1 / 34

CH7: escape behavior in crayfish behavior features & functional anatomy neuronal architecture

PART 3: MOTOR STRATEGIES #15: ESCAPE BEHAVIOR IN CRAYFISH. CH7: escape behavior in crayfish behavior features & functional anatomy neuronal architecture adaptive modulation summary: chapter 7. BEHAVIOR & FUNCTIONAL ANATOMY. walking is normal mode of locomotion

cian
Download Presentation

CH7: escape behavior in crayfish behavior features & functional anatomy neuronal architecture

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. PART 3: MOTOR STRATEGIES #15: ESCAPE BEHAVIOR IN CRAYFISH • CH7: escape behavior in crayfish • behavior features & functional anatomy • neuronal architecture • adaptive modulation • summary: chapter 7

  2. BEHAVIOR & FUNCTIONAL ANATOMY • walking is normal mode of locomotion • integrated motor escape response  tail flip • tail propulsion using flexor & extensor muscles

  3. BEHAVIOR & FUNCTIONAL ANATOMY • lateral giant: • tail stimulus • move up & back • rapid • 3 types of tail flip response • medial giant: • anterior stimulus • move back • rapid • nongiant • slower

  4. BEHAVIOR & FUNCTIONAL ANATOMY • tail flip can be elicited by • electrical stimulus • tactile stimulus • responses are comparable • triggers initiate complex motor sequences

  5. NEURONAL ARCHITECTURE • typical invertebrate CNS plan (ganglia + connectives) • brain • SOG complex • 5 thoracic ganglia • 6 abdominal ganglia... contain tail flip circuitry • ganglia communicate & are coordinated via connectives • peripheral comm. via roots • 1: swimmerets • 2: extensors • 3: flexors (motor only)

  6. NEURONAL ARCHITECTURE • 2 pairs of prominent giant axons • lateral giant interneurons (LGI) • cell bodies & dendrites in each abd. segment • electrical synapses (septate / segmental) • axons project  next segment • lateral giant escape • medial giant intern. (MGI) • cell bodies & dendrites in brain • ~ single fast neuron • medial giant escape

  7. NEURONAL ARCHITECTURE • giant interneurons  motor giant neurons (MoGs) • MoGs  flexor muscles • sensory input to: • head  MGI  all MoGs • tail  LGI  1-3 MoGs • focus on LGls

  8. NEURONAL ARCHITECTURE • LGI tail flip circuitry • sensory input: ~1000 hairs with sensory neurons • sensory interneurons:  LGIs & brain • A: phasic • C: tonic • LGIs

  9. NEURONAL ARCHITECTURE • LGI tail flip circuitry • sensory input: ~1000 hairs with sensory neurons • sensory interneurons:  LGIs & brain • A: phasic • C: tonic • LGIs • MoGs

  10. NEURONAL ARCHITECTURE • LGI tail flip circuitry • sensory input: ~1000 hairs with sensory neurons • sensory interneurons:  LGIs & brain • A: phasic • C: tonic • LGIs • MoGs • flexor muscles: • 5 / segment • + other input

  11. NEURONAL ARCHITECTURE • chemical synapses (slow) at input & output • electrical synapses (fast) elsewhere • sensory  LGI • directly () short latency • indirectly () long latency

  12. NEURONAL ARCHITECTURE • chemical synapses (slow) at input & output • electrical synapses (fast) elsewhere • sensory  LGI • directly () short latency • indirectly () long latency • sensory influence  fast flexor motor neurons • LGI  MoGs & segmental giant (SG)... very fast !

  13. NEURONAL ARCHITECTURE • LGIs  SG (electrical) • SGs  fast flexor motor neurons (electrical)

  14. NEURONAL ARCHITECTURE • LGI neurons at center of circuit • convergence of sensory input  LGI • divergence of LGI output  motor

  15. NEURONAL ARCHITECTURE • 3 components of “flipping out” behavior • rapid flexion of abdomen • re-extension of abdomen • swimming • independent behavior modules

  16. NEURONAL ARCHITECTURE • LGIs only involved in flexion • 2 abdominal sensory input channels •  biphasic LGI spike (EPSP) • indirect chemical • direct electrical

  17. NEURONAL ARCHITECTURE • rapid flexion response to abrupt tail stimulus because • sensory - interneuron chemical synapses depress with prolonged stimuli • electrical synapses  LGI have high threshold & short time constants • sensory input  presynaptic LGI inhibition

  18. NEURONAL ARCHITECTURE • 2 pathways from LGI (elect)  • MoG (chem)  flexor muscles • SG (elect)  FFs (chem)  flexor muscles • FFs threshold below that of signal from SG... • no delay in signal

  19. NEURONAL ARCHITECTURE • LGI fast speed from • large diameter axons • electrical synapses • LGI sufficient & necessary for tail flip response ?

  20. NEURONAL ARCHITECTURE • LGI sufficient & necessary for tail flip response... • sufficient: • inject current •  tail flip • necessary: • sever MoG* • stimulate tail flip • hyperpolarize LGI • measure severed MoG output •  “command neurons”

  21. NEURONAL ARCHITECTURE • LGI makes all-or-nothing decision to escape ? • what about upstream sensory decision ? ... • graded, not all-or-none synaptic input • together... explains why there is no partial tail flip

  22. NEURONAL ARCHITECTURE • command neuron • firing or stimulation elicits complex behavior... • eg,coordinated / rhythmic appendage movement • criteria: neuron should demonstrate • activity necessary & sufficient to elicit behavior • normal response to sensory stimulus • normal pattern of activitation • no single LGI satisfied criteria • they are in series, linked abdominal segments • act as functional unit

  23. NEURONAL ARCHITECTURE • LGI inhibitory signals: “command-derived inhibition” • ensures that additional flexor responses do not occur

  24. NEURONAL ARCHITECTURE • LGI inhibitory signals: “command-derived inhibition” • ensures that additional flexor responses do not occur • LGI spikes inhibit further LGI & MGI spikes • sensory, LGIs, MoGs & muscles inhibited

  25. NEURONAL ARCHITECTURE • further inhibition of • extension • slow flexor and slow extensor systems • widespread inhibitory influence • critical timing (details... ) • every level of tail flip circuitry

  26. NEURONAL ARCHITECTURE • read and be sure you understand text sections on • re-extension • swimming • problems... journal questions

  27. ADAPTIVE MODULATION • other influences on tail flip responses ? • does not always work • modulated by • restraint-induced inhibition • motivation (feeding) • learning

  28. ADAPTIVE MODULATION • restraint-induced inhibition • blocked by nerve cord transection • decreased facilitation of reflex • increased inhibition at higher levels • voluntary tail flip remains

  29. ADAPTIVE MODULATION • motivational modulation of escape behavior • feeding raises threshold of tail flip response • must be eating to influence response • cut nerve cord abolishes feeding- induced increase

  30. ADAPTIVE MODULATION • feeding modulates LGI firing only • degree of inhibition relative to stimulus • “competition”

  31. ADAPTIVE MODULATION • modulation of escape behavior by learning • repetition... what is important & what is not • habituation: reduced response with repeated stimuli • self-induced habituation by water movement ? • prevented by command-derived inhibition

  32. SUMMARY • anterior tactile stimulus  tail flip response • mediated by lateral giant interneurons (LGI) • sensory hair inputs • LGIs sufficient & necessary for response  widespread activation of flexor system • command neurons, trigger escape response • command-derived inhibition, cancels competing response, enables subsequent elements

  33. SUMMARY • command-derived inhibition, cancels competing response, enables subsequent elements • reextension from sensory feedback (reafference), via stretch receptors (muscle receptors, MROs) & sensory hairs on tailfan • swimming from central pattern generator activated by sensory input with prolonged delay • modulated by various influences... restraint, feeding, learning

  34. NEUROBIOLOGY CALENDAR • NO CLASS on T.3.20 • SECTION 3 REVIEW on R.3.22 • 2nd MIDTERM EXAM: • written, 15% of final grade • ASSIGNED (web page) @ 6 pm T.3.27 • DUE (eMail) @ 3 pm R.3.29

More Related