Hi, all
One simple question.
We know about Lettvin- Maturana article. However, I have heard that both in the behavioral and ( I am not absolutely sure) even in electrophysiological experiments the real good effect was obtained ONLY when the movement of an object was not linear and smooth but sporatic and stochastic. I have observed similar effects in frogs auditory midbrain (and even medullar) neurons ( Bibikov N.G. Addition of noise enhanced neural synchrony to amplitude-modulated sounds in the frog's midbrain. Hear. Research. 2002. v.173 . n1. p.21-28.)
I am very interested to know about some reasonable demonstration and modelling of this effect in the visual system of the frog.
Thank you.
Bibikov N.G.
Dr. Biol. Corr.memb. RANS
Head of bioacoustics lab.
N.N.Andreyev Acoustics Institute
Schvernik st. 4
Moscow 117036
Tel.: 7 099 17236311
Fax: 7 495 126 8411
e mail: bibikov@akin.ru or nbibikov1@yandex.ru

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I'm not familiar with the Lettvin-Maturana paper. Can you direct me to the citation? This seems like a really fascinating topic, and I look forward to hearing what others think.
No question about this paper.
Can you say something about my queation?
Hello Dr. Bibikov
You ask an interesting question; it would fascinate (but not shock) me to learn of neurons that act as you describe. However, I have never heard of such neurons. The most likely person to be able to give you a more definitive answer about whether such neurons have been described before (at least in the visual domain) would be Barry Frost at Queen's University (frost@psyc.queensu.ca). At least, he would be the person I would look to for an educated answer...
Good luck with your search.
I don't remember Lettvin, et al's paper considering stochastic motion effects (although it has been a while since I read it). I don't recall any paper that explores it.

If I were to model neural noise rejection I would have the brain circuit adaptively raise the threshold of direct sensory neuron and simultaneously increase the pathway's synaptic weighting at some downstream neuron in order to amplify the remaining small signal.

The auditory system of frogs is very interesting and since you are in the field I suspect you know of Albert Feng's work at the University of Illinois.
For those not familiar with the paper I included their most important data in this review of the frog retina here: http://neurocomputing.org/FrogEye.aspx

Well, to a three year old question, I can give some inside info.  The answer: ...as a grad student of Lettvin's I was privy to being present when some of these experiments were duplicated for other reasons in the '60's. In particular, we (about 5 of us) were playing with the "bug" detector.  We were looking at the responses to one bug, two bugs...etc. up to 5 presented as a cluster moving in tandem. A single smooth movement of a single 'bug' produced a fine response. Interestingly, as the number increased, the response decreased until 5 or so did not elicit a response. The collective movement was smooth, not sporatic and stochastic. Certainly, a bit of jitter does improve the response. In an experiment I am now doing with Ed Gruberg who was then a post-doc in Lettvin's lab and is now at Temple Univ, Philadelphia...about 6 miles from where I am located, we use a stimulus that is deliberately jittered, but I want to emphasize that the jitter is not necessary for the response originally described.


Bill Saidel


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