1. Final
The neural network: Making simple neurons part of complex machines
Primary olfactory processing networks
Eyeblink conditioning circuits
Take home points about networks:
Evolved to perform specific functions (broadly defined).
Circuit diagrams typically described at one or more levels of complexity.

2. Establishing a causal relationship between neurons and behavior
Correlation does not mean causation!!!
Establishing a causal relationship means:
Establishing the neuron or neuropil (a discrete region of neural interaction) is necessary for the behavior to occur.
Ablation
Pharmacology
Gene silencing
Establishing that the neuron or neuropil is sufficient for the behavior to occur.

3. Establishing a causal relationship between neurons and behavior
Test example: The Crayfish escape response is mediated by the lateral giant interneuron (LGI).
Correlation: Every time animal is tactilely stimulated, LGI fires and the escape response (tail flip) occurs.
Sufficiency: Every time the LGI is stimulated the escaper response occurs.
Necessity: If LGI is action potentials are blocked even tactile stimulation will fail to elicit behavior.

4. For reference the length of a football field is 91.44 meters
Conduction velocity of a squid giant axon is ~25m/s
Conduction velocity of a myelinated motor unit ~120m/s
Interesting facts about the human brain:
Number of neurons (adult):
Est: 1012
Number of neurons in cerebral cortex (adult):
Est: 20,000,000,000
Number of synapses (adult):
1014 (2,000-5,000 per neuron)
Power consumption (adult):
20-40 Watts (0.5-4 nW/neuron)
Percentage of body:
2% weight, % cells, 20-44% power consumption
Atrophy/death of neurons:
50,000 per day (between ages 20 and 75)
Probably more on Fridays
Maximum firing frequency of a neuron (across species):
250-2,000 Hz (0.5-4 ms intervals)
Signal propagation speed inside axon:
90 m/s sheathed, <0.1 m/s unsheathed

5. Sensory systems: our connection to the world
Taste
Smell
Touch
Vision
Audition
Vestibular (balance)
Nocioception (pain)
Proprioception (joint position)
This weeks reading assignment is posted: Moss and Sinha 2003

6. Gothic Bat Wahlberg's Epauleted Bat (megabat) Frog Eating Bat
Pallid bat
Wahlberg's Epauleted Bat
(megabat)
Gothic Bat
Chapin's Free-Tailed Bat
Echo location in bats
For more interesting bat images and links go to:

7. hairy-legged vampire bat
Bat man
Vampire bats
hairy-legged vampire bat
For taxonomic information and detailed descriptions of various bat families got to:

8. Sonar (sound navigation and ranging) is a technique that uses sound propagation under water to navigate or to detect other watercraft. There are two kinds of sonar, active and passive.
Bats use echolocation which is the same as Active Sonar
Ghost Faced Bat

9. Bat ears are built the same as ours; bats are just far more specialized
Typical bat ear
Human ear
Echo locating bats can:
Have a ~60 degree field of aural view (per pulse)
Detect sounds as high as 200Khz (optimal freq is species specific)
Detect objects less than a mm in diameter
Discriminate:
Object size
Object trajectory
Objects made of foam vs hard plastic vs live food
Insects based on wing flapping of the insect
Differences in echo delays as small as 10ns!

10. FM and CF sound production in bats
Echo locating bats use one or both (predominantly):
Frequency Modulated (FM) pulses kHz
Broadband signals
< 5 ms in duration
Pulse starts high frequency, sweeps down
used to calculate target distance/detail
Constant Frequency (CF) pulses
Narrow frequency band
Fewer harmonics
Typically greater than 5 ms
Provides Doppler shift information
(object movement relative to the bat)

11. Different bats have different calls with different spectral profiles
Source:

12. Different bats have different calls with different spectral profiles
Spotted bat
Source:

13. Different bats have different calls with different spectral profiles
Pallid Bat
Source:

14. Different bats have different calls with different spectral profiles
Big Brown Bat
Source:

15. Townsend's Big Eared Bat
Different bats have different calls with different spectral profiles
Source:

16. Specific parameters that bats extract from echoes about objects
Distance: (FM). Based on echo delay
Subtended angle or angular size. Based on echo loudness; (CF-FM)
Absolute object size, based on Delay + loudness (CF-FM)
Azimuth: the horizontal position (angle) of an object relative to the face. Based on aural delay (CF-FM)
Elevation of object (vertical angle relative to face) differential loudness based on changing ear position
Texture of object based on FM
Velocity/relative velocity of object
(change in distance relative to bat) Doppler shift

17. Doppler shift and acoustic fovea
The speed of sound at sea level:
m/s
km/h
mph
knots
340
1225
761
661
Movement relative to a sound source will compress or stretch sound waves

18. Doppler shift and acoustic fovea
Doppler shift compensation
Bats have a very narrow frequency band that they are particularly sensitive to.
Thus if they emit sounds at the most sensitive frequency and the object is moving Doppler shift will produce an echo that falls to one side of the optimal frequency
Bats therefore actively adjust their pulse emission frequency to compensate for this

19. What kinds of information can bats glean about targets from echoes?
Each moth species has a characteristic wing beat frequency and amplitude.
Bats are able to discriminate insects based on the different Frequency-amplitude profiles.

20. What kinds of information can bats glean about targets from echoes?
Bats are able to discern echo delay differences of 10ns
Equates to a distance of 2mm

21. Echolocation and foraging behavior in bats
Final
Echolocation and foraging behavior in bats
Four stages:
Active searching (seeking a target)
Approach/stalk (target acquired moving to intercept or waiting to pounce).
Active tracking (chasing)
Terminal stage (capture)
As the behavior progress to stage 4 FM pulse rate increases, FM range decreases

22. Bats in action: Interpreting the bat flight video