notes-science-neuro-neuroProgrammes

Simplifying programmes

What do the common ancestors of smart species have in common?

What species are smartest?

Some abnormally smart species and groups of species, both absolutely and compared to their relatives, are primates, cetaceans, elephants, parrots, corvidae (see http://en.wikipedia.org/wiki/Avian_IQ ), octopuses (probably less smart than the others but still notable for being pretty smart and for their smartness compared to their relatives).

What are the common ancestors?

Primates, cetaceans, and elephants are mammals. Mammals all seem relatively clever, although perhaps this is an artifact of our being more easily able to recognize mammalian cleverness, being mammals ourselves.

Parrots and corvidae are avians. Avians seem fairly clever. The common monophyletic grouping of avians and mammals is amniotes.

Octopuses are cephalopods. Cephalopods seem relatively clever. Cephalopods are molluscs (spelled mollusks by some). Many molluscs do not seem clever, although as noted above, maybe it is simply difficult for us to empathize with them. The common monophyletic grouping of amniotes and molluscs is bilaterians. Bilateria is pretty darn general, and doesn't give us much to go on (see also http://en.wikipedia.org/wiki/Evolution_of_nervous_systems ). Many bilaterians are not so clever (although, i suppose, they all have pretty elaborate nervous systems and tend to exhibit behavior and learning).

So, i propose a the following approach:

• Study the common features of mammals
• Study the common features of avians
• Study the common features of amniotes
• Study the common features of cephalopods
• Study the common features of bilaterians
• Find the set of all nervous system features which can be found in homologus form in both mammals and avians, as well as the set of structures in mammalian and avian nervous systems which are striking instances of convergent evolution
• Find the set of all nervous system features which can be found in homologus form in both mammals and avians and cephalopods, as well as the set of structures in mammalian and avian and cephalopod nervous systems which are striking instances of convergent evolution

Then restrict further study (at least, within this programme) to the features identified in the last two bullet points.

Which nervous organs are necessary for intelligent behavior?

For example, the amygdala is not necessary; you may behave strangely without yours, but you will still be able to, say, talk, identify objects, move your limbs in a planned manner to pick up food and eat it. But if you took out a person's basal ganglia, they would be unable to move normally (we can hypothesize that they may still be able to think, but we can't currently test that).

Now there are some things necessary for survival at all. For instance, stuff that regulates breathing and hormones. So subtract these; we only want neural structures that are necessary for intelligent behavior, but not necessary for bare survival. Things that, if you removed them, you would get a stupid lump, but a live lump.

Some organs that seem necessary are (at this stage this list is just notes on things to investigate, i'm not sure that they all belog):

• neocortex (not all parts, but at least some of it)
• thalamus, thalamic reticular nucleus
• basal ganglia (at least parts)

5ht:

• raphe nucleus (5ht)

na:

• Locus coeruleus (na, implicated in vigilance)

ach:

• nucleus accumbens (GABA, Ach, implicated in reward)
• medial septal nucleus (ach, implicated in reward)
• nucleus basalis of meynert (ach, implicated in alertness)
• pedunculopontine nuleus and the rest of the pontomesencephalotegmental complex (ach, implicated in sleep)

da:

• Ventral tegmental area (da, implicated in reward)

histimine:

• tuberomamillary nucleus (histamine, implicated in sleep)
• reticular activating system
• interpeduncular nucleus of the brainstem (implicated in REM sleep)
• what else?

Take the conjunction of the simplifying programmes