H exam 1 H CH6: flight in locusts H locust flight H flight system H sensory integration during flight H summary PART 3: MOTOR STRATEGIES #13: FLIGHT IN LOCUSTS I

H locusts can sustain flight for hours  100s of miles H phytophageous – eat living plants H travel in swarms & strip vegetation H order: Orthoptera H family: Acrididae H > 1200 spp. H research: large tropical / subtr. spp. H Schistocerca gregaria * H Locusta migratoria LOCUST FLIGHT

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

H tethered locust flight H triggered by wind (receptors on head)... later H measure everything... to study flight motor behavior H lift H body position H wing position H muscle recording BEHAVIOR

H tethered fly flight BEHAVIOR

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

H wing beat stable H ~ 20 Hz, cycle 50 ms H ~ 7 ms out of phase H hindwing > forewing BEHAVIOR

H complex pattern H up (elevation) & down (depression) H back & forth  pronate H can vary angle of attack rather than wing beat BEHAVIOR

H 10 muscle prs / wing H 4 depressors... activated at top of stroke H 6 elevators... activated at bottom of stroke H hind 1 st... fore 2 nd H subtle timing differences H cuticle flexibility important ANATOMY

H Schistocerca gregaria CNS H brain H S1-3 H T1-3 H A1-11 FLIGHT SYSTEM

H Schistocerca gregaria CNS H brain H S1-3 H T1-3 H A1-11 FLIGHT SYSTEM

H Schistocerca gregaria CNS... flight-relevant bits... H brain H S1-3 H T1-3 H pro H meso H meta H A1-11 FLIGHT SYSTEM

H Schistocerca gregaria CNS... flight-relevant bits... H brain H S1-3 H T1-3 H pro H meso H meta H A1-11 FLIGHT SYSTEM

H 1 – 5 motor neurons drive each muscle H  10 muscles / wing H ~ few neurons FLIGHT SYSTEM

H old idea... sensory input leads to motor output ( eg, reflexes such as knee-jerk) H if so... how does rhythmic behavior occur ( eg,flight)? H proprioceptive feedback to CNS: H information about internal state H monitored by receptors ( eg, posture in humans) CENTRAL PATTERN GENERATOR

H proprioception in rhythmic movement H triggered by preceding component of movement H eg, backward swing of leg (R 2 )  proprioceptive sensory signal (S 1 )  forward swing (R 1 )... etc H chain reflex or peripheral-control hypotheses: H sensory feedback critical for rhythmic behavior CENTRAL PATTERN GENERATOR

H proprioception in locust flight ? H 3 classes of proprioceptors H wing hinge stretch receptors:  wing  H tegula:  wing  H campaniform sensilla: on wing veins,  by force of lift as wing  CENTRAL PATTERN GENERATOR

H proprioception in locust flight ? H sufficient receptors to explain chain reflex mechanism for flight H once triggered, keeps going because of proprioception H does this happen? CENTRAL PATTERN GENERATOR

H proprioception in locust flight ? H cut sensory nerves between wings & thorax (deafferentation).. H tethered flight H air to head H normal flight pattern H ½ frequency (10 Hz) H  some form of central pattern generator in CNS CENTRAL PATTERN GENERATOR

H proprioception in locust flight ? H cut sensory nerves between wings & thorax (deafferentation) H later showed normal H muscle action potentials H CNS motor neuron output H stimulation of sensory nerves  wing beat freq  normal H not ~ phase ! CENTRAL PATTERN GENERATOR

H conclusions: proprioceptive feedback... H modulates average activity level of central pattern generator H not needed for basic pattern CENTRAL PATTERN GENERATOR

H small # of motor neurons for each muscle... H  measure EMG of muscles to estimate action potentials of innervating neurons H recordings with 14 electrodes in flight muscles during flight H revealed fundamental features of normal flight CELLULAR ORGANIZATION

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

H is a neuron part of the pattern generator?... test with reset experiment... H if YES... depolarizing neuron (injecting current) should rest rhythm of behavior / muscle contraction H if NO... may only receive signals from pattern generator CELLULAR ORGANIZATION

H conducted reset experiment with ~ 80 motor neurons H none showed reset...  not pattern generator H fig. 6.10a shows normal H firing of motor neurons (top) H recordings from muscles (bottom) CELLULAR ORGANIZATION

H what about interneurons? H 3 goals achieved: H reset experiments H inject current & record from other neurons H fill with dye to follow patterns of innervation CELLULAR ORGANIZATION

H what about interneurons? H bilateral pairs in thoracic ganglia H extensive branching... as might be expected ~ motor control CELLULAR ORGANIZATION

H reset experiment with interneurons... H several showed reset...  pattern generator ! H fig. 6.10b shows normal H phasic firing of interneurons (IN301 & IN511) H recordings from muscles (M112) CELLULAR ORGANIZATION

H reset experiment with interneurons... H several showed reset...  pattern generator ! H fig. 6.10b shows normal H phasic firing of interneurons (top) H recordings from muscles (bottom) H further studies showed flight rhythm from excitatory & inhibitory activity within the network  motor neurons CELLULAR ORGANIZATION

H rhythm from excitatory & inhibitory activity within the network  motor neurons H IN504 EPSP  IN301 H IN301 IPSP  IN511 H IN301 EPSP*  IN501 H IN501 IPSP  IN301 H delay suggests additional intercalating interneuron CELLULAR ORGANIZATION

H connectivity among flight interneurons complex H how do circuits  rhythmic output ? H focus on simple part of circuit H IN301 fires... excites IN501 H IN501 fires... inhibits IN301 H delay H something excites IN301 H oscillatory properties CELLULAR ORGANIZATION

H reset of IN part of the pattern generator ? H depolarization H shifts IN501 spiking H shifts muscle activity CELLULAR ORGANIZATION

H IN301 & IN of the known parts of the pattern generator CELLULAR ORGANIZATION

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