Lecture 11-From Eye To Brain Flashcards
What are the learning objectives for understanding visual information processing?
Understand how visual information is transmitted from the eye to the brain
* Understand the different types of visual information processing along various visual pathways * Understand the coding properties of neurons along visual pathways * Understand lateral inhibition and receptive fields
What are the main components of brain organization reviewed in the presentation?
Four lobes (frontal, parietal, temporal, occipital)
* Cortex (all convolutions) * Subcortex (everything below the convolutions)
Describe the visual pathways and functions.
Eyes -> Subcortex (lateral geniculate nucleus, LGN)
* Subcortex -> Cortex (LGN to primary visual cortex, V1 in the occipital lobe) * Beyond V1: Visual information travels along the ventral stream (WHAT pathway) and the dorsal stream (WHERE pathway)
What did the Mishkin and Ungerleider (1982) study demonstrate?
The study demonstrated that visual information travels along two pathways beyond V1:
* Ventral Stream (WHAT pathway) involved in pattern vision * Dorsal Stream (WHERE pathway) involved in spatial vision
What are the coding properties of neurons along the visual system?
Rods and Cones: Changes in illumination
* Retinal Ganglion (RG) Cells: Spots of light * LGN Cells: Spots of light * V1 Cells: Lines of different orientations * Beyond V1 (Ventral Visual Stream): Complex features (e.g., IT cortex cells responding to faces)
What is retinotopic mapping?
Retinotopic mapping is the point-to-point mapping of the external world onto a brain area. It is present in V1 and before but not beyond V1.
How does lateral inhibition enhance visual perception?
Lateral inhibition enhances contrast and brightness contrast through center-surround architecture of retinal ganglion cells (RGCs).
What is the Hermann Grid Illusion and how is it explained?
The Hermann Grid Illusion involves seeing black spots at the intersections of a grid, explained by the center-surround architecture of RGCs which send signals that make intersections appear darker than the streets.
How do retinal ganglion cells (RGCs) respond to light and dark dots?
RGCs send maximum signals when presented with light or dark dots, but send no signal when bathed in diffuse light or darkness.
What happens to the Hermann Grid Illusion when you focus directly on an intersection?
The black dot vanishes because at the fovea, cones are packed more tightly and the RGC assembly is smaller, falling completely within the intersection and street.
How are images built neurally from basic visual information?
Going from dots (RGCs) to lines (V1 cells)
* From lines to complex features and objects (e.g., faces in the IT cortex)
