Cricket Singing

Question 1

Why sing?

Answer 1

to attract mates

Question 2

phonotaxis

Answer 2

moving toward sound

Question 3

mechanism

Answer 3

forewings raised and moved in and out over one another
during closing scraper pings off each peg of file
around 5000 pings/s sets up tone which is species specific
harp plus air volume resonates- 100dB of sound

Question 4

Huber (1950s)

Answer 4

local brain stimulation or injection of cholinergic agonists- useful tool

Question 5

Hedwig (2000)

Answer 5

control of song stridulation by a command neuron descending from brain
• Has a dorsal soma position, anterior dendritic process and axon that descends in the contralateral connective
• Present each side of the NS
• Stridulation can be suppressed by cercal inputs from the terminal ganglia without directly inhibiting the descending command activity

Question 6

Song Motor Program

Answer 6

one neuron each side of brain- higher spike rate in this neuron will cause wings to move over another and start singing
when stopped only need to excite neuron a little to start singing again

Question 7

Central Pattern Generator (CPG)

Answer 7

if all thoracic nerves cut, male produces song pattern similar to intact male
basic song pattern does not require proprioceptive feedback
essential neurons are in 2nd and interneurons in 3rd thoracic and abdominal ganglia
but sensory feedback is important in creating effective song- enable cricket to hold wings at the right angle

Question 8

Interneurons for the CPG

Answer 8

muscles for singing are same as those for flying
motor patterns for song and flight could be produced by same rhythm
but different interneurons involved in singing and flying
Schoneich & Hedwig (2010) identified and characterized a small number of interneurons involved in timing syllables in the song motor program
excited and inhibited in time with syllables
3 on left and right spiked just before each wing opening
2 of those could reset time of syllables so a part of clock for rhythm
others spiked spiked just before each wing closing but did not reset
additional interneurons organise syllables into chirps

Question 9

Jacob & Hedwig (2016)

Answer 9

lesion studies show chirps and syllables are generated in abdominal ganglia

Question 10

Schoneich et al (2015) 5 neurons that active as coincidence detectors to detect pulse pattern of the male calling song in females (HOW IS SYLLABLE RATE DETECTED)

Answer 10

• AN1 and LN2 reliable copy sound pattern with slight adaptation
• LN3 EPSP and spike response to first pulse always lower than the second pulse
• LN4 responds to first pulse with inhibition and subsequent depolarization that rarely elicits a spike but the second pulse evokes larger spike and triggers activity
• LN5 alternates between inhibition and subsequent depolarization in response to each sound pulse- couldn’t record or evoke spike- concluded it was a nonspiking neuron

Question 11

Ears

Answer 11

ear drums behind front leg
neurons respond best to tone of song specific to their species
around 50 receptors excited by tympanum vibration

Question 12

Auditory Neurons

Answer 12

many neurons tuned to species song
only pass on relevant signals
receptor axons terminate in 1st thoracic ganglion
synpase with very small number of target neruons on own side
2 interneurons confined to ganglion
2 interneurons sending axon to brain- 1 excited by tone of species song (mate recognition and location), 1 excited by high freq tones (bats)
2 axons going to 2nd and 3rd thoracic ganglia
DN1 sends auditory info toward hind end
AN1 send info to brain
T1 and ON1 help cricket locate the noise

Question 13

Feature Detection

Answer 13

phonotaxis- turning toward sound
tone is species specific
Hedwig & Poulet (2004)- used trackball system and found they will not track continual sound; the rate of syllables is what matters
takes a little time from cricket to start running, turns each pulse- step by step steerinG

Question 14

Directional Hearing

Answer 14

brain neurons not directly responsible for steering; but activating phonotactic behaviour
direction from which song is coming; both physical and neuronal mechanisms enhance difference in LR ear response
sound from one side causes larger vibrations on tympanum
steering seems to involve only 1st thoracic ganglion neurons

Question 15

Neuronal Enhancement

Answer 15

one target of auditory neurons is omega neuron
one on left one on right
brains probably involved in detecting sound direction

Question 16

How does a male cricket not deafen himself?

Answer 16

male own song is loud
idea of corollary discharge- motor commands have 2 different targets
one to control motor neurons
one to control sensory responses
Poulet & Hedwig showed responses to sound by omega neuron is reduced when male cricket sings
identified corollary discharge interneuron responsible for inhibition
CDI is excited within the thoracic ganglia by the song CPG- CDI inhibits omega neuron