4.2 Flashcards
Which comes first: migration, synaptogenesis, or
myelination?
Migration occurs first
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 14Carbon 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, indicating that some of those neurons formed after birth.
What was Sperry’s evidence that axons grow to a specific target instead of attaching at random? (in frogs)
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.
If axons from the retina were prevented from showing spontaneous activity during early development, what would be the probable effect on development of 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.
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 (NGF)
At what age does a person have the greatest number of neurons— early in life, during adolescence, or during adulthood?
The neuron number is greatest 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 devel- oping 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 turned in the direction it had associated with lights.
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 of 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.
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 in the motor cortex. If the sensory representation of two fingers overlaps too much, the person cannot feel them separately or move them separately.
Why is immaturity of the prefrontal cortex not a satisfactory
explanation for risky behaviors in adolescents?
As teenage years progress, risky behaviour seems to increase. Even though the prefrontal cortex is becoming more mature.
What is one way in which older adults compensate for less efficient brain functioning?
Many of them compensate by activating additional brain areas.
