Lesson 3: Neural Processing Flashcards
Where is lateral inhibition performed?
horizontal and amacrine cells transmit inhibitory signals across the retina
Chevreul illusion/ staircase illusion
perceived light and dark bands at the borders, which are not present in the actual physical stimuli
Mach bands
Light and dark bands created at fuzzy borders
When is the Chevreul illusion decreased?
when the dark to light progression of the staircase pattern is
opposite to the luminance ramp
When is the Chevreul illusion increased?
if the pattern progresses in the same direction as the ramp
Limulus experiment
The Limulus eye is made up of hundreds of tiny structures called ommatidia, and each ommatidium has a small
lens on the eye’s surface that is located directly over a single receptor. Possible to illuminate and record from a single receptor without illuminating its neighboring receptors. A= large response, A+B = medium response, and intense B= decrease in A. Explained by lateral inhibition
Hermann grid
straight lines = dark spots at the intersections
curvy lines= dark spots eliminated
Chevreul illusion
four gray rectangles placed side by side, ranging from light on the left to dark on the right.
What are the optic nerves made out of?
nerves, nerve fibers that are the axons of the retinal ganglion cells
receptive field
“the retinal region over which a cell in the visual system can be influenced (excited or inhibited) by light”
- receptive fields of many different nerve fibers overlap
center-surround organization (cats)
the area in the “center” of the receptive field responds differently to light than the area in the “surround” of the receptive field
How are the receptive fields of a cat separated?
excitatory center = excitatory area, increase in firing
inhibitory surround = inhibitory area, decrease in firing
center-surround antagonism
interactions between the center and surround regions of the receptive fields of photoreceptor cells in the retina
where are the receptive fields located?
on receptor surfaces because that is where the stimuli are received. The retina in the case of the eye.
Where do signals leaving the eye in the optic nerve travel to? (3)
lateral geniculate nucleus (LGN 90%), then the occipital lobe/striate cortex/area V1 (visual receiving area), the superior colliculus (controlling movements of the eyes 10%)
Complex cells
respond only when a correctly oriented bar of light moves across the entire receptive field
end-stopped cells
fire to moving lines of a specific length or to moving corners or angles
Accidental finding
Hubel and Wiesel’s finding that some neurons in the cortex respond only to oriented lines and others respond best
to corners was an extremely important discovery because it
extended the idea first proposed in connection with center-surround receptive fields that neurons respond to some patterns of light and not to others
feature detectors
simple, complex, and end-stopped cells
sensory coding
sensory code refers to how neurons represent various characteristics of the environment.
selective rearing
animal is reared in an environment that contains only certain types of stimuli, then neurons that respond to these stimuli will become more prevalent
specificity coding
the object can be represented by the firing of a specialized neuron that responds only to that object
Sparse coding
particular object is represented by a pattern of firing of only a small group of neurons, with the majority of neurons remaining silent
