exam 1 CH6: flight in locusts

locust flight flight system sensory integration during flight summary

PART 3: MOTOR STRATEGIES#13: FLIGHT IN LOCUSTS I

locusts can sustain flight for hours 100s of miles phytophageous – eat living plants travel in swarms & strip vegetation order: Orthoptera family: Acrididae > 1200 spp. research: large tropical / subtr. spp.

Schistocerca gregaria* Locusta migratoria

LOCUST FLIGHT

2 main problems associated with locust flight coordinated rhythmic wing beat course control

LOCUST FLIGHT

tethered locust flight triggered by wind (receptors on head)... later measure everything... to study flight motor behavior

lift body position wing position muscle recording

BEHAVIOR

tethered fly flight

BEHAVIOR

2 prs of wings... 2 sets of flight muscles... 2nd & 3rd thoracic segments

ANATOMY

wing beat stable

~ 20 Hz, cycle 50 ms

~ 7 ms out of phase

hindwing > forewing

BEHAVIOR

complex pattern

up (elevation) & down

(depression)

back & forth pronate

can vary angle of attack

rather than wing beat

BEHAVIOR

10 muscle prs / wing 4 depressors... activated

at top of stroke 6 elevators... activated at

bottom of stroke hind 1st ... fore 2nd subtle timing differences

cuticle flexibility important

ANATOMY

Schistocerca gregaria CNS brain S1-3 T1-3 A1-11

FLIGHT SYSTEM

Schistocerca gregaria CNS brain S1-3 T1-3 A1-11

FLIGHT SYSTEM

Schistocerca gregaria CNS... flight-relevant bits... brain S1-3 T1-3

pro meso meta

A1-11

FLIGHT SYSTEM

Schistocerca gregaria CNS... flight-relevant bits... brain S1-3 T1-3

pro meso meta

A1-11

FLIGHT SYSTEM

1 – 5 motor neurons drive each muscle 10 muscles / wing ~ few neurons

FLIGHT SYSTEM

old idea... sensory input leads to motor output (eg, reflexes such as knee-jerk) if so... how does rhythmic behavior occur (eg ,flight)? proprioceptive feedback to CNS:

information about internal state monitored by receptors (eg, posture in humans)

CENTRAL PATTERN GENERATOR

proprioception in rhythmic movement triggered by preceding component of movement

eg, backward swing of leg (R2) proprioceptive sensory signal (S1) forward swing (R1)... etc

chain reflex or peripheral-control hypotheses: sensory feedback critical for rhythmic behavior

CENTRAL PATTERN GENERATOR

proprioception in locust flight ? 3 classes of proprioceptors

wing hinge stretch

receptors: wing tegula: wing campaniform sensilla: on

wing veins, by force of lift as

wing

CENTRAL PATTERN GENERATOR

proprioception in locust flight ? sufficient receptors to explain

chain reflex mechanism for flight once triggered, keeps going

because of proprioception does this happen?

CENTRAL PATTERN GENERATOR

proprioception in locust flight ? cut sensory nerves between wings & thorax (deafferentation)..

tethered flight air to head normal flight pattern ½ frequency (10 Hz) some form of central pattern generator in CNS

CENTRAL PATTERN GENERATOR

proprioception in locust flight ? cut sensory nerves between wings & thorax (deafferentation) later showed normal

muscle action potentials CNS motor neuron output

stimulation of sensory nerves wing beat freq normal

not ~ phase !

CENTRAL PATTERN GENERATOR

conclusions: proprioceptive feedback...

modulates average activity level of central

pattern generator

not needed for basic pattern

CENTRAL PATTERN GENERATOR

small # of motor neurons for each muscle...

measure EMG of muscles to estimate action

potentials of innervating neurons

recordings with 14 electrodes in flight muscles

during flight

revealed fundamental features of normal flight

CELLULAR ORGANIZATION

features of normal flight: elevators & depressors of wing activated by alternating 20 Hz bursts elevators & depressors of opposing wings synchronous hindwing depressors active ~ 5 ms before forewing

~ motor neurons

CELLULAR ORGANIZATION

is a neuron part of the pattern generator?... test with reset experiment...

if YES... depolarizing neuron (injecting current) should rest rhythm of behavior / muscle contraction if NO... may onlyreceive signals from pattern generator

CELLULAR ORGANIZATION

conducted reset experiment with ~ 80 motor neurons none showed reset... not pattern generator

fig. 6.10a shows normal firing of motor neurons (top) recordings from muscles (bottom)

CELLULAR ORGANIZATION

what about interneurons? 3 goals achieved:

reset experiments inject current & record

from other neurons fill with dye to follow

patterns of innervation

CELLULAR ORGANIZATION

what about interneurons?

bilateral pairs in thoracic ganglia

extensive branching...

as might be expected

~ motor control

CELLULAR ORGANIZATION

reset experiment with interneurons... several showed reset... pattern generator !

fig. 6.10b shows normal phasic firing of interneurons (IN301 & IN511) recordings from muscles (M112)

CELLULAR ORGANIZATION

reset experiment with interneurons... several showed reset... pattern generator !

fig. 6.10b shows normal phasic firing of interneurons (top) recordings from muscles (bottom)

further studies showed flight rhythm from excitatory & inhibitory activity within the network motor neurons

CELLULAR ORGANIZATION

rhythm from excitatory & inhibitory activity within the network motor neurons

IN504 EPSP IN301 IN301 IPSP IN511 IN301 EPSP* IN501 IN501 IPSP IN301

delay suggests additional intercalating interneuron

CELLULAR ORGANIZATION

connectivity among flight interneurons complex how do circuits rhythmic output ? focus on simple part of circuit

IN301 fires... excites IN501 IN501 fires... inhibits IN301 delay something excites IN301 oscillatory properties

CELLULAR ORGANIZATION

reset of IN501... part of the pattern generator ? depolarization shifts IN501 spiking shifts muscle activity

CELLULAR ORGANIZATION

IN301 & IN501... 2 of the known parts of the pattern generator

CELLULAR ORGANIZATION

BREAK