Transcript sensory integration during flight

PART 3: MOTOR STRATEGIES
#14: FLIGHT IN LOCUSTS II
 CH6: flight in locusts
 locust flight
 flight system
 sensory integration during flight
 summary
PART 3: MOTOR STRATEGIES
#14: FLIGHT IN LOCUSTS II
 CH6: flight in locusts
 locust flight
 flight system
 sensory integration during flight
 summary
CELLULAR ORGANIZATION
 IN301 & IN501... 2 of the known parts of the pattern
generator
PROPRIOCEPTIVE FEEDBACK
 how does proprioceptive feedback work ? ... so far...
 it can influence average pattern frequency
 it has no “essential” role in pattern generation
 experiment...
 wingbeat imposed on 1 forewing
 how does sensory feedback from this wing
influence flight rhythm of the other 3 wings ?
 observed that wings phase lock to imposed
frequencies...  proprioception does  CPG
PROPRIOCEPTIVE FEEDBACK
 what are the roles of the 3 types of receptors ?
 synaptic connections  CPG interneurons
 stimulate wing hinge
receptor  fires wing
depressor neuron
  inhibits elevator
 stimulate campaniform
 opposite effect
  proprioceptors can initiate & maintain flight rhythm
PROPRIOCEPTIVE FEEDBACK
 tegulae ?...
 neurons in phase
with elevator
motor neurons
 neurons excite
IN566
 IN566 excites
elevator motor
neuron
PROPRIOCEPTIVE FEEDBACK
 tegulae ?...
 stimulation of afferent neurons resets flight rhythm
PROPRIOCEPTIVE FEEDBACK
  wing proprioceptors are elements of the CPG:
1. phasically active ~ wingbeat cycle
2. activation  initiate, entrain & maintain oscillation
3. deafferentation  reduces operation of CPG
4. reset CPG when stimulated
PROPRIOCEPTIVE FEEDBACK
 how do wing proprioceptors  flight... 2 main inputs
1. wing depression  excites tegulae 
 excites elevator motor neurons
2. wing elevation  excites wing hinge stretch 
 excites depressor motor neurons
 inhibits wing elevator motor neurons
PROPRIOCEPTIVE FEEDBACK
 why is CPG control so complicated ?
1. stable core oscillating circuit, and
2. sensitive to sensory  appropriate to situation
 central rhythm generator integrated with sensory
 normal flight pattern
SENSORY INTEGRATION DURING FLIGHT
 course control ?
 must make rapid steering adjustment ~ wind
SENSORY INTEGRATION DURING FLIGHT
 uses 3 different sensory systems... exteroceptors
1. compound eyes
2. ocelli (simple eyes)
3. wind-sensitive hairs
SENSORY INTEGRATION DURING FLIGHT
 uses 3 different sensory systems... exteroceptors
1. compound eyes... 3D but
 complex
 ~ slow (100 ms  thorax ~ 2 wingbeat cycles)
2. ocelli (simple eyes)
3. wind-sensitive hairs
 simple
 ~ fast
SENSORY INTEGRATION DURING FLIGHT
 uses 3 different sensory systems... exteroceptors
1. compound eyes... 3D but complex & slow
2. ocelli (simple eyes)... pitch & roll, fast
3. wind-sensitive hairs... yaw & pitch, fast
SENSORY INTEGRATION DURING FLIGHT
 uses 3 different sensory systems... exteroceptors
1. compound eyes... 3D but complex & slow
2. ocelli (simple eyes)... pitch & roll, fast
3. wind-sensitive hairs... yaw & pitch, fast
 2 sensorimotor pathways
1. slow  head position,
steering by legs & abdomen
SENSORY INTEGRATION DURING FLIGHT
 uses 3 different sensory systems... exteroceptors
1. compound eyes... 3D but complex & slow
2. ocelli (simple eyes)... pitch & roll, fast
3. wind-sensitive hairs... yaw & pitch, fast
 2 sensorimotor pathways
1. slow  head position, steering by legs & abdomen
2. fast  thorax, course deviation information
DEVIATION-DETECTING INTERNEURONS
 ocelli (simple eyes)... detect horizon deviation
 3 pairs of deviation-detecting neurons (DDNs)
 DNI – ipsilateral ocellus
 DNM – medial ocellus
 DNC – contralateral ocellus
DEVIATION-DETECTING INTERNEURONS
 ocelli (simple eyes)... detect horizon deviation
 3 pairs of deviation-detecting neurons (DDNs)
 DNI – ipsilateral ocellus
 DNM – medial ocellus
 DNC – contralateral ocellus
 respond to different deviations
~ movement detectors*
DEVIATION-DETECTING INTERNEURONS
 ocelli (simple eyes)... detect horizon deviation
 3 pairs of deviation-detecting neurons (DDNs)
 DNI – ipsilateral ocellus
 DNM – medial ocellus
 DNC – contralateral ocellus
 respond to different deviations

~ movement detectors*
relay to thoracic ganglia
DEVIATION-DETECTING INTERNEURONS
 ocelli (simple eyes)... detect horizon deviation
 3 pairs of deviation-detecting neurons
 DNC – contralateral ocellus*
 relay to thoracic ganglia
 integrated with
 air current stimuli  hairs
 visual stimuli  eyes
DEVIATION-DETECTING INTERNEURONS
 ocelli (simple eyes)... detect horizon deviation
 3 pairs of deviation-detecting neurons (DDNs)
 respond to different deviations ~ movement

detectors*
integrated with air current
stimulus to hairs* and eyes
 hair signals  ocelli signals
DEVIATION-DETECTING INTERNEURONS
 ocelli (simple eyes)... detect horizon deviation
 3 pairs of deviation-detecting neurons (DDNs)
 respond to different deviations ~ movement


detectors *
integrated with air current
stimulus to hairs* and eyes
 hair signals  ocelli signals
 ocelli signals  hair signals
multimodal input critical... feature detector neurons
FLIGHT CONTROL CIRCUITRY
 DDNs integrated into thoracic circuitry via thoracic
interneurons (TINs)
 only works during flight
 influenced by the CPG
 phase-gated = signal at
appropriate phase of
of cycle  course control
 ... but not part of the CPG
 TINs integrate sensory
with phase-locked CPG
SUMMARY
 locusts have 2 pairs of wings @ thorax
 beat @ 20 Hz, 7 ms offset cycles
 10 pairs of muscles / wing: 4 depressors, 6 elevators
 driven by 1-5 neurons / muscle
 isolated thoracic circuitry  rhythmic motor output
 central pattern generator... influenced by
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proprioceptive sensory feedback
3 types of sensilla: wing hinge, tegula, campaniform
activation  rhythmic motor output,  part of CPG
CPG = central oscillating core + sensory feedback
SUMMARY
 CPG = central oscillating core + sensory feedback
 3 primary exteroceptor types on head  flight
 activate descending neurons, deviation-detecting


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neurons (DDNs) are 1 type
multimodal DDNs detect flight deviations
DDNs  thoracic interneurons (TINs)
TIN  motor neurons via interneurons
tonic sensory signal  phasic signal by CPG gating
 course control during flight
 CPG  rhythms (1) wingbeat & (2) sensory signal