W5 Reading
What the bat’s voice tells the bat’s brain
Three problems that the echolocating bat must solve: (i) auditory scene analysis, (ii) sensorimotor
transformations, and (iii) spatial memory and navigation
Introduction
- Need to consider the natural context which biologically relevant sensory information is
acquired and behaviour executed – neural activity may change with behaviour in animals
Bat echolocation – behaviour to neurobiology
- Most echolocating species use ultrasonic calls, but a few use sonar calls that are audible to
humans
- Build 3D image of objects by computing horizontal and vertical positions of targets from
differences in perceived arrival time, intensity and spectrum of echoes to each ear – same
acoustic cues as other mammalian auditory systems
o Perceives size from intensity, velocity from doppler shift, shape from spectrum
- Structure of calls has 3 designs
o Frequency modulated – durations of 0.5-20ms often with harmonics
o Constant frequency – CF bats calls last tens of milliseconds and echo’s doppler shift
helps estimate target motion
o Brief ultrasonic clicks – produce calls through larynx unlike the FM and CF-FM bats
- Species also categorised by duty cycle of their calls – percentage of time their pulse occupy –
FM bats low duty (<15%) CF-FM bats high (>30%)
- Active sensing system is similar to echolocation in dolphins, electrolocation in electric fish,
whisking-somatosensory system of rodents etc
o all these systems use importance of the motor component for perception: either
production of the signals used to probe the environment (in echolocation and
electrolocation) or the movement of the sensor organs (in whisking, sniffing, and
vision)
o In bats, very adaptive e.g in hunting, as nears the insect calls and rate they are
produced increases allowing accuracy of attack
Auditory system of echolocating bats
- Delay-tuned neurons
o Facilitated response when presented with pairs of sounds separated by time interval
o Helps with target distance, echo azimuth and elevation
- Sharp frequency tuning
o In CM-FM and frequencies of bats dominant CF components are overrepresented in
the ascending auditory pathway
o Allow detection of doppler shifts of target echoes
- Doppler shift constant frequency area
o Neurons detecting rapid doppler modulations (e.g wing flutter)
o CF/CF areas have neurons for doppler magnitude (target velocity)
o FM-FM areas have neurons for echo delay or target range
What the bat’s voice tells the bat’s brain
Three problems that the echolocating bat must solve: (i) auditory scene analysis, (ii) sensorimotor
transformations, and (iii) spatial memory and navigation
Introduction
- Need to consider the natural context which biologically relevant sensory information is
acquired and behaviour executed – neural activity may change with behaviour in animals
Bat echolocation – behaviour to neurobiology
- Most echolocating species use ultrasonic calls, but a few use sonar calls that are audible to
humans
- Build 3D image of objects by computing horizontal and vertical positions of targets from
differences in perceived arrival time, intensity and spectrum of echoes to each ear – same
acoustic cues as other mammalian auditory systems
o Perceives size from intensity, velocity from doppler shift, shape from spectrum
- Structure of calls has 3 designs
o Frequency modulated – durations of 0.5-20ms often with harmonics
o Constant frequency – CF bats calls last tens of milliseconds and echo’s doppler shift
helps estimate target motion
o Brief ultrasonic clicks – produce calls through larynx unlike the FM and CF-FM bats
- Species also categorised by duty cycle of their calls – percentage of time their pulse occupy –
FM bats low duty (<15%) CF-FM bats high (>30%)
- Active sensing system is similar to echolocation in dolphins, electrolocation in electric fish,
whisking-somatosensory system of rodents etc
o all these systems use importance of the motor component for perception: either
production of the signals used to probe the environment (in echolocation and
electrolocation) or the movement of the sensor organs (in whisking, sniffing, and
vision)
o In bats, very adaptive e.g in hunting, as nears the insect calls and rate they are
produced increases allowing accuracy of attack
Auditory system of echolocating bats
- Delay-tuned neurons
o Facilitated response when presented with pairs of sounds separated by time interval
o Helps with target distance, echo azimuth and elevation
- Sharp frequency tuning
o In CM-FM and frequencies of bats dominant CF components are overrepresented in
the ascending auditory pathway
o Allow detection of doppler shifts of target echoes
- Doppler shift constant frequency area
o Neurons detecting rapid doppler modulations (e.g wing flutter)
o CF/CF areas have neurons for doppler magnitude (target velocity)
o FM-FM areas have neurons for echo delay or target range
