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Biol 448: Final > Bat Echolocation > Flashcards

Bat Echolocation Flashcards

1
Q

What did Lazzaro find about bats?

A
  • producing sound and being able to hear is vital for navigating
  • removed eyes = fine
  • plugged ears = not fine
  • tubes in ears = fine
  • plugged tubes in ears = not fine
  • tapped mouths shut = not fine
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2
Q

What did Griffin find about bats?

A
  • animal rights activist
  • using theory determined that they use ultrasound and coined the term echolocation
  • used an ultrasound detector made by Peterson
  • discovered that bats hit or touched a wire more if it was thinner (<0.5mm)
  • as bats got closer to target their pulse rate increased and pulse duration decreased
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3
Q

What did Simmons find about bats?

A
  • use delay between pulse and echo
  • trained bats to land on one of two platforms
  • used speakers to play back a phantom echo
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4
Q

What are the two components of the emitted ultrasound? What environment is each useful in?

A
  • Frequency modulated (FM) component: useful in forests

- Constant frequency (CF) component: useful in open spaces

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5
Q

What kind of bat is Eptesicus?

A
  • FM bat

- produce broad band signal 100 khz to 25 khz

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6
Q

How is distance deciphered?

A
  • use time delay from pulse to echo
  • FM bats use frequency analysis and time analysis
  • echo intensity: far away if weak
  • frequencies returned: high frequencies don’t travel far
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7
Q

How is the subtended angle deciphered?

A
  • the loudness of the echo determines the subtended angle

- problem: could be small and close or far away and large

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8
Q

How is absolute size deciphered?

A
  • using a combination of distance info (delay) and subtended angle (amplitude)
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9
Q

What does a azimuth angle tell the bats and how is it found?

A
  • location in the horizontal plane

- by binaural cues

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10
Q

What does elevation tell the bats and how is it found?

A
  • location in vertical plane

- moving ears in various positions

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11
Q

What kind of bat is rhinolophus?

A
  • CF-FM bat
  • pulses with long constant frequency then rapid downward FM sweep
  • sensitive to 83 KHz
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12
Q

What is the doppler shift problem?

A
  • if the predator and prey are still, the frequency will return the same
  • if predator and prey are moving towards each other, the frequency will increase
  • problem: returning frequency could be outside of species specific frequency range
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13
Q

How do bats compensate for the doppler shift problem? What research was done to discover this?

A
  • when moving forward they lower the frequency emitted so the returning frequency will be within the specific range
  • bats placed on swing and recorded pulses
  • also means that the loud pulse emitted is out of their range and they avoid deafening
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14
Q

What is the acoustic fovea?

A
  • increase in sensitivity to a narrow range of frequencies

- results from a range of adaptations

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15
Q

What kind of bat is Pteronotus?

A
  • CF-FM bat with several harmonics

- harmonic at 60 Hz is the loudest

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16
Q

What are the pulse and echo also called?

A
  • pulse = noise

- echo = signal

17
Q

How is velocity determined by the bats?

A
  • analyze the doppler shift echoes to determine if the bat is gaining or not
18
Q

How is flutter determined?

A
  • position of the wing of prey
  • if wing is ‘close’ to bat will produce a higher frequency
  • if wing is horizontal there is a smaller surface area for the echo to bounce off of, decrease in amplitude
19
Q

How does rhinolophus use its different components?

A
  • uses CF component to determine flutter while hanging still

- uses FM component for tracking and capture

20
Q

What special adaptations do bats have in the outer ear?

A
  • large pinna and tragus which allows them to detect faint echoes
  • nose leaves to direct sound coming from nose
21
Q

What occurs when the human pinna is distorted?

A
  • can no longer differentiate where sound is coming from
22
Q

What is the structural discontinuity of the basilar membrane?

A
  • abrupt thickening and lengthening where the species specific CF component frequency is cast
  • results in expanded region for preferred frequencies and increase in sensory neurons in critical range
  • (basilar membrane thins and widens at low frequency end)
23
Q

How do hair cells work?

A
  • cells are stimulated by the movement of the basilar membrane
  • pressure causes them to bend and the tip links pull open K channels
  • get K influx that depolarizes the cell
  • causes Ca influx
  • then K efflux to repolarize
  • hair cells don’t generate an action potential, they release NT
24
Q

What is the hearing threshold? How are bats specialized?

A
  • determines how weak a stimulus can be presented and still be heard
  • at species specific frequency they have a low threshold to be able to detect quiet echoes
25
Q

What is Q10?

A
  • tells us how sharply tuned the auditory neurons are
  • the larger the Q10 the more sharply tuned
  • tuning curve allows us to calculate Q10
  • Q10 = best excitatory frequency/width of V shape 10 db above threshold
26
Q

How does the inferior colliculus process? Who found this?

A
  • George Pollak
  • neurons in inferior colliculus are sensitive to pulse-echo delay
  • fire once or twice for pulse and for echo
  • increased stimulus does not change firing raes
  • important for distance (and velocity)
27
Q

How does the auditory cortex process sound? Who discovered this?

A
  • Suga by looking at Pteronotus
  • FM-FM area: orderly arranged neurons respond to unique combinations of FM component of pulse and echo (distance)
  • CF-CF area: sensitive to unique combinations of CF component pulse and echo to encode velocity
28
Q

How is sound processed specifically in the FM-FM area?

A
  • neurons in this areas respond well to an FM component followed by an FM echo
  • three types of delay sensitive neurons; comparison of call FM1 to pulse FM2, FM3, FM4
29
Q

Where does the FM-FM area get its input from?

A
  • from different groups in the inferior colliculus tuned to FM1, FM2, FM3 or FM4
  • inferior colliculus - medial geniculate nucleus - cortex
30
Q

Why is the neural response to FM1 pulse delayed?

A
  • FM1 pulse delayed at medial geniculate nucleus but response to echo is not
  • because MGN neurons are coincidence detectors that respond to certain pulse-echo delay
31
Q

How is sound processed specifically in the CF CF component?

A
  • CF1-CF2 and CF1-CF3 neurons respond to combination of tones
  • preferred CF1 frequency increases along one axis
  • frequencies of harmonics increase along right angles of CF1 axis
  • creates a dual frequency coordinate system meaning a specific location represents a target velocity
32
Q

How does the DSCF area process sound?

A
  • code for certain frequencies and amplitudes of echoes specifically doppler shifted CF2 signals
  • respond to echo regardless of pulse
  • cortical part of acoustic fovea
33
Q

How is the DSCF area arranged?

A
  • columns are arranged radially
  • from one column to the next specific amplitude changes
  • moving outward along the spoke, the frequency increases
34
Q

What did Suga find?

A
  • a pharmacological inactivation of the DSCF area resulted in frequency discrimination disruption but not delay disruption
  • an inactivation of the FM-FM area resulted in disruption of delay discrimination but not frequency discrimination
35
Q

What is the reason for using many harmonics?

A
  • allows bats to broaden bandwidth
36
Q

Why do bats not get confused with one another?

A
  • they are cortically deaf to one another

- cortical neurons need a dual password to fire

Biol 448: Final (7 decks)

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