55-101 Lecture Notes - Extrastriate Body Area, Atp Synthase, Receptive Field

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Published on 1 Feb 2013
Outline of Lecture 64 (03-26 B; Connor)
Visual System II – Ventral Pathway (Shape and Color)
I. Introduction to the ventral pathway
- The ventral pathway processes shape and color
- It is composed of V1, V2, V4, (V8), and inferotemporal regions (ant., post., central)
- Other miscellaneous regions
- Lateral occipital (LO): object/shape
- Fusiform face area (FFA): face stimuli or complex shape stimuli
- Parahippocampal place area (PPA): landscapes and building interiors
- Extrastriate body area (EBA): bodies and body parts
II. V1: simple orientation tuning
- V1 cells are tuned to the orientation of lines/edges
- Simple cells: tuned to orientation, position variant
- Have on/off receptive fields structured to recognize edges, perhaps as a result of convergent
input of multiple LGN cells whose receptive fields are aligned
- Complex cells: also tuned to orientation, but position invariant
- This property may be a result of convergent input of multiple simple cells
- Hypercomplex cells: added property of end-stopping (tuned to short lines)
- Columnar organization: each column is orientation tuned, and exact orientation shifts gradually
from column to column
- Color contrast is mediated by single- or double-opponent receptive fields
III. V2: more complex visual processing than V1
- V2 has a thick-thin-pale-thin stripe pattern
- Thick: tuned to motion, depth
- Thin: tuned to color and is organized in a hue map
- Pale: tuned to shape
- V2 cells have property of figure ground segmentation: tuned to properties of object outside
receptive field (e.g. what side is the object on?)
- Unlike V1, will respond to illusionary contours
IV. V4: curvature tuning
- V4 cells are tuned to curvature, the start of part-based coding
- Color tuning in V4 is complex
V. Inferior temporal regions: highest level of ventral pathway, parts-based coding
- Integrates edge and contour information to code objects as a collection of geometrical parts
- Even complex objects like faces can be represented in a parts-based way
Summary of major ideas
- See Objectives on p. 1
- Understand the concept that further down the pathway, cells generally have larger receptive
fields and visual processing is more complex
- Understand how image processing can result from a convergent network
- Understand the different roles of V1, V2, V4, IT, and the types of cells that make them up
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