Stop & Check Questions in Module 6

• Through which mechanism do we perceive low-frequency sounds (up to about 100 Hz)?

  At low frequencies, the basilar membrane vibrates in synchrony with the sound waves, and each responding axon in the auditory nerve sends one action potential per sound wave.
• How do we perceive middle-frequency sounds (100 to 4000 Hz)?

  At intermediate frequencies, no single axon fires an action potential for each sound wave, but different axons fire for different waves, and so a volley (group) of axons fires for each wave.
• How do we perceive high-frequency sounds (above 4000 Hz)?

  At high frequencies, the sound causes maximum vibration for the hair cells at one location along the basilar membrane.
• How is the auditory cortex like the visual cortex?

  Any of the following:

  (a) Both vision and hearing have “what” and “where” pathways.

  (b) Areas in the superior temporal cortex analyze movement of both visual and - auditory stimuli. Damage there can cause motion blindness or motion deafness.

  (c) The visual cortex is essential for visual imagery, and the primary auditory cortex is essential for auditory imagery.

  (d) Both the visual and auditory cortices need normal experience early in life to develop normal sensitivities.
• What is one way in which the auditory and visual cortices differ?

  Damage to the primary visual cortex leaves someone blind, but damage to the primary auditory cortex merely impairs perception of complex sounds without making the person deaf.
• What evidence suggests that human concepts rely on activation of the relevant sensory or motor areas of the cortex?

  People with damage to the auditory cortex regard many sound-related words, such as “thunder,” as if they were nonwords.
• Which method of sound localization is more effective for an animal with a small head? Which is more effective for an animal with a large head? Why?

  An animal with a small head localizes sounds mainly by differences in loudness because the ears are not far enough apart for differences in onset time to be useful. An animal with a large head localizes sounds mainly by differences in onset time because its ears are far apart and well suited to noting differences in phase or onset time.
• What evidence suggests that absolute pitch depends on special experiences?

  Absolute pitch occurs almost entirely among people who had early musical training and is also more common among people who speak tonal languages, which require greater attention to pitch.
• Which type of hearing loss—conductive deafness or nerve deafness—would be more common among members of rock bands and why?

  Nerve deafness is common among rock band members because their frequent exposure to loud noises causes damage to the cells of the ear.
• Why do many older people have trouble hearing speech in spite of wearing hearing aids?

  In some cases the language areas of the cortex have become less responsive. Also, auditory areas of the brain have decreased levels of inhibitory neurotransmitters, and the result is decreased ability to focus attention on one speaker in a noisy environment.
• People with damage to the vestibular system have trouble reading street signs while walking. Why?

  The vestibular system enables the brain to shift eye movements to compensate for changes in head position. Without feedback about head position, a person would not be able to correct the eye movements, and the experience would be like watching a jiggling book page.
• How do jalapeños produce a hot sensation?

  Jalapeños and other hot peppers contain capsaicin which stimulates receptors that are sensitive to painful heat.
• In what way is somatosensation several senses instead of one?

  We have several types of receptors, sensitive to touch, heat, and so forth, and different parts of the somatosensory cortex respond to different kinds of skin stimulation.
• What evidence suggests that the somatosensory cortex is essential for the conscious perception of touch?

  People are conscious of only those touch stimuli that produce sufficient arousal in the primary somatosensory cortex. Also, cells in the somatosensory cortex respond to what someone experiences, even if it is an illusion.
• How do the responses to skin sensations differ between the somatosensory cortex and the insular cortex or the anterior cingulate cortex?

  The somatosensory cortex is necessary for conscious perception of the location and type of skin sensation. The insular cortex and anterior cingulate cortex respond to the pleasantness.
• Suppose you suffer a cut through the spinal cord on the right side only. For the part of the body below that cut, will you lose pain sensation on the left side or the right side? Will you lose touch sensation on the left side or the right side?

  You will lose pain sensation on the left side of the body because pain information crosses the spinal cord at once. You will lose touch sensation on the right side because touch pathways remain on the ipsilateral side until they reach the medulla.
• In what ways are hurt feelings similar to physical pain?

  Hurt feelings activate the cingulate cortex, just as physical pain does. Also, acetaminophen decreases hurt feelings (as well as pleasant feelings).
• Why do opiates relieve dull pain but not sharp pain?

  Endorphins block messages from the thinnest pain fibers, conveying dull pain, but not from thicker fibers, carrying sharp pain.
• How do ibuprofen and other nonsteroidal anti-inflammatory drugs decrease pain?

  Anti-inflammatory drugs block the release of chemicals from damaged tissues, which would otherwise magnify the effects of pain receptors.
• In what way is chronic pain like memory?

  One mechanism for memory is that repeated stimulation at a synapse increases its later response to the same type of stimulation. Similarly, repeated pain messages increase a synapse’s response to similar stimuli, and therefore the result is chronic pain.
• Do opiates increase or decrease itch sensations?

  Opiates increase itch by blocking pain sensations. (Pain decreases itch.)
• Suppose someone suffers from constant itching. What kinds of drugs might help relieve it?

  Two kinds of drugs might help—histamines or capsaicin—depending on the source of the itch.
• Suppose you find a new, unusual-tasting food. How could you determine whether we have a special receptor for that food or whether we taste it with a combination of the other known taste receptors?

  You could test for cross-adaptation. If the new taste cross-adapts with others, then it uses the same receptors. If it does not cross-adapt, it may have a receptor of its own. Another possibility would be to find some procedure that blocks this taste without blocking other tastes.
• If someone injected into your tongue a chemical that blocks the release of second messengers, how would it affect your taste experiences?

  The chemical would block your experiences of sweet, bitter, and umami but should not prevent you from tasting salty and sour.
• Why are supertasters more sensitive to tastes than other people are?

  They have more taste buds.
• In what way do olfactory receptors resemble metabotropic neurotransmitter receptors?

  Like metabotropic neurotransmitter receptors, an olfactory receptor acts through a G protein that triggers further events within the cell.
• What is the mean life span of an olfactory receptor?

  Most olfactory receptors survive a little more than a month before dying and being replaced.
• What factors contribute to individual differences in olfactory sensitivity?

  People differ in olfactory sensitivity because of genetics, age, and gender.
• What evidence indicates that people learn their synesthetic associations, at least in some cases?

  Some people have letter-color synesthesia that matches the colors of refrigerator magnets they played with in childhood.
• If someone reports seeing a particular letter in color, in what way is it different from a real color?

  Someone who perceives a letter as yellow (when it is actually in black ink) can nevertheless see it on a yellow page.