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Video instructions and help with filling out and completing Form 5495 Opinions

Instructions and Help about Form 5495 Opinions

Now as I've listened to the talks and as I look out into the audience and actually see some good morning some rather famous psychiatrists it recalled my somewhat failed medical school career for I went to medical school and I wanted to become a psychiatrist but during my first clinical rotation in medical school my clinical incompetence was immediately recognized and I was called in by the Dean who offered to allow me to graduate from medical school if I promised never ever to practice medicine on live patients and I agreed happily and I did an internship in pathology to keep my promise and the chair of pathology came to me after a year of autopsies and offered to certify me in pathology if I promise never ever to practice medicine on dead patients and so I stand before you to talk to you about a problem in neuroscience a rather elusive problem the problem of how the sensory world is represented in the brain now I'd like you to think about this problem because it's an utterly astonishing problem because the sensory world can consists of a set of physical properties wavelengths of light that encompass vision frequencies of sound chemical structures that make for smell and taste but how can you possibly represent these quantifiable physical parameters in a brain that simply has one thing in it neurons and these neurons can only do one meaningful thing that is they can fire they elicit an electrical discharge to allow communication among themselves and moreover they can only vary in their firing in their spiking in two parameters time and space so this world out there this rich world that we experience has to be represented by this monotonic array of neurons and in fact as I will tell you the representation of the world in the brain bears no physical resemblance to the world outside of it so the brain is abstracting the world it is as much an abstraction as a piece of abstract art that attempts to relay a rather figurative image in completely disordered forms and lines and colors the brain inside the brain the firing of neurons bears no resemblance to the world the brain is not a camera there is no ensemble of neurons in the form of a square when you see a square and recalling an image does not recapitulate the action of a movie camera this is an astonishingly complex problem that I will not solve for you but how do we how does one address this problem now this problem is interesting and it's been considered in the past for over 3,000 years Plato and is a republic considered this problem in what is known as the allegory of the cave in which prisoners see no aspect of the world but rather only see shadows and it opposed imposes the question of illusion and reality indeed one of the temptations of having a brain is to try and use it to solve the mystery of its own nature it's tempting it's been tempting to think that the nature of thinking could be uncovered by thinking alone philosophers tried this from the beginning of recorded history and then the philosophers were joined by the psychologists the sociologists the economists but we haven't fared very well and so the biologists entered the fray and we still remain at a very primitive level of understanding but how do we begin to approach this problem as a biologist so let me try and describe to you the nature of the representation of smell we've already heard a great deal about smell I'm going to talk about a different nose then know'm has talked about in reality most mammals perhaps not humans have two noses they have a main nose called the main olfactory epithelium which resides in the posterior recess of the nose and then they have a separate nose called the vomeronasal organ other people call it the erotic nose and that's responsible for many of the named effects that know'm talked about and interestingly as we will see these two noses project to different parts of the brain the erotic nose the vomeronasal organ projects to a part of the brain already described the emotive brain the amygdala whereas the main nose projects to multiple areas including cognitive brain so let's consider this my student Linda Baca I'm going to talk about work done by many students and that's because I'm a very religious man and I do nothing and as it is written in Leviticus the work of the righteous is done by others so my student identified about the genes that encode the receptors that sit on the tips of the neurons in your nose that recognize the world odors in the environment remarkably Linda observed that there are in most mammals at least a thousand genes encoding odorant receptors you only have 20,000 genes in your chromosome for so over 5% of the information in your chromosome is dedicated to the recognition of odors or remarkable observation consistent with the importance of smell for the survival and reproduction of most animal species here we got very fortunate it turned out that you have many millions of neurons in your nose but each neuron makes only one of these receptors and a given odor will activate 50 of these receptors each neuron in the nose sends a process back to the brain and all the neurons that Express the same kind of receptor send their process to a fixed point in the brain if you have a thousand receptors you have a thousand points are we together a remarkable okay an odor comes along it activates 50 receptors in the nose 50 out of a thousand the number of possible combinations is about 10 with 23 zeroes after it that's the number of different odors you can discriminate and so an odor come comes along it.

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