Greg Detre
26/11/99
contrast = (a � b)/average
sino-soidal grating = way of coding the size selectivity
visual acuity = 60 cycles/degree
cortex introducing filters of � complexity
decomposing the image into different size levels of spatial frequency � efficient coding
Blakemore � subjects stare at high frequency on TV for 30 mins
fatigued the neurons � indicate tuning curve in human visual system
depth � positional disparity on the retina � cues�� ����� stereopsis
colour
bundles up information in the striate cortex
Hubel + Wiesel
columnar representation of orientation + binocularity
orderly representation at the level of the minimum of abstract orientation
cortical module � hypercolumn (ocularity/orientation)���� ����� rectilinear model
found out that in the upper layers of the striate cortex, some non-orientated neurons
regularly distributed non-oriented blobs � more specific for colour-processing
IV = input lamina for all areas
relayed � upper areas (multi-synaptic relay)
� to V then VI
output from layers II, III, V, VI
VI feedback output � thalamocortical
II, III � cortex
V = dominant sub-cortical non-thalamic output zone
superior colliculus = sensorimotor
dorsal ventral stream
examples
spatial form conveyed by colour (p-cells)
spatial form present in movement (m-cells)
selection for direction of movement or velocity
relatively unselective for the form of the object
cortical cell will only respond to dual sinosoidal pattern if tuned to oblique
MT pathway = min form analysis, mainly motion
motion blindness
achromatopsia
floodlight with different colours
so that spectral reaching the eye is very different
still able to see the �tune� colour
if remove other colours for comparison, lose colour constancy (V4)
face recognition
receptive field �, for generalising independent of position