Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download central pattern generator
Document related concepts
Transcript
PART 3: MOTOR STRATEGIES #13: FLIGHT IN LOCUSTS I exam 1 CH6: flight in locusts locust flight flight system sensory integration during flight summary LOCUST FLIGHT 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 BEHAVIOR 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 ANATOMY 2 prs of wings... 2 sets of flight muscles... 2nd & 3rd thoracic segments BEHAVIOR 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 ANATOMY 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 FLIGHT SYSTEM 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 CENTRAL PATTERN GENERATOR 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 CELLULAR ORGANIZATION 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 only receive 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 BREAK
