#hebbian learning

[neurosciencenews]

Two Seemingly Opposing Forces in the Brain Cooperate to Enhance Memory Formation

Hebbian plasticity reacts to activity at the synapses by inciting them to get stronger while HSP reacts to it by making them weaker.

The research is in iScience. (full open access)

[neurosciencenews]

The Brain Learns Completely Differently than We've Assumed Since the 20th Century

The brain is a complex network containing billions of neurons, where each of these neurons communicates simultaneously with thousands of other via their synapses (links). However, the neuron actually collects its many synaptic incoming signals through several extremely long ramified "arms" only, called dendritic trees.

The research is in Scientific Reports. (full open access)

[neurosciencenews]

Implanting Fear

Read the full article Implanting Fear at NeuroscienceNews.com.

Two mechanisms work in tandem to form memories of frightening events.

The research is in PNAS. (full access paywall)

Research: "Hebbian and neuromodulatory mechanisms interact to trigger associative memory formation" by Johansen, J. P., Diaz-Mataiz, L., Hamanaka, H., Ozawa, T., Ycu, E., Koivumaa, J., Kumar, A., Hou, M., Deisseroth, K., Boyden, E. S., and LeDoux, J. E. in PNAS. doi:10.1073/pnas.1421304111  

Image: Although a beep and a mild electric shock become associated through Hebbian plasticity, the presence of noradrenaline is needed to create a fear memory. Image credit: RIKEN Brain Science Institute.

[neurosciencenews]

Mathematical Model Shows How the Brain Remains Stable During Learning

Read the full article Mathematical Model Shows How the Brain Remains Stable During Learning at NeuroscienceNews.com.

Complex biochemical signals that coordinate fast and slow changes in neuronal networks keep the brain in balance during learning, according to an international team of scientists from the RIKEN Brain Science Institute in Japan, UC San Francisco (UCSF), and Columbia University in New York. 

The research is in Neuron. (full access paywall)

Research: “Modeling the Dynamic Interaction of Hebbian and Homeostatic Plasticity” by Taro Toyoizumi, Megumi Kaneko, Michael P. Stryker, and Kenneth D. Miller in Neuron. doi:10.1016/j.neuron.2014.09.036

Image: The theory and experimental findings showed that fast Hebbian and slow homeostatic plasticity work together during learning, but only after each has independently assured stability on its own timescale. This image is for illustrative purposes only. Credit Nicolas P. Rougier.

[isomorphismes]

Hebbian History

memeengine replied to your post: Or can the influence of any ancestor ever fade down to zero? (Or, well… to arbitrarily small size?)

An AR[1] process can go arbitrarily ↓0 as time↑∞. But in real life the sins of the fathers set their childrens' teeth on edge in a stiffer, more heriting, architectural way. (I was alluding to that with the new-parents post scriptum.)

I don't know of any "grande classes of models" wherein you stay stuck from where the past put you, but for example you could say

if ($income >= 10 guineas) { $opportunities = 1000; } else { $opportunities = 3; }.

  I'm neither an expert on history nor do I find the econometrics super compelling, but ∃ some theories of the past carving out a channel for the future.

In central Africa -- the form of governance from 1000, 1500, 1800 AD still has an influence on GDP per capita today. Even once you statistically control for other "obvious" determinants of production power. (Here I learned the interesting term "ethnofract"--a measure of ethnic disparity.)

In the southeastern US -- a county's history of slave-holding has statistical relevance to. (Nathan Nunn is a co-author.)

In socialist Sweden -- the class mobility from generation to generation is greater than in free-market United States.

According to Arvind Thornton, north-western European social norms of family size, structure, and intra-/inter-relationships set the stage for "industrial revolution" type anti-Malthusian family structures that inform major subcultures all over the OECD today. I.e., a small nuclear family wherefrom kids form their own families in a separate home; high value placed upon individualism; etc. 

Among US states, the number of highway lane-miles in a state, as proposed in 1944 by the Franklin D. Roosevelt Administration, predicts how much ARRA grant money it got 65 years later.

In British-colonial Jamaica and French-colonial Haiti, an oligarchic political form in the 1700's passed on poverty to its 'fterbears. Sugar plantations financed European vacations, fine liberal educations, and leisure for the elites, but sugar is not an investment in the future. Indeed, growth markets might have overthrown the political structure by empowering the hands, so the positive-sum games were forestalled by the landed interests. (Story can be found on Daron Acemoglu's website.)

(A similar argument has been applied to Europe in the Needham question: why did Europeans dominate the globe rather than Asians, when the Asians were ahead earlier on in the race? Perhaps because of the over-powerful Chinese government.)

In Louisiana, USA -- juridical forms differ from the other 49 States. Since Louisiana's French colonial history bequeathed it a civil-law rather than a common-law system of justice, not just its laws but the underlying reasoning for how they're executed, differs orthogonally to other interstate legal variations.

Come to think of it: any common-law system, by design, to carve a river that the future will follow.

In all of the statistical examples we've got to ask if it's possible to statistically control for parameter changes. To which the correct answer is: No. Well, maybe. Um, in a local sense any parameter change can be estimated as linear. If the underlying function is ≥once-differentiable. So, err. I'll have to get back to you on that.

(I'll look up paper links later...if you as a reader know the papers or related ones you could also do me the favour and post links in the Reply or Disqus Comments. =) )