Visual Perception and the Brain

Dale PurvesDuke Institute for Brain SciencesAbout the CourseNot the usual approach to visionThe focus will be on perception as a guide to strategy and mechanisms, rather than the other way aroundEight modules over 8 weeks in short segmentsSelf assessment and questionsResources (glossary, readings, website)The premise of the course: no one understands vision (or brain operation generally), and we should therefore be open minded about what may seem strange ideasThe instructor (purveslab.net)Module # 1The Phenomenology of What We SeeWhat we do know at this point is that the standard anatomical and physiological approaches to vision have not been able to explain perception.

An alternative is to stand back and consider the what the phenomenology of what we see is trying to tell us about how vision works.Definitions and DistinctionsPerception Physical measurements Psychophysical measurementsThe Strange Way We See Things

The Perception of Luminance (i.e., relative lightness) Sinauer Associates, Inc.

Sinauer Associates, Inc.

Seeing gray as black or white Sinauer Associates, Inc.

The Cornsweet edge even harder to explain Sinauer Associates, Inc.

Color Sinauer Associates, Inc.

Geometry Sinauer Associates, Inc.

aAn example of angle perception Sinauer Associates, Inc.

Sinauer Associates, Inc.Even though we behave successfully in the physical world, we dont see it according to measured realityThese are not illusions but just the way we see stuff.

So why is our perception so misleading with respect to reality?Why We Dont See the World the Way it Really Is:The Inverse ProblemThe inverse problem as it applies to luminance

Sinauer Associates, Inc.

The inverse problem as it applies to seeing geometry Sinauer Associates, Inc.

The inverse problem as it applies to seeing motion Sinauer Associates, Inc.The Main Points The significance of visual images for behavior in the physical world is inherently uncertainThis means that the real world is unknowable by any direct, logical operation on retinal imagesHow then does vision succeed in a hidden physical world? Next time: The organization of the visual system and the nature of visual stimuli