Transcript cricket
A corollary discharge maintains auditory sensitivity during sound production Interdisciplinary Program in Brain Science Eye Movement & Vision Research LAB Hwang, Jae Won http://luna.cas.usf.edu/~husband/percept/corolary.htm Corollary Discharge Theory The brain may discriminate self-motion (movement of the eye) from object motion (something moving in the environment) by comparing activity in the eye muscles with retinal image movement. If a corollary motor signal (C) and a sensory signal (S) reach the Comparator at the same time, then eye movement is inferred and not object movement. http://home.dongguk.edu/user/ento/file2/c.figure.htm Cricket 귀뚜라미의 날개는 앞날개1쌍과 뒷날개1쌍이 있는데 수컷이 소리를 낼 수 있는 것은 앞날개 에 있는 줄과 마찰편 때문입니다. 앞날개는 배 끝까지 덮지는 못하지만 배 옆구리로 날개가 꺾이면서 옆구리까지 덮게 됩니다. 뒷날개는 퇴화하여 작아지거나 반대로 발달하는 것도 있 습니다. 뒷날개의 역할은 귀뚜라미가 나는 데 사용할 수 있다는 것입니다. 귀뚜라미의 귀는 특이하게도 앞다리 종아리 마 디에 있습니다. 사진은 앞다리의 바깥쪽(오른 쪽 사진)과 안쪽(왼쪽 사진)을 보여주고 있는데 사진에서 보이는 하얀 고막이 바로 귀입니다. http://www.zoo.cam.ac.uk/zoostaff/hedwig/index.html Release of Singing Behavior Microinjections of neuroactive substances like cholinergic agonists or ACh esterase blockers into the brain are most effective in grasshoppers and in crickets. Stridulation may last for many minutes and different song patterns are released. Calling song stridulation is released in the cricket Gryllus bimaculatus by microinjection of eserine into the protocerebrum. http://www.a-msystems.com/physiology/products/electrodes/suction.asp Suction Electrode The Suction Electrode is used to record or stimulate a tissue which remains submerged in saline. It is a popular choice to overcome the difficulties associated with air and oil recordings. With the Suction Electrode, it is quite easy to record extracellularly from very small hearts (insects), intestinal nerves, eye neurons and to stimulate muscles by an electrical pulse to their neurons. Auditory System of Cricket synapse 60 Auditory Afferent Neuron (along 5th prothoracic nerve) Ear(right) Omega 1 Neuron Prothoracic Ganglion 60 Auditory Afferent Neuron (along 5th prothoracic nerve) Ear(left) synapse Omega 1 Neuron Two Fundamental Problems Speaking and singing present the auditory system of the caller with two fundamental problems : • Discrimination between self-generated and external auditory signals • Prevention against desensitization Sonorous Singing • Intracellular recordings were made from the dendritic region of ON1 • An Inhibitory input influenced auditory processing. - Max spike fq. of ON1(176±28Hz) was much lower than at rest(376 ±50Hz). -Vertical Scale bar intracellular : 25mV extracellular : 10mV wing : 1mm - Horizontal Scale bar : 250ms Silent Singing • Sound production was prevented by removing one forewing. • ON1 received inhibitory postsynaptic potentials(IPSPs) during the syllables. - The activity of ON1 during sonorous stridulation is due to the cricket’s own song. • ON1 response to external acoustic stimuli was inhibited during the chirps. - Only excitatory postsynaptic potentials, and occasionally a spike, were elicited by the stimuli during silent chirps. Fictive Singing • To determine whether the inhibition was elicited by sensory feedback or by the network of neurons that generate the motor pattern. • Either thoracic or thoracic and abdominal galglia was isolated from muscles and sense organs, except for the fifth prothoracic nerve. • IPSPs were also present in the fictively singing cricket. • IPSPs even persisted when the ear were removed. Auditory Afferents • Primary afferent depolarizations (PADs) were presented with a similar timing to the IPSPs in ON1. - Vertical Scale bar intracellular : 15mV extracellular : 10mV wing : (a) 1mm, (b) 0.25mm, (c) 0.5mm - Horizontal Scale bar : 250ms Auditory Afferents(cont’d) • The PADs did not affect spike production in the auditory afferents. • But in many sensory systems, PADs have an inhibitory function as they reduce synaptic efficacy at the afferent terminals. Effectiveness of Inhibition • At rest and during the chirp interval each sound pulse evoked a burst of spike in ON1 with an average maximum spike frequency of 376±50Hz. -Vertical Scale bar intracellular : 25mV wing : 1mm - Horizontal Scale bar : 100ms • During silent chirps ON1 responded with bursts of only 123±29Hz. Effect of Inhibition on ON1 • At 80dB SPL each sound pulse elicited a burst of spikes with 203±24Hz. • When normal singing was mimicked with 100dB SPL chirps, the response to the following 80dB SPL test stimuli was reduced to 30±1Hz. -Vertical Scale bar intracellular : 25mV current : 20nA - Horizontal Scale bar : 100ms Effect of Inhibition on ON1(cont’d) • Injected hyperpolarizing current prevented ON1 from spiking during the 100dB SPL chirp. The average maximum response to subsequent 80dB SPL stimuli was a burst of spikes at 143±32Hz, which was significantly higher than the response without current injection. Conclusion • In the cricket an efferent signal(a ‘corollary discharge’) modulates auditory information processing at two levels of the auditory system : PADs in auditory afferent terminals and IPSPs in ON1. • Inhibition by the corollary discharge reduces the neural response to self-generated sound and protects the cricket’s auditory pathway from self-induced desensitization.