Connectionists: how the brain works?

[Geoffrey Goodhill]

Hi All,

A great example of successful Ockham-inspired biology is Alan Turing's model for pattern formation (spots, stripes etc) in embryology (The chemical basis of morphogenesis, Phil Trans Roy Soc, 1953). Turing introduced a physical mechanism for how inhomogeneous spatial patterns can arise in a biological system from a spatially homogeneous starting point,  based on the diffusion of morphogens. The paper begins:

"In this section a mathematical model of the growing embryo will be described. This model will be a simplification and an idealization, and consequently a falsification. It is to be hoped that the features retained for discussion are those of greatest importance in the present state of knowledge."

The paper remained virtually uncited for its first 20 years following publication, but since then has amassed 8000 citations (Google Scholar). The subsequent discovery of huge quantities of molecular detail in biological pattern formation have only reinforced the importance of this relatively simple model, not because it explains every system, but because the overarching concepts it introduced have proved to be so fertile.

Cheers,

Geoff


On Mar 20, 2014, at 6:27 AM, Michael Arbib wrote:

> Ignoring the gross differences in circuitry between hippocampus and cerebellum, etc., is not erring on the side of simplicity, it is erring, period. Have you actually looked at a Cajal/Sxentagothai-style drawing of their circuitry?
> 
> At 01:07 PM 3/19/2014, Brian J Mingus wrote:
>> Hi Jim,
>> 
>> Focusing too much on the details is risky in and of itself. Optimal compression requires a balance, and we can't compute what that balance is (all models are wrong). One thing we can say for sure is that we should err on the side of simplicity, and adding detail to theories before simpler explanations have failed is not Ockham's heuristic. That said it's still in the space of a Big Data fuzzy science approach, where we throw as much data from as many levels of analysis as we can come up with into a big pot and then construct a theory. The thing to keep in mind is that when we start pruning this model most of the details are going to disappear, because almost all of them are irrelevant. Indeed, the size of the description that includes all the details is almost infinite, whereas the length of the description that explains almost all the variance is extremely short, especially in comparison. This is why Ockham's razor is a good heuristic. It helps prevent us from wasting time on unnecessary details by suggesting that we only inquire as to the details once our existing simpler theory has failed to work.
>> 
>> > On 3/14/14 3:40 PM, Michael Arbib wrote:
>> >> At 11:17 AM 3/14/2014, Juyang Weng wrote:
>> >>> The brain uses a single architecture to do all brain functions we are aware of!  It uses the same architecture to do vision, audition, motor, reasoning, decision making, motivation (including pain avoidance and pleasure seeking, novelty seeking, higher emotion, etc.).
>> >>
>> >> Gosh -- and I thought cerebral cortex, hippocampus and cerebellum were very different from each other.