Dr. Moira van Staaden
office: LSC 304
phone: 2-0341
Email: mvs@caspar.bgsu.edu
Problems:
o Recognition
o Localization
Insect CNS architecture
o Brain with (1) mushroom bodies, and (2) the central body
complex
o Several ganglia (subesophogeal, thoracic, abdominal ganglia)
o Apparently no 'auditory center'
[FIG 10]
Sensory receptors >> Prothoracic ganglion >> Auditory Interneurons (6 types)
[FIGS 12 & 13]
Functional Auditory Processing
1. Localization problem
[FIG 11]
o Synapse with 2nd order neurons
- Interneurons with cell bodies in prothoracic ganglion
- Bilateral pair of mirror image interneurons
o Song presented ipsilaterally > ON rhythmically
depolarised, copying temporal pattern
o Impulses reach output region <1 ms
o No obvious temporal processing or filtering in prothoracic ganglion
o Song presented contralaterally > ON hyperpolarized
o No impulses in response to sound
o Mutual inhibition of left and right ON accentuates directional
information
o Solves localization problem ......... and more.....
2. Recognition problem
3 hypotheses:
- Common Element
- Delay Line
- Anded High and Low Pass Filters
Need:
- pathway with hi-fidelity temporal response
- neurons firing preferentially to high syllable rate
- neurons firing preferentially to low syllable rate
- cell 'anding' inputs from both of these
Have:
o AN 1, 2, and 3 receive synaptic input from ON and sensory
neurons
AN1 and AN3 - copy temporal song pattern
- strong directional sensitivity
- show no preference for species-specific syllable rate
o Brain has 4th and 5th order interneurons
- no distinct axons
- classes based on characteristic branching patterns
BNC1 - overlap with AN1 and BNC2
BNC2 - overlap BNC1 only
- 'song recognizers'
Some most sensitive at CF of calling song
Strong response, but not hi fi
Marked preference for SRR of species-specific song
[FIG 14]
o Functioning as Feature Detectors for species-specific
value of SRR
o Physiological responses correspond with behavioral responses
o Consistent with Schildberger's model of song recognition
o Limitations of cricket model
- no good molecular phylogeny
- frogs also have simple stereotyped signals (species identity, location)
Leptodactylidae: 30 spp in Central & South America
e.g. Túngara frog (Ryan et al.)
- Advertisement calls = 'whines'
- Physalaemus pustulosus and P. petersi add 'chucks'
- Sexual vs Natural selection
Comparable neurophysiology - tuning curves the same
Mate choice tests >>Conspecifics preferred vs all heterospecifics
[FIG 15]
Modifications:
coloradorum whine >> coloradorum whine + pustulosus chuck
pustulosus single pulse >> double-pulse
Supports Sensory Exploitation hypothesis:
- females exhibit preferences for traits that don't yet exist
in males
- males have opportunity to evolve calls better 'exploiting' female
sensory bias
- controversial
Last modified: 00/04/28