1. PY202 Overview

2. Meta issue How do we internalise the world to enable recognition judgements to be made, visual thinking, and actions to be executed.

3. Basic issues Methodologies for studying perception and cognition. Neurophysiology of low- (early) and high-level (late) vision (including retina, LGN, cortical processing). Construction and representation (including surface perception, figure-ground, object and face processing). Attention.Imagery.

4. Methods and Issues Neurophysiology and low-level vision (simple properties, small receptive fields). Neurophysiology and high-level vision (complex properties, large receptive fields). Psychophysics and neurophysiology. Cognitive Psychology and the needle-in- the-haystack.

5. Possible Exam Questions

6. Define the concept of the receptive field (RF) of a neuron in the visual system. Describe the evidence for the RF properties of neurons in the primate visual system between the level of retinal ganglion cells up to primary visual cortex (V1). The receptive field of a visual neuron is the region of the retina within which light affects the firing rate of the neuron. The RFs of cells with well-defined “on” and “off” regions, which includes retinal ganglion cells, LGN cells, and simple cells in primary visual cortex, are mapped using small spots of light and observing which locations affect the firing rate of the cell. The responses of these cells to more complex patterns of light can then be predicted by thinking of any pattern as being composed of small spots of light and “adding up” the effects of all these spots. The RFs of complex and hypercomplex cells are mapped using moving bars or edges of particular orientations.

7. Describe the evidence for the trichromatic theory of color vision. Psychophysics. By varying the amounts of a fixed set of three different wavelengths in the visible spectrum people can find a match for the color of any given wavelength of light. For example, by varying the amounts of red, green, and blue people can match any given color. Physiology. The cone receptors in the retina come in three different types: Some fire most strongly when illuminated by long wavelengths of light (red), others fire most strongly when illuminated by middle wavelengths of light (green), and still others fire most strongly when illuminated by short wavelengths of light (blue). Also, the pigment molecules in the cells that fire most strongly when illuminated by long wavelengths of light selectively absorb long wavelengths of light (rather than the middle or short wavelengths). Similarly, the pigment molecules in the cells that fire most strongly when illuminated by middle (short) wavelengths of light selectively absorb middle (short) wavelengths of light.

8. ‘Are faces just another class of object.’ Discuss. Consider the ways in which face processing might differ from object processing – in functional (from cognitive experiments) and anatomical (from neurophysiological and neuropsychological experiments) terms. In functional terms how do representations of objects differ from those of faces? (e.g. describe the effects of inversion on recognition) In anatomical terms, are there areas of cortex that encode only faces/objects? (e.g. the fusiform face area) Are there some objects that might act like faces – functionally and anatomically? (e.g. what happens when objects become highly familiar.

9. Describe the different roles that have been suggested for the ventral and dorsal pathways in visual cortex, and the evidence that demonstrates these different roles. Ventral - "WHAT" pathway - identification of objects independently of location; Neurons in inferior temporal areas that respond to faces, hands, and other complex stimuli; These neurons have very large receptive fields; they are not very selective for location; Lesion studies with monkeys; When presented with a pair of objects, they can no longer select the one that they have seen before; Still perform well on a localisation task; Lesions in humans produce identification deficits; Visual Agnosia - inability to recognise objects; Prosopagnosia - inability to recognise faces; difficulty in making age and gender judgements about pictures of faces.

10. Dorsal - "WHERE" or "HOW" pathway - representing objects' locations and/or allowing their manipulation; Lesion studies with monkeys; Deficits in selecting location near a landmark object; Still perform well on recognition task; Lesions in humans; spatial neglect - Unable to attend to any object on one side of space, regardless of its shape or identity; Difficulty in learning path through a maze. Although there are important differences between these two pathways, there are a multitude of connections between them. The processing in each pathway is obviously strongly affected by the other pathway.