Studied by 7 peopleWhich comes first, migration, synaptogenesis, or myelination?
Migration (migration occurs early in development, while synaptogenesis occurs next and throughout life, and myelination is later and also takes decades)
New receptor neurons form in which sensory system?
Olfaction
What evidence indicates that new neurons form in the human hippocampus and basal ganglia?
The mean carbon concentration of the DNA of human neurons in the hippocampus and basal ganglia corresponds to a level slightly more recent than the year the person was born.
What was Sperry's evidence that axons grow to a specific target instead of attaching at random?
If he cut a newt's eye and inverted it, axons grew back to their original targets, even though the connections were inappropriate to their new positions on the eye.
Proliferation
the production of new cells
stem cells
undifferentiated cells that divide and produce daughter cells that develop more specialized properties
migrate
movement of brain neurons
differentiates
to develop the axon and dendrites that give a neuron its distinctive properties
synaptogenesis
formation of synapses
myelination
process by which glia produce the insulating fatty sheaths that accelerate transmission in many vertebrate axons
neural darwinism
principle of competition among axons
If axons from the retina were prevented by showing spontaneous activity during early development, what would be the probable effect of development on the thalamus?
The axons would attach based on a chemical gradient but could not fine-tune their adjustment based on experience. Therefore, the connections would be less precise.
nerve growth factor (ngf)
a protein that promotes the survival and growth of axons in the sympathetic nervous system and certain axons in the brain
apoptosis
a programmed mechanism of cell death
neurotrophin
a chemical that promotes the survival and activity of neurons
fetal alchohol syndrome
a group of alcohol-related birth defects that includes both physical and mental problems
What process assures that the spinal cord has the right number of axons to innervate all the muscle cells?
The nervous system builds more neurons than it needs and discards through apoptosis those that do not make lasting synapses.
What class of chemicals prevents apoptosis in the sympathetic nervous system?
Neurotrophins, such as nerve growth factor.
At what age does a person have the greatest number of neurons?
Early in life
Anesthetic drugs and anxiety-reducing drugs increase activity of GABA, decreasing brain excitation. Why would we predict that exposure to these drugs might be dangerous to the brain of a fetus?
Prolonged exposure to anesthetics or anxiety-reducing drugs might increase apoptosis of developing neurons. Increased GABA activity decreases excitation, and developing neurons undergo apoptosis if they do not receive enough excitation.
In the ferret study, how did the experimenters determine that visual input to the auditory portions of the brain actually produced a visual sensation?
They trained the ferrets to respond to stimuli on the normal side, turning one direction in response to sounds and the other direction to lights. Then they presented light to the rewired side and saw that the ferret again turn in the direction it had associated with lights.
An enriched environment promotes growth of axons and dendrites in laboratory rodents. What is known to be one important reason for this effect?
Animals in an enriched environment are more active, and their exercise enhances growth of axons and dendrites.
far transfer
benefit from practicing something less similar (weak effect)
Name two kinds of evidence indicating that touch information from the fingers activates the occipital cortex of people blind since birth.
First, brain scans indicate increased activity in the occipital cortex while blind people perform tasks such as feeling two objects and saying whether they are the same or different. Second, temporary inactivation of the occipital cortex blocks blind people's ability to perform that task, without affecting the ability of sighted people.
Which brain area shows expanded representation on the left hand in people who began practicing stringed instruments in childhood and continued for many years?
Somatosensory cortex (postcentral gyrus) of the right hemisphere
focal hand dystonia
(musician's cramp) a disorder where one or more fingers is in constant contraction or where moving one finger independently of others is difficult
What change in the brain is responsible for musician's cramp?
Extensive practice of violin, piano, or other instruments causes expanded representation of the fingers in the somatosensory cortex, as well as displacement of representation of one or more fingers int he motor cortex. If the sensory representation of two fingers overlaps too much, the person cannot feel them or move them separately.
In early development, what is the relationship between the sensory systems and muscle movements?
The first muscle movements occur before the sensory systems develop.
Which parts of the cerebral cortex are most likely to deteriorate in Alzheimer's disease and other conditions?
The areas that mature at the latest age, such as the prefrontal cortex.
In which areas of the human brain do some new neurons develop during adulthood?
The hippocampus and the basal ganglia.
When Sperry cut a newt's optic nerve and turned the eye upside down, what happened?
Axons of the optic nerve grew back to their original targets.
In the sympathetic nervous system, which of the following prevents apoptosis?
Nerve growth factor
Why does the spinal cord have the right number of axons to innervate all the muscle cells?
The spinal cord makes an excess of neurons, but those that fail to innervate a muscle die.
At what age does a person have the largest number of neurons?
Before or shortly after birth
If a pregnant woman drinks alcohol, alcohol harms the brain of the fetus not only while it is in the system, but also while it is washing away after drinking. What is the danger while alcohol is washing away?
Overstimulation at glutamate synapses can poison the mitochondria.
In the ferret study, what evidence indicated that visual input to the auditory portions of the brain actually produced a visual sensation?
Ferrets that learned to turn one way in response to light in the normal eye turned the same way to light in the rewired eye.
An enriched environment including social interactions promotes growth of axons and dendrites in laboratory rodents. What else can produce the same effect?
Physical activity
According to most research, what are the effects of computerized programs to practice memory skills?
Temporary improvement of the skills that were practiced.
If a person is born blind, what happens to the occipital ("visual") cortex?
Its cells become responsive to touch or hearing.
In people who practice violin or other stringed instruments for many years, what changes in the cerebral cortex?
A larger than average portion of the cortex responds to fingers of the left hand.
What causes musicians cramp?
Rewiring of the cerebral cortex
closed head injury
a result of a sharp blow to the head that does not puncture the brain
Stroke (cerebrovascular accident)
result of interrupted blood flow to the brain resulting from either a blood clot or a ruptured artery
hemorrhage
type of stroke resulting from a ruptured artery
ischemia
a type of stroke resulting from a blood clot
edema
accumulation of fluid
tissue plasminogen activator (tPA)
drug that breaks up blood clots
What are the two kinds of stroke, and what causes each kind?
The more common form, ischemia, is the result of an occlusion of an artery. The other form, hemorrhage, is the result of a ruptured artery.
Why is tPA not helpful in cases of hemorrhage?
The drug tPA breaks up blood clots, and hemorrhage results from a ruptured blood vessel, not a blood clot.
Diaschisis
decreased activity of surviving neurons after damage to other neurons
After someone has had a stroke, would it be best (if possible) to direct stimulant drugs to the cells that were damaged or somewhere else?
It is best to direct a stimulant drug to the cells that had been receiving input from the damaged cells. Presumably, the loss of input has produced diaschisis.
denervation supersensitivity
(receptor supersensitivity) increased sensitivity to neurotransmitters by a postsynaptic neuron after loss of input
Is collateral sprouting a change in axons or dendritic receptors?
Axons
Is denervation supersensitivity a change in axons or dendritic receptors?
Dendritic receptors
collateral sprouts
newly formed branches of an axon
phantom limb
a continuing sensation of an amputated body part
What is responsible for the phantom limb experience?
Synapses that used to receive input from the now amputated part become vacant. Axons representing another part of the body take over those synapses. Now stimulation of this other part activates the synapses associated with the amputated area, but that stimulation feels like the amputated area.
deafferented
to remove or disable the sensory nerves from a body part
A monkey that loses sensation from one arm stops using it, but a monkey that loses sensation from both arms does use them. Why?
A monkey that loses sensation in one arm is capable of moving it, but finds it easier to walk with the three intact limbs. When both arms lose their sensations, the monkey is forced to rely on them.
Tissue plasminogen activator (tPA) is helpful in reducing the effect of a stroke only under which of these conditions?
It is helpful only if administered within the first hours after a stroke.
What would be the purpose of giving a drug that stimulates dopamine receptors to a stroke patient?
To combat diaschisis
Name two procedures that decrease the damage caused by strokes in laboratory animals, although physicians so far have seldom tried them with people.
Decreased body temperature and cannabinoids.
In which species, if any, can axons regrow in the spinal cord?
In fish
Where does collateral sprouting take place?
In the axon
Where does denervation supersensitivity take place?
At synapses
What causes the phantom limb experience?
Reorganization of the sensory cortex
Suppose a patient uses only the right arm following injury that blocked all sensation from the left arm. Of the following, which is the most promising therapy?
Tie the right arm behind the person's back.
What was Ibn al-Haytham's evidence that we see only because light enters the eyes, not by sending out sight rays?
First, you can see distant objects such as stars far faster than we could imagine any sight rays reaching them. Second, when light strikes an object, we see only the light rays that reflect off the object ad into the eyes.
law of specific nerve energies
statement that whatever excites a particular nerve always sends the same kind of information to the brain
If someone electrically stimulated the auditory receptors in your ear, what would you perceive?
Because of the law of specific nerve energies, you would perceive it as sound, not as shock. (Of course, a strong enough shock would spread far enough to excite pain receptors also).
If it were possible to flip your entire brain upside down, without breaking any of the connections to sense organs or muscles, what would happen to your perceptions of what you see, hear, and so forth?
Your perceptions would not change. The way visual or auditory information is coded in the brain does not depend on the physical location within the brain. Seeing something as "on top" or "to the left" depends on which neurons are active but does not depend on the physical location of those neurons.
pupil
opening in the center of the iris in which light enters through
retina
the rear surface of the eye which is lined with visual receptors
bipolar cells
type of neuron in the retina that receives input directly from the receptors
ganglion cells
type of neuron in the retina that receives input from the bipolar cells
optic nerve
ganglion cell axons that exit through the back of the eye and continue to the brain
blind spot
area at the back of the retina where the optic nerve exits; it is devoid of receptors
What makes the blind spot of the retina blind?
The blind spot has no receptors because it is occupied by exiting axons and blood vessels.
midget ganglion cells
ganglion cells in the fovea of humans and other primates
rods
type of retinal receptor that detects brightness of light
cones
type of retinal receptor that contributes to color perception
photopigments
chemicals contained in rods and cones that release energy when struck by light
You sometimes find that you can see a faint star on a dark night better if you look slightly to the side of the star instead of straight at it. Why?
If you look slightly to the side, the light falls on an area of the retina with more rods and more convergence of input.
If you found a species with a high ratio of cones to rods in its retina, what would you predict about its way of life?
We should expect this species to be highly active during the day and seldom active at night.
trichromatic theory (young-helmoltz theory)
theory that color is perceived through the relative rates of response by three kinds of cones, each one maximally sensitive to a different set of wavelengths
visual field
area of the world that an individual can see at any time
negative color afterimage
result of staring at a colored object for a prolonged length of time and then looking at a white surface, the image is seen as a negative image, with a replacement of red with green, green with red, yellow and blue with each other, and black and white with each other
opponent-process theory
idea that we perceive color in terms of opposites
According to the opponent-process theory, under what circumstance would you perceive a white object as blue?
If you stared at a bright yellow object for a minute or so and then looked at a white object, it would appear blue.
According to the opponent process theory, what causes you to perceive red?
Activity of the long-wavelength cone is not sufficient. A perception of red occurs only if the long-wavelength cone has a high ratio compared to the other two types of cones.
retinex theory
concept that the cortex compares information from various parts of the retina to determine the brightness and color for each area
When a television set is off, its screen appears gray. When you watch a program, parts of the screen appear black, even though more light is actually showing on the screen than when the set was off. What accounts for the black perception?
The black experience arises by contrast with the brighter areas around it.
Why is color vision deficiency a better term than color blindness?
Very few see the world in black and white. The more common condition is difficulty discerning red from green.
color vision deficiency
inability to perceive color differences
What happens when you see something?
Light rays reflect off the object and strike your retina.
What is the route from retinal receptors to the brain?
Receptors connect to bipolars, which connect to ganglion cells, which send axons to the brain.
Where does the optic nerve exit from the retina?
At the blind spot
Why is vision most acute at the fovea?
Each receptor in the fovea has a direct line to the brain
Vision in the periphery of the retina has poor sensitivity to detail but great sensitivity to faint light. Why?
Toward the periphery, the retina has more convergence of input.
Why do some people have greater than average sensitivity to brief, faint, or rapidly changing visual stimuli?
They have more axons from the retina to the brain.
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