The Neuronal Replicator Hypothesis

Chrisantha Fernando1,2,3

Eörs Szathmary1,4,5

1Collegium Budapest (Institute for Advanced Study), Budapest, Hungary2Centre for Computational Neuroscience and Robotics, Sussex University, UK

3MRC National Institute for Medical Research, Mill Hill, London, UK4Parmenides Foundation, Kardinal-Faulhaber-Strase 14a, D-80333 Munich,

Germany5Institute of Biology, Eötvös University, Pázmány Péter sétány 1/c, H-1117

Budapest, Hungary

Origin of Life and the Origin of Mind

Wallace didn’t believe the mind could be explained by evolution. Darwin did.

Is there natural selection in the brain? Could it explain human generative

problem solving, curiosity, and creativity? Natural selection destroyed the

explanatory power of Divine creativity. Would natural selection in the brain

destroy the explanatory power of Self?

What I don’t need to explain…

Performance on tasks where random variation with reward biased selection could work… Stroop Task WCST Tower of London

Instrumental tasks with

low dimensionality

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Instrumental Conditioning: Random exploration + stabilization of good

changes.

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But SHC can’t explain generative creativity in insight problems

How do we solve insight problems?

What neural mechanisms underlie complex operant behaviour?

Why do we play, listen to music, do PhDs, and go to Rothko exhibitions?

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But we think that Natural Selection CAN explain generative creativityNatural selection happens when you’ve

got units that can Reproduce (replication with errors) Transmit heritable variations

For example The adaptive immune system works by natural

selection. (controlled) So do genetic algorithms for engineering airbus

wing shapes, etc… (artificial)

Darwinism is not just Selectionism

A good solution can be copied and varied, i.e. parallel search resources can be appropriately distributed.

Offspring are mutated rather than oneself. Larger population sizes and elitism can a. increase the

sensitivity of selection to beneficial variants, b. prevent loss of good solutions.

Important when most changes are harmful. Variability can be structured by natural selection.

If there is variation in variability, i.e. non-trivial neutrality and lineage selection

X

A

B

A’

A’

B’

B’

If(F(A’) > F(B’) & F(A’) > F(X)) choose A

If(F(B’)> F(A’) & F(B’) > F(X)) choose B

Else(kill A & B and try again)(1 + 2 + 4) ES

But how could replication happen in the brain? We propose at least two kinds of

mechanism. Copying of connectivity patterns (SLOW) Copying of activity patterns (FAST)

Connectivity Copying

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2. Causal Inference

1. Formation of 1->1 Mapping2. (Topographicity)

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Parents killing children, and children killing parents

4. Fitness calculation

3. Activity gating

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Stop activity spread

Error Correction Neurons

I could evolve bigger networks with these extra mechanisms

Activity Copying

1. Topograpicity

2. Bistability

3. Gating

Minimal unit of activity replication = 2 bistable neurons

Parents killing children, and children killing parents (again)

Structuring Search of Activity Replicators

It is possible to combine Hebbian learning and natural selection to achieve structured variability.

Previously successful evolutionary solutions can be used to bias future evolutionary search.

Lamarckian inheritance in the brain.

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Richard Watson’s HIFF

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- Search in biased towards the previous local optima

Recombination

Further Work

How does the brain evolve representations of complex state-action spaces?

Neuronal chromosomes (chunking/hierarchical coupling) of state action pairs (options by synchrony).

Episodic memory may be a step in constructing such spaces (IAC algorithm).

assign value (fitness) to state-action pairs? Maximize first derivative of predictability Requires feed-forward emulators (Probabalistic robotics) Co-evolution of goals/solutions

Select actions to execute? Select actions that maximize intrinsic fitness.

Further Work

Find behavioural evidence for neuronal replicators. Instrumental Learning: Find behaviours that

exhibit phenotypes consistent with multiple underlying neuronal replicators.

Entropic irreversibility (in the absence of memory/convergent evolution).

Behavioural pathologies in instrumental learning tasks best explainable by historical contingency.

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Further Work

Find neurophysiological evidence for neuronal replicators Topographic mapping, STDP, bistability, and

gating are known processes. Rapid synaptic remodelling has been observed Spontaneous neuronal activity (e.g. in sleep)

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Thanks to

Richard GoldsteinRichard WatsonK.K. KarishmaPhil Husbands