Thread

1. fooker · 1789806765 · focus · HN ↗

   So, what we colloquially call 'reptile brain' turns out to be somewhat accurate.

   1. HarHarVeryFunny · 1789821711 · focus · HN ↗

      There is some truth (but not accuracy) to it, but not for this reason.

      This article is about brainstem (aka hindbrain) vs the rest (midbrain + forebrain).

      Evolutionally older animal lineages like fish, reptiles, birds all have midbrain + forebrain as well as the brainstem, so reptilian brain != brainstem.

      Where there is some truth to our older "reptilian" brain is that the part of the forebrain called the pallium, that exists even in fish (& reptiles), has much expanded/evolved in mammals giving us our cortex and hippocampus, so you could kinda say that we have a reptilian brain + cortex. Note though that mammals didn't evolve from reptiles - they evolved in parallel from a common ancestor, so maybe better to say we have a fish brain + cortex (& hippocampus).

      While the cortex is what gives mammals their intelligence, in birds the pallium evolved in a different way to give them theirs.

      1. computerdork · 1789838476 · focus · HN ↗

         am no expert in brain development, still have read about evolution. I like aspects of the way you mentioned this, but seems that putting cortex separately from fish brain isn't quite right. As you mentioned, the cortex is simply a part of the fish brain that evolved much (much, much) larger than a fish's. Maybe:

         Fish Brain = brain stem + small cortex (+ other parts of brain)

               |
          (evolved into)
               |
               V
         

         Human Brain = brain stem + gigantic cortex (+ other parts of brain)

         Sorry, know this is splitting hairs, but just thought it a useful distinction to make.

         1. HarHarVeryFunny · 1789844392 · focus · HN ↗

            That's not quite right - a fish does not have a cortex.

            The pallium of a fish and mammal are structured differently. A fish's (& bird's) pallium has a clustered (aka "nuclear") organization, while a mammal's has a mostly layered organization which is what is referred to as the cortex.

            There is also more to a brain than just brainstem + pallium. In a vertebrate it's brainstem (aka hindbrain) + midbrain + forebrain, with the pallium being part of the forebrain.

            1. computerdork · 1789851784 · focus · HN ↗

               Ah, I stand corrected:) Maybe a better diagram might be to merge our ideas:

               Fish Brain = brain stem + pallium + other parts of brain[1]

                     |
                (evolved into)
                     |
                     V
               

               Human Brain = brain stem + gigantic cortex(which directly evolved from the pallium) + other parts of brain[1]

               Good to know:)

               [1] Am using "other parts of the brain" to cover any parts of the brain not covered by the brain stem and cortex

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