Okay, let me clarify. This question has to do with my aliens and how they hear.

My aliens have 3 antennae, a left antenna, a right antenna, and a central antenna. Each antenna has 3 sets of sensors.

The infrasound sensors can detect sounds below 20 Hz (human threshold of hearing) miles away from the source.

The mid-frequency sensors can detect sounds between 20 Hz and 20,000 Hz (human hearing range) a few miles away from the source but not nearly as far as the infrasound sensors.

The ultrasound sensors can detect sounds above 20,000 Hz at most a few yards away from the source. This allows mother aliens to hear their babies inside the eggs. Adult aliens don't usually make sounds in this part of the spectrum.

And these aliens can tell what direction the sound is coming from as well as distance.

These sets of sensors all have their own nerves. So there are 9 auditory nerves. These nerves get bundled up in the bottom of the antennae forming 3 auditory nerve bundles. These nerve bundles in turn get bundled up into 1 auditory nerve complex.

This is where I have to mention the brain within a brain. Because so much information is being picked up by the antennae (frequency, intensity, distance from source, and direction to source), it makes sense to me to have a brain specialized for hearing within a larger brain that does all the other brain functions.

Each nerve within the auditory nerve complex branches out to every main section of this auditory brain. Then the auditory brain processes the sound and sends it to the rest of the brain. When the signal gets to the cerebral cortex is when the alien is able to figure out the source of the sound and respond to the sound.

Is this brain within a brain plausible given that there is so much information about the sound being picked up by the sensors?

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    $\begingroup$ How is this different than hearing center in human brain? Or visual center, that processes much more information than nine audio nerves would provide? $\endgroup$
    – Mołot
    Commented Apr 24, 2017 at 4:32
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    $\begingroup$ A note on your specifications: we can't define sensitivity based on sound source distance without defining sound source strength. Receivers are rated in ratio power sensitivity, which is more a measure loudness than of distance. A distance specification is useless without a reference source. $\endgroup$
    – user29032
    Commented Apr 24, 2017 at 5:05
  • $\begingroup$ Are you asking how much information is shared amongst different parts of their brain, and if perhaps some of that distribution results in a so–called fragmented consciousness? $\endgroup$ Commented Apr 24, 2017 at 5:22
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    $\begingroup$ Worth noting: sound is actually far easier to handle than other senses. The bandwidth requirements are quite low. Managing motion while touching things is actually quite a lot more difficult than processing audio. $\endgroup$
    – Cort Ammon
    Commented Apr 24, 2017 at 6:27

3 Answers 3


Plausible, yes, but I honestly think your way overestimating the amount of brainpower needed, probably.

First off, though you haven't said how your antenna work, the sound perception model is based off resonance. To sense sound, you have to let something vibrate. I am assuming here that you're probably using some combination of the human auditory model (many tiny resonant cavities or resonant hairs in the antenna) and broadband antenna pickup (which would be based on trying to sense frequencies, namely the low ones, based off figuring out what frequency the whole antenna is resonating to). All that to say, the ear type part of the processing needs very little brain power, therefore your 20-20kHz signals are covered simply with a mechanism we already understand that really does its own processing. The highpitched detector could be a single very small resonator in the tip.

The one part of that model that worries me is the low-end pick up. Finding the resonant tone should be pretty easy, unless there is more than one. The only process that I see for the brain to make sense of the signals coming in on the LF band is basically doing a Fourier transform. For just a handful of frequencies, this shouldn't be too intensive.

So, using the model you specify, only a little more than the average amount of brain would be needed for audio processing. Because of their three antenna direction finding would be very easy (our brains already do this with binural imaging), and the addition of a third input only makes it easier.

The caveat, if you're trying to make them require an extra brain, is to say that the whole antenna covers the entire frequency range. This case would require the Fourier transform mechanism for the whole required spectrum, which would not be cheap (processing wise) on brain capacity. In this case, each antenna is really just like a microphone. It is a single input device with a good response over all the required frequency components, and it requires a complicated algorithm in the grey matter to be processed.

That said, grey matter is a very dense computing medium. While the second case is possible, the work that neural networks are best at is more in line with case 1 than case 2.

  • $\begingroup$ So, a basal ganglion on the antenna or antennae, which does all the spatial figuring for the sounds. Why not? It might not even be much of an additional brain, at that. $\endgroup$ Commented Apr 24, 2017 at 5:16

The human brain is already like that. It s not one monolithc brain, there is the allocortex/neocortex etc... Each part is speciliazed to do something.

Most advanced animals are like that too so we already have a brain within a brain.

  • $\begingroup$ Or, like the corpus callosum between the hemispheres of dolphins, humans, mice, et al. $\endgroup$ Commented Apr 24, 2017 at 5:21
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    $\begingroup$ The corpus callosum is a connection between two halves, not a processing center. $\endgroup$
    – JDługosz
    Commented Apr 25, 2017 at 6:37
  • $\begingroup$ @JDługosz I didn't actually say that any of the axons in the corpus callosum perform their own limiting or generation or variation of signals. They could, but that would be beyond most contemporary knowledge and not likely. I mentioned it because not only is it a component joining two parts of the brain, but because of the very fact that it is needed. $\endgroup$ Commented Sep 6, 2017 at 5:48

Let me first list some info:

According to this Wikipedia article , some worms have something that you could consider a second minor brain.

Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain"

Then, in this other Wikipedia article, it is explained how the "organization" of the brain could change thanks to an evolution processes.

So, I suppose that in your world you can come up with an explanation of the "brain within brain" concept based on evolution.

  1. Yous aliens' ancestors were worm-like, with a nervous system spread along their body.
  2. With the evolution, the worm-like ancestors developed antennae. Since you probably physically need a smaller sensor for higher frequency and bigger sensor for lower ones, those sensors developed at the opposite side of the worm.
  3. The "tail brain" specialized in managing one of the sensors, let's say the smaller one, while the "main brain" the bigger one.
  4. The world in which the worm-like aliens used to live was infected with a bacteria that hits the brain.
  5. So with the evolution, the worm-like aliens developed a protective film around the brain that was able to avoid the bacteria to penetrate the alien's brain.
  6. Again, with evolution, the work-like alien became a bigger walking being. The "tail brain" was then in a position that was not useful anymore because it was too far from the main brain.
  7. The "tail brain" slowly migrated up "into" the "main brain". The defensive film developed at step 4) would have prevented the "tail brain" to "merge" with the "main brain".
  8. So, you end up with a "brain within the brain" alien.

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