Psych 159: Physiological Basis of Perception

Instructor: Don MacLeod

Class meetings: Lectures, Tuesday and Thursday 12.30 am to 1.50 pm, 1507 McGill

Office Hours: Wednesdays, 10-12, Room 5121 McGill; Tel 534-3975.

Email: dmacleod@ucsd.edu

Web: http://www-psy.ucsd.edu/~dmacleod  (and click on “courses” link)

 

Aims and scope: We consider the process of perception as a causal chain that starts with the sensory stimulus and continues through successive stages of neural representation, culminating finally in the construction of a behaviorally useful representation of the environment. We will be aiming for a research-level treatment of current understanding of selected topics. To make this job easier, we consider mainly visual perception, and select a limited number of problems within that field for in-depth treatment, especially those for which the nature of physiological constraints on perception is clearest. The inquiry focuses particularly on how both subjective (or "psychophysical") and objective (electrophysiological, neuroanatomical) approaches can be brought to bear on the same issues about visual processing, and on the difficulties and successes in achieving consistency between the findings of the two approaches.

Format: This is a seminar style class, and active participation is allowed/ encouraged/ required by the relatively small size of the group. The reading for each meeting should be done in advance. In class, much of the time will be group discussion elaborating on the reading. Systematic exposition will consist of both lectures (by me) and presentations by students. The lectures will use the topics in the text as a starting point. But they will not necessarily follow the text very closely—they will leave out some topics, and often introduce new material to update and elaborate the discussion in the text, The lectures, and your own presentations, will use the text chapters as a stem onto which a lot of more advanced material will be grafted. . For that reason, but also because participation in class will contribute to your grade, you should consider the lectures mandatory rather than optional, if you want to do well.

 

Reading:

There will be one text plus (more important) selected online Readings.

Text: Sensation & Perception

by Jeremy Wolfe and others. (Sinauer, 2006)

This text is available at the Bookstore.  I like it a lot, so I am trying it for this class this year although it is not very challenging for a second course in Perception.  To add depth to our discussions, we will be supplementing the text with brief on-line readings for most meetings of the class. These additional assigned readings are mostly yet to be chosen (denoted by TBA below), but they will have an importance at least comparable with the text, and they will generally be considerably more challenging to read with insight.

I will want each of you to email me, by midnight the day before each class, at least one question, inspired by the assigned reading or by other relevant reading such as web explorations, which you think would be helpful for stimulating or guiding discussion (or equally useful, instead of a question you can briefly articulate a “position statement” that you are prepared to defend). I will distribute these (or at least a selection from them) in class. In order to be useful, these questions should reflect thoughtful attention to the reading. Where possible, please include in your text some relevant quote and/or page number from the reading. Please put Psychology 159 in the subject line of your message. Instead of  contributing a question or comment, you could introduce some interesting demonstration or discussion from the web.

Prerequisites and desiderata: Psych 102, Introduction to Perception, is listed as required. Confident students are not excluded, however, especially if they have some background in neurobiology or physiological psychology. Quite a few of the topics we consider will be treated quantitatively, so an enthusiasm for thinking quantitatively, or some background in physics or engineering, is also a great advantage…and an aversion to thinking quantitatively is a corresponding handicap.

Evaluation (tentative plan):

Tentative plan is to have only a final exam (no midterm).  Besides this you are asked to produce one substantial paper  and one 20 minute presentation to the class.

The paper will be due (tentatively) at the beginning of class on Thursday of Week 7. A recommended length is 10 pages (double spaced type please). The choice of topic is up to you, provided it's relevant to the themes of the course. Discuss it with me first if you're uncertain. Originality will be appreciated, but it isn't mandatory. Possible topics will be discussed in class. You should choose a topic and tell me your choice at least a week before the paper is due. You are expected to consult the research literature beyond the recommended readings in preparing your paper.

Format of the paper is flexible, but: use citations in your paper to justify your claims. Cite authors by name and date, e.g. (Smith & Jones, 1922). Include complete references at the end of the paper in any standard format, e.g. APA format. Include an abstract (a summary of the key points, in less than 1 page). You are encouraged to replace one of the papers with a more concrete project: for instance you could conduct a perception experiment, do a computer simulation, or create an informative visual demonstration. Please submit the paoer to me by email as well as a hard copy. A project could also be accompanied by a short written report if you like.

Your presentation should be a short and snappy but comprehensible (to your classmates) account of some topic that the text discusses. Please discuss your choice of topic with me beforehand. One possible choice (though not the best one) is to just summarize and clarify part of the textbook chapter we are dealing with on the day of your presentation, perhaps developing your own understanding of that topic using other sources like the recommended readings. Much better is to introduce some new material that has a connection to the material in the text (for instance, briefly summarize some recent piece(s) of research that have something to say about the topic of the day). 

It’s a good idea to use some graphics for your presentation. PowerPoint is a good way to go. I will have a computer graphics projector. If you can use your own laptop (with VGA output; bring an adapter if it’s an Apple  IBook), that will be fine. Otherwise, I will generally have mine. If we have to use my laptop, you can best bring your ppt file to class on a flash drive. Alternatively, we will have a projector for overhead transparencies if that’s your preference (N.B. 16 point minimum font size for legibility!).

Tentative distribution of points: Paper/project/presentations (25% for each of two),  final (40%) and class participation (10%). Final exams will be include essay type questions as well as short answer/multiple choice questions—about a 50/50 split between essay type and short answer questions in the total grade. Tentative format for essay questions: you will be asked to answer 4 (final) out of 6 questions. These 6 questions will be selected by us from a list of up to 30 questions that I will give out at the lectures, at least a week in advance of the exam. Questions and grading will try to reward understanding rather than detailed factual knowledge. Of the material in the text, the most important topics will be the ones emphasized in the lectures, and the most important material within each topic is the material that is essential to our understanding of the subject, rather than specific facts. Answers will require thoughtful consideration of text and lectures. Feel free to help me (and yourself) by providing me with candidate questions that you think would be appropriate for inclusion in the exam. I expect to use only a small proportion of questions that are submitted this way, but formulating (and answering) questions is in any case a productive way of organizing high-level study.

SCHEDULE (**TENTATIVE)

Week 1 Thursday: The problem of perception

Week 2 Tuesday: How the retinal image is formed. Read Chapters 1 and 2 first

            Lecture topic: optical limitations on the quality of vision

Week 2 Thursday: Retinal organization  Read & Discuss Field et al: Retinal Processing near absolute threshold

Lecture topics:  (1) How photoreceptors respond to light

(2) Light and Dark adaptation: how sensitivity is regulated

 

Week 3 Tuesday: Functional organization of the retina: receptive fields  Read and discuss: Chapter 3 +TBA

Lecture topics:  (1) Why isn't vision perfect? Resolution and receptive fields

(2) Spatial frequency representation

Week 3 Thursday: Perception and recognition of objects.  Reading: Chapter 4 +TBA

Week 4 Tuesday:  Color vision: Why we are all partially color blind   Reading: Chapter 5+TBA

Week 4 Thursday: Physiological Basis of Color Appearance  Reading: Jacobs knock-in mouse

Lecture topic: Color and lightness constancy

Week 5 Tuesday: Primary visual cortex, space perception and form vision  Reading: Chapter 6 + Central visual disorders

            Lecture topic:  (1) Physiological Basis of Depth Perception

Week 5 Thursday: Higher cortical areas and form vision; Motion   Reading: Chapter 7 +TBA

Week 6 Tuesday:   More about visual cortex.          Reading: Crick and Koch on consciousness

Lecture topics: (1) Streams and functional specialization in the cortex

(2) Illusions, aftereffects and the brain

Week 6 Thursday: Attention and Scene Perception; Development.       Reading: Chapter 8;  Mike May

            Lecture topic: Recovered vision and Mike May

Week 7 Tuesday:   Vision review                 Reading: Why isn’t vision perfect?;          Crick and Koch again

            Lecture topic:  Why isn’t vision perfect?

Week 7 Thursday: Hearing and the ear                   Reading:  Chapter 9

Week 8 Tuesday:   Hearing in the Environment                   Reading: Chapter 10  

Week 8 Thursday:  Music and Speech       Ch.11; McDermott and Oxenham on Music and the Brain

Week 9 Tuesday:   Touch     Ch.12                                                              PAPER DUE

Week 9 Thursday:  Smell     Ch. 13; Linda Buck's Nobel Lecture

Week 10 Tuesday:  Taste Ch. 14

Week 10 Thursday:  Review

Lecture topic: Perception as a Constructive Process

 

FINAL: as in schedule of classes.

Additional recommended reading: general

The text will not be challenging to those who have already done Psych 102. I will distribute copies of a few other readings during the quarter as they are relevant. There are no other required readings, but if you want to do well (and still more, if you are keen to advance your understanding of the subject) you will want to read further. For a start, anyone who hasn’t completed Psych 102 might find it useful to look over a more introductory (Psych 102 or equivalent) text for review of background. Two good examples:

R. Sekuler and R.Blake, Visual Perception, Knopf, 1985

E.B.Goldstein, Sensation and Perception, Wadsworth, 1989 ( a little more physiologically oriented, and so marginally preferable here, to Sekuler and Blake).

T.N.Cornsweet, Visual Perception, Academic Press, 1970 is that rarity: a thinking person’s textbook. Fun, but limited to low levels of visual processing that can be understood in physiological (or at least in mechanistic) terms.

Richard Gregory, Eye and Brain, Princeton, 1990 is shorter, more selective, less technical and even more fun than Cornsweet.

S. E. Palmer, Vision Science: From Photons to Phenomenology, MIT 1999 is an excellent and comprehensive survey of our understanding of visual perception, encompassing phenomenological and cognitive as well as physiological viewpoints.

Useful for a more advanced and up to date, mathematically oriented survey of most of the course material: Wandell B.A. Foundations of Vision. Sinauer Associates Inc., 1995.

Still more advanced, but useful for getting into current issues in preparing papers, are the proceedings of recent scientific symposia:L. Spillmann & J.S. Werner (Eds.) Visual Perception: The Neurophysiological Foundations. Academic Press 1990 and C. Blakemore (ed.). Vision: Coding and Efficiency, Cambridge (1990).  These are sophisticated summaries of current thinking at the frontiers of research.

 

Recommended reading: specific topics

Other books recommended for a clear and comprehensive account of part of the material:

P.K. Kaiser and R.M.Boynton, Human Color Vision, Optical Society of America, 1996. This discusses not only color vision but also visual sensitivity (altogether, about 1/3 of the course material) in a sufficiently advanced but understandable way. Most useful are chapters 1-7 and 10, especially chapters 5, 6 and 7.  For a state-of-the-art discussion of current issues in color vision you could also try R. Mausfeld and D. Heyer, Colour Perception: Mind and the Physical World, Oxford, 2003.

D. Marr, Vision, Freeman, 1982 is the most influential book on vision written this century, outlining what has become known as the "computational" approach, which unites the artificial intelligence and physiological points of view on vision. Especially good on stereo.

Chapter 4 of The Computational Brain, by Pat Churchland and Terry Sejnowski, is a good briefer treatment along Marr's lines, again concentrating on depth and 3D shape.

S. Zeki, A Vision of the Brain, Blackwell, 1993 is a beautifully illustrated but peculiarly one-sided and controversial discussion of the special role of different regions of the cerebral cortex in vision. A broader and less idiosyncratic, but less up-to-the minute, account of the physiological basis of vision with a focus on the cortex is D.H.Hubel, Eye, Brain, and Vision, Freeman, 1988.

R. W. Rodieck, The First Steps in Seeing, Sinauer, 1998. is a challenging in its rigor and attention to detail, but it is written clearly so that an interested and thoughtful reader can understand it without much prior knowledge. Focus is heavily on early stages in vision, mainly the eye and the retina. Complements Zeki, where the focus is on cortex.

   

D.B. Dusenbery, Sensory Ecology, Freeman 1992 is an interesting survey of sensory processes in animals.

 

David M. Regan, Human Perception of Objects, Sinauer, 2000 discusses in some depth the early visual processing of spatial form defined by luminance, color, texture, motion, and binocular disparity.

 

A few of the many useful Web resources:

o      ViperLib. A vast and interesting online collection of images that illustrate scientifically interesting points about vision.

o      Illusions Gallery. A collection of visual illusions with tutorial information.

o      Color Systems and Images An historical collection of color systems (Hans Irtel).

o      Interactive Illustrations of Color Perception by John F. Hughes, Jeff Beall, and Adam Doppelt, Brown University. (Requires a Hot Java compatible browser to use the interactive illustrations).

o      The Joy of Visual Perception a Web book by Peter Kaiser at York University

o      Sensation and Perception Tutorials. from John Krantz at Hanover

o      Space=time receptive fields of cortical neurons by Izumi Ohzawa.

o      A collection of single image random dot “magic eye” stereograms

o      Vischeck.  A site with a program that can simulate how images and web pages would look to people with different types of color deficiencies. 

o      Webvision: The Neural Organization of the Vertebrate Retina A wonderful up-to-date resource on the retina.

o      Visual ecology Web site of the leading research group on such things as eye design.

o      Quantitative data on mechanisms of color vision  from Prof. Andrew Stockman, London. Mainly useful for advanced readers, especially for modeling how the eye responds to color

o      "Change blindness" demonstrations These show strikingly how little we take in of what we don’t specifically attend to.