Gain Control Flashcards
what is gain control
a universal thing that happens everywhere in brain -computerisation theory
what does gain control allow
neurons to control sensitivity and we need it because neurons have to code things that have large dynamic ranges
what does gain control lead to
brain uncover a large range of senses - even though can only sense small range of stimuli
what is the visual system
retina to LGN to cortex
what is contrast
average luminance variation in part of visual field
what is contrast in the visual system
the currency
the grey area are measured neural responses in LGM
what is adaptation
wave photons show wahts happening in LGN
what is LGN
cells are tuned for eye of origin but not for orientation or spatial frequency
what does contrast gain control equation say
neuronal inputs are divided by sum of local averge response
what is V1
aka striate cortex, area 17
describe measurements of gain control in V1
for low contrast- not much response
high contrast things saturate away
describe gain control ealry
happens before or in LGN
short-range gain control is very different when you put the mask into other eye
describe gain control in visual cortex
neural activity moderated by local activity of group
receptive fields in cortex are large so normalisation jappens over wide regions
what are 4 signatures of cortical gain control
long range tuning (orientation) slow(neurons in cortex dont like fast flicker-unlike LGN) complex features(facial expression etc)
describe visual perception
u can measure neural responses using nothing more than CRT screen
