Advances in Visual Perception PSYC 526 Fall Profs

Advances in Visual Perception PSYC 526 Fall Profs. Fred Kingdom & Kathy Mullen

Techniques for studying biological vision q Psychophysics q Neurophysiology q Brain Imaging

Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the Wadsworth Group, a division of Thomson Learning Page 40 (21) Methods for recording activity of a neuron

Courtesy of David Hubel, supplied by Tony Movshon, New York University

Courtesy of Geoff Boynton, Salk Institute, California

Courtesy of Geoff Boynton, Salk Institute, California

Courtesy of Geoff Boynton, Salk Institute, California

Lecture 1 An EXCEEDINGLY Brief History of Vision !

Empedocles (492 -432 BC)

Galen (2 nd century AD)

Summary of Greek ideas q Eyes emitted rays of light q Objects were active agents in perception q Replicas, or images of the outside world are carried to the brain

Alhazen (965 -1039 AD)

Pin-hole camera Object Image

Descartes (1596 -1650)

Viewing the retinal image (Descartes)

Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the Wadsworth Group, a division of Thomson Learning Page 5 (26) René Descartes’ conception of brain and mind

The ‘homunculus fallacy’

Newton (1642 -1727)

Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the Wadsworth Group, a division of Thomson Learning Page 157 (38) A beam of light separated into its Wavelengths

By the end of the renaissance……. q The lens in the eye produced the retinal image q A “sensorium” (or ‘homunculus’) in the head was able to see the contents of the image q The world we perceive is not a simple copy of physical reality

Helmholtz (1821 -1894)

Simultaneous colour contrast Simultaneous brightness contrast

What is the brain assuming here ?

By the end of the 19 th century…. . q Different sensations (pain, touch, smell, sight, hearing) are mediated by different physiological structures in the nervous system q Within a modality (e. g. sight) different nerve fibres respond selectively to different stimuli (e. g. different ranges of wavelength) q Perception is affected by in-built knowledge of the world, i. e. is not a simple transformation of the raw sensory input