Chapter 3: Neural Processing Flashcards
Lateral inhibition
Inhibition that is transmitted across the retina
Chevreul illusion (staircase illusion)
The 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
Describe the experiment that demonstrated the effect of lateral inhibition in the Limulus (Test Yourself 3.1)
Used the crab to demonstrate how lateral inhibition can affect the response of neurons in a circuit
Illuminating of the neighbouring receptors of at B inhibited the firing caused by stimulation of receptor A
The decrease in the firing of receptor A is caused by lateral inhibition that is transmitted from B to A across the limulus eye by the fibers if the lateral plexus
Receptive field
The area that caused the neuron to fire the nerve fiber’s (a ganglion cell, not a receptor)
The region of the retina that must receive illumination in order to obtain a response in any given fiber
The area of the retina that, when stimulated, influences the firing of the neurons
Excitatory area
Presenting a spot of light to the center increases firing
Inhibitory area
Presenting a spot of light to the center decreases firing
Inhibitory-center, excitatory surround receptive field
Responds with inhibition when the center is stimulated and excitation when the surround is stimulated
Excitatory-center, inhibitory-surround receptive field
Responds with excitation when the center is stimulated and inhibtion when the surround is stimulated
Excitatory-center, inhibitory-surround receptive field
Responds with excitation when the center is stimulated and inhibition when the surround is stimulated
Important Rule
The receptive field is always on the receptor surface because this is where the stimuli are received
Lateral geniculate nucleus
(LGN) signals leaving the eye in the optic nerve travel here
The occipital lobe is the Visual receiving area
The place where signals from the retina and LGN first reach the cortex
Superior colliculus
Plays an important role in controlling the movements of the eye
Striate cortex
The visual receiving area
- called this because it has a striped appearance when viewed in cross sectional or area V1 to indicate that it is the first visual area in the cortex
Simple cortical cells
Cells with side-by-side receptive fields
Excitatory and inhibitory area arranged side by side. Responds best top bars of a particular orientation
Complex cells
Respond best to bars of a particular orientation.
-only respond when a correctly orientated bar of light moves across the entire receptive field
(not stimulated by stationary flashes of light)
End stopped cells
Fire to moving lines of a Specific length or to moving corners or angles (responded best to a medium sized corner that is moving upward)
Page 15 of Chapter 3
Types of cells and their characteristics of receptive field
Selective adaptation
Firing causes neurons to eventually become fatigued or adapt.
This adaption cases two physiological effects:
1) The neurons firing rate decreases
2) The neuron fires less when the stimulus is immediately presented again
Contrast threshold
The minimum intensity difference between two adjacent bars that can just be detected
Inferotemporal cortex
When removed in monkeys, they could not tell the difference in objects
Sensory coding
Where the sensory code refers to how neurons represent various characteristics of the environment
Specificity coding
The idea that an object could be represented by the firing of a specialized neuron that responds only to that object
Population coding
The representation of a particular object by the pattern of firing of a large number of neurons
Sparse coding
Occurs when a particular object is represented by a pattern of firing of only a small group of neurons with the majority of neurons remaining silent
Contextual modulation
The effect of stimulating outside the receptive field
Hartline noted that the receptive fields of many different nerve fibers overlap
This means that shining light on a particular point on the retina activates many ganglions cell fibers
The optic nerve which leaves the back of the eye, contains about
Contains about 1 million optic nerve fibers in the human
Cats receptive field are arranged in
a center-surround organization, in which the area in the ‘center’ of the receptive field responds differently to light than the area in the surround of the receptive field
Center-surround antagonism
Small spot of light presented to the excitatory center of the receptive field causes a small increase in the rate of nerve firing (increasing that light size increases the response, but do not go into the inhibition zone)
Selective rearing
The idea is that if an animal is reared in an environment that contains only certain types of stimuli, then neurons at respond to these stimuli will become more prevalent
Neural plasticity or experience-dependant plasticity
The idea that the response properties of a neuron can be shaped by perceptual experience (having an animal that grew up in an environment with only vertical lines will lead that animals visual system having neurons that respond predominately to verticals)
Spatial submasion (summation?)
If convergence is high, then spatial summation is high
Spatial summation means that the process of something over space because of convergence. One ganglion cell where that receptive field for that ganglion cell is 120 rods, so it summates over that field.
Rods and cones synapse with cells
do not bother with horizontal or amacrine cells
Rods and cones synapse with bipolar cells, which then synapse with ganglion cells
