Monday, January 22, 2018

The Gallistel-King conjecture; an update

As time goes by, bets against the veracity of the Gallistel-King conjecture (see here and here) are becoming longer and longer. Don’t get me wrong. The cog-neuro world is not about to give up on its love affair with connectionism. It’s just that as the months pass, the problems with this (sadly, hyper Empiricist) view of things becomes ever more evident and this readies people for a change. Moreover, as you can’t beat something with nothing but a promise of something (you actually need a concrete something), it is heartening to see that the idea of classical computation within the neuron/cell is becoming ever more conventional. Here is a recent report that shows how far things have come.

It shows how living cells can classically compute, in the sense of programmable circuits (“predictable and programmable RNA-RNA interactions”), which “resemble” conventional electronic circuits” with the added feature that they “self-assemble” within cells “sense incoming messages and respond to them by producing a particular computational output.” Furthermore, “these switches can be combined…to produce more complex logic gates capable of evaluating and responding to multiple outputs, just like a computer may take several variables and perform sequential operations like addition and subtraction in order to reach a final result.” Recall, that as Gallistel has long argued, being able to compute a number and store it and use it for further computation is precisely the kind of neural computation we need to be cognitively adequate. We now know that cells have the chemical wherewithal to accomplish this using little RNA circuits, and that this is actually quite easy for the cell to do (“The RNA-only approach to producing cellular nanodevices is a significant advance, as earlier efforts required the use of complex intermediaries, like proteins”) reliably.

So, the idea that cells can classically compute is true. It would be surprising if evolution developed an entirely novel computational procedure instead of exploiting the computational potential of ready available ones to get our cognitive capacities off the ground. This is possible (of course) but seems like a weird way to proceed if the ingredients for a standard kind of computation (symbolic) are already there for the taking. This is the point of the Gallistel-King conjecture, and to me, it seems like a very good one.

1 comment:

  1. Against this background, you may also be interested in these (recent) papers:

    (1) This suggests that a neuron can even learn a sequence of (at least) two timed responses: Jirenhed, D.-A., Rasmussen, A., Johansson, F., & Hesslow, G. (2017). Learned response sequences in cerebellar Purkinje cells. Proceedings of the National Academy of Sciences of the United States of America, 114(23), 6127–6132.

    (2) This reviews the observation that activity-dependent and spontaneous remodelling of synapses are--roughly--equally common: Ziv, N. E. & Breener, N. (in press). Synaptic tenacity or lack thereof: Spontaneous remodeling of synapses. Trends in Neurosciences.