1
$\begingroup$

This is my claim, or what I [mis?]understood:

Hypothalamus is well-known for its role in homeostasis (self-regulation including, but not limited to, temperature/energy) and also reactions / stimuli like fear, fighting, hunger (which we could refer as the primitive needs, say), and it aims to appear (prosencephalon needs more divisions) in the 5th week of pregnancy (in the neural tube).

As I read from several scattered sources in the www, like this one, this one regarding pregnancy, and wikipedia.

This is what I'm asking for:

I would like a reference telling, if any, relationships and evolution between the primitive/embryonic process of homeostasis and the fears / survival instinct we experience when we... fear something considering, if available, different degrees of responses since the 5th week of pregnancy AND... say, the first months (or first year) of already-born baby.

I'd expect here:

  • That my claim is wrong, undecidable, irrelevant, or with few elements there being true, and WHY / to what extent.
  • Reliable source(s) describing this evolution.
$\endgroup$
  • 1
    $\begingroup$ What is your theory or claim exactly? Your question is a bit difficult to parse. It is important to recognize that the hypothalamus is a collection of nuclei; they can interact with one another but there is no reason they must. I'm also not sure about the kind of evidence you are looking for: I suspect there are not all that many studies involving presenting fearful stimuli to humans in utero. $\endgroup$ – Bryan Krause Sep 18 '18 at 22:39
2
$\begingroup$

TLDR: the hypothalamus is involved in fear processing, but not in the way you think.

Wikipedia has a decently sourced article on the hypothalamus and it does play some role in fear processing:

Fear processing

The medial zone of hypothalamus is part of a circuitry that controls motivated behaviors, like defensive behaviors.[29] Analyses of Fos-labeling showed that a series of nuclei in the "behavioral control column" is important in regulating the expression of innate and conditioned defensive behaviors.[30]

Antipredatory defensive behavior

Exposure to a predator (such as a cat) elicits defensive behaviors in laboratory rodents, even when the animal has never been exposed to a cat.[31] In the hypothalamus, this exposure causes an increase in Fos-labeled cells in the anterior hypothalamic nucleus, the dorsomedial part of the ventromedial nucleus, and in the ventrolateral part of the premammillary nucleus (PMDvl).[32] The premammillary nucleus has an important role in expression of defensive behaviors towards a predator, since lesions in this nucleus abolish defensive behaviors, like freezing and flight.[32][33] The PMD does not modulate defensive behavior in other situations, as lesions of this nucleus had minimal effects on post-shock freezing scores.[33] The PMD has important connections to the dorsal periaqueductal gray, an important structure in fear expression.[34][35] In addition, animals display risk assessment behaviors to the environment previously associated with the cat. Fos-labeled cell analysis showed that the PMDvl is the most activated structure in the hypothalamus, and inactivation with muscimol prior to exposure to the context abolishes the defensive behavior.[32] Therefore, the hypothalamus, mainly the PMDvl, has an important role in expression of innate and conditioned defensive behaviors to a predator.

Social defeat

Likewise, the hypothalamus has a role in social defeat: Nuclei in medial zone are also mobilized during an encounter with an aggressive conspecific. The defeated animal has an increase in Fos levels in sexually dimorphic structures, such as the medial pre-optic nucleus, the ventrolateral part of ventromedial nucleus, and the ventral premammilary nucleus.[36] Such structures are important in other social behaviors, such as sexual and aggressive behaviors. Moreover, the premammillary nucleus also is mobilized, the dorsomedial part but not the ventrolateral part.[36] Lesions in this nucleus abolish passive defensive behavior, like freezing and the "on-the-back" posture.[36]

Just based on that it's easy overemphasize the importance of the hypothalamus in fear processing; it's actually not that central. If you want the popsci version, then the amygdala gets the center stage in regulating fear. From a review of the "Neuronal circuits for fear and anxiety":

enter image description here

I don't see why the homeostasis circuitry would be involved in fear processing (as you propose), and as far as I can tell, it isn't.

$\endgroup$
  • $\begingroup$ Interesting article. Something I forgot to add, is that often the terror attractions in parks play with stuff like, say, low frequency (sound) waves and slightly lower... temperature, quite like certain unethical practices like cold chambers used to keep people about to be interrogated. That also made me think that there was a documented relationship between both things. $\endgroup$ – Luis Masuelli Sep 19 '18 at 16:04
  • $\begingroup$ Please note: I'm not an expert, or even a student, at all regarding any of these topics (I'm an IT engineer). And thanks for the patience :). $\endgroup$ – Luis Masuelli Sep 19 '18 at 16:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.