Is the brain organized in a hierarchical manner?
Discussion this week about it being organized as a *heterarchy*, which can be defined as something lacking a hierarchical organization.
Here's a thread about this and why a heterarchy doesn't mean the brain is spaghetti!

I suggested the following principle of brain organization : *Massive Combinatorial Anatomical Connectivity*
Rich connectivity is not limited to specific sectors of the brain such as the popular PFC.
https://www.sciencedirect.com/science/article/abs/pii/S1364661317300360

It encompasses all brain sectors, cortical and subcortical (amygdala, thalamus, brainstem, cerebellum).
Anatomical properties include: (i) massive
interconnectivity; (ii) high global accessibility; and (iii) the existence of a ‘connectivity core’ or ‘rich-club’ of regions.

Another outstanding treatment of this idea is that by Markov, Kennedy and collaborators who suggest a bow-tie organization.

Markov et al. described a core set of 17 regions spanning
parietal, temporal, and frontal cortex that was marked by 92% connectivity density (92% of the
connections that could exist were present).
This was only cortex, imagine when we add thalamus, amygdala, etc.!

When people emphasize *heterarchy* the point is NOT to suggest that anything goes. The brain is highly structured anatomically, in a way that has a deep evolutionary history of at least 500 million years with vertebrates.
(that discussion for another day!)

*Amygdala*: basolateral and separately central.
There are lots and lots of other examples that can be highlighted against hierarchical organization, the above were relatively arbitrary. I like the amygdala so much that I'll described that another time!