought to model certain aspects of relapse to addictive behavior and has previously almost exclusively been studied in drug self-administration paradigms. It has now also become established in the place conditioning literature and provides an additional and technically easy approach to this important phenomenon. The enormous number of studies to be covered in this review prevented in-depth discussion of many methodological, pharmacological or neurobiological aspects; to a large extent, the presentation of data had to be limited to a short and condensed summary of the most relevant findings.

Measuring reward with the conditioned place preference (CPP) paradigm: update of the last decade.

Rationale: Among the various experimental protocols that have been used to measure drug reward in laboratory animals, conditioned place preference (CPP) has been one of the most popular. However, a number of controversial issues have surrounded the use of this experimental protocol. Objective: The present review provides a theoretical overview of some critical issues relevant to CPP. The advantages and limitations of CPP are also covered. Results: Based on modern and traditional theoretical formulations of Pavlovian conditioning, CPP appears to reflect a preference for a context due to the contiguous association between the context and a drug stimulus. Within this theoretical framework, it seems clear that CPP measures a learning process that is fundamentally distinct from drug self-administration. The main advantages of CPP are that it: (1) tests animals in a drug-free state; (2) is sensitive to both reward and aversion; (3) allows for simultaneous determination of CPP and locomotor activity; (4) is adaptable to a variety of species; (5) typically yields dose-effect curves that are monophasic rather than biphasic; and (6) has utility in probing the neural circuits involved in drug reward. The main limitations of CPP are that it: (1) is subject to interpretation based on the notion of novelty seeking; (2) is cumbersome for providing the graded dose-effect curves needed for answering some pharmacological questions; (3) is difficult to interpret when animals prefer one context prior to drug conditioning; and (4) lacks face validity as an experimental protocol of drug reward in humans. Conclusion: Despite some limitations, CPP provides unique information about the rewarding effect of contextual cues associated with a drug stimulus.

/pdf/conditioned-place-preference-what-does-it-add-to-our-4y93s2yvkv.pdf

Conditioned place preference: What does it add to our preclinical understanding of drug reward?

http://www.demenzemedicinagenerale.net/pdf/RethinkingEmotionalBrain.pdf

Rethinking the Emotional Brain

Amygdala, hippocampus and discriminative fear conditioning to context.

https://tspace.library.utoronto.ca/bitstream/1807/11475/1/MQ29181.pdf

Discriminative fear conditioning to context expressed by multiple measures of fear in the rat.

http://psych.utoronto.ca/users/caroline/Publications/Antoniadis%20et%20al%20BBR%2000%20aging.pdf

Circadian rhythms, aging and memory

The significance of circadian phase for performance on a reward-based learning task in hamsters.

Modulation of the acoustic startle response is a simple and objective indicator of emotionality and attention in rodents and humans. This finding has proven extremely valuable for the analysis of neural systems associated with fear and anxiety. Until recently, there have been few efforts to develop acoustic startle measurement in non-human primates. Here we review recent work in which whole body acoustic startle amplitude has been measured in rhesus monkeys. Initial studies revealed that the amplitude of whole body startle in monkeys, as in rodents and humans, is directly proportional to acoustic stimulus intensity and gradually habituates with repeated exposures. Presentation of a weak acoustic stimulus 25-5,000 msec before a startle stimulus reduces startle amplitude by 40-50% depending on inter-stimulus interval length (prepulse inhibition). We have also measured significant fear-potentiated startle in the presence of a visual stimulus after pairing it with an inescapable pulse of pressurized air (fear-potentiated startle). This effect was reduced by diazepam and morphine, but not by buspirone. Ibotenic acid-induced lesions of the amygdala prevented the acquisition of fear-potentiated startle but, remarkably, did not prevent the expression of fear-potentiated startle when fear conditioning was carried out prior to the lesion. Finally, we have developed an objective measure of fear inhibition in monkeys using a novel conditioned inhibition procedure identical to one used in rats and humans. Our data demonstrate that acoustic startle in non-human primates successfully bridges rodent and human research. The opportunity now emerges to link concepts developed in rodents to the more complex neuroanatomical and cognitive processes common to monkeys and humans.

Elena A. Antoniadis

Papers

Amygdala, hippocampus and discriminative fear conditioning to context.

Discriminative fear conditioning to context expressed by multiple measures of fear in the rat.

Circadian rhythms, aging and memory

The significance of circadian phase for performance on a reward-based learning task in hamsters.

Acoustic startle reflex in rhesus monkeys: a review.