Subtitles section Play video Print subtitles The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resources for free. To make a donation or to view additional materials from hundreds of MIT courses, visit MIT OpenCourseWare at ocw.mit.edu. PROFESSOR: This is our first introductory meeting of the course, which is 9.04. And we are going to cover vision and audition in this course, and there are going to be two of us lecturing. My name is Peter Schiller, and this is Chris Brown. And I will be talking about the vision portion, and Chris will be lecturing about the auditory portion. Now, what I'm going to do is I'm going to hand out the syllabi that we have, in this case, for the first half of the course. And that we are going to discuss in some detail today for the first half of the lecture, and Chris is going to discuss it for the second half. So that is the basic plan for today. And I will go through some of the basic procedures and issues that we may want to deal with at this very introductory portion. So first of all, let me talk about the reading assignments. If you have the handout, they are ready for you. If you look at the second page, that's where we have the assigned readings for the vision half of the course. Now, for that half of the course, the top eight assignments are all articles in various journals. We don't have a textbook for this portion of the course. And then in addition to the assigned readings, we have recommended readings that are listed there. And then another important factor that is listed there-- let me first say that the lectures will be put on Stellar, in most cases, after each lecture. And in addition, the videos that we are now recording will also become available, but they will not be available until well after each lecture. So I would advise each of you to come to the lectures rather than hoping to read the assigned material only or to eventually look at the videos. The reason I'm telling you this is that our analysis has shown that those students who attend the lectures regularly get much better grades on the exams than the students who do not. So I strongly will urge all of you to come to as many lectures as you possibly can. Now, the additional requirement that you're going to have for this course is to write two research reports, one for vision and one for audition. And the assigned written report that you need to put together is in a paper at the bottom of the second page. In this case, it's going to be a paper that was written quite some years ago, a very important and remarkable paper that has been published by Oster and Barlow, as you can see. And the task for you will be to not just report what they had reported, because that's repetitious, but to do a bit of research and write about what has been discovered since the remarkable findings that these two people had made at the time. All right. So that's the research report. And then I want to specify the exams. We are going to have a midterm exam, and the exact date for this has already been set on October 23. All right? But as I say, you can find this, and I will specify that in more detail in just a minute. And then we are going to have a final exam at the end of the term. The exact date for this, as always at MIT, will not have been set until probably sometime in November. So now let me also specify the grade breakdown. I think that's important for all of us. The written report for each half of the course-- there's going to be one report, as I've already said, for vision and one for audition-- and that will constitute 10% of the grade for each. And the midterm exam, this constitutes 25%. The final exam constitutes 55% of the overall grade. And in that, 15% will be on vision and 40% on audition. So if you add that up, you can see that vision and audition are set up to be exactly equally weighed for the exams. MICHELLE: Hi. I'm Michelle. I'll be helping the professors, especially with [INAUDIBLE]. PROFESSOR: So I'm Chris Brown, and I'm one of the instructors. I'll be teaching the second half. And my research is on two areas, brain stem auditory reflexes, like the startle reflex and the middle ear muscle reflex. And I also work on animal models of the auditory brain stem implant, which is a neural prosthesis that's used in deaf individuals. PROFESSOR: All right. And I'm Peter Schiller, and I work on the visual system. And I'm a professor here in our department. So that's very nice. Thank you for the introductions. And I hope, you guys, we all get to know each other. I'm very impressed that there's so many seniors here. That's actually unusual. I don't remember having this high a percentage of seniors in the class. That's really very nice, very nice. OK. So now we are going to talk, for the first part of today's lecture, about what aspects of visual processing we are trying to understand and, therefore, what we are going to try to cover in this course in terms of topics. OK? So first of all, what we are going to do for several lectures is to talk about the layout and organization of the visual system itself. Most of it we will discuss as it applies to higher mammals, in particular monkeys and primates and humans. Then we are going to talk about specific aspects of visual processing. We're going to try to understand how we adapt in vision, and, very interestingly, how we are able to perceive colors and process them accurately. Another fascinating topic is how we are capable of analyzing motion. That's a complex, very interesting topic, as is depth perception. And the reason depth perception is particularly interesting is because, as you know, the retinal surface is essentially a two-dimensional arrangement. And yet from whatever falls on these two dimensions in the left and right eyes, somehow the brain needs to convert to be able to see the third dimension. And as a result, several mechanisms have evolved to accomplish that, and we are going to discuss them. Then, again, another very complex topic is how we can recognize objects. Perhaps the most complex of those is our incredible ability to recognize faces. And that is highlighted, of course, by the fact that if you look at more simple organisms, like, I don't know, monkeys, they all look the same to you. But human beings, who are actually more similar to each other than perhaps monkeys are, we are really capable of telling them apart and readily recognize them over long periods of time. So it's a very interesting topic. And yet another topic that we will discuss is how we make eye movements. As you probably know, or you're aware of, that we are constantly moving your eye. You make saccadic eye movements about three times a second, thousands of times a day, hundreds of thousands of times, to be able to see things clearly in the world. So we are going to try to understand how that incredible ability has evolved and how it is realized by the brain. OK. So now to look at exactly how we are going to cover this, let me go through this. During the next lecture, which is September 9, we are going to look at the basic layout of the retina and the lateral geniculate system, as well as how the visual system in general is wired. Then on September 11, we're going to look at the visual cortex, then at the ON and OFF channels, so-called, that you'll realize what they are once we talk about it. And then there's another set of channels that originates in the retina, which are the midget and parasol channels. We'll discuss those, try to figure out why did they evolve and what is their role in being able to see the world in realistic fashion. Then we're going to talk about adaption and color, depth perception, form perception. And then we're going to have a lot of fun on October 2, and we're going to look at illusions and also visual prosthesis, because one of you, in particular, is interested in that topic. Then we are going to talk about the neural control of visually guided eye movements. That's going to consist of two sessions. And then we're going to talk about motion perception and another aspect of eye movements when we pursue something with smooth eye movements. And then we're going to have an overview. And then, lastly, on October 23rd, we are going to have the midterm exam. That's going to cover questions from all of these lectures. I should tell you right now that the midterm exam is going to consist of multiple-choice questions. So you're not going to, maybe, asked to write anything. You're going to have to just pick from each of the questions the correct answer. All right. So now what I would like to talk about next in a summary fashion are what we call the tools of the trade. What has happened over the many years that scientists tried to understand how the visual system and, for that matter the brain, works, what kinds of methods have been employed. And so I'm going to talk about each of these just very briefly this time, and then they will come up repeatedly during all of the lectures. Now, the first method I'm going to talk about is called psychophysics. I'm sure most of you know what that is. It's a scientific way to study behavior of humans and animals to determine how well they can see. Now, there are several procedures with this. I'm going to describe one that's used both in humans and monkeys. And what you can do nowadays, you can use a color monitor, and I will describe that in just a second. After that, I will talk about anatomy. I will talk about electrophysiology, pharmacology, brain lesions, imaging, and optogenetics. So now let's start with psychophysics in more detail. So here is a color monitor, and either monkeys or humans can be trained to first look at a fixation spot. And that's important because we want to always be able to present stimuli in selected locations of the visual field or selected locations along the retina. This is particularly important, because when you study the brain, different regions of the visual field representation are located in different areas, for example, in the visual cortex. So what you do then is you can present a single stimulus like this, and the task of the human or the monkey is to either make a saccadic eye movement to it, say that's where it is, or to press a lever that's in front of them. And then on each trial, it appears someplace else. You can present it in many different locations, and maybe one of those locations will be relevant to what part of the brain you are studying. And then what you do, you can systematically vary all kinds of aspects of the stimulus. You can vary the color. You can vary the contrast. You can vary the size. You can vary the shape. And by systematically varying this, you can create curves to describe exactly how well you can see any particular thing like, for example, just how much contrast you need to perceive something. All right.