"while much data is consistent with the fear model of amygdala function, it has never been directly tested, in part due to overreliance on the fear conditioning task. In support of the fear model, amygdala neurons appear to signal threats and/or stimuli predictive of threats. However, recent studies in a natural threat setting show that amygdala activity does not correlate with threats, but simply with the movement of the rat, independent of valence. This was true for both natural threats as well as conditioned stimuli; indeed there was no evidence of threat signaling in amygdala neurons. Similar findings are emerging for prefrontal neurons that modulate the amygdala. These recent developments lead us to propose a new conceptualization of amygdala function whereby the amygdala inhibits behavioral engagement...
What do we mean by behavioral engagement? The term refers to a basic process that governs transactions between mammals and their environment: whether or not to engage with (or disengage from) stimuli or situations. It is a process akin to decision-making, although it is unclear whether it is deliberative in all species and conditions. This process is particularly critical for ethologically significant situations such as decisions related to foraging, interactions with conspecifics or confrontations with predators, in short problems the nervous system has evolved to address...
The above illustrates how a community of scientists, present authors included, can be biased by relying on an attractive, controlled laboratory paradigm. Amygdala researchers were motivated by their interest in the mechanisms of associative memory and emotional learning. They were understandably concerned with the need to achieve rigorous control over key experimental variables and to minimize the influence of confounding factors. This led to the adoption of a simple learning paradigm that restricted the range of possible conditioned behaviors."
I think that this is the beginning of us critically abandoning some of our old categorization methods. There is no empirical definition of boundary in the brain to "prove" that all of these named regions are truly distinct from the tissue around them, or that all the neurons in that region are united by a common function. And defining that function is challenging because, frankly, there isn't a principled manner in which functions are divided across the brain. Some regions are clearly designed to control breathing rate, while others have a variety of impacts on a variety of systems that are sometimes contradictory.
We need names and boundaries and definitions to communicate about things, yes, but let's not forget that it is always going to be much more complicated than that.
related: emotions are not what you think they are (other one on the amygdala?)
FB: "the same neurons and circuits that were thought to mediate learned fear have been shown to respond to rewards and support the acquisition of responses driven by positively valenced [unconditioned stimulus]. Nevertheless, the study of fear learning sustained the early notion that activity of neurons in the amygdala serves to signal threat and in turn generates defensive behaviors. Surprisingly, this foundational assumption was not fully tested until recently."
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