The visual system

IV

The visual cortices

The primary visual pathway

From perret-optic.ch

Primary vision

Structure of the primary visual cortex-

The headquartes

Information flow

2/3

1

4b4a

4cα

5

4cβ

6

PM

Higher areas

Higher areas

Intra V1

Intra V1

Superior colliculus, pulvinar, pons

LGN, thalamic interneurons

Visual columns-RFs and orientations

200 μm

Orientation map

How does orientation selectivity arise?

Ferster et al. (1996), Reid & Alonso (1996)

Receptive fields in different cortical layers

Layers IV and VI

Simple cells

Layers II and III

Complex cells

Are complex cells more complex, or just more active?

Adapted from Kandel et al. (2000)

Complex cell!

Are complex cells more complex, or just more active?

Crowder et al. (2007)

Higher visual areas:The Where and What

Magnocellular!

Parvocellular!

Higher visual areas:Inferotemporal cortex

Fusiform face area

Halle Berry Cells

Halle

Berry

Contour perception is fed back to V1

Lamme (1995)

Higher visual areas:The Where and What

Magnocellular!

Parvocellular!

Motion perception is fed back to V1

Muckli et al. (2005)

Summary IV – The visual cortex…

• continues the segregation in magno- and

parvocellular pathway as the Where and What

pathway

•is segregated into six layers, all of which fulfill

different tasks in coordinating activity from the

thalamus, other cortical areas and the brain stem

• is organized in response preference columns,

according to ocular dominance, stimulus orientation,

contrast, length etc.

• contains neurons with simple and complex

responses

•is in constant feedback-feedforward loops with the

Where and the What pathways