Greg Detre
26/11/99
visual + retina
how complex can you get?
why don't we have just a spectrometer � why contrast etc.?
process + remove redundant information
US failed to construct anything fast enough
brain: short cuts assume ≠ 4 inch bus close
store of expected objects�������� fuzzy matching � undefined
chain: single cell respond to face/hand in monkeys
don�t know enough beyond corners + lines + movement
retina is backwards
if evolution, why not like limulus(???)
no AP until ganglion cells (3 cells down, transmitter released)
all hyper-polarising���������� very close together, no conduct nerves
retinal, bipolar, horizontal, ganglion (first AP), amacrine
complicated depolarising mechanisms
looking for contrast not absolute light
retina � very actively maintained system
raptors � detect in the IR � modified pigment
bad colour vision������� rodents � molecules in � which are IR-detectable�������� raptors see tracks
different opsin � different � sensory range
owls � asymmetric hearing����������������� birds � colour droplets
snakes � IR detector (�)
fibres � middle of cortex then out � different layers
2 different eyes����������� orientation������������ monkeys/cats different numbers of layers
visual cortex ordered to store semi-logically � different parameters
3D matrix � position, orientation, binoc��������� colour
why cont(???) movement�������������� focusing a fovea
eye muscles tremor����������������� saccadic rhythm (reading)
(inhib by curare)�������� not vector-based detection system
bleaching
no reason why it should be orderly
analyse different parts of the matrix toglean information about depth etc.
colour � pairs of opposites, not spatially localised
blue receptiveness
stored � anatomical changfes in synapse
shorter term � local circuit
long-term synaptic bouton made
array being constantly interrogated���������� extracted to memory
Hubel & Wiesel cats - usually show a bar
looking at the surround, infinte �/span> grating
sinosoidal easier to generate than a square wave
the more familiar the image, the � the grade image you need
film company, face recognition library
sensory cortex, cerebellum, ganglion in medulla � orderly
MRI � see region of the brain with bigger bloodflow if deoxy