S&P 7 - Receptive Fields and Feature Detectors

how many photoreceptors per eye?

~105 million

how many ganglion cells per eye?

~1 million

receptive field

area of sensory neuron that, when stimulated, results in a change in the activity of the neuron

on cells

cells that activate when a stimulus appears (ex. light turns on)

off cells

cells that activate when a stimulus disappears (ex. light turns off)

on-off cells

cells that activate when a stimulus appears or disappears

center-surround antagonism

on-center, off-surround cells - firing rate increases when light hits the center of the ganglion cell’s receptive field

off-center, on-surround cells - firing rate increases when light hits the outside of the ganglion cell’s receptive field

receptive fields of LGN cells

respond best to small spots of light

also respond to bars of light

& stimuli that move across the receptive field in any direction

receptive fields in simple cortical cells (visual cortex)

some on and off areas, some center-surround

respond best to bars of light

more specialized than LGN cells

have preferred orientation

receptive fields in complex cortical cells (visual cortex)

larger quantity than simple

respond to both light and dark stimuli

some respond preferentially to color, motion, size, length