VISUAL PATHWAYS Organization of LGN of thalamus Organization of Visual Cortex What Stream How Stream The Binding Problem

LGN Organization Retinotopic maps Six Layers – Three from ipsilateral eye – Three from contralateral eye

Visual Cortex Organization Location columns Orientation columns Ocular dominance columns Hypercolumns

What and How Streams What Stream (Ventral Pathway) – Pattern recognition – Projects to the temporal lobes How Stream (Dorsal Pathway) – Location and movement – Projects to the parietal lobes Crosstalk between pathways

What Stream Input from Parvocellular ganglions P-cell layers in LGN Visual Cortex Inferotemporal Cortex - form

More on the Inferotemporal Cortex Some neurons respond best to faces – Fusiform Face Area Damage causes prosopagnosia Experience determines what patterns the neurons respond to

How Stream Input from Magnocellular ganglions M-cell layers in LGN Visual Cortex Medial Temporal Cortex (MT) - movement Parietal Lobes

The Binding Problem Information about the same stimulus is represented in many different brain areas How do we combine this information into a unitary perception? – Synchronized firing of neurons – Waves of firing

Sensory Coding Sensory Code - pattern of neural responses that represents perception of the environment – Specificity Coding - specialized neurons respond to particular stimuli – Distributed Coding - the pattern of response of many neurons