Communication and Cortex

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Communicationand Cortex

• The computational
• neuroethology of mouse vocalizations

Robert Liu Sloan-Swartz Center for Theoretical
Neurobiology University of California at San
Francisco
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Basic questions in neural coding

• How does the brain process behaviorally-relevant
  stimuli?
• Is the structure of natural stimuli efficiently
  represented by neurons?

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Computational neuroethology

• Study organism in natural contexts (etho-)
• Look for strong stimulus-behavior links
• What are the properties of the stimulus?
• Determine relevant neural areas (neuro-)
• How do neurons represent stimulus properties?
• Use behavior to constrain neural codes
• Study coding algorithms (compu-)
• Use info theory to probe efficiency of neural
  codes

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Auditory processing in mice

• Obvious behavioral context communication
• Vocalizations are natural input to auditory
  system
• Behavioral response provides an observable output

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Auditory processing in mice

• Obvious behavioral context communication
• Vocalizations are natural input to auditory
  system
• Behavioral response provides an observable output
• Why the mouse?
• Opportunities to employ genetic techniques
• Extensive research on peripheral and non-cortical
  central auditory system
• Rich ultrasound communication behaviors

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Mouse pup ultrasounds

• Pup isolation calls maternal retrieval

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Categorical perception of pup calls

• Spectral domain
• Categorical perception of bandwidth-limited
  ultrasound noise as pup-like (Ehret Haack,
  1982)

90
Noise model
Frequency (kHz)
60
30
0
40
80
120
Time (ms)
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Categorical perception of pup calls

• Spectral domain
• Categorical perception of bandwidth-limited
  ultrasound noise as pup-like (Ehret Haack,
  1982)

Pup-like
90
Noise model
Frequency (kHz)
60
Response
30
0
40
80
120
22.5
Time (ms)
BW (kHz)
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Adult mouse encounter calls

• Ultrasounds when males encounter females

100
25
100
Frequency (kHz)
25
100
25
0
200
400
600
Time (ms)
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Computational neuroethology

• Study organism in natural contexts (etho-)
• Look for strong stimulus-behavior links
• What are the properties of the stimulus?
• Determine relevant neural areas (neuro-)
• How do neurons represent stimulus properties?
• Use behavior to constrain neural codes
• Study coding algorithms (compu-)
• Use info theory to probe efficiency of neural
  codes

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Frequency content of natural calls

• What frequencies make up a call?

One frequency extracted as a function of time
Whistle-like simplicity
Spectrogram
Histogram
100
100
75
75
Frequency (kHz)
Frequency (kHz)
50
50
25
25
0
40
80
0
20
40
Time (ms)
Number of 1 ms bins
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Pup call frequencies and durations

• Frequency and duration clusters
• Main 67 kHz/59 ms
• Aux 93 kHz/30 ms

150
100
Duration (ms)
50
0
40
60
80
100
Typical frequency (kHz)
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Pup call frequencies and durations

• Frequency and duration clusters
• Main 67 kHz/59 ms
• Aux 93 kHz/30 ms
• Main cluster lt22.5 kHz bandwidth for
  categorization
• Natural distribution contributes to category
  formation?

150
100
Duration (ms)
50
0
40
60
80
100
Typical frequency (kHz)
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Natural acoustic categories

• Adt 80 kHz/23 ms
• Pup and adult calls clearly separate
• ROC 91 correct
• Adult call category to be distinguished from pup
  calls?
• Perhaps other cues also necessary to categorize

150
100
Duration (ms)
50
0
40
60
80
100
Typical frequency (kHz)
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Call repetition periods
100

• Periods between call onsets different

Pup
25
Freq (kHz)
100
Adt
25
0
100
200
300
400
500
600
Time (ms)
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Call repetition periods
100

• Periods between call onsets different
• Adult calls repeat more quickly than pup calls
• 100 ms vs. 180 ms
• ROC 97 correct (frequency, duration, and
  period)

Pup
25
Freq (kHz)
100
Adt
25
0
100
200
300
400
500
600
Time (ms)
10
Probability (1/s)
5
0
0
100
200
300
400
500
Repetition period (ms)
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Conclusions

• Study organism in natural contexts (etho-)
• What are the properties of the natural calls?
• Spectral and temporal clustering of pup and adult
  calls
• Determine relevant neural areas (neuro-)
• How do neurons represent vocalization properties?
• Stimulus-locked neural oscillations reflect pup
  call periods
• Use behavior to constrain neural codes
• The peak spike count in auditory cortex may
  support a categorical distinction

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Collaborators

• Jennifer Linden
• Michael Merzenich
• Kenneth Miller
• Christoph Schreiner

Mentors
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Electrophysiology

• Experiments on recent CBA/CaJ mothers
• Ketamine and medetomidine anesthesia
• Multiunit activity recorded via tungsten
  electrodes inserted 400-600 microns below the
  surface
• Targeted areas with ultrasound responses
• Two free ?eld speakers (low frequency range from
  3 kHz to 40 kHz high frequency range from 20 kHz
  to 100 kHz)
• TDT System II equipment used to play out stimuli
  and record responses